Article: 98363 of rec.radio.amateur.homebrew From: jgboyles@aol.com Subject: Re: Can I use a 120V Variac to get 220V? Date: 19 Aug 2006 12:55:18 -0700 Message-ID: <1156017318.567094.52980@74g2000cwt.googlegroups.com> References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> w8kzw@hotmail.com wrote: > > > > Hi Jeff, Wire the output of the variac to the primary of the > > transformer, and the secondary to the 220V power input of the Amp. You > > may want to remove the tube(s) or disable the filaments to reduce the > > burden on the step up transformer. > > If the power transformer in the amp has a 110v tap, connect it up and > > then just use the variac. Be careful when you are doing this, there > > are all sorts of lethal voltages present. Good luck. > > Gary N4AST > > Thanks, Gary, but the devil is in the details. > > The 220 out from the step-up transformer is from one end of the > secondary coil to the other. > > The amp is essentially asking for two 110 V lines, working against a > common "ground". > > So, somehow I must go from this: > > 0 <-----220-----> 0 > > to this: > > 0 0 > > 0 > > and therein lies my confusion. > > Here are the connectors labeled: > > > 0 0 > A B > > to this: > > 0 0 > C D > 0 > E > > ... all I need to do is to connect the dots! Jeff, I would just leave the ground floating and connect C and D to the 220V secondary of the transformer. All you are trying to do is energize the HV supply of the amp. If you have a schematic of the amp, you should be able to figure where to supply the 220 to do just that. Gary N4AST Article: 98364 of rec.radio.amateur.homebrew From: "John, N9JG" References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> <1155955586.539941.265270@m73g2000cwd.googlegroups.com> Subject: Re: Can I use a 120V Variac to get 220V? Message-ID: Date: Sat, 19 Aug 2006 19:56:22 GMT Your advice is elegant in its simplicity. "Andrew VK3BFA" wrote in message news:1155955586.539941.265270@m73g2000cwd.googlegroups.com... > > w8kzw@hotmail.com wrote: >> I want to reform the electrolytics in an amp I'm bringing back to life. >> It runs high power, 220 volts ac only. >> >> Can I use my 110 volt variac in conjunction with a 110V to 220V step-up >> transformer to power up the amp? Obviously I'd not go key-down, but I >> do want to ultimately get to the full B+ on the tubes. >> >> How would I wire-up the variac / transformer, assuming it's possible? >> >> Thanks in advance for the help, guys. >> >> 73, >> Jeff >> W8KZW > > Its relatively simple and easy. Connect a 100w light globe in series > with the ac power input - this will limit current to a safe level. Run > for 10 hrs or so, will give caps a chance to reform....start with the > tubes in so the filament current draw limits cap voltage, then later > remove tubes to get virtually full voltage across caps.... > > Andrew VK3BFA. > Article: 98365 of rec.radio.amateur.homebrew From: Gary P. Fiber Subject: Re: VHF/UHF antenna on a motorcycle Date: Sat, 19 Aug 2006 14:22:06 -0700 Message-ID: <330fe2pstnus1k26m9oc623qi2ld4kbkik@4ax.com> References: On Fri, 18 Aug 2006 10:02:01 GMT, "Tom" wrote: >Hello all , > >I would like to install a VHF-UHF antenna on my motorcycle . It's a Suzuki >GSX750 . I did some tests with a Diamond NR-770H and it works well . The >only problem is that the antenna is to big for such a bike . >Afterwards i did a test with a Diamond NR-77 . The antenna is about 43 cm >and that's about the size i would like to use . >The problem i have with this antenna is the swr , it's to high . > >Anyone an idea how i can solve this problem ? > >Many thanks . > >Tom > > Use a 1/2 wave antenna. Many marine shops stock VHF 1/2 wave antennas for mast top mounting on sail boats. The beauty is no counterpoise is required. I think some looking at Randall / Larson you will also find they make 1/2 wave antennas. For the typical automotive installed mobile whip you will need a counterpoise. Generally on the auto that's not a problem as the body is metal and presents a nice large ground plane. Gary K8IZ Article: 98366 of rec.radio.amateur.homebrew From: Andrea Baldoni Subject: Re: AGC signal/noise question... References: <1155856208.223644.33300@m73g2000cwd.googlegroups.com> Message-ID: Date: Sat, 19 Aug 2006 18:05:26 -0500 LenAnderson@ieee.org wrote: : >I'm researching about the matter and I just read that, in a BJT for : >instance, emitter current is inversely proportional to the noise. So, : >if AGC reduces the gain (so current), SNR degrade? : Not necessarily true. Noise, true natural noise, in a bipolar : ... : of how many factors go into noise generation within the : transistor. :-) So, if you have to engineer a (let's start with HF) receiver, do you think it may better to: 1) find a way to insert automatically a stepped attenuation (maybe using a diode switched resistor network) and leaving amplifiers without AGC, thus optimizing them for a particular gain 2) build circuits with so high dynamic range that's completely impossible to have input signals overload them (what's the dynamic range one should normally expect at the antenna input, excluding obvious limit-case situations where the transmitting output is fed into the receiver input...?) 3) use the usual AGC ...I'm thinking the 1 could be a good solution if the demodulator had to be a digital one. That way, a calibrated attenuator simply add bits to the ADC. Hovewer, the 2 is very attractive, providing that all is analog, or the ADC dynamic range is better than the one that could come from the antenna... I've read most use the 3, digitizing the AGC signal maybe with a second ADC channel, to have anyway a sort of more bits of resolution. So probably I'm wrong and the right solution is the 3... but only if adding an AGC never ruin amplifiers performance. : There isn't much FM on HF. What there is would be in : narrow-band Data mode signals. Some of that Data is a : combination of AM and PM similar to a wireline modem's : modulation. In fact I was receiving 144MHz using a converter. : What is needed in an investigation of this is a reasonably- : well-calibrated signal generator with a calibrated attenuator. Unfortunately I have only a Instek function generator, and I'm not very satisfied with any intrument I bought from this firm... Anyway, sooner or later I'll build a dds one... Ah, another question. I have a very precise digital voltmeter. Very precise, 6.5digits (this time from Agilent)... Unfortunately, it's absolutely unable to handle RF. I would like to build a "RF" frontend for it... Any ideas? I'm thinking to a precise rectifier built with an OP AMP followed by a OP AMP integrator... Ciao, AB ... Andrea Baldoni, 2002: messaggio non protetto da copyright. Article: 98367 of rec.radio.amateur.homebrew From: "amstereo@meduci.com" Subject: Re: AM Stereo/FM Stereo Receiver Date: 19 Aug 2006 16:20:16 -0700 Message-ID: <1156029616.494681.270550@m79g2000cwm.googlegroups.com> References: <1155282030.742256.202800@m73g2000cwd.googlegroups.com> You may wish to click on the following link: http://Meduci.com What you described is available for $140 each postpaid to the lower 48 United States. It is based upon Motorola MC13028 decoder chip. Sincerely, Meduci, LLC Jeff Deck You write: >I would like to be able to build, from scratch, an radio receiver for >AM Stereo and FM Stereo. I only have a rough idea of what I need (I DO >need a C-QUAM for example, a MC13028), and I have next to no experience >with electronics (just an electronics lab class, and some education on >computer-programmed boards, during university), so I have no idea where >to start (although I would be able to solder the thing together once I >knew what I had to do). I do know, however, what I want in my >theoretical receiver: a small size that I can carry around, 2 speakers >for stereo output, knob tuning like a regular analog dial radio (i.e., >with a small arrow on a horizontal dial pointing out the frequency), >and possibly the ability to run off batteries or mains (220V 50Hz) as >well as a jack for outputting to headphones (or a computer for >airchecking purposes ;) ). And of course, no old-fashioned tech like >tubes ;). > >I know Chris Cuff has been known to make them, but who knows where he's >been these last few years? (Okay, he did have a few reviews at Amazon >as late as last year... and I just emailed him a few hours ago, but who >knows if he still checks his inbox?) Besides, I've seen his radios at >sites on AM Stereo, and the tuning he uses doesn't exactly lend well to >sensitive tuning (with the frequencies written right on the knob). > >Come on, help me out here. Article: 98368 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: AGC signal/noise question... Date: Sat, 19 Aug 2006 16:57:51 -0700 Message-ID: <12ef9c4hlloatf4@corp.supernews.com> References: <1155856208.223644.33300@m73g2000cwd.googlegroups.com> Andrea Baldoni wrote: > . . . > 2) > build circuits with so high dynamic range that's completely impossible to > have input signals overload them (what's the dynamic range one should > normally expect at the antenna input, excluding obvious limit-case situations > where the transmitting output is fed into the receiver input...?) > . . . One night I heard audio in the background when listening to my direct conversion 40 meter receiver. It was designed specifically to be as immune as possible to AM demodulation, and since I had finished its optimization several years before, I hadn't heard any audio from demodulated AM. (It was common when I was using mixers with poorer balance and dynamic range.) It didn't take long to find the station with my home receiver. It was at about 7335 kHz, a religious HF broadcast station in San Francisco (about 600 miles from here). The broadcast was in Russian, so they were evidently beaming to Russia and I wouldn't be far off the main beam. Some careful measurements showed a signal strength of 250 mV RMS at my receiver terminals. (That's 74 dB over the typical S9 value of 50 uV.) I was using a vertical 4-square array, which isn't at all optimum for that path. I hooked the antenna directly to my oscilloscope and could see the carrier and modulation. I took the receiver on a visit to England, and heard the audio from a large number of AM stations in the background, so I believe the signal levels there from HF broadcasters commonly exceeded the 250 mV I saw only once at home. The problem can of course be reduced by use of very narrow filters, but they're often so close to the 40 meter band edges that even that wouldn't be enough in most cases. I've also encountered some staggeringly strong signals when operating Field Day, when a group with a high or even moderate power transmitter is on the next ridge or otherwise very close. The bottom line is that I'd be hesitant to trust just about any number for a "worst case" maximum signal strength. Be sure to test any proposed design on 40 meters for a while from your location in Europe. Roy Lewallen, W7EL Article: 98369 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: AGC signal/noise question... Message-ID: <0cffe25vf0sgaoeojup6lhtudk6s9m64qp@4ax.com> References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> Date: Sun, 20 Aug 2006 01:39:55 GMT On Fri, 18 Aug 2006 16:33:25 +0200, "i3hev, mario held" wrote: >tim gorman wrote: > >> You might also ask yourself whether it really matters or not. If your signal >> is strong enough to begin driving the AGC to limit the system gain do you >> really care what the noise level actually is? .... > >But you may very well care for the SNR on an interesting weak signal >which you are trying to listen to, while a strong nearby signal >activates your AGC... >:) In theory the system bandwidth should not allow that strong signal to hit the AGC. Of course practical systems this may not be true. However, manual gain control helps if the stronger signal is not overloading the front end causing gain compression and intermodulation. Allison Article: 98370 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: AGC signal/noise question... Message-ID: References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> Date: Sun, 20 Aug 2006 01:44:44 GMT On Fri, 18 Aug 2006 19:54:00 +0200, "i3hev, mario held" wrote: >Michael Black wrote: > >> In that case though, you should be worried about that nearby strong signal >> dropping the gain of the receiver so you can't hear the weak signal... > >may be you are not thinking of cw... :) > >Provided the SNR is good enough, you can filter and post-amplify your >weak signal, e.g. with a good AF filter, or a dsp. > >Of course, if the IF stages are (reasonably) linear in response, you can >disable the AGC, but this would be no answer to the original question ;) Since the SNR is established by the frontend the IF system can have a more relaxed SNR. However be wary of ICs like the MC1350 as the gain reduction occurs the internal noise is bad. I've built several recievers using this part and at ~10db gain reduction the noise jumps way up. I've gone to cascode JFETs as the noise is more predictable and generally lower. The device used does make a difference. Allison Article: 98371 of rec.radio.amateur.homebrew From: "LenAnderson@ieee.org" Subject: Re: VHF/UHF antenna on a motorcycle Date: 19 Aug 2006 20:07:25 -0700 Message-ID: <1156043245.547218.141830@b28g2000cwb.googlegroups.com> References: From: Tom on Fri, Aug 18 2006 3:02 am >I would like to install a VHF-UHF antenna on my motorcycle . It's a Suzuki >GSX750 . I did some tests with a Diamond NR-770H and it works well . The >only problem is that the antenna is to big for such a bike . >Afterwards i did a test with a Diamond NR-77 . The antenna is about 43 cm >and that's about the size i would like to use . >The problem i have with this antenna is the swr , it's to high . > >Anyone an idea how i can solve this problem ? Try contacting your local PD radio repair place. Motorcycle police have been using VHF-UHF radios on their motors for over 40 years. Successfully. They must be doing something right, yes? :-) Quod erat demonstrandum. LenAnderson@ieee.org Article: 98372 of rec.radio.amateur.homebrew From: "LenAnderson@ieee.org" Subject: Re: AGC signal/noise question... Date: 19 Aug 2006 20:12:14 -0700 Message-ID: <1156043534.843690.217490@i42g2000cwa.googlegroups.com> References: From: Andrea Baldoni on Sat, Aug 19 2006 4:05 pm >LenAnder...