Article: 94405 of rec.radio.amateur.homebrew Date: Mon, 19 Sep 2005 10:00:01 -0400 From: Bill Subject: Re: Sir Douglas Hall Dec. 1943 article References: <1d32$432ae319$4232bd13$3229@COQUI.NET> <432e5446$0$12714$ba620dc5@text.nova.planet.nl> Message-ID: Ro wrote: > Where did you find it? > > Roland http://freespace.virgin.net/spontaflex.reflex/ Article: 94406 of rec.radio.amateur.homebrew From: Ken Scharf Subject: Re: Quad 837 Grounded Grid linear amplifier References: <1127148433.642315.146000@g49g2000cwa.googlegroups.com> Message-ID: Date: Mon, 19 Sep 2005 15:48:12 -0400 msg@waste.org wrote: > Greetings: > > We recently acquired materials from the estate of Roger A. Jacobsen, > K9KLN, which included a nice Quad 837 tube linear for 80m -> 20m(?). > Please look at this amp at: > > http://www.cybertheque.org/ham/837_linear/ > > I would appreciate any recollections about the design, chassis > layout, performance and similarities to other 807/1625 grounded- > grid designs. > > Regards, > > Michael Grigoni > Cybertheque Museum > As mentioned on the website, the linear is basicly the same as one that appeared in the 1957 handbook and in early ARRL SSB manuals. That version used modified 1625 tubes, the 837 is very similar to the modified 1625 but with lower plate input ratings. Article: 94407 of rec.radio.amateur.homebrew From: msg Subject: Re: Quad 837 Grounded Grid linear amplifier Date: Mon, 19 Sep 2005 16:03:16 -0500 Message-ID: <11iu9rupmu2u9fb@corp.supernews.com> References: <1127148433.642315.146000@g49g2000cwa.googlegroups.com> Ken Scharf wrote: I should have been a little bit clearer in my original post; the website I referred to is our website and the statements on that site are my statements. I'm really looking for recollections, comparisons to other chassis layouts, construction practices, experiences with the design and operation, etc. etc. I'd like to hear from people who have built, used or are using such a linear. It would be good to see photos of other examples of this design, and also of other grounded-grid(s) cathode driven tetrode/pentode designs which are out there. Specifically, I'd like to know if our amp was built to a published design and/or follows a published chassis layout. Does anyone have the '57 handbook, QST article or version of the SSB manual handy? Regards, Michael Grigoni Cybertheque Museum >> > As mentioned on the website, the linear is basicly the same as one that > appeared in the 1957 handbook and in early ARRL SSB manuals. > That version used modified 1625 tubes, the 837 is very similar to the > modified 1625 but with lower plate input ratings. Article: 94408 of rec.radio.amateur.homebrew From: "Bob Chilcoat" Subject: Problem of nearby transmitter breakthrough Message-ID: Date: Mon, 19 Sep 2005 18:07:25 -0400 Sorry for the crossposting, but I'm looking for more expertise than I have. I usually hang out in the aviation groups, but am an engineer by training. I have a radio problem: I have just completed a special rig for our local airport, but it has a problem. I took a rather old but serviceable Sony digital air band receiver (Air 8), boxed it up in a waterproof enclosure and piped the audio out to an FM microwatt transmitter. The idea of this is that visitors to our airport who like to sit in the parking lot and watch the airplanes can listen on their car radios on FM 88.1 to the radio traffic on our Common Traffic Advisory Frequency (CTAF), which at our airport is 123.00 MHz (AM). Unfortunately, while this setup worked perfectly at home well away from the airport, we have an Automatic Weather Observation Station (AWOS) transmitting continuously on 120.60 MHz only 50-60 feet from the place I need to site the receiver. Even though this is only a 5 Watt transmitter, it overloads the front end of the receiver. As soon as anyone keys on 123.00 and the automatic squelch is triggered, all you hear is the AWOS recording. I've tried quick fix by attenuating the input signal by trimming (shortening) the antenna, but this doesn't really help. This was supposed to be a quick and dirty (gratis) job for the airport, and I've already spent more time and money on it than I wanted to. Any suggestions as to how I might fix this problem? Cheaply? Obviously a better receiver would work (my Yaesu aviation handheld works perfectly at the same location), but I have no other (free) receivers handy. I can move the receiver another 50 feet down the fence, which is my next option, but what if this doesn't work? I can't get it any farther away for several reasons. Anyone have a 120 MHz preselector they can give me? Any really steep (and cheap) 120.6 notch filter designs? Thanks for any help you can offer. -- Bob (Chief Pilot, White Knuckle Airways) Article: 94409 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: Problem of nearby transmitter breakthrough Date: Mon, 19 Sep 2005 15:59:57 -0700 Message-ID: <11iugnfn1m9s35a@corp.supernews.com> References: Are you absolutely sure the offending signal is coming in via the antenna? Is it there if you disconnect the antenna or replace it with a dummy load (termination)? That strongly influences what you need to do to fix it. Roy Lewallen, W7EL Bob Chilcoat wrote: > Sorry for the crossposting, but I'm looking for more expertise than I have. > I usually hang out in the aviation groups, but am an engineer by training. > I have a radio problem: > > I have just completed a special rig for our local airport, but it has a > problem. I took a rather old but serviceable Sony digital air band receiver > (Air 8), boxed it up in a waterproof enclosure and piped the audio out to an > FM microwatt transmitter. The idea of this is that visitors to our airport > who like to sit in the parking lot and watch the airplanes can listen on > their car radios on FM 88.1 to the radio traffic on our Common Traffic > Advisory Frequency (CTAF), which at our airport is 123.00 MHz (AM). > Unfortunately, while this setup worked perfectly at home well away from the > airport, we have an Automatic Weather Observation Station (AWOS) > transmitting continuously on 120.60 MHz only 50-60 feet from the place I > need to site the receiver. Even though this is only a 5 Watt transmitter, > it overloads the front end of the receiver. As soon as anyone keys on > 123.00 and the automatic squelch is triggered, all you hear is the AWOS > recording. > > I've tried quick fix by attenuating the input signal by trimming > (shortening) the antenna, but this doesn't really help. This was supposed > to be a quick and dirty (gratis) job for the airport, and I've already spent > more time and money on it than I wanted to. Any suggestions as to how I > might fix this problem? Cheaply? Obviously a better receiver would work > (my Yaesu aviation handheld works perfectly at the same location), but I > have no other (free) receivers handy. I can move the receiver another 50 > feet down the fence, which is my next option, but what if this doesn't work? > I can't get it any farther away for several reasons. Anyone have a 120 MHz > preselector they can give me? Any really steep (and cheap) 120.6 notch > filter designs? > > Thanks for any help you can offer. > Article: 94410 of rec.radio.amateur.homebrew Message-ID: <432F4312.4060903@nowhere.nil> From: Bob Subject: Re: Problem of nearby transmitter breakthrough References: Date: Mon, 19 Sep 2005 19:00:34 -0400 Put a tee connector on the receive line coax a length of coax on it with a short at the far end. It must be cut to be exactly 1/4 wavelength (including connector spur.) This will appear t be an open circuit at the resonant frequency, but will severely attenuate your nearby unwanted signal. Failing that, a series LC network across the receive line will do a similar task. Try a 47pf trimmer cap in series with a coil made from 4 to 6 turns around a bic pen. (you can remove the pen after making the coil... :) Tune your receiver to the unwanted signal and tune the trimmer until you see the unwanted signal drop out. You may have to experiment with the coil turns and spacing, but this design will also help wipe out the unwanted station. Fortunately your undesired signal is likely a constant-on transmission so it's always there for you to play with. Secondly, you can make and tinker with all this at home (provided you live within receiving range of the airport AWOS) and bring the working product to the airport for installation. Good luck. B. Bob Chilcoat wrote: > Sorry for the crossposting, but I'm looking for more expertise than I have. > I usually hang out in the aviation groups, but am an engineer by training. > I have a radio problem: > > I have just completed a special rig for our local airport, but it has a > problem. I took a rather old but serviceable Sony digital air band receiver > (Air 8), boxed it up in a waterproof enclosure and piped the audio out to an > FM microwatt transmitter. The idea of this is that visitors to our airport > who like to sit in the parking lot and watch the airplanes can listen on > their car radios on FM 88.1 to the radio traffic on our Common Traffic > Advisory Frequency (CTAF), which at our airport is 123.00 MHz (AM). > Unfortunately, while this setup worked perfectly at home well away from the > airport, we have an Automatic Weather Observation Station (AWOS) > transmitting continuously on 120.60 MHz only 50-60 feet from the place I > need to site the receiver. Even though this is only a 5 Watt transmitter, > it overloads the front end of the receiver. As soon as anyone keys on > 123.00 and the automatic squelch is triggered, all you hear is the AWOS > recording. > > I've tried quick fix by attenuating the input signal by trimming > (shortening) the antenna, but this doesn't really help. This was supposed > to be a quick and dirty (gratis) job for the airport, and I've already spent > more time and money on it than I wanted to. Any suggestions as to how I > might fix this problem? Cheaply? Obviously a better receiver would work > (my Yaesu aviation handheld works perfectly at the same location), but I > have no other (free) receivers handy. I can move the receiver another 50 > feet down the fence, which is my next option, but what if this doesn't work? > I can't get it any farther away for several reasons. Anyone have a 120 MHz > preselector they can give me? Any really steep (and cheap) 120.6 notch > filter designs? > > Thanks for any help you can offer. > Article: 94411 of rec.radio.amateur.homebrew From: Bob Subject: Re: Problem of nearby transmitter breakthrough References: Message-ID: Date: Mon, 19 Sep 2005 19:03:04 -0400 Put a tee connector on the receive line coax a length of coax on it with a short at the far end. It must be cut to be exactly 1/4 wavelength (including connector spur.) This will appear t be an open circuit at the resonant frequency, but will severely attenuate your nearby unwanted signal. Failing that, a series LC network across the receive line will do a similar task. Try a 47pf trimmer cap in series with a coil made from 4 to 6 turns around a bic pen. (you can remove the pen after making the coil... :) Tune your receiver to the unwanted signal and tune the trimmer until you see the unwanted signal drop out. You may have to experiment with the coil turns and spacing, but this design will also help wipe out the unwanted station. Fortunately your undesired signal is likely a constant-on transmission so it's always there for you to play with. Secondly, you can make and tinker with all this at home (provided you live within receiving range of the airport AWOS) and bring the working product to the airport for installation. Good luck. B. Bob Chilcoat wrote: > Sorry for the crossposting, but I'm looking for more expertise than I have. > I usually hang out in the aviation groups, but am an engineer by training. > I have a radio problem: > > I have just completed a special rig for our local airport, but it has a > problem. I took a rather old but serviceable Sony digital air band receiver > (Air 8), boxed it up in a waterproof enclosure and piped the audio out to an > FM microwatt transmitter. The idea of this is that visitors to our airport > who like to sit in the parking lot and watch the airplanes can listen on > their car