Article: 94299 of rec.radio.amateur.homebrew From: Allodoxaphobia Subject: Re: beeswax in an oscillator compartment Date: 7 Sep 2005 19:49:46 GMT Message-ID: References: <8Nadnf27areq6ULcRVn-tg@comcast.com> <1126070196.869170.150400@g49g2000cwa.googlegroups.com> On 6 Sep 2005 22:16:36 -0700, Andrew VK3BFA wrote: > Andrew Mitz wrote: >> Beeswax is exceptionally good for protection from an >> ionic environment (salt water, human body). >> >> Rick Karlquist N6RK wrote: >> >> > In 1975, I worked for a marine radio company called Konel. >> > I worked on their first synthesized radio, which I inherited >> > from another designer. The original design had a VCO that >> > was quite microphonic. We didn't even bother with beeswax, >> > we potted itin Red Glyptol. Even that wasn't good enough >> > for two reasons. The speaker was in the same box and the >> > sailors would turn it up so you could hear the radio over >> > the engine noise. Also, the 10,000 HP engines on tug boats >> > produced a lot of vibration which got into the VCO. >> > I designed a VCO with an inductor printed on the PC board, >> > and that did the trick. A few months later, Konel went >> > out of business and few if any radios were produced. >> > >> > "Larry Gagnon" wrote in message >> > news:pan.2004.12.15.21.21.27.858623@fakeuniserve.com... >> > > I posted a few days ago about repairing a VHF marine radio. >> > > Thankfully I solved my problem, locating three cold solder joints >> > > in the VCO, which entailed removing metal shields and all the >> > > beeswax that coated all the components. That was character building >> > > work! >> > > >> > > I gather the beeswax is to ensure rigid components to maintain >> > > stability of the oscillator? Any other reasons for it? Is it >> > > necessary for me to remelt the old wax and spread it around as >> > > before, or can I get away with just reshielding the VCO? > > Had a Yaesu FT-470R 2m ssb/fm transceiver in recently for repair - VCO > was faulty. The module had been encapsulated in expoxy resin, and took > AGES to chip out with a fine wood chisel (and lots of swearing). Broke > a few components doing it, but could replace them so did. Pig of a job. > > I consider this to be the definitive reason why beeswax is a better > potting material for VCO's. > > What more do you want? - its cheap, readily available, easy to use, > recyclable, easy to get out for equipment maintenance, smells ok when > melted (better than modern chemicals) - need I say more? I always have used paraffin -- way more 'solid' and takes more heat to melt than 'normal' candle wax. Maybe I was violating some law... YMMV Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK Article: 94300 of rec.radio.amateur.homebrew From: "gianfranco" Subject: Dayton Message-ID: <7DRTe.52945$HM1.1493597@twister1.libero.it> Date: Thu, 08 Sep 2005 07:20:35 GMT I live in Italy and for some years I visited Dayton hamvention . Really impressive for me coming from Europe . Now I would know if there are in the USA other similar hamfests and some comments from the american collegues . My wish is to try to visit some other hamfest . Thanks for your help Gianfranco Article: 94301 of rec.radio.amateur.homebrew Message-ID: <431FEC42.20101@killspam.internode.on.net> Date: Thu, 08 Sep 2005 17:46:10 +1000 From: Alan Peake Subject: Re: beeswax in an oscillator compartment References: <8Nadnf27areq6ULcRVn-tg@comcast.com> <1126070196.869170.150400@g49g2000cwa.googlegroups.com> <431E9412.10505@killspam.internode.on.net> <1126101905.227799.109980@g14g2000cwa.googlegroups.com> >>Andrew, do you know what the thermal conductivity of beeswax is? >>Alan > > > Nope. Is it remotely relevant to this application? > > Andrew VK3BFA It could be. One problem with temperature compensation is that the various components of an oscillator have differing thermal masses, thermal conductivities and hence thermal time constants. So it helps to have everything thermally connected so all component values change at the same rate. If beeswax conducts heat well, then potting the oscillator with it would assist temperature stability. Alan Article: 94302 of rec.radio.amateur.homebrew Message-ID: <431FECC2.1040901@killspam.internode.on.net> Date: Thu, 08 Sep 2005 17:48:18 +1000 From: Alan Peake Subject: Re: beeswax in an oscillator compartment References: <8Nadnf27areq6ULcRVn-tg@comcast.com> <1126070196.869170.150400@g49g2000cwa.googlegroups.com> <431E9412.10505@killspam.internode.on.net> >> Andrew, do you know what the thermal conductivity of beeswax is? >> Alan >> > http://www.fao.org/docrep/w0076e/w0076e12.htm > Bruno Thanks (or is it Danke) Very informative. Alan Article: 94303 of rec.radio.amateur.homebrew From: Al Subject: Re: beeswax in an oscillator compartment References: <8Nadnf27areq6ULcRVn-tg@comcast.com> <1126070196.869170.150400@g49g2000cwa.googlegroups.com> <431E9412.10505@killspam.internode.on.net> <1126101905.227799.109980@g14g2000cwa.googlegroups.com> <431FEC42.20101@killspam.internode.on.net> Message-ID: Date: Thu, 08 Sep 2005 13:01:03 GMT In article <431FEC42.20101@killspam.internode.on.net>, Alan Peake wrote: > >>Andrew, do you know what the thermal conductivity of beeswax is? > >>Alan > > > > > > Nope. Is it remotely relevant to this application? > > > > Andrew VK3BFA > > It could be. One problem with temperature compensation is that the > various components of an oscillator have differing thermal masses, > thermal conductivities and hence thermal time constants. So it helps to > have everything thermally connected so all component values change at > the same rate. > If beeswax conducts heat well, then potting the oscillator with it would > assist temperature stability. > Alan > > The beeswax also stabilizes the components so they don't vibrate for whatever reason. Vibrations can induce changes in values for susceptible components resulting in modulation of the output frequency. Al Article: 94304 of rec.radio.amateur.homebrew From: "RST Engineering" Subject: Re: RF-circuit board Date: Thu, 8 Sep 2005 08:29:49 -0700 Message-ID: <11i0m7ls0ks7070@corp.supernews.com> References: <1125645575.256209.260480@g47g2000cwa.googlegroups.com> <1125690035.759489.188140@g14g2000cwa.googlegroups.com> <1125835645.355237.20020@z14g2000cwz.googlegroups.com> <1125942615.521449.254260@g44g2000cwa.googlegroups.com> 1.5mm just happens to be 0.062" (1 / 16 ") which is the industry standard board thickness. Jim "Jim" wrote in message news:MK2dnaNpbowKL4HeRVn-3Q@comcast.com... > The application note for the NRF905 does specify FR4 board with 1.54mm > substrate thickness. FR4 is the board material used for almost all > printed > circuit boards, so you can use a regular board and just make sure the > thickness is 1.544mm. Article: 94305 of rec.radio.amateur.homebrew From: "RST Engineering" Subject: Re: RF-circuit board Date: Thu, 8 Sep 2005 08:30:38 -0700 Message-ID: <11i0m97l541pk86@corp.supernews.com> References: <1125645575.256209.260480@g47g2000cwa.googlegroups.com> <1125690035.759489.188140@g14g2000cwa.googlegroups.com> <1125835645.355237.20020@z14g2000cwz.googlegroups.com> <1125942615.521449.254260@g44g2000cwa.googlegroups.com> <1126078729.380780.132680@g49g2000cwa.googlegroups.com> I used it at 2.3 Gig in a 5 watt transmitter and it worked just fine. Jim "Fero" wrote in message news:1126078729.380780.132680@g49g2000cwa.googlegroups.com... > Hi Tom, > > I have got one more question : could this RF-4 material be used for > frequency up to 2,4 GHz too ? ( blue toot ) > Namely, Nordic offers chips for this frequency, too. > > Thanks a lot. > > Fero > Article: 94306 of rec.radio.amateur.homebrew From: dplatt@radagast.org (Dave Platt) Subject: Re: beeswax in an oscillator compartment Date: Thu, 08 Sep 2005 18:27:11 -0000 Message-ID: <11i10jv6kak3l46@corp.supernews.com> References: <431E9412.10505@killspam.internode.on.net> <431FECC2.1040901@killspam.internode.on.net> >>> Andrew, do you know what the thermal conductivity of beeswax is? >> http://www.fao.org/docrep/w0076e/w0076e12.htm >Very informative. http://www.kayelaby.npl.co.uk/general_physics/2_3/2_3_7.html is also interesting, especially if you follow the link to the polymers page at http://www.kayelaby.npl.co.uk/chemistry/3_11/3_11_1.html#3_11_1 It looks as if beeswax and paraffin both have thermal conductivities of about 0.25 ( when measured in W / (m K) ), and that epoxy cast resins are in the range of 0.17 - 0.21. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 94307 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: beeswax in an oscillator compartment Date: Thu, 08 Sep 2005 11:28:27 -0700 Message-ID: <11i10mgeg8mq87b@corp.supernews.com> References: <8Nadnf27areq6ULcRVn-tg@comcast.com> <1126070196.869170.150400@g49g2000cwa.googlegroups.com> <431E9412.10505@killspam.internode.on.net> <1126101905.227799.109980@g14g2000cwa.googlegroups.com> <431FEC42.20101@killspam.internode.on.net> Alan Peake wrote: > > It could be. One problem with temperature compensation is that the > various components of an oscillator have differing thermal masses, > thermal conductivities and hence thermal time constants. . . This is one of several reasons that the best approach in designing an oscillator -- or any other temperature sensitive circuit -- is to use components that each have as small a temperature coefficient as possible. That is, first minimize the inherent drift. Then, if you must, compensate what drift remains. Roy Lewallen Article: 94308 of rec.radio.amateur.homebrew From: "Paul P" Subject: Help identify tower manufacturer Message-ID: Date: Fri, 09 Sep 2005 12:21:46 GMT Gentlemen, I am attempting to identify the tower manufacture of the tower pictured at: http://www.ppinyot.com/antenna.htm. I would like to properly design a base for it given the manufacturers specs plus perhaps pick up additional sections. The tower seems to be of a stamped steel design (not tubular) with stamped steel cross members. It has been well maintained by the silent key's son. I gather it is about 10 to 15 years old. There is an unpainted ladder chained to one side for storage. Please do not confuse this as part of the tower. Also if you happen to recognize the beam please Identify it too. Unfortunately some one discarded all the paper work not knowing it's value. Thanks Paul paul at ppinyot dot com KB3LZP Article: 94309 of rec.radio.amateur.homebrew From: "Steve Nosko" Subject: Re: Stable Regen Receiver--Does it Exist?? Date: Fri, 9 Sep 2005 15:32:08 -0500 Message-ID: References: <1124850656.892394.139930@f14g2000cwb.googlegroups.com> <1125943289.589816.107320@g47g2000cwa.googlegroups.com> Way back when... I listened to the SSB gangs on 40M with my Knight Kit Space Spanner, but then, I'm in my own world. 73, Steve, K9DCI "SpamHog" wrote in message news:1125943289.589816.107320@g47g2000cwa.googlegroups.com... > I assume you are talking about temperature induced drift, as opposed as > frequency lability due to hand effect, changes in regen setting etc. > > I have experienced such stability over time that SSB pitch would stay > dead on for days (run on and off) in the shortwave range with the radio > tuned on a volmet station half a continent away. In this instance, I > was running a 1-tuber with direct heated filament, battery powered, and > cap-throttle regen control, but the lessons apply in general. > > The main tricks in my book are quite simple: > - keep oscillator power as close to zero as humanly possible > - keep voltages stable > - select LARGE components and hookup wires > - ensure ventilation! > > In a word, make sure the oscillator basically runs at ambient > temperature. > > > If you were referring to frequency lability caused by other factors, I > have good news in the hand effect department, and mixed news in the > regen control area. > > > Hand effect can be more or less got rid of by proper shielding or > decoupling. You can find an interesting discussion here: > http://tinyurl.com/dr936 . > > In a word: keep your body away from ANY capacitance related to the > oscillating tank circuit - and that mainly refers to the ANTENNA, not > the variable capacitor or the coil. If there is a sizeable > antenna-case capacitance, then a change in body-case capacitance > affects antenna and inevitably the tank circuit too. > > So the oscillating tank circuit must be properly decoupled (usually by > RF amp/buffer stage ahead of the regen detector) > OR > it must be well enclosed + the antenna coax fed > ... or both. > > I would like to experiment with cap-decoupling by putting a > slitted-shield around the tuning coil, and putting a separate antenna > coil next to it, but never got around to doing so. Even theoretically, > the idea of such a trick gives me a headache. > > > In the regen control department, the mixed news is that capacitive > throttling is considered the "best performing" way to go, but can't > avoid to affect the tuned frequency. > > [ In theory you could, of course, what with a small co-shafted VC that > removes capacitance from the main LC as the throttle cap adds it, but > it must be a pretty complicated law, and I don't know of anyone who > tried it :) ] > > You can instead turn to the gain-control way, DC-controlling one of the > following: > - second grid voltage in a pentode > - plate voltage in a triode > - base voltage in a transistor > or some such like. > > All of the above minimize frequency change especially in tube designs > (where varicap effects are basically nonexistent), but can suffer from > annoying hysteresis, in my experience more than cap throttle. Not sure > where the "high performance" advantage of cap throttle is though... > > Another trick I wish I had tried is changing a *stabilized* voltage, as > opposed to using a simple