@ieee.org wrote: > >: >I'm researching about the matter and I just read that, in a BJT for >: >instance, emitter current is inversely proportional to the noise. So, >: >if AGC reduces the gain (so current), SNR degrade? > >: Not necessarily true. Noise, true natural noise, in a bipolar >: ... >: of how many factors go into noise generation within the >: transistor. :-) > >So, if you have to engineer a (let's start with HF) receiver, do you think >it may better to: There's no "engineering" involved, just a crunching of numbers AFTER you find the input levels versus AGC and how much noise is actually generated...and approximately WHERE this excess noise is coming from. >1) >find a way to insert automatically a stepped attenuation (maybe >using a diode switched resistor network) and leaving amplifiers without AGC, >thus optimizing them for a particular gain I see no need of that at this point. "Getting fancy" with extra circuitry is rather useless without knowing what the problem all this fancy circuitry is supposed to cure. >2) >build circuits with so high dynamic range that's completely impossible to >have input signals overload them (what's the dynamic range one should >normally expect at the antenna input, excluding obvious limit-case situations >where the transmitting output is fed into the receiver input...?) That's NOT the issue here. Noise and signal-to-noise ratios are only important at LOWEST signal levels, not the highest. >3) >use the usual AGC Why not? Decades of designs in many countries have successfully operated with "usual AGC." [voltage-controlled, sometimes current-controlled gain stages driven by a DC control line] >...I'm thinking the 1 could be a good solution if the demodulator had to be >a digital one. That way, a calibrated attenuator simply add bits to the ADC. >Hovewer, the 2 is very attractive, providing that all is analog, or the >ADC dynamic range is better than the one that could come from the antenna... Experiment any way you want but I can't see that as your cure. >I've read most use the 3, digitizing the AGC signal maybe with a second >ADC channel, to have anyway a sort of more bits of resolution. >So probably I'm wrong and the right solution is the 3... but only if adding >an AGC never ruin amplifiers performance. A rather common (for decades of designs and production) AGC action is no more than 6 db change in output for 60 to 100 db of input signal (carrier) change. AGC should be approached from the standpoint of a servo loop. The "error signal" is the change in carrier level at the detector. The controlled items are the RF and IF amplifiers. The time-constant of the error feedback loop (what is commonly called "the AGC line") is quite slow but fast enough to try to keep detector level constant through flutter (rapid reflections at VHF and up) and ionospheric path variations. If "the AGC line" somehow has some noise in it, that noise is probably going to change RF-IF amplifier gain. However, the frequency of that noise is going to be low; it is band- limited by the usual AGC line decoupling. Let's look at SNR with low to higher antenna input levels: 1. Assume you have (for example) 1 uV of noise at no-signal. 2. If the RF signal is 3.16 uV then the signal-plus-noise to noise ratio is 10 db. 3. If the RF signal is 10 uV then the signal-plus-noise to noise ratio is 20 db. 4. If the RF signal is 31.6 uV then the signal-plus-noise to noise ratio is 30 db. The common (for about 40+ years, internationally) level of receiver sensitivity for AM mode signals is a 10 db signal- plus-noise to noise ratio. That's an easy test, done by connecting an AC voltmeter (that can measure RMS voltage) to the detector output. With no signal input, all you get is front-end noise; note that. Apply a known-level RF source to the antenna input, adjust that level to be 10 db higher than the noise level measured with no signal input. Note the RF source level; that is the "minimum sensitivity" level for the common "10 db S+N:N" criterion. For FM or PM it is a bit more complicated. FM and PM rely on quieting through the Limiter stages ahead of the FM detector. For most tests of FM/PM sensitivity you NEED a known-signal-source-level to determine the quieting. >: There isn't much FM on HF. What there is would be in >: narrow-band Data mode signals. Some of that Data is a >: combination of AM and PM similar to a wireline modem's >: modulation. > >In fact I was receiving 144MHz using a converter. That data was omitted. Have you checked out the converter insofar as adding noise? You can get a rough comparison by using another HF receiver. Have you checked your internal (to HF receiver) FM demodulator characteristics? Do you have the manufacturer's specifications on that? Since nearly all FM/PM demods use Limiters, they normally operate with AGC off. >: What is needed in an investigation of this is a reasonably- >: well-calibrated signal generator with a calibrated attenuator. > >Unfortunately I have only a Instek function generator, and I'm not >very satisfied with any intrument I bought from this firm... > >Anyway, sooner or later I'll build a dds one... You can't work in the dark (without instruments) when trying to troubleshoot electronics. A DDS (Direct Digital Synthesis) signal generator gives you very precise FREQUENCY. For years there have been L-C oscillator based signal generators which have been stable enough in frequency to determine AGC action. What you really need to investigate the AGC is PRECISE RF ATTENUATION -and- a way to calibrate the maximum RF output. [an ordinary diode detector could do that if it was itself calibrated against a known RF source LEVEL] >Ah, another question. I have a very precise digital voltmeter. Very >precise, 6.5digits (this time from Agilent)... Unfortunately, it's >absolutely unable to handle RF. >I would like to build a "RF" frontend for it... Any ideas? >I'm thinking to a precise rectifier built with an OP AMP followed by a >OP AMP integrator... The usual method of making a "precise" RF voltmeter is to begin with a wideband video amplifier with gain controls setting the gain in the full-scale ranges desired. However, the BACK END needs attention, particularly if you want TRUE RMS measurement. The "less precise" HP3400A AC voltmeter could do that True RMS within 1% using an analog meter readout (mirrored scale on meter). The 3400A used a pair of matched heaters and thermocouples. Amplified AC heated one heater. A high-gain DC op-amp had inputs (opposing) from both thermocouples. Op-amp output heated the second heater. This was self-balancing. The AC Voltage indicated actually came from the DC op-amp output. If you are going to measure AC-RF volts of both sinewaves and noise, you need True RMS indication. Without that the noise (random stuff) read by simple averaging rectifiers will be DOWN by as much as 50% compared to a sinewave input. There are three basic types of AC voltmeters made: Rectify- average (common to handheld multimeters); Logarithmic (now a standard of high-end bench multimeters) using special ICs for True RMS conversion to DC; Thermal (now out of favor in new designs but using the first-principles of measuring the effective heating of a resistive load). Thermocouple sensors are reliable, can handle overloads, but a diode string biased for forward conduction can produce DC voltage changes of -2 mV / degree C heating. For some references, you can search the Internet for "RMS to DC" conversion, or begin at www.ednmag.com, go to their Archives button, select issue for May 11, 2000, and look at the "How It Works" article by Jim Williams of Linear Technology Corporation. LTC made an IC that was a dual heater-sensor, the LT1088, but that IC is now discontinued. The article shows a "front end" as well as the whole AC voltmeter circuit. LenAnderson@ieee.org Article: 98373 of rec.radio.amateur.homebrew From: "LenAnderson@ieee.org" Subject: Re: AGC signal/noise question... Date: 19 Aug 2006 20:19:19 -0700 Message-ID: <1156043959.936323.84540@75g2000cwc.googlegroups.com> References: >nospam@nouce.bellatlantic.net wrote: >> On Fri, 18 Aug 2006 19:54:00 +0200, "i3hev, mario held" >> wrote: >> >Michael Black wrote: > >> However be wary of ICs like the MC1350 as the gain reduction occurs >> the internal noise is bad. I've built several recievers using this >> part and at ~10db gain reduction the noise jumps way up. I've gone >> to cascode JFETs as the noise is more predictable and generally >> lower. The device used does make a difference. > >> Allison I have to disagree on the MC1350 and way back 30 years to its predecessor, MC1590. The prototype HF receiver presently on my workbench has a NF of 5.5 and that hardly rises more than that with AGC current applied to the AGC pin. BTW, that receiver, single-conversion with one IF at 21.4 MHz, uses only MC1350s up to the detector, including the one mixer stage. [ LO is a separate PLL board ] LenAnderson@ieee.org Article: 98374 of rec.radio.amateur.homebrew From: Alan Subject: Re: VHF/UHF antenna on a motorcycle Date: Sun, 20 Aug 2006 11:54:22 +0800 Message-ID: <45nfe29sgf57sd2g4gts1am5ov4cl7dutl@4ax.com> References: <1156043245.547218.141830@b28g2000cwb.googlegroups.com> On 19 Aug 2006 20:07:25 -0700, "LenAnderson@ieee.org" wrote: >From: Tom on Fri, Aug 18 2006 3:02 am > >>I would like to install a VHF-UHF antenna on my motorcycle . It's a Suzuki >>GSX750 . I did some tests with a Diamond NR-770H and it works well . The >>only problem is that the antenna is to big for such a bike . >>Afterwards i did a test with a Diamond NR-77 . The antenna is about 43 cm >>and that's about the size i would like to use . >>The problem i have with this antenna is the swr , it's to high . >> >>Anyone an idea how i can solve this problem ? Talk to your local two way radio supplier/service company about a "ground independant" antenna. Alan -- Sell your surplus electronic components at http://ozcomponents.com Search or browse for that IC, capacitor, crystal or other component you need. Article: 98375 of rec.radio.amateur.homebrew From: mike Subject: Re: Can I use a 120V Variac to get 220V? References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> <1155955586.539941.265270@m73g2000cwd.googlegroups.com> Message-ID: Date: Sun, 20 Aug 2006 08:11:33 GMT John, N9JG wrote: > Your advice is elegant in its simplicity. And OPTIMISTIC in it's generality. While one might imagine situations where this technique is useful, it would be better to define a strategy that takes into consideration the exact configuration of the PS in your unspecified amplifier. If your caps don't need reforming, any technique will work. If they do, you're gonna have some current flow. It's not hard to imagine a scenario whereby you have 25W or more dissipated in your caps. I don't call this safe. A 100W light