radios on FM 88.1 to the radio traffic on our Common Traffic > Advisory Frequency (CTAF), which at our airport is 123.00 MHz (AM). > Unfortunately, while this setup worked perfectly at home well away from the > airport, we have an Automatic Weather Observation Station (AWOS) > transmitting continuously on 120.60 MHz only 50-60 feet from the place I > need to site the receiver. Even though this is only a 5 Watt transmitter, > it overloads the front end of the receiver. As soon as anyone keys on > 123.00 and the automatic squelch is triggered, all you hear is the AWOS > recording. > > I've tried quick fix by attenuating the input signal by trimming > (shortening) the antenna, but this doesn't really help. This was supposed > to be a quick and dirty (gratis) job for the airport, and I've already spent > more time and money on it than I wanted to. Any suggestions as to how I > might fix this problem? Cheaply? Obviously a better receiver would work > (my Yaesu aviation handheld works perfectly at the same location), but I > have no other (free) receivers handy. I can move the receiver another 50 > feet down the fence, which is my next option, but what if this doesn't work? > I can't get it any farther away for several reasons. Anyone have a 120 MHz > preselector they can give me? Any really steep (and cheap) 120.6 notch > filter designs? > > Thanks for any help you can offer. > Article: 94412 of rec.radio.amateur.homebrew From: novatech@eskimo.com (Steven Swift) Subject: Re: DDS and phase noise. Date: 20 Sep 2005 00:44:56 GMT Message-ID: References: <3ibji1th4av4j4fhb0sdu6mtet8ctscd9t@4ax.com> "W3JDR" writes: >From what I've seen in the data sheets, the closer you operate the RF output >to the Nyquist limit (Fref/2), the cleaner the spurs get. I've seen numbers >of -90 dB or better on even some of the cheapo Analog Devices parts. >Joe >W3JDR It has to do with where the spurs end up. If you are close to Fref/2, lots of the spurs alias down to base band. Worst case is Fref/3. With the proper choice of filters, and band choice you can find areas where spurs are almost non-existent. If you have a narrow band application, your frequency planning can find those holes. Make sure you have your peak detector turned on. There are lots of sources of spurs-- phase truncation, amplitude truncation, noise, etc. -- Steven D. Swift, novatech@eskimo.com, http://www.novatech-instr.com NOVATECH INSTRUMENTS, INC. P.O. Box 55997 206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA Article: 94413 of rec.radio.amateur.homebrew From: "Aussie Medic" References: Subject: Re: Problem of nearby transmitter breakthrough Message-ID: Date: Tue, 20 Sep 2005 01:27:44 GMT I am making some assumtions here. You state that you only hear the AWOS when a transmission occurs on the CTAF freq. I would think this means that the receiver is NOT receiving the AWOS signal all the time or it would trigger the system constantly. If you listen to the receiver output while at the airport does it contain the AWOS audio or just the CTAF audio? My inclination is that the AWOS sig is being picked up by the interface circuitry between your receiver and the 88.1 transmitter. If this is the case then more bypassing and rf filtering is needed on the interface. Then again I could be barking up the wrong tree here, only some suggestions, hope it helps. Cheers "Bob Chilcoat" wrote in message news:wEGXe.4566$H24.1943@fe11.lga... > Sorry for the crossposting, but I'm looking for more expertise than I > have. I usually hang out in the aviation groups, but am an engineer by > training. I have a radio problem: > > I have just completed a special rig for our local airport, but it has a > problem. I took a rather old but serviceable Sony digital air band > receiver (Air 8), boxed it up in a waterproof enclosure and piped the > audio out to an FM microwatt transmitter. The idea of this is that > visitors to our airport who like to sit in the parking lot and watch the > airplanes can listen on their car radios on FM 88.1 to the radio traffic > on our Common Traffic Advisory Frequency (CTAF), which at our airport is > 123.00 MHz (AM). Unfortunately, while this setup worked perfectly at home > well away from the airport, we have an Automatic Weather Observation > Station (AWOS) transmitting continuously on 120.60 MHz only 50-60 feet > from the place I need to site the receiver. Even though this is only a 5 > Watt transmitter, it overloads the front end of the receiver. As soon as > anyone keys on 123.00 and the automatic squelch is triggered, all you hear > is the AWOS recording. > > I've tried quick fix by attenuating the input signal by trimming > (shortening) the antenna, but this doesn't really help. This was supposed > to be a quick and dirty (gratis) job for the airport, and I've already > spent more time and money on it than I wanted to. Any suggestions as to > how I might fix this problem? Cheaply? Obviously a better receiver would > work (my Yaesu aviation handheld works perfectly at the same location), > but I have no other (free) receivers handy. I can move the receiver > another 50 feet down the fence, which is my next option, but what if this > doesn't work? I can't get it any farther away for several reasons. Anyone > have a 120 MHz preselector they can give me? Any really steep (and cheap) > 120.6 notch filter designs? > > Thanks for any help you can offer. > > -- > Bob (Chief Pilot, White Knuckle Airways) > > > Article: 94414 of rec.radio.amateur.homebrew From: "Dale Parfitt" References: <432F4312.4060903@nowhere.nil> Subject: Re: Problem of nearby transmitter breakthrough Message-ID: Date: Tue, 20 Sep 2005 02:00:13 GMT "Bob" wrote in message news:432F4312.4060903@nowhere.nil... > Put a tee connector on the receive line coax a length of coax on it with a > short at the far end. It must be cut to be exactly 1/4 wavelength > (including connector spur.) This will appear t be an open circuit at the > resonant frequency, but will severely attenuate your nearby unwanted > signal. > > Failing that, a series LC network across the receive line will do a > similar task. Try a 47pf trimmer cap in series with a coil made from 4 to > 6 turns around a bic pen. (you can remove the pen after making the coil... > :) Tune your receiver to the unwanted signal and tune the trimmer until > you see the unwanted signal drop out. You may have to experiment with the > coil turns and spacing, but this design will also help wipe out the > unwanted station. > > Fortunately your undesired signal is likely a constant-on transmission so > it's always there for you to play with. Secondly, you can make and tinker > with all this at home (provided you live within receiving range of the > airport AWOS) and bring the working product to the airport for > installation. > > > Good luck. > > > B. While this approach looks good on paper, it often fails badly when the desired frequency is so close in to the notch frequency. I just put a quarter wave stub on our VNA and found that while it does diminish the 123 signal -33dB, it also attenuates the 120.6 signal by a whopping -22dB. There is also an enormous VSWR upset -120:1 or so- this is perhaps not important in your receive only application. Each year we build hundreds of filters for this exact application- AWOS/UNICOM separation. Typical insertion loss is under 1dB while the notch is >-40dB. The filter is about the size of a cigarette pack exclusive of the N connectors. W4OP Article: 94415 of rec.radio.amateur.homebrew From: "H. P. Friedrichs" Subject: Re: The Perfect Ham Store? Date: Mon, 19 Sep 2005 19:56:28 -0700 Message-ID: <11iuuj1b9ob25a1@corp.supernews.com> References: <1125008389.118793.289820@g14g2000cwa.googlegroups.com> <1125335627.933550.94170@g47g2000cwa.googlegroups.com> <1125353081.965959.186860@f14g2000cwb.googlegroups.com> ES: My advice... a) Start somewhere---with something. It doesn't matter what. Yes there is much to be said for planning and strategizing. On the other hand, too many people spend so much time thinking about doing things that they never actually do them. b) The "perfect ham store" is the store YOU'd shop at if it existed. If you want to establish the perfect ham store, then create it according to your vision. c) Whatever you do, make is scaleable. Running out plunking down thousands for shop space, equipment, advertising, and whatever is a risky proposition. Start with a single kit, a single service, a single piece of your own software, and market it on the web. If it fails, your exposure was small and whatever money lost can be justified as tuition for the lessons you learned. Just try something else. If it doesn't fail, you will have a small amount of capital with which to leverage the next product or service. HPF AC7ZL eternalsquire@comcast.net wrote: > > Problem is, I don't know just where to start. > > The Eternal Squire > Article: 94416 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: Problem of nearby transmitter breakthrough Message-ID: References: Date: Tue, 20 Sep 2005 03:00:06 GMT On Mon, 19 Sep 2005 18:07:25 -0400, "Bob Chilcoat" wrote: > >I've tried quick fix by attenuating the input signal by trimming >(shortening) the antenna, but this doesn't really help. This was supposed Bad thing to do and likely didn't reduce the signal as much as you'd like. Try an attenuator, enough to kill the offending signal. Once that is known the next step may be easier. IF the attenuation needed is under 10DB and leving it in is acceptable your done. Usually local signals are plenty strong enough. If you need more than 10DB. Try a suckout stub tuned to the awos at 120.6 as others have suggested. That should be enough as your listening on 123. >(my Yaesu aviation handheld works perfectly at the same location), but I >have no other (free) receivers handy. I can move the receiver another 50 >feet down the fence, which is my next option, but what if this doesn't work? I'd try that first, distance will always help the problem. Allowing for a plastic case on the RX distance is more liklely helpful than filtering. The problem is the case of the RX is plastic and there is no shielding so any filter will be compromized by back door entry. A metalic water proof box with filtered ins and outs for RX and fm TX will be needed then. It's possible to make a filter with a steep enough curve for that by using a bandpass section for 123 and a notch section at 120.6 using sections of UT141 (.141" copper jacket coax). Allison KB1GMX Article: 94417 of rec.radio.amateur.homebrew From: "Bob Chilcoat" References: Subject: Re: Problem of nearby transmitter breakthrough Message-ID: Date: Mon, 19 Sep 2005 23:35:12 -0400 The receiver is already in a (steel) waterproof box. Tomorrow I will try moving the receiver as far away as I can. If that doesn't fix the problem, I'll try the stub antenna notch filter solution. I have a BNC Tee. Can anyone point me to the 1/4 wave length formula for 120.6 MHz? Does 0.591 meters (23 5/16") sound right? I'm pretty sure right now that the interference is coming in on the antenna. It's not enough to trip the squelch, but as soon as someone keys on 123 and trips the squelch, the AWOS is on the audio. OTOH, I guess that doesn't prove anything... I suppose the wiring to the 88.1 MHz transmitter or its wiring could be picking up the 120.6, although all that wiring is shielded (one audio line with shield terminated at only one end, and one 3v power line with its shield as return). The transmitter itself is in an unshielded plastic box, but that's mounted flat against the bottom of a 10" ground plane for the transmitter antenna. The last possibility is the 6v power line going into the receiver box. It's not shielded and starts at a wall wart transformer/psu very near the AWOS xmitter. I could put a few turns through a ferrite toroid just outside the box, I suppose. Couldn't hurt. Gotta find a suitable torroid. Allison, I'm not experienced enough at this stuff to visualize how to make a bandpass section out of coax. I can follow the stub notch filter, but the bandpass isn't there. Could you explain a bit more? Thanks to you all for all the help. -- Bob (Chief Pilot, White Knuckle Airways) wrote in message news:b4uui15brprovh2js0qv035hmv751rek02@4ax.com... > On