throttle pot. That could be done with a > variable regulator IC and might remediate the hysteresis. > > Another trick is to use a couple of effects working in opposite > directions, such as a resistive throttle that adds gain but shunts more > RF to ground, such as in the Charles Kitchin "Beginner's Radio". > > See www2.arrl.org/tis/info/HTML/regen/ > with many derivatives linked in this article of mine: > http://www.geocities.com/filippo_cattaneo/desert-ratt.html . > > I think the same trick may be in use in the MFJ-8100 regen, but I can't > tell what's trimmer and what's main control pot. > (hand drawn schematic may be here: > www.diagram.com.ua/list/mogik.shtml > sorry Martin!). > > So, there's hope. > Article: 94310 of rec.radio.amateur.homebrew From: Paul Keinanen Subject: Re: lf to HF preselector design needed Message-ID: <8k35i11lmh2sdrn8re7g69gh6d3j8mkqo6@4ax.com> References: <9df4i1546l564jt5uc22lp8gva22v9qdgi@4ax.com> Date: Sat, 10 Sep 2005 12:16:44 +0300 On Fri, 09 Sep 2005 22:01:27 -0400, TRABEM <> wrote: >I need an LF to 30 Khz preselector (passive) for a homebrewed receiver >I'm building. I have most of the details worked out, but I am stuck on >the preselector design. > >I want one band to cover 50 Khz to 500 Khz (or 1 Mhz). That would be 1:10 (or 1:20) frequency range. >The second band would be 1 Mhz to 30 Mhz. That would be 1:30 frequency range and would require a 1:900 reactance range, if only one element (inductance or capacitance) is tuned, which would be completely unrealistic. The alternative would be to tune both the inductance _and_ capacitance in the 1:30 range. However, with a 300 pF variable capacitor, the minimum capacitor would be 10 pF _including_ all stray capacitances, not very realistic. I have no idea what a realistic tuning range would be for a permeability tuned inductor. I have only seen those in FM receivers (87..108 MHz), which only about 20 % tuning range. >50 ohm input with moderate Q (don't want to >have to retune it every 100 Khz. The LF unit can be very high Q, >peaking it every few Khz is ok as most of the signals in that range >are narrowband signals anyway. Input impedance is standard 50 ohms. Maintaining the constant impedance if both inductance and capacitance is tuned would be a challenge. While maintaining the power match makes some sense in HF receivers (and also if you are using some small magnetic loops on LF/MF), but otherwise, I would question the idea to maintain the 50 ohm resistive input impedance on LF (and possibly also MF). On LF, any practical random wire antenna would have a high capacitive reactance. On LF I have simply used a parallel tuned circuit and connected the antenna to the hot end of the circuit with a small (10-100 pF) capacitor. Of course, the tuning scale will not be accurate if you change the antenna, since the antenna stray capacitances will detune the resonant circuit. Use a secondary winding or a source/emitter follower to get the impedance down to feed a 50 ohm receiver input or feed a coaxial cable (if the preselector is just under the antenna). If you intend to use magnetic loop antennas on LF/MF, which have a low efficiency, I would suggest using a (remotely)tunable loop as the preselector, with possibly a preamplifier at the antenna. I would strongly suggest splitting the HF bands and switching in various inductors for various bands and use an ordinary variable capacitor. The situation is quite problematic on LF, since you would need a variable capacitor with a tuning range int several nF to keep the resonant circuit impedances at manageable levels (otherwise, it would be quite "touchy" due to stray capacitances). With practical variable capacitors, you would have to add parallel padding capacitors, with would further reduce the tuning range. Permeability tuning might be an option. You could try making a coil and slide a ferrite bar (from a medium wave antenna) into it, however, I have no experience with this. Paul OH3LWR Article: 94311 of rec.radio.amateur.homebrew From: Bob Bob Subject: Re: lf to HF preselector design needed References: <9df4i1546l564jt5uc22lp8gva22v9qdgi@4ax.com> Message-ID: Date: Sat, 10 Sep 2005 08:25:39 -0500 I realise that you are after a passive solution but I wonder if an op-amp or two in a Q multiplier configuration *for the first band) might be a better idea? You could then tune the feedback/gain of the device with a R/C combination rather than large values of L. You could of course set the gain to 1 if you wanted. Just an idle thought. Cheers Bob W5/VK2YQA TRABEM wrote: > > I need an LF to 30 Khz preselector (passive) for a homebrewed receiver > I'm building. I have most of the details worked out, but I am stuck on > the preselector design. > Article: 94312 of rec.radio.amateur.homebrew From: zzzpk_pkearn_class_a@its-as-easy-as-they-say-multi_band_cb_is_here.eircom.es.it.net (ZZZZPK ) Subject: Re: The FAQ.... Date: Sat, 10 Sep 2005 14:53:44 GMT Message-ID: <4322f335.8873303@news.iol.ie> References: <1126289165.610590.20420@g49g2000cwa.googlegroups.com> <1126358584.224925.205250@g49g2000cwa.googlegroups.com> "huLLy" wrote: : Polymath wrote: : > Oops - forgot to cross-post to our friends in Yankland..... : > : > 11 years of posting under Outlook Express and similar : > packages (Turnpike, DIS) mean dissimilar habits! : : Turnpike and Demon Internet... even then you were bonkers... what was your : Demon account name? Oh yes, cemetery.demon.co.uk : : What a bizarre choice! Why did you choose this? so nice of you to change your posting name to something else other than that of anothers registered callsign. its a pity you dont have the courage to put your own callsign in, in the same way that you could abuse anothers callsign. Article: 94313 of rec.radio.amateur.homebrew From: "Steve H" References: <1126289165.610590.20420@g49g2000cwa.googlegroups.com> <1126358584.224925.205250@g49g2000cwa.googlegroups.com> <4322f335.8873303@news.iol.ie> <1126365409.100410.255070@g44g2000cwa.googlegroups.com> Subject: Re: The FAQ.... Date: Sat, 10 Sep 2005 17:52:11 +0100 Message-ID: <43230f3a$1_1@mk-nntp-2.news.uk.tiscali.com> "Polymath" wrote in message news:1126365409.100410.255070@g44g2000cwa.googlegroups.com... > There's a simpler way for him to deal with > his own deep-seated inadequacy, and that is to > tackle and then pass a 12 WPM Morse Test, and > then to go on and build his own TX! > Gareth, after 10 years of slow learning you passed the Morse test, rumour has it you once even built a "oner". You suffer from social inadequacy almost as much as we suffer from your social inadequacy. Steve H Article: 94314 of rec.radio.amateur.homebrew Message-ID: <43235959.ADC22795@rickfrazier.com> From: Rick Frazier Subject: Re: Help identify tower manufacturer References: Date: Sat, 10 Sep 2005 22:07:59 GMT Paul: It looks a lot like the one I have (except mine is still