bulb will keep you from blowing up the rectifiers while you're blowing up the caps. Assuming you have solid-state rectifiers, go back to the variac and transformer. Depending on the value of the high voltage, There may be issues if you just turn off the tube filaments. The series lamp can still be helpful, but isn't the whole story. It's always helpful to disclose the parameters of the situation when asking for advice. Otherwise, you'll get 10 different solutions based on 10 different assumptions, none of which will be correct. mike > > "Andrew VK3BFA" wrote in message > news:1155955586.539941.265270@m73g2000cwd.googlegroups.com... > >>w8kzw@hotmail.com wrote: >> >>>I want to reform the electrolytics in an amp I'm bringing back to life. >>> It runs high power, 220 volts ac only. >>> >>>Can I use my 110 volt variac in conjunction with a 110V to 220V step-up >>>transformer to power up the amp? Obviously I'd not go key-down, but I >>>do want to ultimately get to the full B+ on the tubes. >>> >>>How would I wire-up the variac / transformer, assuming it's possible? >>> >>>Thanks in advance for the help, guys. >>> >>>73, >>>Jeff >>>W8KZW >> >>Its relatively simple and easy. Connect a 100w light globe in series >>with the ac power input - this will limit current to a safe level. Run >>for 10 hrs or so, will give caps a chance to reform....start with the >>tubes in so the filament current draw limits cap voltage, then later >>remove tubes to get virtually full voltage across caps.... >> >>Andrew VK3BFA. >> > > > Article: 98376 of rec.radio.amateur.homebrew From: "Andrew VK3BFA" Subject: Re: Can I use a 120V Variac to get 220V? Date: 20 Aug 2006 02:40:12 -0700 Message-ID: <1156066812.072148.253150@i3g2000cwc.googlegroups.com> References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> mike wrote: > John, N9JG wrote: > > Your advice is elegant in its simplicity. > > And OPTIMISTIC in it's generality. > While one might imagine situations where this technique is > useful, it would be better to define a strategy that takes > into consideration the exact configuration of the PS in > your unspecified amplifier. Gee, that sounds like the opening page of a PowerPoint presentation - your not a manager by proffession, are you? And if you have an engineering degree, and want to engage in endless metaphysical speculation, thats a very good idea.....whatever it was.....amongst the verbiage.... > > If your caps don't need reforming, any technique will work. > If they do, you're gonna have some current flow. It's not > hard to imagine a scenario whereby you have 25W or more > dissipated in your caps. I don't call this safe. A 100W > light bulb will keep you from blowing up the rectifiers while > you're blowing up the caps. Rubbish. Where do you get this 25w figure from, and across how many capacitors in a (typical) series string - oh, and lets ignore idling current through transformer and bleeeder resistors, and filamnet current drain, and blowers, and dial lamps, and.....which would further reduce available volts across the caps.... And whats this "imagine a scenario" stuff - I thought you were trying to be precise and were chiding me for my lack of hard data.... > > Assuming you have solid-state rectifiers, go back to the > variac and transformer. Depending on the value of the high voltage, > There may be issues if you just turn off the tube filaments. > The series lamp can still be helpful, but isn't the whole story. So, what voltage do you set the variac too? - how do you work it out? > > It's always helpful to disclose the parameters of the situation > when asking for advice. Otherwise, you'll get 10 different > solutions based on 10 different assumptions, none of which will be > correct. > mike True. There are probably 10 different ways of puting out a fire, but the easiest is dumping a bucket of water on it. Honestly, this is ridiculous - most modern (ie, last 40 years) caps are fine, will survive horrendous abuse, and unless you have the manufacturers data sheets for these capacitors, (and the power transformer, and the rectifiers) how are you going to set these parameters anyway? - this is a linear amplifier, not the space shuttle. Why do people insist on making things sooooo complicated, almost theoretical physics level - it isnt. Dont let irelevant theory get in the way of practical electronics. The intial switch on of ANYTHING that hasnt been powered up for years is going to be the time it dies - at least the bulb will stop it bursting into flames, the variac method will jsut slowly ramp up volts until something blows catasphropically (I know, used to do this, got sick of replacing fuses in the variac.) As well, you have the added complication of multiple, lashed together transformers which MUST all be correctly phased and able to take the load current . a recipe for confusion at least. And no, I cant spell. Spend too much time with soldering irons rather than physics journals. Andrew VK3BFA. > > "Andrew VK3BFA" wrote in message > > news:1155955586.539941.265270@m73g2000cwd.googlegroups.com... > > > >>w8kzw@hotmail.com wrote: > >> > >>>I want to reform the electrolytics in an amp I'm bringing back to life. > >>> It runs high power, 220 volts ac only. > >>> > >>>Can I use my 110 volt variac in conjunction with a 110V to 220V step-up > >>>transformer to power up the amp? Obviously I'd not go key-down, but I > >>>do want to ultimately get to the full B+ on the tubes. > >>> > >>>How would I wire-up the variac / transformer, assuming it's possible? > >>> > >>>Thanks in advance for the help, guys. > >>> > >>>73, > >>>Jeff > >>>W8KZW > >> > >>Its relatively simple and easy. Connect a 100w light globe in series > >>with the ac power input - this will limit current to a safe level. Run > >>for 10 hrs or so, will give caps a chance to reform....start with the > >>tubes in so the filament current draw limits cap voltage, then later > >>remove tubes to get virtually full voltage across caps.... > >> > >>Andrew VK3BFA. > >> > > > > > > Article: 98377 of rec.radio.amateur.homebrew From: "Brenda Ann" Subject: Re: What is wrong with Hawaii, Alaska, and Canada Date: Sun, 20 Aug 2006 21:41:48 +0900 Message-ID: References: <5DYFg.9998$xp2.7906@newsread1.news.pas.earthlink.net> -- Say no to institutionalized interference. Just say NO to HD/IBOC! "Brian" wrote in message news:5DYFg.9998$xp2.7906@newsread1.news.pas.earthlink.net... >I ship to anyone that wants to pay for it. I do avoid APO/FPO shipping, >and > not because of scams but because of very very poor delivery chances on > anything not a 1 ounce letter. > > I sent several boxes of supplies to friends serving in Iraq with the US > Marine Corps...most of the boxes languished in a warehouse in Germany for > about 4 weeks before being hauled to Iraq...then it was another 2 or 3 > weeks > befire they actually got the stuff. Needless to say, never ship a puppy > or > kitten to a war zone. I have one realative that was in Iraq for a year > (the > last time). I mailed him a Christmas package at the end of October. He > got > home in February and still hadn't received it. > Yes, shipping to OIF/OEF is very very slow. This is because nobody wants to go in there. Regular fuel shipments can take 2 weeks to cross the country. Shipping to APO/AE (Europe), APO/AA (Americas) and APO/AP (Pacific region) is fairly steady, at least going by Priority. Parcel Post or Media Mail go by SAM (Space Available Mail) and can take months to get ANYWHERE within the military postal system. This is because EVERY other class of mail gets priority over SAM, and some of those parcels don't leave the mil hub for weeks (stateside). Article: 98378 of rec.radio.amateur.homebrew Message-ID: <44E85D74.4050504@atnet.net> From: Bob W7AVK Subject: Re: What is wrong with Hawaii, Alaska, and Canada References: <5DYFg.9998$xp2.7906@newsread1.news.pas.earthlink.net> Date: Sun, 20 Aug 2006 06:02:44 -0700 What I've done sending goodies to our troops is to use the flat rate Priority Boxes available free at the post office. All you can stuff into it for the 2 pounds rate or $8.10. Mose have been delivered within a couple weeks. If interested might check out http://www.anysolder.com 73 Bob W7AVK Article: 98379 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: AGC signal/noise question... Message-ID: References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> Date: Sun, 20 Aug 2006 16:06:30 GMT On 19 Aug 2006 20:19:19 -0700, "LenAnderson@ieee.org" wrote: > >>nospam@nouce.bellatlantic.net wrote: >>> On Fri, 18 Aug 2006 19:54:00 +0200, "i3hev, mario held" >>> wrote: >>> >Michael Black wrote: >> >>> However be wary of ICs like the MC1350 as the gain reduction occurs >>> the internal noise is bad. I've built several recievers using this >>> part and at ~10db gain reduction the noise jumps way up. I've gone >>> to cascode JFETs as the noise is more predictable and generally >>> lower. The device used does make a difference. >> >>> Allison > > I have to disagree on the MC1350 and way back 30 years to its > predecessor, MC1590. The prototype HF receiver presently on > my workbench has a NF of 5.5 and that hardly rises more than > that with AGC current applied to the AGC pin. Read EMRFD page 6.16 (ARRL press) they tested the 1350 and at the point where the gain cell has equal conduction on both legs the noise rises significantly. I duplicated the test fixture and yes, it's noisy, from around 6db to around 11db in my fixture when gain is reduced by 10db and that was at 16mhz. In a reciever that used it I went to two cascode stages using JFETs and the difference noise was notable for weak signals just into the agc range. I restrict the 1590/1350/ca3028 for lower perfomance recievers now. I also verified that the 1590 does same and also the CA3028 wired as differential AGC. Even tried three 2n3904s and same result. The agc range was good and at full gain the noise was ok but the noise increase at partial agc was surprizing. > BTW, that receiver, single-conversion with one IF at 21.4 MHz, > uses only MC1350s up to the detector, including the one mixer > stage. [ LO is a separate PLL board ] I do most of my RX experimentation at 6/ 2M and 70cm SSB so noise and overload perfomance are important to me. Images are also a big problem as I'm near a lot of VHF/hf broadcast. Allison Article: 98380 of rec.radio.amateur.homebrew From: "Alain" Subject: Help Leader LSW-359 Manuals Date: Sun, 20 Aug 2006 19:49:42 +0200 Message-ID: <44e8a0ba$0$5985$636a55ce@news.free.fr> Hello, I seek the manual operator and characteristics of the sweep signal generator Leader LSW-359 Thanks for helping me. Alain XXXf1mdt@free.frXXX (-X) Article: 98381 of rec.radio.amateur.homebrew From: "LenAnderson@ieee.org" Subject: Re: AGC signal/noise question... Date: 20 Aug 2006 12:46:25 -0700 Message-ID: <1156103185.261420.21420@74g2000cwt.googlegroups.com> References: From: nos...@nouce.bellatlantic.net on Sun, Aug 20 2006 9:06 am >On 19 Aug 2006 20:19:19 -0700, "LenAnder...@ieee.org" > wrote: >>>nos...