Mon, 19 Sep 2005 18:07:25 -0400, "Bob Chilcoat" > wrote: > >> >>I've tried quick fix by attenuating the input signal by trimming >>(shortening) the antenna, but this doesn't really help. This was supposed > > Bad thing to do and likely didn't reduce the signal as much as you'd > like. Try an attenuator, enough to kill the offending signal. Once > that is known the next step may be easier. > > IF the attenuation needed is under 10DB and leving it in is acceptable > your done. Usually local signals are plenty strong enough. > > If you need more than 10DB. Try a suckout stub tuned to the awos > at 120.6 as others have suggested. That should be enough as your > listening on 123. > >>(my Yaesu aviation handheld works perfectly at the same location), but I >>have no other (free) receivers handy. I can move the receiver another 50 >>feet down the fence, which is my next option, but what if this doesn't >>work? > > I'd try that first, distance will always help the problem. Allowing > for a plastic case on the RX distance is more liklely helpful than > filtering. The problem is the case of the RX is plastic and there is > no shielding so any filter will be compromized by back door entry. > A metalic water proof box with filtered ins and outs for RX and fm TX > will be needed then. > > It's possible to make a filter with a steep enough curve for that by > using a bandpass section for 123 and a notch section at 120.6 using > sections of UT141 (.141" copper jacket coax). > > Allison > KB1GMX > > Article: 94418 of rec.radio.amateur.homebrew From: Darko <9a3li_makni_@hamradio.hr> Subject: OT: Motorola R2001x Date: Tue, 20 Sep 2005 07:36:44 +0200 Message-ID: Hello! Im looking for anyone who have experience in reparing old Motorola R2001(2)x test-set. Thanks ! Darko Article: 94419 of rec.radio.amateur.homebrew From: Paul Keinanen Subject: Re: Problem of nearby transmitter breakthrough Message-ID: References: Date: Tue, 20 Sep 2005 10:41:27 +0300 On Mon, 19 Sep 2005 18:07:25 -0400, "Bob Chilcoat" wrote: >Sorry for the crossposting, but I'm looking for more expertise than I have. >I usually hang out in the aviation groups, but am an engineer by training. >I have a radio problem: > >I have just completed a special rig for our local airport, but it has a >problem. I took a rather old but serviceable Sony digital air band receiver >(Air 8), What is intermediate frequency (IF) of the receiver ? Some offending signal (or mixing product) could fall on the image frequency and get through that way. >boxed it up in a waterproof enclosure and piped the audio out to an >FM microwatt transmitter. The idea of this is that visitors to our airport >who like to sit in the parking lot and watch the airplanes can listen on >their car radios on FM 88.1 Is the interface present when this transmitter is turned off and the signal is monitored through the speaker ? If the transmitter cables are disconnected, does this change anything ? >to the radio traffic on our Common Traffic >Advisory Frequency (CTAF), which at our airport is 123.00 MHz (AM). >Unfortunately, while this setup worked perfectly at home well away from the >airport, we have an Automatic Weather Observation Station (AWOS) >transmitting continuously on 120.60 MHz only 50-60 feet from the place I >need to site the receiver. Even though this is only a 5 Watt transmitter, >it overloads the front end of the receiver. One thing to try is to rotate the antenna, so that the receiver antenna is in opposite polarisation than the transmitter position, one in vertical polarisation, the other horizontal polarisation. This will attenuate the offending signal by 10-20 dB. The null might be quite narrow, so you would have to slowly rotate your receiver antenna to find it. >As soon as anyone keys on >123.00 and the automatic squelch is triggered, all you hear is the AWOS >recording. If you defeat the squelch, do you constantly hear the AWOS transmission ? Does it matter if the 88.1 MHz FM transmitter is on or not ? Any other VHF transmitters on site (VOR?) that might take part in the mixing process ? Do you hear any other background noises than the AWOS recording ? Paul OH3LWR Article: 94420 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: Problem of nearby transmitter breakthrough Message-ID: References: Date: Tue, 20 Sep 2005 12:32:55 GMT On Mon, 19 Sep 2005 23:35:12 -0400, "Bob Chilcoat" wrote: >The receiver is already in a (steel) waterproof box. Tomorrow I will try >moving the receiver as far away as I can. If that doesn't fix the problem, >I'll try the stub antenna notch filter solution. I have a BNC Tee. Can >anyone point me to the 1/4 wave length formula for 120.6 MHz? Does 0.591 >meters (23 5/16") sound right? Wavelength is 300/F in meters. One quarter wave is 75/f in meters. However your using coax cable and the speed of light (nominally 300 in the examples cited) is slower depending on the coax used. for foam types it's about .8 (varies by brand) and for solid types usually around .66 (still varies some). So for 120.6 a 1/4 wave section is 75/120.6=.62189M (24.4838"). A section of RG58 (solid dialetric) would be .66 that length or .4104M (16.159"). To give you an idea of how critical that length is the 1/4Wave of the same coax for 123mhz is .4024M (15.84"). So even small variations in VF (velocity factor for the coax) or gutting error can make for big mistuning. Generally speaking simple stubs work best if the two frequencies are widely seperated such as 2m band and pagers at 153mhz (5mhz minimum seperation). >I'm pretty sure right now that the interference is coming in on the antenna. >It's not enough to trip the squelch, but as soon as someone keys on 123 and >trips the squelch, the AWOS is on the audio. OTOH, I guess that doesn't >prove anything... Sounds like intermod. The front end of the reciever is being grossly overloaded. The average airband radio the difference of 120.6 and 123mhz is so small to the front end that overload is common. >I suppose the wiring to the 88.1 MHz transmitter or its wiring could be >picking up the 120.6, although all that wiring is shielded (one audio line >with shield terminated at only one end, and one 3v power line with its >shield as return). The transmitter itself is in an unshielded plastic box, >but that's mounted flat against the bottom of a 10" ground plane for the >transmitter antenna. The last possibility is the 6v power line going into >the receiver box. It's not shielded and starts at a wall wart >transformer/psu very near the AWOS xmitter. I could put a few turns through >a ferrite toroid just outside the box, I suppose. Couldn't hurt. Gotta >find a suitable torroid. RF will com into the box anyway it can. Via power, antenna, audio and even a poor connection between the cover and the box. FYI: I'd bet anything that a few hundred feet of seperation from the AWOS cures it or substantually improves it. >Allison, I'm not experienced enough at this stuff to visualize how to make a >bandpass section out of coax. I can follow the stub notch filter, but the >bandpass isn't there. Could you explain a bit more? If I had a way to post a schematic It would help. Suffice to say its something that you'd need hardware to tune. The idea is that using coax sections it's possible to get the equivelent of high Q tuned circuits and couple them loosely for selectivity. Basically a open ended 1/4 wave section of coax is a similar to a tuned cavity save for a cavity at 123mhz is nearly 25" tall making coax less bulky. So using an open stub creates a notch at some frequency, a shorted stub is a tuned (resonant) pass at the same given the same length. Visualize a feed from antenna, T with shorted stub(for 123), a 1/4 wave section for 120.6 section, another T with a open stub for 120.6. Thats the starting point and it may be adaquate at that. However to really make it work there is more and It's hard for me to describe here. Sufficient to say VHF filters with that kind of selectivity are not trivial to design and build. Also obvious you need some instrumentation to tune the beast for best results. Which is why there are people that build custom filters for tasks like this. Allison kb1gmx Article: 94421 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: Problem of nearby transmitter breakthrough Message-ID: References: <432F4312.4060903@nowhere.nil> Date: Tue, 20 Sep 2005 12:54:57 GMT On Tue, 20 Sep 2005 02:00:13 GMT, "Dale Parfitt" wrote: > >"Bob" wrote in message >news:432F4312.4060903@nowhere.nil... >> Put a tee connector on the receive line coax a length of coax on it with a >> short at the far end. It must be cut to be exactly 1/4 wavelength >> (including connector spur.) This will appear t be an open circuit at the >> resonant frequency, but will severely attenuate your nearby unwanted >> signal. >> B. > > >While this approach looks good on paper, it often fails badly when the >desired frequency is so close in to the notch frequency. I just put a >quarter wave stub on our VNA and found that while it does diminish the 123 >signal -33dB, it also attenuates the 120.6 signal by a whopping -22dB. >There is also an enormous VSWR upset -120:1 or so- this is perhaps not >important in your receive only application. >Each year we build hundreds of filters for this exact application- >AWOS/UNICOM separation. Typical insertion loss is under 1dB while the notch >is >-40dB. The filter is about the size of a cigarette pack exclusive of the >N connectors. > >W4OP The 1/4 wave stub works because of huge impedence upset it introduces. However having a short (or nearly so) on the coax for transmitting would be deadly for transmitters. The problem is sections of coax have only moderate Q as resonators and they are also resonant at harmonics. I'd approach the problem by pulling the RF amp out of the radio and loosely coupling to the mixer. Even a RX with 15uV sensitivity is adequate for miles around an airport. Allison Article: 94422 of rec.radio.amateur.homebrew Date: Tue, 20 Sep 2005 11:22:14 -0400 From: Bill Subject: Re: Problem of nearby transmitter breakthrough References: Message-ID: nospam@nouce.bellatlantic.net wrote: > On Mon, 19 Sep 2005 23:35:12 -0400, "Bob Chilcoat" > wrote: > > >>The receiver is already in a (steel) waterproof box. Tomorrow I will try >>moving the receiver as far away as I can. If that doesn't fix the problem, >>I'll try the stub antenna notch filter solution. I have a BNC Tee. Can >>anyone point me to the 1/4 wave length formula for 120.6 MHz? Does 0.591 >>meters (23 5/16") sound right? > > > Wavelength is 300/F in meters. One quarter wave is 75/f in meters. > However your using coax cable and the speed of light (nominally 300 in > the examples cited) is slower depending on the coax used. for foam > types it's about .8 (varies by brand) and for solid types usually > around .66 (still varies some). > > So for 120.6 a 1/4 wave section is 75/120.6=.62189M (24.4838"). > A section of RG58 (solid dialetric) would be .66 that length or .4104M > (16.159"). > > To give you an idea of how critical that length is the 1/4Wave of the > same coax for 123mhz is .4024M (15.84"). > > So even small variations in VF (velocity factor for the coax) or > gutting error can make for big mistuning. years ago, many cable pay-tv signals were scrambled simply with an interfering carrier inserted at 2.25 MHz above the video carrier. The 'decoder' was simply a notch trap that removed the carrier. It was quite easy to remove this 'scrambling carrier' with a stub of coax, twinlead or even zip cord. Once you know the approximate length its a matter of just trimming away in 1/4" intervals. I forget if the qurater-wave stub remained open and the half-wave stub was shorted, or vice versa, but you get the drift...it only takes a few minutes to try. That said, its easy to do sitting on the floor behind the tv with a steady signal but if you are trying to trap an intermittent signal in the field it might be rather maddening without a test oscillator and a means of measuring the signal. Then its placement into the 'system' of iffy impedance may cause it to shift slightly. IF you could find an old cable TV "Channel A" or "Channel 14" positive trap it would be a cinch to retune