in the standard galvanized steel, not painted red). Mine is a Rohn HBX, though what is there could be a BX, depending upon the sections used at the top. It was generally available up to 64' in the BX version, and 56' in the HBX version. The big difference is the top section is smaller on the BX version. Each section is 8 feet tall, and the standard footing http://www.antennasystems.com/towers.html#BXTOWER has some information about the tower. I have a printed copy of the manual somewhere, but it would take months to find it, as I'm in the process of building a new QTH.. I had also found a copy on the internet somewhere, but it was lost during a hard disk crash, but I imagine you could search for the manual given the model number. The base in the pictures is a tilt-over mount for the tower. I used the standard (non tilting) mount, and it served me well with a large Cushcraft X-9 beam on it, plus a 2 meter 11 element beam above that, and several wire antennas off in odd directions. It will be going back up at the new QTH. It is the 48 foot HBX version. Because it is in 8 foot sections, you can take it down or put it up a section at a time, but having done that, I find that it's much much easier, faster and safer to just have a boom truck come out, attach a sling to the top, then disconnect at the bottom and let the boom truck operator just lay it down. Works like a champ, is quick and easy. Needless to say, it's going back up using a boom truck, as I'm not into climbing a tower a dozen times a day any more. Once is quite enough, thank you. I can get the tower up and beam on it with a single climb (sling on top of the tower, boom truck lift into place, climb tower, disconnect sling, boom truck operator connects hook to the antenna, brings it up to me, and I bolt it in place). Connect the coax already in place before the tower went up and viola!, tower up with beam in about an hour. Lots of prep beforehand, but all on the ground where I can take breaks and enjoy a beer or two during assembly. Good Luck, Be safe! Rick AH7H Paul P wrote: > Gentlemen, > > I am attempting to identify the tower manufacture of the tower pictured at: > http://www.ppinyot.com/antenna.htm. I would like to properly design a > base for it given the manufacturers specs plus perhaps pick up additional > sections. > > The tower seems to be of a stamped steel design (not tubular) with stamped > steel cross members. It has been well maintained by the silent key's son. > I gather it is about 10 to 15 years old. There is an unpainted ladder > chained to one side for storage. Please do not confuse this as part of the > tower. > > Also if you happen to recognize the beam please Identify it too. > > Unfortunately some one discarded all the paper work not knowing it's value. > > Thanks Paul > > paul at ppinyot dot com > > KB3LZP Article: 94315 of rec.radio.amateur.homebrew Message-ID: <432372A7.100DD50A@earthlink.net> From: "Michael A. Terrell" Subject: Re: lf to HF preselector design needed References: <9df4i1546l564jt5uc22lp8gva22v9qdgi@4ax.com> <8k35i11lmh2sdrn8re7g69gh6d3j8mkqo6@4ax.com> <8mu5i1tmjbj7ukge3ukij7pks785mp222r@4ax.com> Date: Sat, 10 Sep 2005 23:58:21 GMT TRABEM wrote: > > Thanks Paul, > > My old Drake C line had a multiple ganged permeability tuned inductor > mechanically coupled to a variable cap. > > One of the assemblies tuned the front end, one peaked the driver > stage, etc. > > It covered from 1 Mhz to 30 Mhz with a half turn on the front panel > preselector control. Most likely the variable C and L tuned together > maintained a desirable Q across all the bands. > > I was hoping for something similar, but have no idea where to get > permeability tuned inductors today. > > Regards, > > T Fair Radio used to have some in their catalog, and they were used in all of the old Delco (and some other brands) car radios of the '60s and '70s. -- ? Michael A. Terrell Central Florida Article: 94316 of rec.radio.amateur.homebrew From: Roy Lewallen Subject: Re: lf to HF preselector design needed Date: Sat, 10 Sep 2005 18:13:12 -0700 Message-ID: <11i715a1qscrc36@corp.supernews.com> References: <9df4i1546l564jt5uc22lp8gva22v9qdgi@4ax.com> <8k35i11lmh2sdrn8re7g69gh6d3j8mkqo6@4ax.com> <8mu5i1tmjbj7ukge3ukij7pks785mp222r@4ax.com> <432372A7.100DD50A@earthlink.net> Michael A. Terrell wrote: > > Fair Radio used to have some in their catalog, and they were used in > all of the old Delco (and some other brands) car radios of the '60s and > '70s. Just about all the radios I've seen with mechanical pushbuttons for station presets used permeability tuned inductors -- the pushbuttons each just positioned a ferrite core to a preset depth in a coil. It wouldn't be difficult to construct one, unless you're mechanically declined like I am. Roy Lewallen, W7EL Article: 94317 of rec.radio.amateur.homebrew From: et472@FreeNet.Carleton.CA (Michael Black) Subject: Re: lf to HF preselector design needed Date: 11 Sep 2005 02:35:54 GMT Message-ID: References: <9df4i1546l564jt5uc22lp8gva22v9qdgi@4ax.com> <8k35i11lmh2sdrn8re7g69gh6d3j8mkqo6@4ax.com> <8mu5i1tmjbj7ukge3ukij7pks785mp222r@4ax.com> <432372A7.100DD50A@earthlink.net> "Michael A. Terrell" (mike.terrell@earthlink.net) writes: > TRABEM wrote: >> >> Thanks Paul, >> >> My old Drake C line had a multiple ganged permeability tuned inductor >> mechanically coupled to a variable cap. >> >> One of the assemblies tuned the front end, one peaked the driver >> stage, etc. >> >> It covered from 1 Mhz to 30 Mhz with a half turn on the front panel >> preselector control. Most likely the variable C and L tuned together >> maintained a desirable Q across all the bands. >> >> I was hoping for something similar, but have no idea where to get >> permeability tuned inductors today. >> >> Regards, >> >> T > > > Fair Radio used to have some in their catalog, and they were used in > all of the old Delco (and some other brands) car radios of the '60s and > '70s. > I thought it was the norm for car radios to be permeability tuned, right up to the time synthesizers came along. No manually tuned car radio that I've looked at had a variable capacitor, with the exception of a relatively recent one that had a frequency counter for the readout. Car radios would be the best source of the mechanics, at least for front end tuning and not oscillator use. Of course, the issue isn't changing the permeability of a coil, that's easy with a tuning slug, but making it easy to do that from a front panel control, ie the knob doesn't move in and out. The pre-synthesized car radios would proved the mechanism. But you did see the occasional article in the old days about making up such a mechanism, though those tended to be for oscillators where there was more fuss because they wanted/hoped for linear tuning. Michael VE2BVW Article: 94318 of rec.radio.amateur.homebrew Message-ID: <4323B2B0.BD9CE4F8@earthlink.net> From: "Michael A. Terrell" Subject: Re: lf to HF preselector design needed References: <9df4i1546l564jt5uc22lp8gva22v9qdgi@4ax.com> <8k35i11lmh2sdrn8re7g69gh6d3j8mkqo6@4ax.com> <8mu5i1tmjbj7ukge3ukij7pks785mp222r@4ax.com> <432372A7.100DD50A@earthlink.net> Date: Sun, 11 Sep 2005 04:32:22 GMT Michael Black wrote: > > I thought it was the norm for car radios to be permeability tuned, right > up to the time synthesizers came along. No manually tuned car radio > that I've looked at had a variable capacitor, with the exception of > a relatively recent one that had a frequency counter for the readout. > > Car radios would be the best source of the mechanics, at least for > front end tuning and not oscillator use. Of course, the issue isn't > changing the permeability of a coil, that's easy with a tuning slug, > but making it easy to do that from a front panel control, ie the knob > doesn't move in and out. The pre-synthesized car radios would proved > the mechanism. But you did see the occasional article in the old > days about making up such a mechanism, though those tended to be > for oscillators where there was more fuss because they wanted/hoped > for linear tuning. > > Michael VE2BVW Some of the cheap imported car radios used the same plastic cased variable capacitor with mylar film between the plates that were used in a six transistor pocket radio. They didn't have a tuned front end and amp like the US made car radios. They were ok if you only wanted to listen to a local station but they were very poor quality radios. I think I would use a variable capacitor and electronically switch the inductor for different ranges, like the broadband L-C Based VCO in the telemetry receivers I worked on. Diodes were used to short segments of the inductor, at the grounded end and the band segment was controlled by simple logic. Bias on hard to short a tap to ground, and reverse bias it to prevent it from clipping the RF when its off. They used discrete +/- 12 or 15 volt switching , but a decent buffer amp would work and could be driven by CMOS or TTL compatible logic. If the receiver has any switched DC signals to show which band its on, you could make it change bands without touching it. You could even sample the L.O. with a counter circuit and use the output to control the tuning. If you want to g to extremes, you could add a microprocessor with lookup tables to drive a stepper motor that can adjust the variable capacitor(s) for you as you tune the radio. -- ? Michael A. Terrell Central Florida Article: 94319 of rec.radio.amateur.homebrew From: "Mike Andrews" Subject: Re: phase angle and impedance of resonant circuits Date: Sun, 11 Sep 2005 19:30:13 +0000 (UTC) Message-ID: References: <1125441521.799326.31340@f14g2000cwb.googlegroups.com> <11h9smd2nk4gvf2@corp.supernews.com> <1125473546.791826.289710@o13g2000cwo.googlegroups.com> <1125473918.294745.212200@f14g2000cwb.googlegroups.com> <11haq6pluumpvdc@corp.supernews.com> <1126415834.424360.81740@g44g2000cwa.googlegroups.com> eternalsquire@comcast.net wrote: > I GOT IT! I GOT IT! I GOT IT! > Thanks for all your help! I just wrote the exam with a 92% pass. > The Eternal Squire Way cool! See you on HF, if this storm will ever go away. Now go for your white belt -- if we're in the same organization. -- Mike Andrews / Michael Fenwick Barony of Namron, Ansteorra mikea@mikea.ath.cx / Amateur Extra radio operator W5EGO Tired old music Laurel; webBastard; SCAdian since AS XI Article: 94320 of rec.radio.amateur.homebrew From: Spam_Bin@NO_SPAM.wyenot.servebeer.com Subject: Re: Butterworth bandpass filter question Message-ID: References: Date: Sun, 11 Sep 2005 20:56:34 GMT It looks like the filter is designed for 50 ohms in and out. The transformer inductance is also a part of the filter. It's value should be about the same as L1 so to use it at 50k to 200K, you'll need to rewind for a lot more turns on the primary and both secondaries if you keep the same core material. Scaling it all and then optimizing for Coil Q of 40 and regular cap and coil values, I get new values like: L1 680nH -> 100uH C1 470pF -> .022uF C21 180pF -> .027uF L2 1.8uH -> 100uH C22 470pF -> .022uF T1 680nH (13:6:6 Turns) -> 100uH (1911:882:882 Turns) I strongly recommend changing T1 to a much higher mU core material. This should result in -3dB points at 50 and 200 kHz, flat pass-band and -30dB at 20 and 500 kHz. Good luck finding a 50 Ohm antenna at these frequncies. An active antenna may be the way to go, otherwise you'll need many acres for all the wire. On Sun, 11 Sep 2005 12:09:16 -0400, TRABEM <> wrote: >I am trying to scale an existing front end receiver (butterworth >bandpass) filter to a different frequency range. Unfortunately, it has >a transformer in the original design, so I'm stuck. I also don't know >how to handle the load presented by the active front end component >other than it's probably not significantly reactive. > >The existing filter is for a 7 Mhz receiver, I'd like to have a >similar filter design for 50 to 200 Khz. > >The filter components and transformer winding details are in the >document at: > >http://www.amqrp.org/kits/softrock40/SoftRock40%20Assy%20v1.pdf > >The input chip is an FST3126, spec sheet is at: > >http://www.fairchildsemi.com/ds/FS/FST3126.pdf > >The spec for the T30-2 transformer core is at: > >http://partsandkits.com/T30-2.htm > >I have aade filter design software, but it isn't allowing me to plug >in the transformer into the design page of the software....so, I need >to know it's equivalent circuit I think. > >The transformer winding details are on page 4 of the document and the >schematic of the front end is page 9. Ultimately, I need new values >for L1, L2, C20, C21 and C22. > >If someone can give me a reasonable guess as to the equivalent circuit >of the transformer and the IC (U5), I can do the rest of the job >myself using the aade filter software. > >Thanks, > >T Article: 94321 of rec.radio.amateur.homebrew Message-ID: <4324E54D.1B6CA2C7@earthlink.net> From: "Michael A. Terrell" Subject: Re: Amphenol Microphone Connectors (Heathkit, etc.) References: <1126467283.868773.248440@g47g2000cwa.googlegroups.com> Date: Mon, 12 Sep 2005 02:17:16 GMT hhc314@yahoo.com wrote: > > I'm selling my excess of new Amphenol microphone connectors on eBay. I > had to purchase a box of 25, but I only need 3, so I'm selling the > balance. > > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5808187910&rd=1&sspagename=STRK%3AMESE%3AIT&rd=1 > > Those of you who would be interested in these items know what they are > and how difficult to find today. > > Harry C. Your E-bay ad is very misleading. First of all, the Amphenol logo on the box is from the '70s, not the '50s. While it is true that Amphenol no longer makes that connector, its because they sold that product line to WPI http://www.wpi-interconnect.com/ several years