@nouce.bellatlantic.net wrote: >>>> On Fri, 18 Aug 2006 19:54:00 +0200, "i3hev, mario held" >>>> wrote: >>>> >Michael Black wrote: > >>>> However be wary of ICs like the MC1350 as the gain reduction occurs >>>> the internal noise is bad. I've built several recievers using this >>>> part and at ~10db gain reduction the noise jumps way up. I've gone >>>> to cascode JFETs as the noise is more predictable and generally >>>> lower. The device used does make a difference. > >>>> Allison > >> I have to disagree on the MC1350 and way back 30 years to its >> predecessor, MC1590. The prototype HF receiver presently on >> my workbench has a NF of 5.5 and that hardly rises more than >> that with AGC current applied to the AGC pin. > >Read EMRFD page 6.16 (ARRL press) they tested the 1350 and at the >point where the gain cell has equal conduction on both legs the noise >rises significantly. I duplicated the test fixture and yes, it's >noisy, from around 6db to around 11db in my fixture when gain is >reduced by 10db and that was at 16mhz. In a reciever that used >it I went to two cascode stages using JFETs and the difference noise >was notable for weak signals just into the agc range. I restrict the >1590/1350/ca3028 for lower perfomance recievers now. Apparently I hit some nerve on my disagreement. My first experience with the MC1590 was in 1973 and a need to operate over 55-64 MHz. Electronic gain control was essential and it had to be fast. Motorola supplied some additional information which was later incorporated into appnotes. The MC1350 was marketed around '73 along with the MC1330 video detector as a TV IF system. It didn't sell that well in quantities (presumably) and both were dropped from active production (Lansdale acquired masks and now makes the MC1350). The 1350 (8-pin DIP) should use the same die in the metal can MC1590. While neither one was ever touted as a super-champ low-noise device, it is what I consider respectable as to NF. The fact that it has differential input and differential output is convenient from the standpoint of circuit design. Especially so when input impedances (each side) has a dependable 5K R in parallel with about 5 pF total capacitance. Gain of both begins to fall above 75 MHz with output loads of 100 Ohms resistive. I've found no noticeable difference between differential input v. single-ended. That IC is what I term a "double Gilbert cell" in that AGC control current affects both differential inputs equally (or very nearly so). Whether one connects to both inputs or just one shouldn't make any difference other than output gain. >I also verified that the 1590 does same and also the CA3028 >wired as differential AGC. Even tried three 2n3904s and >same result. The agc range was good and at full gain the >noise was ok but the noise increase at partial agc was surprizing. I've never encountered any "surprising" increase in noise at any AGC input to a 1590 or 1350 causing partial gain reduction. That is as true in 2005 as it was in 1973. If there is a SNR of 10 db at an RF carrier input of 3 uV and a gain reduction of 10 db for a 10 uV RF input results in 3 db more noise in the front end, the SNR with a 10 uV input is still higher than the one at 3 uV. What has been "lost" there? Let's look at the original problem starting this thread: There was a claim of "increased noise" with AGC on, but no quantifiable data. The sudden segue to stating that a certain IC is "bad" is a leap that defies good design practices to me. I'm not impressed that the ARRL had some test data in a publication; having been hands-on with this Motorola design for a number of years, I have a number of RCA lab notebook pages filled with my testing of it along with a patent involving it granted 1974...besides my own hobby notebooks. Low-noise input amplifier design is an entirely separate subject and there are a number of other active devices which can do lower NFs than 5. What was orignally needed was some way of getting some numbers and test configuration of Andrea's problem...to pin down a possible reason for alleged increased noise with AGC applied, presumably a "partial AGC" application. [I can't quantify "partial" as a numeric value...maybe others can?] >I do most of my RX experimentation at 6/ 2M and 70cm SSB so >noise and overload perfomance are important to me. Images >are also a big problem as I'm near a lot of VHF/hf broadcast. [ I live about 6 miles from 50 KW KMPC on AM...] If we can get back to the original claim of "increased noise with AGC applied" we might be able to help Andrea some. We don't know what Andrea has for a main receiver and interjecting some "badness" remarks by the ARRL about a certain IC isn't going to help clarify Andrea's problem. LenAnderson@ieee.org Article: 98382 of rec.radio.amateur.homebrew From: "Spokesman" References: Subject: Re: What is wrong with Hawaii, Alaska, and Canada Date: Sun, 20 Aug 2006 15:52:05 -0400 Message-ID: This is a multi-part message in MIME format. ------=_NextPart_000_0031_01C6C470.96048E20 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable "Paul Hinman" wrote in message = news:aLfEg.400583$Mn5.137675@pd7tw3no... I frequently see postings in the ham radio related newsgroups for = items currently being offered on E-Bay. All to often I that items will be shipped only to the lower 48 states, = leaving hams in Hawaii, Alaska, and Canada out of the picture. What is = the problem. In Canada we are well served by FEDEX and the United = States Postal Service. Amateur radio equipment crosses the border with = out any problem. I realize that Hawaii and Alaska may be a bit far from = the "lower 48" but the same delivery services are available even though = surface transportation may be a little bit slow. In the US you also = have UPS, the folks in Brown which we Canadians prefer not to use = because the often make the border crossing more difficult than it needs = to be and we don't like getting stuck with brokerage fees. So why the discrimination, if the buyer knows that delivery may take a = little longer and is prepared to accept the fact then it becomes a non = problem. If the seller is intimidated by the prospect of complicated = paperwork, he needn't be. Please leave it up to the buyer to decide = whether he wants to bib or not. I can not speak for shipments to Europe, Africa, India, China, or the = South Pacific but for fellow Americans, or friendly northern neighbours, = I think that people should be prepared to deal with us. Thanx for letting get this off my chest and I realize that I have = cross posted this to four different newsgroups but I wanted to get to a = broad audience. Paul --=20 Paul S. Hinman - VE6LDS long West 113 deg 27 min 20 sec lat North 53 deg 27 min 3 sec Maidenhead Locator DO33gk=20 ------=_NextPart_000_0031_01C6C470.96048E20 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
"Paul Hinman" <paul.hinman@shaw.ca> wrote = in message=20 news:aLfEg.400583$Mn5.1376= 75@pd7tw3no...
I frequently see postings in = the ham radio=20 related newsgroups for items currently being offered on = E-Bay.

All to=20 often I that items will be shipped only to the lower 48 states, = leaving hams=20 in Hawaii, Alaska, and Canada out of the picture.  What is the=20 problem.  In Canada we are well served by FEDEX and the United = States=20 Postal Service.  Amateur radio equipment crosses the border with = out any=20 problem.  I realize that Hawaii and Alaska may be a bit far from=20 the  "lower 48" but the same delivery services are available even = though=20 surface transportation may be a little bit slow.  In the US you = also have=20 UPS, the folks in Brown which we Canadians prefer not to use because = the often=20 make the border crossing more difficult than it needs to be and we = don't like=20 getting stuck with brokerage fees.

So why the discrimination, = if the=20 buyer knows that delivery may take a little longer and is prepared to = accept=20 the fact then it becomes a non problem.  If the seller is = intimidated by=20 the prospect of complicated paperwork, he needn't be.  Please = leave it up=20 to the buyer to decide whether he wants to bib or not.

I can = not speak=20 for shipments to Europe, Africa, India, China, or the South Pacific = but for=20 fellow Americans, or friendly northern neighbours, I think that people = should=20 be prepared to deal with us.

Thanx for letting get this off my = chest=20 and I realize that I have cross posted this to four different = newsgroups but I=20 wanted to get to a broad audience.

Paul
--=20
Paul S. Hinman - VE6LDS
long West 113 deg 27 min 20 sec
lat  North 53 deg 27 min 3 sec
Maidenhead Locator DO33gk=20
------=_NextPart_000_0031_01C6C470.96048E20-- Article: 98383 of rec.radio.amateur.homebrew From: jgboyles@aol.com Subject: Re: Can I use a 120V Variac to get 220V? Date: 20 Aug 2006 14:58:12 -0700 Message-ID: <1156111092.533615.250060@m79g2000cwm.googlegroups.com> References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> Andrew VK3BFA wrote: > mike wrote: > > John, N9JG wrote: > > > Your advice is elegant in its simplicity. > > > > And OPTIMISTIC in it's generality. > > While one might imagine situations where this technique is > > useful, it would be better to define a strategy that takes > > into consideration the exact configuration of the PS in > > your unspecified amplifier. > > Gee, that sounds like the opening page of a PowerPoint presentation - > your not a manager by proffession, are you? > > And if you have an engineering degree, and want to engage in endless > metaphysical speculation, thats a very good idea.....whatever it > was.....amongst the verbiage.... > > > > If your caps don't need reforming, any technique will work. > > If they do, you're gonna have some current flow. It's not > > hard to imagine a scenario whereby you have 25W or more > > dissipated in your caps. I don't call this safe. A 100W > > light bulb will keep you from blowing up the rectifiers while > > you're blowing up the caps. > > Rubbish. Where do you get this 25w figure from, and across how many > capacitors in a (typical) series string - oh, and lets ignore idling > current through transformer and bleeeder resistors, and filamnet > current drain, and blowers, and dial lamps, and.....which would further > reduce available volts across the caps.... And whats this "imagine a > scenario" stuff - I thought you were trying to be precise and were > chiding me for my lack of hard data.... > > > > Assuming you have solid-state rectifiers, go back to the > > variac and transformer. Depending on the value of the high voltage, > > There may be issues if you just turn off the tube filaments. > > The series lamp can still be helpful, but isn't the whole story. > > So, what voltage do you set the variac too? - how do you work it out? > > > > It's always helpful to disclose the parameters of the situation > > when asking for advice. Otherwise, you'll get 10 different > > solutions based on 10 different assumptions, none of which will be > > correct. > > mike > > True. There are probably 10 different ways of puting out a fire, but > the easiest is dumping a bucket of water on it. > > Honestly, this is ridiculous - most modern (ie, last 40 years) caps are > fine, will survive horrendous abuse, and unless you have the > manufacturers data sheets for these capacitors, (and the power > transformer, and the rectifiers) how are you going to set these > parameters anyway? - this is a linear amplifier, not the space shuttle. > > Why do people insist on making things sooooo complicated, almost > theoretical physics level - it isnt. Dont let irelevant theory get in > the way of practical electronics. > > The intial switch on of ANYTHING that hasnt been powered up for years > is going to be the time it dies - at least the bulb will stop it > bursting into flames, the variac method will jsut slowly ramp up volts > until something blows catasphropically (I know, used to do this, got > sick of replacing fuses in the variac.) > > As well, you have the added complication of multiple, lashed together > transformers which MUST all be correctly phased and able to take the > load current . a recipe for confusion at least. > > And no, I cant spell. Spend too much time with soldering irons rather > than physics journals. > > Andrew VK3BFA. All he was asking was how to hook up a variac. Seemed simple enough. Gary N4AST Article: 98384 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: AGC signal/noise question... Message-ID: <2phhe21tmriborj1ghc22k0lcr3sjdo01v@4ax.com> References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> Date: Sun, 20 Aug 2006 22:03:18 GMT On 20 Aug 2006 12:46:25 -0700, "LenAnderson@ieee.org" wrote: shortend>>>>> >>Read EMRFD page 6.16 (ARRL press) they tested the 1350 and at the >>point where the gain cell has equal conduction on both legs the noise >>rises significantly. I duplicated the test fixture and yes, it's >>noisy, from around 6db to around 11db in my fixture when gain is >>reduced by 10db and that was at 16mhz. In a reciever that used >>it I went to two cascode stages using JFETs and the difference noise >>was notable for weak signals just into the agc range. I restrict the >>1590/1350/ca3028 for lower perfomance recievers now. > > Apparently I hit some nerve on my disagreement. > > My first experience with the MC1590 was in 1973 and a need to > operate over 55-64 MHz. Electronic gain control was essential > and it had to be fast. Motorola supplied some additional > information which was later incorporated into appnotes. > > The MC1350 was marketed around '73 along with the MC1330 > video detector as a TV IF system. It didn't sell that > well in quantities (presumably) and both were dropped > from active production (Lansdale acquired masks and now > makes the MC1350). The 1350 (8-pin DIP) should use the > same die in the metal can MC1590. While neither one was > ever touted as a super-champ low-noise device, it is what > I consider respectable as to NF. Wide open and at >20db reduction the noise figure is not bad at all. Only that the apparent increase is noteable. I've seen it occur with other topologies including simple bipolar or FET stages (even tubes). > The fact that it has > differential input and differential output is convenient > from the standpoint of circuit design. Especially so when > input impedances (each side) has a dependable 5K R in > parallel with about 5 pF total capacitance. Gain of both > begins to fall above 75 MHz with output loads of 100 Ohms > resistive. I've found no noticeable difference between > differential input v. single-ended. Those are the feature of the part that makes them desireable. > That IC is what I term a "double Gilbert cell" in that > AGC control current affects both differential inputs > equally (or very nearly so). Whether one connects to > both inputs or just one shouldn't make any difference > other than output gain. I call that circuit an analog four quadrant multiplier for what it does not how it's made. The feature of the Gilbert cell that applies for the AGC use is the lack of DC shift at the output points keeping downstream DC coupled stages at their undistrubed bias points. However the active device that is in the agc control positions is still a noise generator (as are all active devices) and as agc increases it's contribution is additive to the RF path devices. Makes little difference if the node where outputs are combined see no DC shift the various diff amp transistor as individual pairs do see a significant shift (100% collector current to near 0). It's easier to see using the older MC1550 or CA3028 diffamps or even discretes in a diffamp with current source. >>I also verified that the 1590 does same and also the CA3028 >>wired as differential AGC. Even tried three 2n3904s and >>same result. The agc range was good and at full gain the >>noise was ok but the noise increase at partial agc was surprizing. > > I've never encountered any "surprising" increase in noise > at any AGC input to a 1590 or 1350 causing partial gain > reduction. That is as true in 2005 as it was in 1973. If > there is a SNR of 10 db at an RF carrier input of 3 uV and > a gain reduction of 10 db for a 10 uV RF input results in > 3 db more noise in the front end, the SNR with a 10 uV > input is still higher than the one at 3 uV. What has been > "lost" there? The surprize is that I'd not considered the possibility that the SN+N/N could degrade unevenly due to applied agc. So I'd never paid attention until I was trying to improve an earlier reciever design (ca1978) of my own and at the same time aquired a copy of EMRFD and did some testing to verify their resuts. Since the design was optimized for low RF gain and high overload thresholds I was revisiting anything that could better the design without loosing those features. Note it's a single conversion system with high IF. The problem was a MDS of -136dbm but the 10db Signal+N/N point was around -110dbm and at ~121dbm it was worse than at -130! The front end was common gate RF amp (2n4416s) driving a pair of 4416s in a single balanced mixer. Low noise but limited gain for better overload performance. No agc before the IF. If needed there are switchable resistive attenuators (3, 6,12db or 19db total). Measured gain from antenna to IF is only 16db (after all losses). Disable the agc or increase the threshold and it wasn't as measurable or appeared to disappear.. The hunt was on. The results were a surprize as there is no data for noise output with no input or signal to noise with gain reduction. My Moto databooks go way back, as do my National, RCA and Signetics library. More current datasheets do not reflect any improved information. The revised RX used two stages of mpf102 Jfet in cascode plus a diferential pair of 2n3904s to resolve the 5-10V agc to be compatable with the new fet amp to replace the two MC1350s and the problem of decreasing signal to noise as signal increased with agc active disappeared. Not to say the fet amps did not do the same thing only that the rate of noise increase was a smoother curve >from max gain to min gain. In retrospect a delaying AGC to the first of the two 1350s could potentially have the same effect but was not investigated. I may revisit it at some time as I still have the original if module in the junkbox. > Let's look at the original problem starting this thread: > There was a claim of "increased noise" with AGC on, but > no quantifiable data. Thats a problem, the lack of data or information on the circuit. Also I've repaired a few commercial radios that due to component failure or "golden screwdriver" had the various operating conditions sufficiently altered as to cause a similar problem. > The sudden segue to stating that a > certain IC is "bad" is a leap that defies good design > practices to me. I'm not impressed that the ARRL had some > test data in a publication; having been hands-on with this > Motorola design for a number of years, I have a number of > RCA lab notebook pages filled with my testing of it along > with a patent involving it granted 1974...besides my own > hobby notebooks. That's nice but are the test results in error from two different sources? No. However, it's was a noteable weak point. But calling it bad is your words. It's a point that needs to be understood and allowed for. In a design with more RF gain and/or less mixer noise it many not have been a factor or less of one. Also in the case that brought it to a point for me even altering how agc is applied might have achieved a better result. Since the 1350 is at IF for most designs the noise is likely from front end causes should be investigated first. One would hope the design had secured the system noise performance before the IF. However in low gain systems or system with no gain before the mixer and first filters this may be problematic. > Low-noise input amplifier design is an entirely separate > subject and there are a number of other active devices > which can do lower NFs than 5. What was orignally needed > was some way of getting some numbers and test configuration > of Andrea's problem...to pin down a possible reason for > alleged increased noise with AGC applied, presumably a > "partial AGC" application. [I can't quantify "partial" > as a numeric value...maybe others can?] > >>I do most of my RX experimentation at 6/ 2M and 70cm SSB so >>noise and overload perfomance are important to me. Images >>are also a big problem as I'm near a lot of VHF/hf broadcast. > > [ I live about 6 miles from 50 KW KMPC on AM...] 10 miles from the Needham towers in MA. Not less than 8 VHF broadcasters, then the usual crowd of UHF and now the HDTV-UHF broadcasters and no small party of FM broaccasters. Oh and WKOX 1200 AM three miles away. Then I have 9 hams within a 1 mile circle and two within 1500ft running KW level at VHF. RFI are us. I understand overload as >+15dbm on coax is common here. It's an interesting design challenge to do low noise figure RX and at the same time be overload resistant in a harsh environment. > If we can get back to the original claim of "increased > noise with AGC applied" we might be able to help Andrea > some. We don't know what Andrea has for a main receiver > and interjecting some "badness" remarks by the ARRL about > a certain IC isn't going to help clarify Andrea's problem. Having tested and understood the problem I would say the authors of EMRFD did a fair job of pointing out the points where a device needs better understanding. A blanket "it's great" is lore, testing it and understanding it is engineering. Having done the work to understand it better I can appreciate the perfomance of the part and it's limitations. I still use it and have a tube of them because it's a useful part. Just like the often reviled SA602 mixer. It's relevence is I've seen this before and understood it's origin and also elsehere. The other aspect is that if a commonly accepted part is not fully understood and can lead to undesired effects then, why not others. AGC is not a trivial thing to be tacked on and considered a problem solver. Protects the ears but it's place in the reciever is not always understood. It does not always solve things like gross overload at the front end or possibly further down or outside the agc detectors bandwidth. But a lack of information about his radio doesn't help us either. We do not know for instance what topology is used for RF and if any agc is even applied to it. Allison Article: 98385 of rec.radio.amateur.homebrew From: "Roger (K8RI)" Subject: Re: Can I use a 120V Variac to get 220V? Message-ID: <8p4ie25psm2f3dcrbrof92sgrbtrc57hnv@4ax.com> References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> <1155955586.539941.265270@m73g2000cwd.googlegroups.com> Date: Sun, 20 Aug 2006 22:00:38 -0400 On Sun, 20 Aug 2006 08:11:33 GMT, mike wrote: >John, N9JG wrote: >> Your advice is elegant in its simplicity. > >And OPTIMISTIC in it's generality. >While one might imagine situations where this technique is >useful, it would be better to define a strategy that takes >into consideration the exact configuration of the PS in >your unspecified amplifier. > >If your caps don't need reforming, any technique will work. >If they do, you're gonna have some current flow. It's not >hard to imagine a scenario whereby you have 25W or more >dissipated in your caps. I don't call this safe. A 100W >light bulb will keep you from blowing up the rectifiers while >you're blowing up the caps. I had this happen with a 3 week old amp. One of the low voltage caps blew. It sounded like a shotgun being fired in my basement. The "can" hit the top of the 8877 amp and flattened out like a 38 wadcutter hitting something solid. It doesn't have to be a boat anchor to have a cap blow. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com Article: 98386 of rec.radio.amateur.homebrew From: w8kzw@hotmail.com Subject: Re: Can I use a 120V Variac to get 220V? Date: 21 Aug 2006 10:19:22 -0700 Message-ID: <1156180762.325147.141100@74g2000cwt.googlegroups.com> References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> Thanks for the (mostly helpful) replies, guys. Applying each one of the two ends of the 220V coil of the transformer to the 220V legs of the amplifier plug made sense. I guess I was mostly wrestling with how to handle the gounded / grounding lug of the amplifier plug. Gary said to just leave it floating, but wouldn't grounding it be safer? Article: 98387 of rec.radio.amateur.homebrew From: jgboyles@aol.com Subject: Re: Can I use a 120V Variac to get 220V? Date: 21 Aug 2006 13:42:42 -0700 Message-ID: <1156192962.932636.260320@b28g2000cwb.googlegroups.com> References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> w8kzw@hotmail.com wrote: > Thanks for the (mostly helpful) replies, guys. > > Applying each one of the two ends of the 220V coil of the transformer > to the 220V legs of the amplifier plug made sense. I guess I was > mostly wrestling with how to handle the gounded / grounding lug of the > amplifier plug. > > Gary said to just leave it floating, but wouldn't grounding it be safer? Since you will be running the variac through a 110/220v isolation transformer, you will lose reference to the utility ground, so there is no reason to connect up the ground on the amp. If by some chance the 110v windings in the amp are on different cores, or are actually 2 transformers, then you would need a common (ground) reference for the two. This is probably not your case, be nice if you had a schematic. Gary N4AST Article: 98388 of rec.radio.amateur.homebrew From: Andrea Baldoni Subject: Re: AGC signal/noise question... References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> Message-ID: Date: Mon, 21 Aug 2006 16:15:01 -0500 LenAnderson@ieee.org wrote: : If we can get back to the original claim of "increased : noise with AGC applied" we might be able to help Andrea : some. We don't know what Andrea has for a main receiver : and interjecting some "badness" remarks by the ARRL about : a certain IC isn't going to help clarify Andrea's problem. Sorry for the short answer. The receiver is a Yaesu FR-101 with his internal 2m converter. Actually, I'm doing some recalibration but I didn't found at now nothing really out. I just noted that, mostly noticeable in FM mode (by noise increasing) but present in all modes looking s-meter, the response of the IF was not a gaussian with a flat top. In the center there was a little decreasing area. If you tune it perfectly, you had a sligtly less signal than little up or down in freq. So I started recalibrating. I had stopped because I had trouble with the noise blanker. In the manual, there is a indication of a test point where hook a voltmeter, but there is not any test point nor any indication