it. I don't think any of the commercial vendors would sell them as one-off, though...they only cost about $6 new. Maybe somebody has one in a junquebox? -Bill- I'm surprised my junkbox didn't yield one :) Article: 94423 of rec.radio.amateur.homebrew Message-ID: <43302D7C.CFEAFC51@earthlink.net> From: "Michael A. Terrell" Subject: Re: Problem of nearby transmitter breakthrough References: Date: Tue, 20 Sep 2005 15:40:44 GMT Bob Chilcoat wrote: > > Sorry for the crossposting, but I'm looking for more expertise than I have. > I usually hang out in the aviation groups, but am an engineer by training. > I have a radio problem: > > I have just completed a special rig for our local airport, but it has a > problem. I took a rather old but serviceable Sony digital air band receiver > (Air 8), boxed it up in a waterproof enclosure and piped the audio out to an > FM microwatt transmitter. The idea of this is that visitors to our airport > who like to sit in the parking lot and watch the airplanes can listen on > their car radios on FM 88.1 to the radio traffic on our Common Traffic > Advisory Frequency (CTAF), which at our airport is 123.00 MHz (AM). > Unfortunately, while this setup worked perfectly at home well away from the > airport, we have an Automatic Weather Observation Station (AWOS) > transmitting continuously on 120.60 MHz only 50-60 feet from the place I > need to site the receiver. Even though this is only a 5 Watt transmitter, > it overloads the front end of the receiver. As soon as anyone keys on > 123.00 and the automatic squelch is triggered, all you hear is the AWOS > recording. > > I've tried quick fix by attenuating the input signal by trimming > (shortening) the antenna, but this doesn't really help. This was supposed > to be a quick and dirty (gratis) job for the airport, and I've already spent > more time and money on it than I wanted to. Any suggestions as to how I > might fix this problem? Cheaply? Obviously a better receiver would work > (my Yaesu aviation handheld works perfectly at the same location), but I > have no other (free) receivers handy. I can move the receiver another 50 > feet down the fence, which is my next option, but what if this doesn't work? > I can't get it any farther away for several reasons. Anyone have a 120 MHz > preselector they can give me? Any really steep (and cheap) 120.6 notch > filter designs? > > Thanks for any help you can offer. > > -- > Bob (Chief Pilot, White Knuckle Airways) Rather than building a trap, why not use a narrow bandpass filter? Also, if you are that close to both transmitters, try attenuating the signal from the antenna to prevent overloading the receiver. One other idea. if the signal is from a transmitter at the airport, why not see if you can take the audio feed to that transmitter and feed the FM transmitter. -- ? Michael A. Terrell Central Florida Article: 94424 of rec.radio.amateur.homebrew From: "Caveat Lector" References: <1125008389.118793.289820@g14g2000cwa.googlegroups.com> <1125335627.933550.94170@g47g2000cwa.googlegroups.com> <1125353081.965959.186860@f14g2000cwb.googlegroups.com> <11iuuj1b9ob25a1@corp.supernews.com> Subject: Re: The Perfect Ham Store? Message-ID: <27WXe.15544$mH.850@fed1read07> Date: Tue, 20 Sep 2005 08:44:01 -0700 Gotta remember - Hams are cheap -- they visit the local store -- try out the gear - ask a zillion questions, then go away and mail order off the web to save a measly dollar or two. Then they go back to the local store and ask them to help program the unit. I had a Ham offer me $7 for a $25 book, I replied -- which Chapter do you want (;-) -- CL -- I doubt, therefore I might be ! "H. P. Friedrichs" wrote in message news:11iuuj1b9ob25a1@corp.supernews.com... > ES: > > My advice... > > a) Start somewhere---with something. It doesn't matter what. Yes there is > much to be said for planning and strategizing. On the other hand, too many > people spend so much time thinking about doing things that they never > actually do them. > > b) The "perfect ham store" is the store YOU'd shop at if it existed. If > you want to establish the perfect ham store, then create it according to > your vision. > > c) Whatever you do, make is scaleable. Running out plunking down thousands > for shop space, equipment, advertising, and whatever is a risky > proposition. Start with a single kit, a single service, a single piece of > your own software, and market it on the web. > > If it fails, your exposure was small and whatever money lost can be > justified as tuition for the lessons you learned. Just try something else. > > If it doesn't fail, you will have a small amount of capital with which to > leverage the next product or service. > > HPF > AC7ZL > > eternalsquire@comcast.net wrote: > > >> >> Problem is, I don't know just where to start. >> >> The Eternal Squire >> Article: 94425 of rec.radio.amateur.homebrew Message-ID: <43307ADC.3080301@worldnet.att.net> From: D Peter Maus Subject: Re: Problem of nearby transmitter breakthrough References: Date: Tue, 20 Sep 2005 21:10:53 GMT Bob Chilcoat wrote: > Sorry for the crossposting, but I'm looking for more expertise than I have. > I usually hang out in the aviation groups, but am an engineer by training. > I have a radio problem: > > I have just completed a special rig for our local airport, but it has a > problem. I took a rather old but serviceable Sony digital air band receiver > (Air 8), boxed it up in a waterproof enclosure and piped the audio out to an > FM microwatt transmitter. The idea of this is that visitors to our airport > who like to sit in the parking lot and watch the airplanes can listen on > their car radios on FM 88.1 to the radio traffic on our Common Traffic > Advisory Frequency (CTAF), which at our airport is 123.00 MHz (AM). > Unfortunately, while this setup worked perfectly at home well away from the > airport, we have an Automatic Weather Observation Station (AWOS) > transmitting continuously on 120.60 MHz only 50-60 feet from the place I > need to site the receiver. Even though this is only a 5 Watt transmitter, > it overloads the front end of the receiver. As soon as anyone keys on > 123.00 and the automatic squelch is triggered, all you hear is the AWOS > recording. > > I've tried quick fix by attenuating the input signal by trimming > (shortening) the antenna, but this doesn't really help. This was supposed > to be a quick and dirty (gratis) job for the airport, and I've already spent > more time and money on it than I wanted to. Any suggestions as to how I > might fix this problem? Cheaply? Obviously a better receiver would work > (my Yaesu aviation handheld works perfectly at the same location), but I > have no other (free) receivers handy. I can move the receiver another 50 > feet down the fence, which is my next option, but what if this doesn't work? > I can't get it any farther away for several reasons. Anyone have a 120 MHz > preselector they can give me? Any really steep (and cheap) 120.6 notch > filter designs? > > Thanks for any help you can offer. > ' The technical solutions, so far presented, are about as good as you're going to get while still keeping the cost reasonable. However, you ARE dealing with a consumer grade radio that was simply not designed to any particular standard of interference rejection. And that you've packaged this with a transmitter operating within the FM band also offers the potential for overload artifacts on a broad spectrum of frequencies. Sony Air 8, however, was known to experience this kind of problem even off-airport. It would even pass 11 meter CB on a good day if the signal was close, or large enough. As did some Sony FM broadcast rigs of the period when an aircraft was reasonably nearby. I lived 2 miles off the approach end of 30L/30R at Lambert, St Louis for years, and I'd get aircraft to tower chatter on my Sony portable at 103.3, 102.5, even 93.7 everytime an aircraft went overhead. The front end was simply not robust enough to withstand a close-in assault of any magnitude. Nor was the chassis shielded well enough to prevent leakage through the IF's. Your real option may to select a different receiver. If you're doing this as a favor to the airport, you may get a decommissioned rig culled from a wrecked aircraft, or one that's been sitting on the shelf at one of the FBO's, donated to the cause. In that case, robust interference rejection is assured for your purpose. There is, however another, and potentially greater issue at play here. Rebroadcast of non broadcast radio frequencies may be in violation of several communications acts. Brush up on your regs, and be sure you're in compliance. In today's climate, there is always some asshat who has to make trouble for his jollies bringing the letter of the law down on fairly innocuous activities that may actually benefit someone. And with overlapping laws written the way they are, today, you may be in compliance with one law, while in violation of another. One of my colleagues, downstate, got a spanking for a similar type of service involving Air/Water show comms for a small airport near his home. Someone complained. Even though there was no interference was measured, and all hardware was in compliance for license free application. Unauthorized rebroadcast of comm channels was the issue. So, make sure your ducks are in a row. Article: 94426 of rec.radio.amateur.homebrew From: Ken Scharf Subject: Re: Quad 837 Grounded Grid linear amplifier References: <1127148433.642315.146000@g49g2000cwa.googlegroups.com> <11iu9rupmu2u9fb@corp.supernews.com> Message-ID: Date: Tue, 20 Sep 2005 17:59:48 -0400 > > Specifically, I'd like to know if our amp was built to a published design > and/or follows a published chassis layout. Does anyone have the '57 > handbook, > QST article or version of the SSB manual handy? I have a copy of the '57 HB, but I'm not sure if I can scan it due to software problems. If I get my flatbed scanner working I'd be happy to make a copy available. Or, I could just photo copy it and snail mail it to you. Article: 94427 of rec.radio.amateur.homebrew From: Spike Subject: Re: Recommended reading for _REAL_ Radio Hams Date: Wed, 21 Sep 2005 00:21:15 +0100 Message-ID: References: <1126951418.730335.258350@g14g2000cwa.googlegroups.com> <432befc1$1_4@mk-nntp-2.news.uk.tiscali.com> <1126956334.407558.33070@g14g2000cwa.googlegroups.com> <9_VWe.422$bR.1@newsfe7-win.ntli.net> Brian Reay wrote: >I have to agree Frank, the fundamental reason why a wire has inductance is a >very basic fact, I believe taught at KS3 science. Let's hope that any 'colloquialisms' or 'idiomatic expressions' are suitably flagged, as some people appear to believe that such statements count as fundamental science and carry on into a form of adulthood still using them but without any further thought. >Makes you wonder about degrees from the UoE, does it not? I believe it was claimed to be 'avant-garde' at the time - possibly the sort of environment where lecturers sent off the students to research things for themselves, after giving a few pointers, rather than just writing it all on the board. Some can cope with this, and some can't.....rather in the manner of those who must wait for the outcome of an inquiry to tell them what officially happened, rather than working out the various scenaria for themselves. from Aero Spike Article: 94428 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: The Perfect Ham Store? Date: Tue, 20 Sep 2005 17:06:16 -0700 Message-ID: <11j18vsp8gfsc96@corp.supernews.com> References: <1125008389.118793.289820@g14g2000cwa.googlegroups.com> <1125335627.933550.94170@g47g2000cwa.googlegroups.com> <1125353081.965959.186860@f14g2000cwb.googlegroups.com> <11iuuj1b9ob25a1@corp.supernews.com> <27WXe.15544$mH.850@fed1read07> Caveat Lector wrote: > Gotta remember - Hams are cheap -- they visit the local store -- try out the > gear - ask a zillion questions, then go away and mail order off the web to > save a measly dollar or two. Then they go back to the local store and ask > them to help program the unit. > > I had a Ham offer me $7 for a $25 book, I replied -- which Chapter do you > want (;-) Years ago, I was in the last real radio store in Portland. They were on their last legs, and that's