ago. Switchcraft http://www.switchcraft.com/ 2501 series is a fully compatible, and better quality connector line. Then there are still imported connectors that mate with this old industry standard. $10 each is an outrageous price. You can find these at a lot of online surplus dealers and almost any place that deals in older musical equipment. BTW, I still have 3 of the 2501F Switchcraft connectors for $3.50 each, and a good supply of the self shorting 2501 MP chassis mount connector that short circuits the input when you remove the connector for $2 each. This item is NLA from the OEM. I got a good price from a surplus dealer who doesn't have any idea what they are, so I bought 25 to replace all of the microphone connectors on my restored antique test equipment. http://home.earthlink.net/~mike.terrell/Epcon.html Note: the current stock on the shorting connector is shown as 3, but I can still get about 1000 additional connectors. -- ? Michael A. Terrell Central Florida Article: 94322 of rec.radio.amateur.homebrew From: Paul Keinanen Subject: Re: Butterworth bandpass filter question Message-ID: <2k2ai15p86rraoqt11sgl72fu1cpo7om8o@4ax.com> References: <6vKdnb33bpFiL7neRVnysw@pipex.net> Date: Mon, 12 Sep 2005 09:53:52 +0300 On Sun, 11 Sep 2005 23:43:36 +0100, "Highland Ham" wrote: >> The existing filter is for a 7 Mhz receiver, I'd like to have a >> similar filter design for 50 to 200 Khz. >=========================== >If you are happy with the HF receiver as is, would it not be easier and >more effective to build an LF (50 - 200 kHz) to HF converter. This should >be an easy project and you can select a quiet "HF band" for the conversion. What would this solve ? You still need some selectivity in front of converter. I would also question the need for a bandpass filter, but a good low pass filter would definitively required in any case. I would suggest a low pass filter below 150 kHz in Europe, Africa and Middle-East and below 500 kHz in the rest of the world to get the very strong LW/MW broadcast band signals out of the mixer. If 455 kHz IF is used, the LPF would have to be below 400 kHz in the rest of the world. >I have seen designs with a SBL-1 mixer SBL-1 is specified for 1-500 MHz on the RF and LO port, so not really suitable for this band. However, the SBL-3 goes from 25 kHz to 200 MHz. The SRA-6H goes from 10 kHz to 50 MHz and should be able to handle up to +10 dBm signals. >but also a number with the NE612 >osc/mixer. I have used the Datong LF converter, which uses the Siemens S042 mixer/osc IC similar to the NE602/612 and it definitively needs a preselector in front of it to get away with spurious responses all over the LF band from broadcast stations. Paul OH3LWR Article: 94323 of rec.radio.amateur.homebrew From: "myhealthpod" Subject: More layoffs at your workplace? Date: Mon, 12 Sep 2005 17:18:36 Message-ID: MORE LAYOFFS AT YOUR JOB? Are you worried? I was.. http://www.automaticbuilder.com/20258 Build you Residual Income today. Wait no more.. Don't wait till the day your employee ID tag is taken away.. http://www.automaticbuilder.com/20258 --- MAF Anti-Spam ID: 20050912040711F9f9OcD1 Article: 94324 of rec.radio.amateur.homebrew From: "Reg Edwards" Subject: Re: Butterworth bandpass filter question Date: Mon, 12 Sep 2005 17:39:22 +0000 (UTC) Message-ID: References: <6vKdnb33bpFiL7neRVnysw@pipex.net> <2k2ai15p86rraoqt11sgl72fu1cpo7om8o@4ax.com> > The concept is > explained in a QEX article in greater detail, Im happy to send the url > to anyone who wants to learn more about these high performance direct > conversion receivers. =================================== How do you know the QEX article is not a load of of old-wives tales. Article: 94325 of rec.radio.amateur.homebrew From: "john jardine" Subject: Re: Butterworth bandpass filter question Date: Tue, 13 Sep 2005 00:46:03 +0100 Message-ID: References: wrote in message news:euj8i1po8dsokkeedfc4ofouqtsh97mihe@4ax.com... [...] > Thanks, > > T Heresy maybe but I'd be inclined to just dump the transformer and bandpass coils and caps and 10ohms etc. Use opamps for a low pass and a high pass filter. Then add another inverting opamp to provide the antiphase for the mixer chip. High 'Atmospherics' at these low frequencies mean pretty much any opamp will be OK. Use a resistor to present any input Z to the Ant'. The FST3126 (or 74HC4066) works well with opamp drive. regards john Article: 94326 of rec.radio.amateur.homebrew From: "W3JDR" References: <6vKdnb33bpFiL7neRVnysw@pipex.net> <2k2ai15p86rraoqt11sgl72fu1cpo7om8o@4ax.com> Subject: Re: Butterworth bandpass filter question Message-ID: Date: Mon, 12 Sep 2005 23:08:13 GMT If you read Gerald Youngblood's first QEX article on the SDR-1000 software-defined radio, you will see on page 7 another embodiment of this type of mixer/detector. It was originally popularized and patented by Dan Tayloe, but has recently been reconfigured (for patent purposes as much as anything else I suspect), and renamed 'quadrature sampling detector' (QSD). The original embodiment shown in the QEX article has no transformers. As a passing comment, one of the writers here said a mixer IS a detector. He's absolutely correct. A detector is just a special case of frequency mixing where the RF is mixed directly down to DC baseband. As another writer said, ALL mixers/detectors, regardless of whether they're the modern switching type or the antique-type based on square-law nonlinearity, have an overload point beyond which they make unacceptable distortion. Switching mixers, which include most double-balanced diode mixer (DBM) modules and most Gilbert-cell IC mixers, just happen to be more linear than many square-law devices up to the overload point, then they go to hell in a handbasket. The QSD is a just special case of switching mixer that can produce quadrature baseband outputs very conveniently, but it is a bit better in the distortion department than many diode DBM's. Joe W3JDR wrote in message news:ai9bi1trpko1jjk6mg75pi6mmur6qb9b81@4ax.com... > >> >>What would this solve ? You still need some selectivity in front of >>converter. >> >>I would also question the need for a bandpass filter, but a good low >>pass filter would definitively required in any case. I would suggest a >>low pass filter below 150 kHz in Europe, Africa and Middle-East and >>below 500 kHz in the rest of the world to get the very strong LW/MW >>broadcast band signals out of the mixer. If 455 kHz IF is used, the >>LPF would have to be below 400 kHz in the rest of the world. >> >>>I have seen designs with a SBL-1 mixer >> >>SBL-1 is specified for 1-500 MHz on the RF and LO port, so not really >>suitable for this band. However, the SBL-3 goes from 25 kHz to 200 >>MHz. The SRA-6H goes from 10 kHz to 50 MHz and should be able to >>handle up to +10 dBm signals. >> >>>but also a number with the NE612 >>>osc/mixer. >> >>I have used