on the schematic where the exact point is. The transformer is T116, maybe someone could help. Tomorrow I'll figure out what to do, I think I'll hook the voltmeter as to measure the voltage rectified, at the gate of the FET. If you have the schematic (it's freely downloadable in many places) maybe you could tell if I'm right. Anyway, thankyou very much you want to help troubleshooting my receiver, but I was using what I noted (increase in noise with AGC on) mainly to start a general discussion about AGC implementation and effects, and his future in digital receivers as well as in homebrew very high-end ones. It has started, and it's very interesting. Ciao, AB ... Andrea Baldoni, 2002: messaggio non protetto da copyright. Article: 98389 of rec.radio.amateur.homebrew From: Andrea Baldoni Subject: Re: AGC signal/noise question... References: <1155856208.223644.33300@m73g2000cwd.googlegroups.com> <12ef9c4hlloatf4@corp.supernews.com> Message-ID: <-N-dnT3VvvMyr3fZRVnyrg@kpnqwest.it> Date: Mon, 21 Aug 2006 17:24:47 -0500 Roy Lewallen wrote: : The bottom line is that I'd be hesitant to trust just about any number : for a "worst case" maximum signal strength. Be sure to test any proposed : design on 40 meters for a while from your location in Europe. Uh. Very interesting, Roy. Even a receiver with AGC has his own limits and probably what you experienced would have surely overload most commercial ones... Some numbers must be fixed, even if very high ones. So, how one could proceed? Ciao, AB ... Andrea Baldoni, 2002: messaggio non protetto da copyright. Article: 98393 of rec.radio.amateur.homebrew From: "Andrew VK3BFA" Subject: Re: Can I use a 120V Variac to get 220V? Date: 21 Aug 2006 17:46:00 -0700 Message-ID: <1156207560.495067.75020@m79g2000cwm.googlegroups.com> References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> j > > All he was asking was how to hook up a variac. Seemed simple enough. > > Gary N4AST True. But why lose the chance for an argument? - my issue was with the over complication of a simple task....and if someone needs to ask questions on how to set up a variac and a transformer, then the keep it simple approach (ie, the light bulb) has much to recomend it. Andrew VK3BFA. Article: 98394 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: AGC signal/noise question... Message-ID: <6tpke2h5uksplnv3ud85rki5nfbdjjnca5@4ax.com> References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> Date: Tue, 22 Aug 2006 02:16:20 GMT On Mon, 21 Aug 2006 16:15:01 -0500, Andrea Baldoni wrote: >LenAnderson@ieee.org wrote: > >: If we can get back to the original claim of "increased >: noise with AGC applied" we might be able to help Andrea >: some. We don't know what Andrea has for a main receiver >: and interjecting some "badness" remarks by the ARRL about >: a certain IC isn't going to help clarify Andrea's problem. > >Sorry for the short answer. The receiver is a Yaesu FR-101 with his internal >2m converter. Actually, I'm doing some recalibration but I didn't found at >now nothing really out. I just noted that, mostly noticeable in FM mode >(by noise increasing) but present in all modes looking s-meter, the response >of the IF was not a gaussian with a flat top. In the center there was a >little decreasing area. If you tune it perfectly, you had a sligtly less >signal than little up or down in freq. Dual conversion for HF and triple conversion of 2m. There would not be RF agc on the 2m converter. In FM modes you should see limiting so agc is behavour is different. >So I started recalibrating. I had stopped because I had trouble with the >noise blanker. In the manual, there is a indication of a test point where >hook a voltmeter, but there is not any test point nor any indication on the >schematic where the exact point is. The transformer is T116, maybe someone >could help. Tomorrow I'll figure out what to do, I think I'll hook the >voltmeter as to measure the voltage rectified, at the gate of the FET. >If you have the schematic (it's freely downloadable in many places) maybe >you could tell if I'm right. Likely a test point that is not marked on the board. I don't have a print handy. >Anyway, thankyou very much you want to help troubleshooting my receiver, >but I was using what I noted (increase in noise with AGC on) mainly to >start a general discussion about AGC implementation and effects, and his >future in digital receivers as well as in homebrew very high-end ones. It >has started, and it's very interesting. Having experimented with recievers since before EE school and still many decades later I find it challenging. Always looking for and at new ideas. Allison Article: 98395 of rec.radio.amateur.homebrew From: bill.meara@gmail.com Subject: SolderSmoke #30: Solar pwr, IRF 510 amp, QST 50, BITX20, rockbound rigs, solar min? Date: 21 Aug 2006 23:16:15 -0700 Message-ID: <1156227375.140032.44290@75g2000cwc.googlegroups.com> WE'VE MOVED! WE'VE MOVED! WE'VE MOVED! Please note new site for SolderSmoke. http://www.soldersmoke.com Check out a video clip of "The Making of Solder Smoke #30" and "A Video Tour of M0HBR" at http://www.gadgeteer.us/VIDEO.HTM SolderSmoke! A SHOW FOR ELECTRONICS HOMEBREWERS! http://www.soldersmoke.com Topics discussed in SolderSmoke #30: -- Bill goes solar powered -- Mike and the rock-bound rig -- Steve Weber's IRF-510 amp -- QST 50 Challenge -- Farhan's BITX20 -- New Gadgeteer Video page -- The earliest homebrewers -- MIT courses on-line -- Sound of the Sun, and Jupiter -- Solar minimum at last? -- MAILBAG: NT7S, WA8KNE, ZL1SAM, N3UMW, WB7AEI, NE1OB, NS5Z, K8WPE Listen at: http://www.soldersmoke.com Tired of listening to Led Zepplin or NPR on your I-Pod? Wouldn't you like to be able to carry with you the kinds of ham radio conversations that you listen to while in your radio shack? Mike, KL7R, in Juneau, Alaska, and Bill, M0HBR, in London, England meet regularly on the ECHOLINK system to discuss their homebrew radio projects. We are making them available as PODCASTS. NEW RSS FEED: You can subscribe to the program, have them downloaded to your MP-3 player, and listen to them at your convenience. To subscribe, just cut and paste this URL into your I-poder (or similar) software. http://www.soldersmoke.com/soldersmoke.rss If you don't have an MP3 player you can just go to the site below and listen to the latest program (and earlier editions) using the audio software on your computer. http://www.soldersmoke.com Here's the homepage for our show. All our programs are available here: http://www.soldersmoke.com We hope you enjoy the program. Please send us feedback. 73 from London Bill M0HBR N2CQR CU2JL http://www.gadgeteer.us Article: 98396 of rec.radio.amateur.homebrew From: Jim Subject: Re: VHF/UHF antenna on a motorcycle Message-ID: References: Date: Tue, 22 Aug 2006 08:51:14 -0500 I'm going through same process, just got back into motorcycles again with a CBX. Not many metal surfaces to mount mag mount or ground plane type antennas. One possibility to make a dipole would be to take two BNC type HT flex antennas, and hook them to the ends of a BNC "T" fitting, and feed them in the center of the "T", making a vertical dipole, Then you would have problem of getting antenna away from rest of bike, say with small piece of small diameter PVC pipe mounted like a regular antenna would be mounted, getting the two ducky antennas up away from the bike frame. the side of plastic windscreen would be a possiblity, up as high as possible. If you find a commercial solution please let me know, I'd be interested too, especially if you find a combo 2m/440 solution. A 440 dipole would not be large, and could possibly be fed in center and taped to the windscreen. Jim, WA5DXP On Fri, 18 Aug 2006 10:02:01 GMT, "Tom" wrote: >Hello all , > >I would like to install a VHF-UHF antenna on my motorcycle . It's a Suzuki >GSX750 . I did some tests with a Diamond NR-770H and it works well . The >only problem is that the antenna is to big for such a bike . >Afterwards i did a test with a Diamond NR-77 . The antenna is about 43 cm >and that's about the size i would like to use . >The problem i have with this antenna is the swr , it's to high . > >Anyone an idea how i can solve this problem ? > >Many thanks . > >Tom > > Article: 98397 of rec.radio.amateur.homebrew From: hq105862@hotmail.com Subject: selecting bias inductors for amps Date: 23 Aug 2006 04:08:57 -0700 Message-ID: <1156331337.369646.48320@i3g2000cwc.googlegroups.com> Hi, I've been sleceting inductors for chip amplifiers based on the datasheets, but I would really like to understand what I should be doing. If I am designing an amplifer that is to operate over say 3.4 to 4.2GHz, should I be looking for an inductor with self resonance above that band, or at centre frequency, and why? (I know that at self resonance, the inductor will be resistive, below inductive, and above capacitive, but I don't know what I should be looking for.) Should I be looking for high Q or low Q, and for what reasons would I choose each. What numerical values actually equate to High Q and Low Q? Is Q of 9 low, and Q of 35 high, for example? thanks Article: 98398 of rec.radio.amateur.homebrew From: "Joel Kolstad" Subject: Re: selecting bias inductors for amps Date: Wed, 23 Aug 2006 09:46:52 -0700 Message-ID: <12ep1jthn8vi4a5@corp.supernews.com> References: <1156331337.369646.48320@i3g2000cwc.googlegroups.com> wrote in message news:1156331337.369646.48320@i3g2000cwc.googlegroups.com... > If I am designing an amplifer that is to operate over say 3.4 to > 4.2GHz, should I be looking for an inductor with self resonance above > that band, or at centre frequency, and why? The "safe" advice is to choose one where the SRF is above the band you're designing for, but strictly speaking you can usually get away with SRF within the band or even a little below. Your inductor can be modeled as an "ideal" inductor with a capacitor in parallel. Up until resonance, the reactance of the physical inductor is positive and varies (roughly) linearly with frequency. At resonance, the reactance of the capacitor is equal but opposite that of the inductor so you have Yin = 1/sC + sL = 0 --> an open circuit. Above resonance, the physical inductor still has positive reactance but now it's decreasing with frequency... not what you want! > (I know that at self resonance, the inductor will be resistive, below > inductive, and above capacitive, but I don't know what I should be > looking for.) You're looking for an impedance that's "significantly" (conservately, at least 10x but realistically often 4x is fine -- the more conservative you are, the less insertion loss you'll get) greater than the characteristic impedance of your transmission line. (If you run it through a calculator, you'll see that 50 ohms in parallel with, say, j*50*10 is still *very* close to 50 ohms, and even 50 ohms in parallel with j*4*50 really isn't half bad). > Should I be looking for high Q or low Q, and for what reasons would I > choose each. About the only upside of a high Q inductor for biasing is slightly lower insertion loss, and a very significant downside is that the inductor's resonances above the band you're interested in will be "strong" and can cause large (>1dB), narrow perturbations (resonances) in the system's insertion loss. A lower Q will tend to "smooth out" those resonances. Indeed, if you're looking to build a wideband bias circuit, you often use several inductors in series (small-medium-large, say) *with resistors in parallel that purpose de-Q the inductors*. Without the de-Qing resistors, the high-Q inductors have nasty interactions (two or three together will conspire to appear as something approaching a short circuit at some frequency!)... > What numerical values actually equate to High Q and Low Q? I'd call "high" Q>100 and "low" Q<10. High Q inductors are generally not obtainable in "chip" form; you need air cores or exotic dielectrics to get such high Q's at VHF/UHF. (For that matter, at least in my mind, high Q inductors generally shouldn't be used for biasing -- they're used for filters. :-) ) > Is Q of 9 low, and Q of 35 high, for example? 