just what the owner told me -- people would come in, get demos of all the units, try them out, then go home and mail order one. I did, by the way, buy the radio he took so much time to demonstrate and explain. But the store was out of business shortly thereafter. We get what we collectively deserve. You want low prices, you get low prices. Hello, Wal-Mart; goodbye, service. The modest success of EZNEC, however, does give me hope. Roy Lewallen, W7EL Article: 94429 of rec.radio.amateur.homebrew From: "Nick Kennedy" References: Subject: Re: transformer basic question Message-ID: Date: Tue, 20 Sep 2005 21:43:30 -0500 wrote in message news:ej6ri154ombo5lcsgjhfcp16spjimj8cb8@4ax.com... > Is the value of a capacitor placed in series with the secondary of a > transformer multiplied (as viewed from the primary) by the turns ratio > or the square of the turns ratio? > > Thanks, > > T Since I just started playing with the LMS impedance bridge featured in this months QST (and the current QEX), I thought it would be interesting to try to answer this one by experiment. I have an old audio matching transformer labeled to transform 20 ohms to 8 ohms, a 2.5 ratio. I took a 10 uF capacitor and measured it at 9 uF, with Z of 14.43/_ -85 degrees at a measurement frequency of 1225 Hz. Hooked it to the low resistance side of the transformer and the meter to the high side. The reading obtained was 1.99 uF or Z = 74.4/_ -62 degrees. So I got a transformation ratio of 4.5 or 5 in terms of capacitance or impedance, instead of the expected 2.5. Now, how far is the transformer from ideal? Measuring its high side inductance with the low side open, I get 10.1 mH. This is the magnetizing inductance of the transformer, which appears in parallel with the transformed capacitive reactance. In a transformer that approaches ideal, the inductance is large enough to have a very large reactance compared to the transformed load from the secondary. In this case it's only sort of negligible. The transformed capacitance of 9/2.5 uF = 3.6 uF has a reactance of -j36.1 ohms. The reactance of the transformer's magnetizing inductance is j77.7 ohms. Combining the two in parallel gives a resultant capacitive reactance of -j67.11. And this is equivalent to 1.94 uF at my measurement frequency. Not too far from the measured value of 1.99 uF. I did neglect leakage inductance, assuming that it would be pretty small for this type of transformer. Another interesting point to note is that the unadorned capacitor had a phase angle of 85 degrees, but the transformed version showed 62 degrees. The equivalent loss resistance of the transformer decreased the quality a fair amount, as one would expect I guess. So I guess the answer to your question is yes, it will be transformed just like a resistive load would be, providing the transformed capacitive reactance is fairly small with respect to the magnetizing reactance of the transformer. 73--Nick, WA5BDU Article: 94430 of rec.radio.amateur.homebrew Date: Tue, 20 Sep 2005 23:37:36 -0400 From: Bill Subject: Re: Building the Ed Romney Handbook regen References: <1127270041.376855.205770@z14g2000cwz.googlegroups.com> Message-ID: <15467$4330d583$4232bd2f$11545@COQUI.NET> Bret Ludwig wrote: > I bought a pile of books recently and among them was the Ed Romney > "Fixing Up Nice Old Radios" book which you may be familiar with. For > those not familiar he reprints the ARRL Handbook two-tube regen set > which uses plug in coils. There is choke coupling to the audio amp with > a 750 Henry choke. > > > I suppose I could get Sowter or Jensen to wind one, but is there an > off the shelf part that will sub for this unobtainable little bugger? > I don't have that book but you can use the winding of an old audio interstage xfmr in most of the ckts where such a choke is called for. That will be in the 10-30 H range and should work just fine. I've had good luck even using the little 200mw $1.99 transistor interstage xfmrs >from Mouser. Don't know how many henries they represent but compared to the coil+resistance in a set of old 1920s phones that served exactly the same function in similar ckts it seems roughly equivalent....on the order of 3-10 H wouldn't be atypical according to the measurements one fellow made. The National SW-3 uses such a 750H choke and you can also find one of several hundred Henries in the old BC-221 freq meters. The audio will be down only slightly using a smaller value but quite honestly I don't see why they used such high values. -Bill Article: 94431 of rec.radio.amateur.homebrew From: "jm" References: <1125008389.118793.289820@g14g2000cwa.googlegroups.com> <1125335627.933550.94170@g47g2000cwa.googlegroups.com> <1125353081.965959.186860@f14g2000cwb.googlegroups.com> <11iuuj1b9ob25a1@corp.supernews.com> <27WXe.15544$mH.850@fed1read07> <11j18vsp8gfsc96@corp.supernews.com> Subject: Re: The Perfect Ham Store? Message-ID: Date: Tue, 20 Sep 2005 23:54:55 -0400 "Roy Lewallen" wrote in message news:11j18vsp8gfsc96@corp.supernews.com... > Caveat Lector wrote: >> Gotta remember - Hams are cheap -- they visit the local store -- try out >> the gear - ask a zillion questions, then go away and mail order off the >> web to save a measly dollar or two. Then they go back to the local store >> and ask them to help program the unit. >> >> I had a Ham offer me $7 for a $25 book, I replied -- which Chapter do you >> want (;-) > > Years ago, I was in the last real radio store in Portland. They were on > their last legs, and that's just what the owner told me -- people would > come in, get demos of all the units, try them out, then go home and mail > order one. I did, by the way, buy the radio he took so much time to > demonstrate and explain. But the store was out of business shortly > thereafter. > > We get what we collectively deserve. You want low prices, you get low > prices. Hello, Wal-Mart; goodbye, service. The modest success of EZNEC, > however, does give me hope. > > Roy Lewallen, W7EL Not "all" hams are like that. I for one am not. But, I DO have a friend who is "cheap" and it sometimes embarrasses me to be with him when he tries to deal. "I" try to meet the person's price - if in reason and if I do need the item. IF not in reason, then I shop around - which is my option to do. What I WON'T do - is embarass them or make a smart ass remark about their price - I'll merely walk away. The only time I've ever retorted to anyone selling something was when they tried to get "new" price out of it, stated it was brand new in the box - when my eyes spotted a "modification" which wasn't done by the factory - and called them on it. Liars piss me off. jm Article: 94432 of rec.radio.amateur.homebrew From: fmmck@aol.com (Fred McKenzie) Subject: Ratcheting Crimp Tool Question Date: Wed, 21 Sep 2005 01:32:56 -0400 Message-ID: In my collection of crimp tools I have an Aim tool with a die for RG-58 BNC connectors, the new West Mountain Radio tool with a die for PowerPole connectors and a Tool Aid set with 5 dies for various insulated and uninsulated terminals. I've noticed that the dies for these tools all look somewhat alike with respect to the way they are mounted to their frames. The dies look as if they would fit all three frames. If the mounting method and dimensions are the same, is there any reason not to use a die with a different frame? Does anyone know of a cross reference of commonly available crimp tools that lists which dies are interchangeable with which frames? 73, Fred, K4DII Article: 94433 of rec.radio.amateur.homebrew From: "Brian Reay" References: <1126951418.730335.258350@g14g2000cwa.googlegroups.com> <432befc1$1_4@mk-nntp-2.news.uk.tiscali.com> <1126956334.407558.33070@g14g2000cwa.googlegroups.com> <9_VWe.422$bR.1@newsfe7-win.ntli.net> Subject: Re: Recommended reading for _REAL_ Radio Hams Message-ID: Date: Wed, 21 Sep 2005 06:03:21 GMT "Spike" wrote in message news:ra61j15181s4g2kmqna9f5ch5sli8jtj7g@4ax.com... Welcome back Spike. > Brian Reay wrote: > >>I have to agree Frank, the fundamental reason why a wire has inductance is >>a >>very basic fact, I believe taught at KS3 science. > > Let's hope that any 'colloquialisms' or 'idiomatic expressions' are > suitably flagged, as some people appear to believe that such > statements count as fundamental science and carry on into a form of > adulthood still using them but without any further thought. Don't worry, kind hearted employers can always recommend a good book ;-) >>Makes you wonder about degrees from the UoE, does it not? > > I believe it was claimed to be 'avant-garde' at the time - possibly > the sort of environment where lecturers sent off the students to > research things for themselves, And someone swapped the signs on the bar and the library as an initiative test? -- 73 Brian, G8OSN www.g8osn.org.uk Article: 94434 of rec.radio.amateur.homebrew Message-ID: <4330F81B.24264A1C@rickfrazier.com> From: Rick Frazier Subject: Re: Ratcheting Crimp Tool Question References: Date: Wed, 21 Sep 2005 06:04:43 GMT Fred: As long as you can determine the closure distance is the same, and the geometry is the same (primarily the way the crimp tool handles the pivot for the jaws), you should be ok. However, if the mounting is only "similar" be very careful of the two things: 1) the width of the crimp tool in regard to the slot in the die. If the slot in the die isn't the same width, it could be mis-registered and cause problems closing. 2) (and most important) be particularly careful that the closure is the same as the original crimp tool. Even a few thousandths of an inch makes a tremendous difference in whether a crimp is performed correctly, too loose (the dies do not close fully and the connection is not crimped with sufficient pressure to make the proper contact) or too tight (the die over-travels relative to the intended distance, which could damage the conductor or terminal used, even to the point where the termination is significantly weaker than intended). Some crimp tools are adjustable to account for potential wear, and I've seen many a crimped connection that failed from improper setting of the tool, either too loose, which typically causes the joint to fail due to heat, etc., or too tight, which typically over crushes the conductor, making the termination break off at the shoulder of the crimp, or actually fracture the terminal material, causing it to fail and drop off under physical stress. Either way, the connection failed and caused problems later on. This is a particularly bad problem if the crimp is covered with heat shrink, as it "looks ok" until you put it under stress, either electrical or physical... Good Luck --Rick AH7H Fred McKenzie wrote: > In my collection of crimp tools I have an Aim tool with a die for RG-58 > BNC connectors, the new West Mountain Radio tool with a die for PowerPole > connectors and a Tool Aid set with 5 dies for various insulated and > uninsulated terminals. I've noticed that the dies for these tools all > look somewhat alike with respect to the way they are mounted to their > frames. The dies look as if they would fit all three frames. > > If the mounting method and dimensions are the same, is there any reason > not to use a die with a different frame? > > Does anyone know of a cross reference of commonly available crimp tools > that lists which dies are interchangeable with which frames? > > 73, Fred, K4DII Article: 94435 of rec.radio.amateur.homebrew From: David Subject: Low power homebrew test equipment Message-ID: Date: Wed, 21 Sep 2005 10:31:53 GMT Does anyone know where I could get details for making the following items. The problem with books I have and ideas on the web are they seem to require much higher power levels and work at lower frequencies. I typically want to test antennas and other equipment at 434MHz and 915MHz with power levels of 20mW. 1. Some sort of high impedance preamp to put in front of a Frequency counter and probe RF circuits. 2. High impedance RF millivolt meter 3. SWR meter for forward and reverse readings. 4. Directional coupler. 5. Sinad Meter Thanks in advance for any info. Regards David Article: 94436 of rec.radio.amateur.homebrew From: Dr. Anton T. Squeegee Subject: Re: OT: Motorola R2001x Date: Wed, 21 Sep 2005 06:20:00 -0700 Message-ID: References: In article , 9a3li_makni_@hamradio.hr says... > Hello! > > Im looking for anyone who have experience in reparing old > Motorola R2001(2)x test-set. You should post that same question on http://batboard.batlabs.com. One of the members works for Motorola's test equipment repair division. Happy hunting. -- Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute. (Known to some as Bruce Lane, ARS KC7GR, kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com "If Salvador Dali had owned a computer, would it have been equipped with surreal ports?" Article: 94437 of rec.radio.amateur.homebrew From: "jm" References: Subject: Re: OT: Motorola R2001x Message-ID: Date: Wed, 21 Sep 2005 10:26:26 -0400 "Dr. Anton T. Squeegee" wrote in message news:MPG.1d9a619c530e24df9896a5@192.168.42.131... > In article , 9a3li_makni_@hamradio.hr > says... > >> Hello! >> >> Im looking for anyone who have experience in reparing old >> Motorola R2001(2)x test-set. > > You should post that same question on http://batboard.batlabs.com. > One of the members works for Motorola's test equipment repair division. > > Happy hunting. > > > -- > Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute. > (Known to some as Bruce Lane, ARS KC7GR, > kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com > "If Salvador Dali had owned a computer, would it have been equipped > with surreal ports?" I'm not so sure that "Motorola" is doing tech support on that era of equipment anymore. There are a few places - very few - that do offer Service Monitor repair and recalibration. One such place is Cardinal Electronics Inc. WWW.CARDINALELEC.COM Another is NS Electronics Service, Inc. WWW.NSELECTRONICS.COM I can't speak for either except to say I bought one that was just calibrated a week or two prior to my purchase - by Cardinal. It seems to be ok! Article: 94438 of rec.radio.amateur.homebrew Date: Wed, 21 Sep 2005 15:54:15 -0400 From: Bill Subject: Re: Building the Ed Romney Handbook regen References: <1127270041.376855.205770@z14g2000cwz.googlegroups.com> <15467$4330d583$4232bd2f$11545@COQUI.NET> <1127327300.845169.219520@f14g2000cwb.googlegroups.com> Message-ID: Bret Ludwig wrote: > > The other question I have is, what relatively common miniature tubes > would be good to sub for the 5 and 6 pin ones in this circuit? I don't know that particular ckt, what tubes is it using? Can you post the schematic or is it on the web somewhere? -Bill Article: 94439 of rec.radio.amateur.homebrew From: "Jeff" Subject: Buffer Amp IC suggestions plse Message-ID: Date: Thu, 22 Sep 2005 09:14:55 +1200 Hi, Ive been trying to locate a suitable unity gain buffer amplifier IC that can drive a 50 load. Application is to buffer a VCO output at 5Mhz. Needs to be 8pin DIP and operate on a single-ended supply. I had found what I wanted in the CLC109, but cant seem to find a supplier. Any suggestions greatly appreciated regarding type and supplier that is user friendly to international countries. JEFF ZL3JK New Zealand Article: 94440 of rec.radio.amateur.homebrew From: Winfield Hill Subject: Re: Buffer Amp IC suggestions plse Date: 21 Sep 2005 15:25:09 -0700 Message-ID: References: Jeff wrote... > > Ive been trying to locate a suitable unity gain buffer amplifier > IC that can drive a 50 load. > Application is to buffer a VCO output at 5Mhz. > Needs to be 8pin DIP LTC's LT1206 comes in TO220, miniDIP and soic packages, and Digi-Key has them in stock for $6.25 each... http://rocky.digikey.com/WebLib/Linear%20Tech/Web%20Data/LT1206.pdf http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=329191 > and operate on a single-ended supply. Oops, +/-5V supply. What's your signal voltage? And did you want your output to have a 50-ohm source impedance? -- Thanks, - Win Article: 94441 of rec.radio.amateur.homebrew From: "Jeff" References: Subject: Re: Buffer Amp IC suggestions plse Message-ID: Date: Thu, 22 Sep 2005 10:56:26 +1200 Needs to drive into 50 ohms. input level approx 150mV at 5Mhz "Winfield Hill" wrote in message news:dgsmk501sr9@drn.newsguy.com... > Jeff wrote... > > > > Ive been trying to locate a suitable unity gain buffer amplifier > > IC that can drive a 50 load. > > Application is to buffer a VCO output at 5Mhz. > > Needs to be 8pin DIP > > LTC's LT1206 comes in TO220, miniDIP and soic packages, > and Digi-Key has them in stock for $6.25 each... > http://rocky.digikey.com/WebLib/Linear%20Tech/Web%20Data/LT1206.pdf > http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=329191 > > > and operate on a single-ended supply. > > Oops, +/-5V supply. What's your signal voltage? And did > you want your output to have a 50-ohm source impedance? > > > > > -- > Thanks, > - Win Article: 94442 of rec.radio.amateur.homebrew From: Spike Subject: Re: Recommended reading for _REAL_ Radio Hams Date: Wed, 21 Sep 2005 23:58:44 +0100 Message-ID: References: <1126951418.730335.258350@g14g2000cwa.googlegroups.com> <432befc1$1_4@mk-nntp-2.news.uk.tiscali.com> <1126956334.407558.33070@g14g2000cwa.googlegroups.com> <9_VWe.422$bR.1@newsfe7-win.ntli.net> Brian Reay wrote: >"Spike" wrote > >Welcome back Spike. Thanks! It was a bit tedious wading through ~2300 ukra postings...... >> Brian Reay wrote: > >Don't worry, kind hearted employers can always recommend a good book ;-) ROFL! >>>Makes you wonder about degrees from the UoE, does it not? >> >> I believe it was claimed to be 'avant-garde' at the time - possibly >> the sort of environment where lecturers sent off the students to >> research things for themselves, > >And someone swapped the signs on the bar and the library as an initiative >test? ooooh.....you are awful......;-) from Aero Spike Article: 94443 of rec.radio.amateur.homebrew From: David Subject: Re: Low power homebrew test equipment References: <1127325493.734844.4080@g49g2000cwa.googlegroups.com> Message-ID: Date: Wed, 21 Sep 2005 23:04:09 GMT Tom, Thanks for the information. I'll take a look at the coupler design in RFsim99. The RF voltage probe and amp are not for the output of the transmitter they are for "looking" at oscillators. I have a frequency counter that goes to 2.5GHz but need to buffer the oscillator so as not to load it down while probing. For lower frequency projects (VHF), I have a Tek 300MHz scope but the probes interfere with the circuits when I try to "see" the waveform of the oscillator. Thanks. > If you have a directional coupler, you are most of the way to an SWR > meter... > > Especially if you are willing to make directional couplers for specific > narrow bands (say 10% or 20% bandwidth), it's pretty easy to do. If > you get the freeware "RFSim99" software, you'll find in it a tool to > design several different types of couplers. One thing they don't make > clear is that the coupling for the microstrip and stripline versions is > for a structure 1/4 wave long. The coupling decreases as the frequency > goes up or down from that length. It's certainly useable at half the > design frequency, and in fact you can find articles on the web about > how the coupling varies with frequency, and for structures that give > broader bandwidth. If you only care about ratios (e.g. for SWR > calculation), then the exact coupling doesn't matter anyway. For your > application, at only 20mW, you'll want fairly high coupling. 20dB > coupling would give you 100mV out to a 50 ohm load, for 20mW in. > > I've seen articles in "Wireless World" for amplified RF probes. But a > simple diode detector probe feeding a high impedance voltmeter will be > a high impedance load to the circuit you are probing, so long as the > diode has low capacitance. You should be able to find Schottky diodes > that have 0.5pF capacitance at very low junction reverse voltage, I > think, though they are likely to be pretty delicate. (Don't zap them > with static!) With a high-resolution DVM to monitor the output, or > with a DC preamp that has high input impedance and extremely low input > offset voltage (such as the Harris chopper-stabilized CMOS part), you > can see RF voltages down to below a millivolt fairly easily. You need > to calibrate the amplitude response, however, and it drifts some with > temperature. With a buffer amplifier, you could use one of the RF > power monitor ICs from vendors like Analog Devices or Linear Technology > and have more stable calibration, reading "linearly in dB". An > advantage of diode detection is that it's very cheap, and you can > afford to put detectors on your directional coupler outputs and just > leave them there--plus they don't require power supplies. That 20dB > coupler with diode detectors and high resolution metering would allow > you to still "see" the reverse-port coupled power down 40dB below 20mW > input with good diode detectors, and it's very unlikely you'll be able > to make the coupler with such good directionality anyway. > > If you don't already have them, you should add "step attenuators" to > your list of equipment. It can be useful for a lot of things. You may > be able to pick up a pair of 1dB step and 10dB step attenuators from > some place like ebay, maybe even at a reasonable price. > > Are you going to be making so many measurements that you need a SINAD > meter?? Do you have an RF generator with calibrated output? > > Lessee...20mW at 50 ohms is just about 1 Vrms. For that much power, > you need sensitive amplifiers and high impedances?? If you really do > need that for probing, you'll need an amplifier at the probe tip. 1pF > at 1GHz is about 160 ohms reactance. But for that very reason, 1GHz > circuits are designed at low impedances, and you shouldn't need a > particularly high impedance to probe for frequencies, at least. > > Cheers, > Tom > Article: 94444 of rec.radio.amateur.homebrew From: "Heytubeguy" Subject: WTB: Heathkit Circular Dial Message-ID: Date: Wed, 21 Sep 2005 23:14:25 GMT Seeking Heathkit VFO circular dial for a cracked one in a SB-401. State price shipped, tnx Joe Article: 94445 of rec.radio.amateur.homebrew From: Chris I Townsend Subject: www.ukradioamateur Date: Thu, 22 Sep 2005 01:38:54 +0100 Message-ID: Hi, Some of you, hopefully many of you, may be aware of the existence of the "Amateur Radio Course" project which provides a number on-line and downloadable tutorials for the various UK amateur radio examinations. Due to the sudden, unexpected and unexplained withdrawal of support by the company who up to now have very kindly hosted our web-site free of charge, and their even more unexpected failure to communicate with me regarding how we might transfer or redirect the URL which they registered for us but now will not let us use, our site is no longer available to the clubs and individuals who benefited from it. Can you therefore help us and please publicise as widely as possible the following information. The "Amateur Radio Course" which was located at www.ukradioamateur.org is now relocated at www.radioamateur.co.uk There may be a number of functions that are not working due to the sudden move, but they will be fixed within the next few days. It remains, as always, a non-profit making activity sponsored and supported entirely by the group of individuals who give up their time and resources free of charge to support and promote interest in the hobby. I apologise for posting this message in so many newsgroups, but I need the new URL to be publicised as rapidly as possible. Many thanks to you for your help, best wishes and 73's Chris G8PUT -- Chris I Townsend (chris@cbnr.net) Article: 94446 of rec.radio.amateur.homebrew From: Winfield Hill Subject: Re: Buffer Amp IC suggestions plse Date: 21 Sep 2005 17:37:28 -0700 Message-ID: References: Jeff wrote... > > Needs to drive into 50 ohms. input level approx 150mV at 5Mhz > > Winfield Hill wrote ... >> Jeff wrote... >>> >>> Ive been trying to locate a suitable unity gain buffer amplifier >>> IC that can drive a 50 load. >>> Application is to buffer a VCO output at 5Mhz. >>> Needs to be 8pin DIP >> >> LTC's LT1206 comes in TO220, miniDIP and soic packages, >> and Digi-Key has them in stock for $6.25 each... >> http://rocky.digikey.com/WebLib/Linear%20Tech/Web%20Data/LT1206.pdf >> http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=329191 >> >>> and operate on a