35 is "middle of the road, drifting towards low." Q=35 is a decent inductor to use for biasing... not too lossy, but lossy enough to avoid the resonance problems discussed above. ---Joel Article: 98399 of rec.radio.amateur.homebrew From: tim gorman Subject: Re: AGC signal/noise question... References: <44e5cf80$0$13738$5fc30a8@news.tiscali.it> <44e5fe81$0$13715$5fc30a8@news.tiscali.it> <1156043959.936323.84540@75g2000cwc.googlegroups.com> <1156103185.261420.21420@74g2000cwt.googlegroups.com> Message-ID: Date: Wed, 23 Aug 2006 14:52:56 -0500 Andrea Baldoni wrote: > > > LenAnderson@ieee.org wrote: > > : If we can get back to the original claim of "increased > : noise with AGC applied" we might be able to help Andrea > : some. We don't know what Andrea has for a main receiver > : and interjecting some "badness" remarks by the ARRL about > : a certain IC isn't going to help clarify Andrea's problem. > > Sorry for the short answer. The receiver is a Yaesu FR-101 with his > internal 2m converter. Actually, I'm doing some recalibration but I didn't > found at now nothing really out. I just noted that, mostly noticeable in > FM mode (by noise increasing) but present in all modes looking s-meter, > the response of the IF was not a gaussian with a flat top. In the center > there was a little decreasing area. If you tune it perfectly, you had a > sligtly less signal than little up or down in freq. > ............... snip ........................... > > Ciao, > AB Are you sure you are seeing an AGC problem? What you describe above, with slightly less signal in the center, is typical of a *filter* with dip in the middle of the passband. This is *not* a result of increased signal strength causing more AGC and thus more noise when the receiver is tuned to exact center on a signal. It is the result of a filter design choice (lower cost) or the result of the filter tuning (tuned for better shape at the edges which causes more dip in the middle). Without knowing more about the receiver I can't make any guesses as to what is in play here but I question if this is an AGC artifact. tim ab0wr Article: 98400 of rec.radio.amateur.homebrew From: "bobbbo" References: Subject: Re: buying stupid in the USA Date: Wed, 23 Aug 2006 20:31:33 -0400 Message-ID: <92901$44ecf536$d1cc7c6f$29385@snip.allthenewsgroups.com> "mike maghakian" wrote in message news:NaKdnUoccopEXXHZnZ2dnUVZ_q2dnZ2d@comcast.com... > sometimes people complain when I point out people paying real stupid prices > for something on eBay. The reason for that is Hamfests and Swap Meets in general are DEAD. Finished! Kaputski! Stick-a-fork-into-it! (etc..etc..) Dayton Included too. I went to Dayton this year after a 5 Year sabbatical. Fully 1/3'rd of the outside vendor spaces were empty. Just 5 Years ago this was a rarity and 10 years ago it was downright impossible. Why? Reasons are many....aging ham/swl population, SK's, health/travel, cost of gas food lodging etc... then again, why drive when you can order new online an it's at your door via UPS in a few days? Ham radio is changing and it is aging. more than HALF the hams I used to talk with on 75M HF just from 10 Years ago are all SK's. That alone speaks volumes folks! E-Bay did not kill hamfests. Hams themselves are dying off and most of the stuff is ending up on e-Bay where it's a feeding frenzy. This too will end in a few (10?) Years time also. In short....Wayne Green (W2NSD) had it right all along folks. Enjoy the rest of the ride. Article: 98401 of rec.radio.amateur.homebrew From: "Mr Fed UP" References: <92901$44ecf536$d1cc7c6f$29385@snip.allthenewsgroups.com> Subject: Re: buying stupid in the USA Message-ID: Date: Wed, 23 Aug 2006 21:05:36 -0500 Yep! All them are reasons I have stopped attending Dayton and many other hamfests. But ebay is also a contributor. I got some 2m old crystal rigs via ebay and shipping cost more than the radios. My last time at Dayton a few years ago it was a costly one day ticket (my health not good either) and $8 to park in a handicap parking spot that might as well been down at the mall it was so far. I thought handicap parking meant CLOSE to the doors. With Gas about $3 a gallon depending on the wind... another $100 bucks down the tail pipe. The items for the most part these days are "vintage" things that have been to more hamfests than I have or they are "Like New" and priced as new. Most "Homebrew" projects in magazines and books these days have little chance of success with the ol' junk box and requires a large part of it to be bought and often via mail. "What radio supply store?" When you do get to a hamfest the people are rude, bump into you, step on you, just same as many drivers on the road have aggressive attitudes. All the fun of the fest's has gone as well as a pleasurable drive getting there has gone. And the total cost of just going is 1/2 the cost of a new 2m rig. UGH!! Oh and don't forget other tech'y things like the cell phones that has displaced a lot of would be radio operators for maybe contacts with more secure and reliable contacts. 2m and 70cm not as impressive as it used to be. "What do you mean, point the antenna UP?" LOL ;-) My wireless home phone and my computer has more MHZ than my radio now. ;-( Maybe it's as well though. Having started in the TUBE days and seeing SMD parts now I can't find, or use if I could find them for projects... might be appropriate that we go out together in a few years. Sorry I missed the original post to this thread. Hope it didn't wander too far... Have rag chew paper too . LOL de K4TWO Gary OT -- emailto: k4two@spamspoiler.arrl.net "bobbbo" wrote in message news:92901$44ecf536$d1cc7c6f$29385@snip.allthenewsgroups.com... > > "mike maghakian" wrote in message > news:NaKdnUoccopEXXHZnZ2dnUVZ_q2dnZ2d@comcast.com... >> sometimes people complain when I point out people paying real stupid > prices >> for something on eBay. > > The reason for that is Hamfests and Swap Meets in general are DEAD. > Finished! Kaputski! Stick-a-fork-into-it! (etc..etc..) > Dayton Included too. I went to Dayton this year after a 5 Year sabbatical. > Fully 1/3'rd of the outside vendor spaces were empty. > Just 5 Years ago this was a rarity and 10 years ago it was downright > impossible. > > Why? Reasons are many....aging ham/swl population, SK's, health/travel, > cost > of gas food lodging etc... then again, why drive when you can order new > online > an it's at your door via UPS in a few days? > > Ham radio is changing and it is aging. more than HALF the hams I used > to talk with on 75M HF just from 10 Years ago are all SK's. That alone > speaks volumes folks! > > E-Bay did not kill hamfests. Hams themselves are dying off and > most of the stuff is ending up on e-Bay where it's a feeding frenzy. > This too will end in a few (10?) Years time also. > > In short....Wayne Green (W2NSD) had it right all along folks. > > Enjoy the rest of the ride. > > Article: 98402 of rec.radio.amateur.homebrew From: "ole droopy-drawers" References: <92901$44ecf536$d1cc7c6f$29385@snip.allthenewsgroups.com> Subject: Re: buying stupid in the USA Date: Wed, 23 Aug 2006 23:04:42 -0400 Message-ID: <26e22$44ed1726$d1cc566b$31136@snip.allthenewsgroups.com> "Mr Fed UP" wrote in message news:gM7Hg.6401$e9.971@bignews4.bellsouth.net... > My wireless home phone and my computer > has more MHZ than my radio now. ;-( > de K4TWO Gary OT Gary my boy, you just broke the DaVinci Code. :-) That statement alone noted above speaks sheer volumes for those educated and or intelligent enough to comprehend the implications of the same. Thanks for a most refreshing posting. Article: 98403 of rec.radio.amateur.homebrew From: m II Subject: Re: buying stupid in the USA References: <92901$44ecf536$d1cc7c6f$29385@snip.allthenewsgroups.com> <26e22$44ed1726$d1cc566b$31136@snip.allthenewsgroups.com> Message-ID: Date: Thu, 24 Aug 2006 03:17:04 GMT ole droopy-drawers wrote: > "Mr Fed UP" wrote in message > news:gM7Hg.6401$e9.971@bignews4.bellsouth.net... > >> My wireless home phone and my computer >> has more MHZ than my radio now. ;-( >> de K4TWO Gary OT > > Gary my boy, you just broke the DaVinci Code. :-) > > That statement alone noted above speaks sheer volumes for those > educated and or intelligent enough to comprehend > the implications of the same. Thanks for a most refreshing posting. That has long been common knowledge to those of us who noticed the downhill slide of radio receiver quality when the Volume knobs became larger than the Tuning knobs. mike Article: 98404 of rec.radio.amateur.homebrew From: Dr. Anton T. Squeegee Subject: Re: buying stupid in the USA Date: Thu, 24 Aug 2006 00:20:00 -0700 Message-ID: References: <92901$44ecf536$d1cc7c6f$29385@snip.allthenewsgroups.com> In article <92901$44ecf536$d1cc7c6f$29385@snip.allthenewsgroups.com>, hrse4@yahoo.com (known to some as bobbbo) scribed... > "mike maghakian" wrote in message > news:NaKdnUoccopEXXHZnZ2dnUVZ_q2dnZ2d@comcast.com... > > sometimes people complain when I point out people paying real stupid > prices > > for something on eBay. > > The reason for that is Hamfests and Swap Meets in general are DEAD. > Finished! Kaputski! Stick-a-fork-into-it! (etc..etc..) You could have fooled me. There's nearly a dozen swaps every year, at different times of said year, here in the PacNorthwest. The SF Bay Area, Lawndale (southern California), and San Diego all have monthly hamateur swap meets. I regularly attend several. They're about as far from "dead" as one can expect. Yes, Greed-bay has had an effect on the quantity and variety of equipment that shows up at such events. However, there still seems to be plenty to go around. Suggestion: Research before you generalize. 73 de KC7GR -- Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute (Known to some as Bruce Lane, KC7GR) http://www.bluefeathertech.com -- kyrrin a/t bluefeathertech d-o=t calm "Salvadore Dali's computer has surreal ports..." Article: 98405 of rec.radio.amateur.homebrew From: hq105862@hotmail.com Subject: Re: selecting bias inductors for amps Date: 24 Aug 2006 00:22:44 -0700 Message-ID: <1156404164.056431.323370@h48g2000cwc.googlegroups.com> References: <1156331337.369646.48320@i3g2000cwc.googlegroups.com> Hi Joel, Thanks for a great reply, and good example of why usenet is so good!. best regards Article: 98406 of rec.radio.amateur.homebrew From: "Gian, I7SWX" Subject: HP Impedance measurements book Date: 24 Aug 2006 02:29:38 -0700 Message-ID: <1156411778.761963.296700@b28g2000cwb.googlegroups.com> Hi All, for those fiddling with measurements and not following the N2PK-VNA project I have just "stolen" from Paul, N2PK, the following message (and downloaded the book). 73 Gian I7SWX There is a wealth of information regarding impedance measurement in: -- 73, Paul, N2PK Article: 98407 of rec.radio.amateur.homebrew Date: Thu, 24 Aug 2006 11:26:37 +0100 From: Highland Ham Subject: Re: HP Impedance measurements book References: <1156411778.761963.296700@b28g2000cwb.googlegroups.com> Message-ID: <_q-dnbFhoeRE43DZnZ2dnUVZ8tCdnZ2d@pipex.net> > There is a wealth of information regarding impedance measurement in: > > ++++++++++++++++++++++++++++++++++ Indeed a knowledge treasure ,at least for an amateur like myself. Great learning stuff Frank GM0CSZ / KN6WH Article: 98408 of rec.radio.amateur.homebrew From: "Joel Kolstad" Subject: Re: buying stupid in the USA Date: Thu, 24 Aug 2006 10:34:42 -0700 Message-ID: <12eropjloqlik6a@corp.supernews.com> References: <92901$44ecf536$d1cc7c6f$29385@snip.allthenewsgroups.com> "Mr Fed UP" wrote in message news:gM7Hg.6401$e9.971@bignews4.bellsouth.net... > My last time at Dayton a few years ago it was a costly > one day ticket (my health not good either) and $8 to park in a handicap > parking spot > that might as well been down at the mall it was so far. I believe the admission prices at Dayton are largely driven by the "going rate" for the Hara Arena; renting large spaces like that is *quite* expensive. The prices are certainly not high compared to similarly sized non-amateur conventions I've attended. The handicapped parking largely seems to be an issue because *so many* people request it these days; it's impossible to have literally 300 handcapped parking spots *all* close to the door. I agree that you're probably better off parking in a handcapped spot at the mall and riding the shuttle bus. I believe that for hamfests to continue being successful, they're going to have to concentrate more on educational seminars, demonstrations, and events (transmitter hunts, contests, etc.) rather than just a swapmeet. I think it's a often sign of trouble when any organization seems to spend an inordinate amount of time worrying about their own numbers rather than just engaging in what it is that brought them together in the first place and letting the membership numbers drive themselves. Ham radio (or at least the ARRL) seem quite preoccupied with membership levels... > My wireless home phone and my computer > has more MHZ than my radio now. ;-( :-) Yeah, I know what you mean. To some degree FCC regulations have held back the