single-ended supply. >> >> Oops, +/-5V supply. What's your signal voltage? And did >> you want your output to have a 50-ohm source impedance? Unless you source with 50 ohms (2x signal plus 50-ohm resistor), and terminate with 50-ohms, the issue becomes how much cable capacitance? Either the load looks resistive (100 ohms in the former case) or capacitive. -- Thanks, - Win Article: 94447 of rec.radio.amateur.homebrew From: Chris I Townsend Subject: www.ukradioamateur 2 Date: Thu, 22 Sep 2005 02:00:35 +0100 Message-ID: Hi, 2nd post, the first contained an error, the new address should have been given as www.ukradioamateur.co.uk Some of you, hopefully many of you, may be aware of the existence of the "Amateur Radio Course" project which provides a number on-line and downloadable tutorials for the various UK amateur radio examinations. Due to the sudden, unexpected and unexplained withdrawal of support by the company who up to now have very kindly hosted our web-site free of charge, and their even more unexpected failure to communicate with me regarding how we might transfer or redirect the URL which they registered for us but now will not let us use, our site is no longer available to the clubs and individuals who benefited from it. Can you therefore help us and please publicise as widely as possible the following information. The "Amateur Radio Course" which was located at www.ukradioamateur.org is now relocated at www.ukradioamateur.co.uk There may be a number of functions that are not working due to the sudden move, but they will be fixed within the next few days. It remains, as always, a non-profit making activity sponsored and supported entirely by the group of individuals who give up their time and resources free of charge to support and promote interest in the hobby. I apologise for posting this message in so many newsgroups, but I need the new URL to be publicised as rapidly as possible. Many thanks to you for your help, best wishes and 73's Chris G8PUT -- Chris I Townsend (chris@cbnr.net) Article: 94448 of rec.radio.amateur.homebrew From: "Jeff" References: Subject: Re: Buffer Amp IC suggestions plse Message-ID: Date: Thu, 22 Sep 2005 14:03:51 +1200 Thanks. The AD817 looks good, and I can source it locally from Australia. Thanks all for your help. JEFF "John Popelish" wrote in message news:CYedna5XIIWNdKzeRVn-rA@adelphia.com... > Jeff wrote: > > Hi, > > Ive been trying to locate a suitable unity gain buffer amplifier IC that can > > drive a 50 load. > > Application is to buffer a VCO output at 5Mhz. > > Needs to be 8pin DIP and operate on a single-ended supply. > > I had found what I wanted in the CLC109, but cant seem to find a supplier. > > Any suggestions greatly appreciated regarding type and supplier that is user > > friendly to international countries. > > JEFF > > ZL3JK > > New Zealand > > > > > An AD817 can deliver +-50 mA and has a gain bandwidth product of 50 MHz. > http://www.analog.com/UploadedFiles/Data_Sheets/289066266ad817.pdf > <4$ from Digikey. > Good for either a gain 1 buffer or a gain 2 with series 50 ohm > resistor, 50 ohm source. Article: 94449 of rec.radio.amateur.homebrew From: fmmck@aol.com (Fred McKenzie) Subject: Re: Ratcheting Crimp Tool Question Date: Wed, 21 Sep 2005 22:47:57 -0400 Message-ID: References: <4330F81B.24264A1C@rickfrazier.com> In article <4330F81B.24264A1C@rickfrazier.com>, Rick Frazier wrote: > As long as you can determine the closure distance is the same, and the > geometry is the same (primarily the way the crimp tool handles the pivot for > the jaws), you should be ok. However, if the mounting is only "similar" be > very careful of the two things: > 1) the width of the crimp tool in regard to the slot in the die. If the slot > in the die isn't the same width, it could be mis-registered and cause > problems closing. > 2) (and most important) be particularly careful that the closure is the same > as the original crimp tool. Rick- Thanks for the pointers. I suppose it is common sense, but I wouldn't have thought about the jaw pivot arrangement making a difference. Today I found an Ideal Industries "Crimp Master" tool with a die for cable TV connectors, in a local store. That makes 4 tools for comparison. Based on your comments, I found that the Tool Aid crimper and the Ideal Crimp Master appear to have compatible dies. The Aim has a smaller die slot width. The West Mountain Radio crimp tool for PowerPole connectors has a similar size die, but the jaw arrangement is different from the others. I tried a couple of the Tool Aid dies in the Crimp Master frame and produced similar crimps with similar pressure compared to using the Tool Aid frame. My next step is to try interchanging dies with a different tool a friend has. Between us, we hope to find what kinds of dies are compatible with our frames. 73, Fred, K4DII Article: 94450 of rec.radio.amateur.homebrew From: fmmck@aol.com (Fred McKenzie) Subject: Re: Problem of nearby transmitter breakthrough Date: Wed, 21 Sep 2005 23:19:13 -0400 Message-ID: References: In article , "Bob Chilcoat" wrote: > Unfortunately, while this setup worked perfectly at home well away from the > airport, we have an Automatic Weather Observation Station (AWOS) > transmitting continuously on 120.60 MHz only 50-60 feet from the place I > need to site the receiver. Even though this is only a 5 Watt transmitter, > it overloads the front end of the receiver. As soon as anyone keys on > 123.00 and the automatic squelch is triggered, all you hear is the AWOS > recording. Bob- By now you have probably solved your problem. If not, someone else suggested that you insert attenuation in the Sony's antenna lead. I think that approach is most likely to produce the results you want. If you were to replace the Sony's antenna with a dummy load, there may still be sufficient signal bleeding into the radio to make your system work. The interfering signal would also bleed into the radio, but at such a low level that the Sony's tuned circuits ought to be able to handle it. If even this does not solve the interference, you may find the problem to be audio rectification inside the 88.1 equipment, perhaps in the oscillator stage! Please keep us informed of what it takes to make it work. 73, Fred, K4DII Article: 94451 of rec.radio.amateur.homebrew From: Mac Subject: Re: Buffer Amp IC suggestions plse Message-ID: References: Date: Thu, 22 Sep 2005 05:00:54 GMT On Thu, 22 Sep 2005 09:14:55 +1200, Jeff wrote: > Hi, > Ive been trying to locate a suitable unity gain buffer amplifier IC that can > drive a 50 load. > Application is to buffer a VCO output at 5Mhz. > Needs to be 8pin DIP and operate on a single-ended supply. > I had found what I wanted in the CLC109, but cant seem to find a supplier. > Any suggestions greatly appreciated regarding type and supplier that is user > friendly to international countries. > JEFF > ZL3JK > New Zealand What you want is a video buffer or video op-amp. Linear Technologies, National Semiconductor, and Analog Devices are among the many companies that make such things. Note that some of these devices get a bit squirrelly if they see a capacitive load. So I recommend that you do something like this: (use courier or other constant-width font for ASCII art schematic) |\ 50 in--|+\__+____/\/\____/> to 50 Ohm load +--|-/ | | |/ | | | +--/\/\-+ | Rf \ /Ra \ / | ----- GND Rf and Ra would be the same value. Use a value recommended by the datasheet, or 1k if the datasheet doesn't recommend a specific value. Follow any other suggestions in the datasheet as well. For example, they may suggest a small capacitor directly from the op-amp output to inverting input. You probably want to terminate the input with a 50 Ohm resistor, too, but I don't know, so I'll leave it out. It sounds like you may need AC-coupling, so you can put blocking capacitors on the input and/or output. Oh, if you put a blocking cap on the input, be sure to also provide a DC (resistive) path to GND or to the mid-rail point if you are going single-supply. Just chose a capacitor big enough so that 1/(2*pi*R*C) is much lower than 5 MHz, your signal of interest. (R in this case is 50 Ohms) There is no problem putting a capacitor like this in the signal path: Since it looks like a short circuit at higher frequencies, it does not capacitively load the amp at frequencies where the amp might be unstable. Also, the series 50 Ohm resistor keeps the overall impedance resistive. HTH --Mac Article: 94452 of rec.radio.amateur.homebrew From: Mac Subject: Re: Buffer Amp IC suggestions plse Message-ID: References: Date: Thu, 22 Sep 2005 05:27:20 GMT On Wed, 21 Sep 2005 15:25:09 -0700, Winfield Hill wrote: > Jeff wrote... >> >> Ive been trying to locate a suitable unity gain buffer amplifier >> IC that can drive a 50 load. >> Application is to buffer a VCO output at 5Mhz. >> Needs to be 8pin DIP > > LTC's LT1206 comes in TO220, miniDIP and soic packages, > and Digi-Key has them in stock for $6.25 each... > http://rocky.digikey.com/WebLib/Linear%20Tech/Web%20Data/LT1206.pdf > http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=329191 > >> and operate on a single-ended supply. > > Oops, +/-5V supply. What's your signal voltage? And did > you want your output to have a 50-ohm source impedance? Maybe an LT1191? digikey #: LT1191CN8-ND (24 in stock at USD 3.25) http://rocky.digikey.com/WebLib/Linear%20Tech/Web%20Data/LT1191.pdf --Mac Article: 94453 of rec.radio.amateur.homebrew From: Winfield Hill Subject: Re: Buffer Amp IC suggestions plse Date: 22 Sep 2005 04:49:14 -0700 Message-ID: References: Mac wrote... > > Maybe an LT1191? digikey #: LT1191CN8-ND (24 in stock at USD 3.25) > http://rocky.digikey.com/WebLib/Linear%20Tech/Web%20Data/LT1191.pdf Ouch, a 30mA supply current! -- Thanks, - Win Article: 94454 of rec.radio.amateur.homebrew Message-ID: <4332C4B5.3010001@nospam.com> From: Fred Bloggs Subject: Re: Buffer Amp IC suggestions plse References: Date: Thu, 22 Sep 2005 14:50:33 GMT Winfield Hill wrote: > Mac wrote... > >>Maybe an LT1191? digikey #: LT1191CN8-ND (24 in stock at USD 3.25) >>http://rocky.digikey.com/WebLib/Linear%20Tech/Web%20Data/LT1191.pdf > > > Ouch, a 30mA supply current! > > Well- why not your super-duper 74HCU04 linear amp or whatever it was?- is that available in Tiny Logic? Article: 94455 of rec.radio.amateur.homebrew From: "Jeff" References: Subject: Re: Buffer Amp IC suggestions plse Message-ID: Date: Fri, 23 Sep 2005 08:32:12 +1200 Thanks for those ideas. I was considering putting a low pass filter after the amp. The 2 shunt caps work out to be 560pF each. JEFF "Mac" wrote in message news:pan.2005.09.22.04.44.20.615469@bar.net... > On Thu, 22 Sep 2005 09:14:55 +1200, Jeff wrote: > > > Hi, > > Ive been trying to locate a suitable unity gain buffer amplifier IC that can > > drive a 50 load. > > Application is to buffer a VCO output at 5Mhz. > > Needs to be 8pin DIP and operate on a single-ended supply. > > I had found what I wanted in the CLC109, but cant seem to find a supplier. > > Any suggestions greatly appreciated regarding type and supplier that is user > > friendly to international countries. > > JEFF > > ZL3JK > > New Zealand > > What you want is a video buffer or video op-amp. Linear Technologies, > National Semiconductor, and Analog Devices are among the many companies > that make such things. > > Note that some of these devices get a bit squirrelly if they see a > capacitive load. So I recommend that you do something like this: (use > courier or other constant-width font for ASCII art schematic) > > > > |\ 50 > in--|+\__+____/\/\____/> to 50 Ohm load > +--|-/ | > | |/ | > | | > +--/\/\-+ > | Rf > \ > /Ra > \ > / > | > ----- > GND > > Rf and Ra would be the same value. Use a value recommended by the > datasheet, or 1k if the datasheet doesn't recommend a specific value. > Follow any other suggestions in the datasheet as well. For example, they > may suggest a small capacitor directly from the op-amp output to inverting > input. > > You probably want to terminate the input with a 50 Ohm resistor, too, but > I don't know, so I'll leave it out. > > It sounds like you may need AC-coupling, so you can put blocking > capacitors on the input and/or output. Oh, if you put a blocking cap on > the input, be sure to also provide a DC (resistive) path to GND or to the > mid-rail point if you are going single-supply. > > Just chose a capacitor big enough so that 1/(2*pi*R*C) is much lower than > 5 MHz, your signal of interest. (R in this case is 50 Ohms) There is no > problem putting a capacitor like this in the signal path: Since it looks > like a short circuit at higher frequencies, it does not capacitively load > the amp at frequencies where the amp might be unstable. Also, the series > 50 Ohm resistor keeps the overall impedance resistive. > > HTH > > --Mac > Article: 94456 of rec.radio.amateur.homebrew From: "Bob Chilcoat" References: Subject: Re: Problem of nearby transmitter breakthrough - Solved! Message-ID: <5WEYe.964$dl2.773@fe08.lga> Date: Thu, 22 Sep 2005 16:58:45 -0400 All, Thanks for all the suggestions, advice and information. I learned a lot about VHF that I didn't know. Should have stayed with it way back when I almost finished my "Novice" amateur license (couldn't manage the Morse code part -- I guess that gives away my age). Fred nailed it, although by the time I saw his note, I'd solved the problem. After relocating the receiver as far away as I could (60 feet, given the limitation of where the units needed to be and sources of power) which didn't really help, I tried some simple filters, etc. During the course of this, someone keyed a mike while I had the antenna disconnected, and it worked fine with no antenna connected! A bit more experimentation indicated that the 120.6 interference dropped out completely while the desired 123 signal could still be picked up from five miles away if I left the short coax jumper inside the box from the receiver to the antenna disconnected at the antenna end. I'm not sure I fully understand why I still get a pretty robust signal this way, but I guess enough 123 MHz RF is leaking in from the bare antenna or all the other wiring. Since the radio traffic of interest is mostly local planes near the airport or in the traffic pattern, a five mile radius is probably more than adequate, and this is certainly the cheapest solution. I will also look into the regulations about rebroadcasting non-commercial radio signals. The transmitter satisfies the part 15(IIRC?) FCC reg about a 100-foot reception limit, but I thought the rules about rebroadcasting were to prevent rebroadcasting. The 100 foot limitation will keep all reception on the airport grounds, but I will do some more research on this. Thanks. As far as an area inside the building where people can listen to the radio is concerned, we already have that. This project is for the people who sit in their cars in the parking lot and watch the planes on their lunch hour, etc. We get quite a few of these. Anything that improves relations with the general public should help alleviate some of the problems we have with the neighbors. I still can't understand how anyone can buy a house near an airport, and then feel that they have a right to complain about airplane noise. The airport has been there since 1946, but that's another issue. Again, thanks for all the help. -- Bob (Chief Pilot, White Knuckle Airways) "Fred McKenzie" wrote in message news:fmmck-2109052319130001@ac838384.ipt.aol.com... > In article , "Bob Chilcoat" > wrote: > >> Unfortunately, while this setup worked perfectly at home well away from >> the >> airport, we have an Automatic Weather Observation Station (AWOS) >> transmitting continuously on 120.60 MHz only 50-60 feet from the place I >> need to site the receiver. Even though this is only a 5 Watt >> transmitter, >> it overloads the front end of the receiver. As soon as anyone keys on >> 123.00 and the automatic squelch is triggered, all you hear is the AWOS >> recording. > > Bob- > > By now you have probably solved your problem. If not, someone else > suggested that you insert attenuation in the Sony's antenna lead. I think > that approach is most likely to produce the results you want. > > If you were to replace the Sony's antenna with a dummy load, there may > still be sufficient signal bleeding into the radio to make your system > work. The interfering signal would also bleed into the radio, but at such > a low level that the Sony's tuned circuits ought to be able to handle it. > > If even this does not solve the interference, you may find the problem to > be audio rectification inside the 88.1 equipment, perhaps in the > oscillator stage! > > Please keep us informed of what it takes to make it work. > > 73, Fred, K4DII Article: 94457 of rec.radio.amateur.homebrew From: "Steve Nosko" Subject: Re: Problem of nearby transmitter breakthrough Date: Thu, 22 Sep 2005 15:59:52 -0500 Message-ID: References: "Bob Chilcoat" wrote in message news:wEGXe.4566$H24.1943@fe11.lga... > ... a rather old but serviceable Sony digital air band receiver > ...piped the audio out to an FM microwatt transmitter. > ... visitors ...can listen on their car radios on ...> Advisory Frequency (CTAF), which at our airport is 123.00 MHz (AM). > ...5 Watt transmitter, > it overloads the front end of the receiver. As soon as anyone keys on > 123.00 and the automatic squelch is triggered, all you hear is the AWOS > recording.> Bob (Chief Pilot, White Knuckle Airways) My turn... Lots of really good ideas here. Make sure it is the Sony antenna that is picking it up... 1- The stub-trap idea may work with some large number of odd-quarter waves. As you stack more odd multiples of quarter waves on (extend the shunt trap length), the dips get closer together and as a result the peak-to-null distance shrinks. A stub that is 21 quarter waves long has peaks and nulls very close together (you could calculate this). Of course the dips will be less deep due to cable loss. This may make it easier to get the desired "Pass / Null" response. You need to make sure the signal is getting into the antenna and not the receiver itself. The 2.4 Mc spacing is quite close. NEW IDEA: 2- Try tuning it on the image (for your 123 Unicom frequency). You will probably need to do this away from the airport . You should hear the Unicom in two places on the dial spaced _TWICE_ the IF frequency away. These radios usually have pretty wide front ends There may be a schematic inside the radio to help determine this. If the IF is 0.455, the image is 0.910 away. This radio probably uses low side injection meaning the LO is below the 123 by 0.455. Therefore you must tune the radio 0.910 HIGHER than 123. This places the on channel further away from the 120.6 AWOS. Not knowing the IF, you have to hunt. -Maybe doing this _AT_ the airport will yield a tuning that fixes it. Just try "tuning around". Related idea, you could also figure out where the RF stage stuff is in the radio and de-tune it upward to get more attenuation at 120.6, but if that works, then just some attenuation in the antenna line may work as well and be easier. 3- Put the radio FAR away, but run the audio in some small coax to the 88.1 closer to the visitors. 4- I like the "cross Polarization" idea. Do a light saber thing with the Sony antenna. There may be a sweat spot that just might get the levels down and fix the IM or whatever is going on.. Mike T. Use the airport receiver... Sounds good, but they probably don't want you messing with it.... and what about the airport's transmissions... 5- HOWEVER, how about simply a microphone right next to this receiver and within earshot of the airport's microphone---ON the 88.1 Tx ?? You may hear other stuff in the FBO, but it may be ok too... Related... I have a little thing I plug into my dual band rig speaker output and it transmits the audio to my car FM radio. They're made for listening to battery operated CD players in your car. 73, Steve, K;9.D,C'I Article: 94458 of rec.radio.amateur.homebrew From: Ross Herbert Subject: Re: Buffer Amp IC suggestions plse Message-ID: References: Date: Fri, 23 Sep 2005 10:09:10 GMT On Thu, 22 Sep 2005 09:14:55 +1200, "Jeff" wrote: >Hi, >Ive been trying to locate a suitable unity gain buffer amplifier IC that can >drive a 50 load. >Application is to buffer a VCO output at 5Mhz. >Needs to be 8pin DIP and operate on a single-ended supply. >I had found what I wanted in the CLC109, but cant seem to find a supplier. >Any suggestions greatly appreciated regarding type and supplier that is user >friendly to international countries. >JEFF >ZL3JK >New Zealand > Here's a dual op-amp in 8 pin DIP which should do what you want http://www.analog.com/UploadedFiles/Data_Sheets/242276322AD8397_0.pdf Article: 94459 of rec.radio.amateur.homebrew From: "johan aeq" References: Subject: Re: Buffer Amp IC suggestions plse Date: Fri, 23 Sep 2005 19:09:45 +0200 Message-ID: <8836e$4334383d$52ad139c$16908@news.versatel.nl> Try a SL560 "Jeff" schreef in bericht news:k3kYe.13434$iM2.1134628@news.xtra.co.nz... > Hi, > Ive been trying to locate a suitable unity gain buffer amplifier IC that can > drive a 50 load. > Application is to buffer a VCO output at 5Mhz. > Needs to be 8pin DIP and operate on a single-ended supply. > I had found what I wanted in the CLC109, but cant seem to find a supplier. > Any suggestions greatly appreciated regarding type and supplier that is user > friendly to international countries. > JEFF > ZL3JK > New Zealand > > Article: 94460 of rec.radio.amateur.homebrew From: "Reg Edwards" Subject: Re: Recommended reading for _REAL_ Radio Hams Date: Sat, 24 Sep 2005 04:44:44 +0000 (UTC) Message-ID: References: <1126951418.730335.258350@g14g2000cwa.googlegroups.com> <432befc1$1_4@mk-nntp-2.news.uk.tiscali.com> <1126956334.407558.33070@g14g2000cwa.googlegroups.com> <9_VWe.422$bR.1@newsfe7-win.ntli.net> <1126971523.139315.3360@g49g2000cwa.googlegroups.com> <432c40cd$1_2@mk-nntp-2.news.uk.tiscali.com> <1127483205.631008.176790@g43g2000cwa.googlegroups.com> <1127536110.784761.233910@f14g2000cwb.googlegroups.com> Polymath, your fine rhetoric is wasted on this subject. --- Reg. Article: 94461 of rec.radio.amateur.homebrew From: class-a-pkearn-znnzpk@multi-band-cb-is-here---its-as-easy-as-they-say.br.eircom.ie.net (znnPK ) Subject: Re: Recommended reading for _REAL_ Radio Hams Date: Sat, 24 Sep 2005 12:23:24 GMT Message-ID: <433544dc.321584@news.iol.ie> References: <1126951418.730335.258350@g14g2000cwa.googlegroups.com> <432befc1$1_4@mk-nntp-2.news.uk.tiscali.com> <1126956334.407558.33070@g14g2000cwa.googlegroups.com> <9_VWe.422$bR.1@newsfe7-win.ntli.net> <1126971523.139315.3360@g49g2000cwa.googlegroups.com> <432c40cd$1_2@mk-nntp-2.news.uk.tiscali.com> <1127483205.631008.176790@g43g2000cwa.googlegroups.com> <1127536110.784761.233910@f14g2000cwb.googlegroups.com> <1127537443.215833.25250@f14g2000cwb.googlegroups.com> "Polymath" wrote: [snip] he who lie down with dogs gets up with fleas. if you dont want fleas, dont lie down. Article: 94462 of rec.radio.amateur.homebrew From: "Mike Kulyk" Subject: For Sale.. OR Swap.. Bearcat 155XL 16 channel scanner.. FOR 2 meter HT Message-ID: Date: Sat, 24 Sep 2005 08:38:52 -0400 Nice scanner.. Was used at a towing company. Desktop unit Looking for a 2 meter HT for general bang around use. OK if it missing stuff. Mike WB2GLW Article: 94463 of rec.radio.amateur.homebrew From: Jock. Subject: Re: Recommended reading for _REAL_ Radio Hams Date: Sat, 24 Sep 2005 18:48:53 +0000 Message-ID: References: <1126971523.139315.3360@g49g2000cwa.googlegroups.com> <432c40cd$1_2@mk-nntp-2.news.uk.tiscali.com> <1127483205.631008.176790@g43g2000cwa.googlegroups.com> <1127536110.784761.233910@f14g2000cwb.googlegroups.com> <1127537443.215833.25250@f14g2000cwb.googlegroups.com> <433544dc.321584@news.iol.ie> <1127566840.773374.256800@z14g2000cwz.googlegroups.com> On 24 Sep 2005 06:00:40 -0700, "Andrew VK3BFA" wrote: > >znnPK wrote: >> "Polymath" wrote: >> >> [snip] >> >> >> he who lie down with dogs gets up with fleas. >> >> if you dont want fleas, dont lie down. > >Hey, who cares.....if you want to know more, you will pursue it. If you >dont, you wont. leave politics to the politicians. Read some more, >build something, enjoy yourself, whatever. How about learning how to punctuate? 73 de Jock. -- Clouseau: 'Does your dog bite?' Man: 'No.' Dog savages Clouseau. Clouseau: 'I thought you said your dog didn't bite.' Man: 'That wasn't my dog.'