development of amateur radio, but on the other hand the number of amateurs out there who could successfully *design* or even *assemble* something similar in complexity to a cell phone is miniscule. > Maybe it's as well though. Having started in the TUBE days and seeing SMD > parts > now I can't find, or use if I could find them for projects... might be > appropriate that we go > out together in a few years. Parts availability today is, in many cases, far better than ever before. Mouser and DigiKey are real treasure troves of inexpensive RF parts, you know in the click of a mouse what the stock status is, and they deliver quickly. ---Joel Kostad Article: 98410 of rec.radio.amateur.homebrew From: "LenAnderson@ieee.org" Subject: Re: HP Impedance measurements book Date: 24 Aug 2006 20:50:40 -0700 Message-ID: <1156477840.713027.277950@i42g2000cwa.googlegroups.com> References: <1156411778.761963.296700@b28g2000cwb.googlegroups.com> Highland Ham wrote: > > There is a wealth of information regarding impedance measurement in: > > > > > ++++++++++++++++++++++++++++++++++ > Indeed a knowledge treasure ,at least for an amateur like myself. > > Great learning stuff > > Frank GM0CSZ / KN6WH You can get a similar appnote from QuadTech at www.quadtech.com "LCR Measurement Primer," 4th Edition, 60 pp. QuadTech took over the LCR bridge and electronic instruments from General Radio Co. A few sites have copies of General Radio's "Experimenter" which might be of interest to those looking behind front panels for intimate details. [nothing beats the HP Journal in my mind but others mileage may vary] Also, at www.tm.agilent.com there is a copy of Hewlett-Packard Journal, Volume 29, Number 4, December 1977, which gives a good description of their old HP-4262A LCR Meter. LenAnderson@ieee.org Article: 98411 of rec.radio.amateur.homebrew From: "hamguy1" Subject: looking for a yaesu ft747gx owners manual Date: Fri, 25 Aug 2006 17:37:24 +1000 Message-ID: <44eea8b3$0$22363$afc38c87@news.optusnet.com.au> gi guys, im in australia i was wondering does anyone have access to a site to download owners manuals etc on cd etc prerfably for free ,thanks in advance david nsw australia . Article: 98412 of rec.radio.amateur.homebrew From: "Guy P. Distaffen" References: <44eea8b3$0$22363$afc38c87@news.optusnet.com.au> Subject: Re: looking for a yaesu ft747gx owners manual Message-ID: Date: Fri, 25 Aug 2006 07:50:05 GMT http://www.three-peaks.net/FT-747GX_Manual.pdf "hamguy1" wrote in message news:44eea8b3$0$22363$afc38c87@news.optusnet.com.au... > gi guys, im in australia i was wondering does anyone have access to a site > to download owners manuals etc on cd etc prerfably for free ,thanks in > advance david nsw australia . > Article: 98413 of rec.radio.amateur.homebrew From: "Gian, I7SWX" Subject: Re: HP Impedance measurements book Date: 25 Aug 2006 02:17:13 -0700 Message-ID: <1156497433.179853.81000@m73g2000cwd.googlegroups.com> References: <1156411778.761963.296700@b28g2000cwb.googlegroups.com> Hi, following Len message I have downloaded the "LCR Measurement Primer," . Nice booklet. I also discovered an applications collection "The LCR Collector" on the same site. There are infos already reported in the Primer but extra measurements. Good sharing 73 Gian I7SWX LenAnderson@ieee.org wrote: > Highland Ham wrote: > > > There is a wealth of information regarding impedance measurement in: > > > > > > > > ++++++++++++++++++++++++++++++++++ > > Indeed a knowledge treasure ,at least for an amateur like myself. > > > > Great learning stuff > > > > Frank GM0CSZ / KN6WH > > You can get a similar appnote from QuadTech at www.quadtech.com > "LCR Measurement Primer," 4th Edition, 60 pp. QuadTech took over > the LCR bridge and electronic instruments from General Radio Co. > > A few sites have copies of General Radio's "Experimenter" which > might be of interest to those looking behind front panels for > intimate details. [nothing beats the HP Journal in my mind but > others mileage may vary] > > Also, at www.tm.agilent.com there is a copy of Hewlett-Packard > Journal, Volume 29, Number 4, December 1977, which gives a good > description of their old HP-4262A LCR Meter. > > LenAnderson@ieee.org Article: 98414 of rec.radio.amateur.homebrew From: mike Subject: Re: Can I use a 120V Variac to get 220V? References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> <1155955586.539941.265270@m73g2000cwd.googlegroups.com> <1156066812.072148.253150@i3g2000cwc.googlegroups.com> Message-ID: Date: Fri, 25 Aug 2006 09:46:50 GMT Andrew VK3BFA wrote: > Rubbish. Where do you get this 25w figure from, Well, you could do the math...it's easy. I was too lazy to do the nonlinear math for the lamp. But an experienced (good) engineer knows how to quickly make approximations to weed out BAD ideas. That skill is uncommon. You'd think it's obvious. And the GOOD engineers do it instinctively. But the other 99% just don't get it. They'll head down the dead-end road 'till they reach the end then bang their head on the barricade. A (good) engineering manager shines a light on those dead-end barricades. See, there are situations where a light bulb can fix a problem. When the problem is largely unspecified, a (good) consultant requests specificity. It's easy to ASSUME that it doesn't have tube rectifiers, but we don't really know. When the consequences can be BAD, and the problem is unspecified, a (good) consultant recommends a conservative approach. And when the original poster merely requested clarification on a conservative approach, it's low risk. Proposing a higher risk option is ill advised. A (good) teacher tries to understand the implications of the question and keep the student out of harm's way. I'm gonna pull some numbers outa my ass, 'cause that's where I keep my common sense. That way, I get a new supply every day. The series light bulb likely works 99.99% of the time. But doing nothing probably works 99.98% of the time. If your estimates are different, state them. How many times have you turned on your amp? How many times has it blowed up because you didn't reform the caps? At the risk of repeating myself...IF your caps NEED reforming, it's wise to bring them up slowly with a variac. Adding the series light bulb will make it even safer, but only if appropriately sized and you're paying attention...there's that pesky specificity again. If you're really interested in reforming caps, take them out and use a variable power supply with a BIG resistor separately for each one. Do it very slowly...but nobody really asked that... Ya see, if you've got series caps...more pesky specificity... a leaky one can cause the good one to fail. But nobody aked that either. And maybe they've got equalizing bleeders that can mitigate the problem...assuming one's not open and making the situation worse...but nobody asked that either. An interesting question might be, "how do you refurbish an amp that hasn't been turned on in a while?" But nobody asked that... Shooting from the hip, firing off the one true, onesizefitsall, solution when you don't know the particulars and are not accountable for the result is... well...it's the "internet way"! mike Article: 98415 of rec.radio.amateur.homebrew Date: Fri, 25 Aug 2006 11:55:52 +0100 From: Highland Ham Subject: Re: looking for a yaesu ft747gx owners manual References: <44eea8b3$0$22363$afc38c87@news.optusnet.com.au> Message-ID: >> gi guys, im in australia i was wondering does anyone have access to a site >> to download owners manuals etc on cd etc prerfably for free ,thanks in >> advance david nsw australia . ======================================== Suggest you go to www.mods.dk select manuals select Yaesu You'll find manual and circuit diagramme somewhere down the bottom of the list. Unless you support the site financially you can download ONLY 1 document each day . Good Luck Frank GM0CSZ / KN6WH Article: 98416 of rec.radio.amateur.homebrew From: "Andrew VK3BFA" Subject: Re: Can I use a 120V Variac to get 220V? Date: 25 Aug 2006 06:04:41 -0700 Message-ID: <1156511081.356559.14800@i42g2000cwa.googlegroups.com> References: <1155929463.373199.177360@74g2000cwt.googlegroups.com> mike wrote: > Andrew VK3BFA wrote: > > > > Rubbish. Where do you get this 25w figure from, > > > Well, you could do the math...it's easy. > Shooting from the hip, firing off the one true, onesizefitsall, solution > when you don't know the particulars and are not accountable for the > result is... > well...it's the "internet way"! > > mike RANT ON.................................................................................. I am NOT disputing your theory - its correct as far as it goes, youve left out lots of other factors that, ideally, should be considered in this case, But its irrelevant to the original question. And in real life I would ignore it as being too anal retentive. If the original poster needed to ask how to hook up two transformers, then your quasi mathematical analysis would be totally innapropriate to the job specifications. Did you think of this at all? It is covered in most 1st year engineering course...(RTFM) My method, with the light bulb, might be crude, (it is crude, so?) but it will work. And have proved that it works, more times than I can remember. Linear and switching power supplies. A simple question - using the light bulb method, whats the WORSE that can happen? If the amp is horribly faulty (and lets not even bother about doing insulation tests on the (old) transformer, that would make it even more complicated) then the light bulb will light to full brilliance. Even an engineer could see that theres something wrong, and then fault find it. (After doing the math, of course) The variac method - again, the same simple question - whats the WORSE thing that could go wrong. And I will answer that, not from theory, but >from practice. The voltage is slowly ramped up until something fails abruptly and catastrophically. With no current limiting beyond a mains fuse in the variac (You did check its rating, didnt you?) the electros will disintigrate like shotgun cartridges generating lots of additional work. (no harm was done to the person, being a trained engineer they had safety goggles on...didnt they?) (The above assumes its a linear supply - if its SMPS, then the switching devices sacrifice themselves in a vain attempot to save the fuse) I have spent my entire working life in this field - working as a technician fixing up the design problems of engineers. Stuff that any competent technician would know NOT to do, from practical experience. In my working life, I have met approx 5 competent engineers. The rest were theoretical bullshit artists who soon moved into management purely on the strength of having a degree - they were as hopeless at that as they were at engineering, but there they had less chance to do actual damage. Are you a "working" engineer - do you own a soldering iron? - lots of theory, plenty of if/but/maybe/ because/planning, but no real appreciation of what the problem is - firing up an old amplifier. Thats all - its not a design exercise, theres no cahce of a Nobel Prize in this one, the project doesnt need to be managed, no consultants needed to give a "proffessional " opinon, no SPICE models needed - just how to power up an amplifier with minimal damage. RANT OFF............................................................................................... woo........ TIRADE ON.............................................................................................. And I am heartily sick of "armchair experts" making life bloody complicated when someone asks a legitimate question that is best answered without a theoretical textbook analysis - I have seen far too many people at radio clubs made to feel inadequate because some smartarse engineer has given a long winded incomprehensible, irrelevant answer to a simple question. These people leave, and dont bother to come to any more meetings, or ask any more questions. One of the best teachers I ever had was an engineer - a very rare person, a brilliant teacher and a competent engineer. He woked out where the question was coming from, ie the level the student was capable of understanding - he then started from basic principles, with great patience, and took the student forward until they could understand the rocket science behind the question. And if you want to see a good textbook using this method, grab a copy of 'The Art of Engineering" by Horowitz(sp) and Hill. read it - you might learn something from it about communication skill. If you cant help, dont hinder. Andrew VK3BFA. I