the Datong LF converter, which uses the Siemens S042 >>mixer/osc IC similar to the NE602/612 and it definitively needs a >>preselector in front of it to get away with spurious responses all >>over the LF band from broadcast stations. >> > > Thanks Paul, and yes....you're correct. Building a conventional > converter would still require a passband filter, so little is to be > gained, except that perhaps someone else has already done the > design:>: > > Also, this receiver design has no mixer, it is simply a detector and a > very linear one to boot. No mixing byproducts are present because > there is no non-linear mixer. In effect, this design is already a > converter....except that it converts to audio directly from the rf > frequency input. > > The "spurious responses all over the LF band from broadcast stations" > probably don't exist in this type of receiver, which is one of the > attractions for VLF use of this technology. > > Take a look at the link to the design in the original message and you > will learn how it operates without mixers and without non-linear > detectors. > > It's WHY I so interested in this particular method of reception and > WHY I want to make a front end for vlf for it. The concept is > explained in a QEX article in greater detail, Im happy to send the url > to anyone who wants to learn more about these high performance direct > conversion receivers. > > Regards and again, Thanks, > > T Article: 94327 of rec.radio.amateur.homebrew Message-ID: <43261E6B.ED5E8398@earthlink.net> From: "Michael A. Terrell" Subject: Re: Amphenol Microphone Connectors (Heathkit, etc.) References: <1126467283.868773.248440@g47g2000cwa.googlegroups.com> Date: Tue, 13 Sep 2005 00:33:04 GMT hhc314@yahoo.com wrote: > > Michael, as an afterthought.... > > I'll immediately send you a Paypal payment for $3.50, if you'll send > me one of your "Imitation Amphenol" connectors postpaid (just like I am > selling my genuine Amphenols) so that I can examine it and compare the > quality of your product with that of Amphenol's (construction, plating, > solderability, etc.). > > I'll even photograph the two different products side-by-side and email > the photo to any newsgroup reader requesting it so they can make up > their own minds. Is that fair or not? > > Put up or shut-up! > > Harry C. Switchcraft is not "Imitation Amphenol" It is an american made product. I can get you a picture of it if you want. Obviously you have never used anything from Switchcraft, or you wouldn't question the quality. It was used in a lot of military and industrial grade equipment, where I have seen more ham gear with Amphenol connectors. As far as Paypal goes, I do not have an account. I don't buy or sell on E-bay, so i really don't need one. The parts i have for sale are the leftovers where I shut down my business due to failing health. I would rather sell them cheap than have them end up in a landfill. I used to sell at a half dozen hamfests every year, but I can't make the long trips anymore. That leaves the Ocala hamfest that is within my driving range, and the locals already know how to find me. I did commercial sound, broadcast and industrial work. I only used Switchcraft, because of their quality and a reasonable delivery time. At the time they were a division of Raytheon, who was a large defense contractor. Here is one online photo of the Switchcraft 2501F connector at Allied Electronics: has 190 pages that sell or mention the Switchcraft 2501 F connector is a page of distributors with it in stock. I can ship you one of the connectors if you want it. $3.50 plus whatever the postage is for the padded bag. Never a handling charge. -- ? Michael A. Terrell Central Florida Article: 94328 of rec.radio.amateur.homebrew Message-ID: <43263022.6D72F818@earthlink.net> From: "Michael A. Terrell" Subject: Re: Amphenol Microphone Connectors (Heathkit, etc.) References: <1126467283.868773.248440@g47g2000cwa.googlegroups.com> Date: Tue, 13 Sep 2005 01:48:42 GMT hhc314@yahoo.com wrote: > > Michael posted: > > "As far as Paypal goes, I do not have an account. I don't buy or sell > on E-bay, so i really don't need one." > > So, why are you posting objections to those of us on eBay and Paypal > who have earned a credible history of performance over the years. We > who use eBay have no knowledge of who you are (because you have no > feedback history), so you could equally be a nice guy or a scam artist. > If you don't want, or don't have an eBay history, and are selling items > on the Internet, chances are that you are some type of scam artist, and > put-down those that would otherwise (based on their established history > of good dealings) pose a competition for you. I am not COMPETING with anyone for sales. I don't care if the parts I have ever sell. When I die whatever is left will be going to the local landfill, rather than let them go to someone who will sell them on E-bay. I don't buy on E-bay because I have more projects and parts left, that time to finish the projects and use up the parts. Also, almost all of my spare money is going into a non profit corporation to help local disabled veterans. I collect and repair old computers for vets who are too poor to buy a computer. I would rather do this than put up with the shit I get from hams these days. Why subject myself to it when I can work when I am well enough, then call the "Vets helping Vets" to tell them that another free computer system is ready for them to give away? Do you do anything for your fellow humans? > On eBay, before sending any seller money, most of us will look up > his/her eBay history. This tells a lot of information, and trust. Not > having a history on eBay, were I to send you $3.50 for one of your > connectors, I would be taking a risk...but not a large risk since the > amount is only $3.50, Were you no a listed and registed seller on > eBay, I wouldn't send you anything...except in this test case...because > you have no established credibility. Same thing holds true, if you > don't have a certified address on Paypal, in which case I can send you > nothing. > > You have evidenced a very loud mouth, and evidently decline my posted > challenge. So....please go away! > > Harry C. I have no objections to anyone who buys or sells on E-bay, or uses Paypal. As far as a loud mouth? It is you who refuses to admit that Switchcraft is a quality product. I am 100% disabled, after 40 years of working in electronic repair, Broadcast and CATV engineering. I spent my last four years working at Microdyne building $20,000 to $80,000 telemetry receivers and systems. I really don't care what you think. -- ? Michael A. Terrell Central Florida Article: 94329 of rec.radio.amateur.homebrew Message-ID: <432633B7.8BE8BDD0@earthlink.net> From: "Michael A. Terrell" Subject: Re: Amphenol Microphone Connectors (Heathkit, etc.) References: <1126467283.868773.248440@g47g2000cwa.googlegroups.com> Date: Tue, 13 Sep 2005 02:03:58 GMT hhc314@yahoo.com wrote: > > Michael responded: > > "I can ship you one of the connectors if you want it. $3.50 plus > whatever the postage is for the padded bag. Never a handling charge." > > But you didn't state what postage is, or address the difference between > your Swithcraft products and those of a real Amphenol product. You > also didn't specify what the postage charge would be. How do I know what the shipping will be if I don't know the zip code? I provide the mailer and label, then pass on whatever the post office charges me. No more, or less. I have sold parts to a small number of people online, in different news groups, and to people that found some rare ICs (NEC MC-5800) on my website. I have sold a number of parts to guys on news:rec.antique.radio+phono > I suppose that I'm a little more open and upfront that you. If you > purchase one if these connectors from me, they will be original > Amphenol products and shipping is FREE. I have a few Amphenol microphone connectors, somewhere. The insulators were soft, and the plating was poor on the center contact so I just don't use them. The springs were easily damaged as well. In fact, I replace them with Switchcraft. $7.50 and free shipping VS $3.50 and probably $1.50 for shipping. Hard choice. I used to ship the parts and let people send me a check after they received it, but no more. For years I had no problems being paid, then all of a sudden no one sent a check, unless it bounced. > I take it that you are declining my previous offer. Your connectors are > imitations, and their cost is not $3.50 but $3.50 plus whatever you > deiced to charge for shipping. My price is at auction $7.50 with no > shipping charges, and this is for original Amphenol products in shiny > new condition. > > What's the bottom line price, including shipping, or your Amphenol > look-alike connectors? What is the zip code? I will find out tomorrow what it will cost. Not that it really matters. You will find fault with anything I send, just so you can be right. BTW did you even look at any of the links I provided with pictures of the connector I have? I doubt it, or you wouldn't have such a pissy attitude. I doubt that you will respond with your zip code, because you just want to bitch about something. You call me names yet I have NO idea who or for that matter what you are, Harry. > Harry C. -- ? Michael A. Terrell Central Florida Article: 94330 of rec.radio.amateur.homebrew From: "W3JDR" References: <6vKdnb33bpFiL7neRVnysw@pipex.net> <2k2ai15p86rraoqt11sgl72fu1cpo7om8o@4ax.com> <84bci1tnrobr74ju55jdt453rnr9a0hsp9@4ax.com> Subject: Re: Butterworth bandpass filter question Message-ID: Date: Tue, 13 Sep 2005 02:37:27 GMT There are easier ways to introduce the bias than to add transformers. Personally, I hate transformers and go out of my way to avoid using them but sometimes they're a necessary evil. I'd venture to say that the transformer in this implementation of Tayloe's detector was introduced to: 1) Improve second-order distortion performance 2) Eliminate the need for differential amplifiers at the output 3) Attempt to skirt some patent issues. These are just my opinions...I'd like to hear different points of view. As to your redesign goals, be aware that the input source resistance is an important part of the inherent bandpass response that this detector has. It's based on commutating filter principles.....you can read up on this by doing a web search. The resistors were probably added to stabilize the selectivity performance in the face of variable antenna impedances. The resistors will add a little to the insertion loss and thus the system noise figure, but this will probably not be an issue at LF frequencies where atmospherics and man-made noise dominate. Overall, I think this is an outstanding detector for an LF receiver. You should be able to get very good quadrature LO phasing using the common & simple Johnson counter approach. Once you get to quadrature detector outputs, an audio frequency DSP should result in a very good receiver. As you probably know, there are several public-domain DSP software packages available for both Windows and Linux that will do a very good job for you. Joe wrote in message news:84bci1tnrobr74ju55jdt453rnr9a0hsp9@4ax.com... > Hi Joe, > > It appeared to me that the transformer was used as a convenient means > to introduce 1/2 of the Vcc to provide DC bias equally to each of the > 4 switch inputs. > > The 10 ohm series resistors look like a resistive impedance matching > scheme to me, with a built in 6+ db loss associated with them. > > I'm thinking of redoing the entire input circuit to take out hte > reistors and to better match the lower impedance of most VLF loop > antnnas. > > Thanks for your comments. > > T > > > > > > On Mon, 12 Sep 2005 23:08:13 GMT, "W3JDR" wrote: > >>If you read Gerald Youngblood's first QEX article on the SDR-1000 >>software-defined radio, you will see on page 7 another embodiment of this >>type of mixer/detector. It was originally popularized and patented by Dan >>Tayloe, but has recently been reconfigured (for patent purposes as much as >>anything else I suspect), and renamed 'quadrature sampling detector' >>(QSD). >>The original embodiment shown in the QEX article has no transformers. >> >>As a passing comment, one of the writers here said a mixer IS a detector. >>He's absolutely correct. A detector is just a special case of frequency >>mixing where the RF is mixed directly down to DC baseband. As another >>writer >>said, ALL mixers/detectors, regardless of whether they're the modern >>switching type or the antique-type based on square-law nonlinearity, have >>an >>overload point beyond which they make unacceptable distortion. Switching >>mixers, which include most double-balanced diode mixer (DBM) modules and >>most Gilbert-cell IC mixers, just happen to be more linear than many >>square-law devices up to the overload point, then they go to hell in a >>handbasket. The QSD is a just special case of switching mixer that can >>produce quadrature baseband outputs very conveniently, but it is a bit >>better in the distortion department than many diode DBM's. >> >>Joe >>W3JDR >> >> >> >> >> wrote in message >>news:ai9bi1trpko1jjk6mg75pi6mmur6qb9b81@4ax.com... >>> >>>> >>>>What would this solve ? You still need some selectivity in front of >>>>converter. >>>> >>>>I would also question the need for a bandpass filter, but a good low >>>>pass filter would definitively required in any case. I would suggest a >>>>low pass filter below 150 kHz in Europe, Africa and Middle-East and >>>>below 500 kHz in the rest of the world to get the very strong LW/MW >>>>broadcast band signals out of the mixer. If 455 kHz IF is used, the >>>>LPF would have to be below 400 kHz in the rest of the world. >>>> >>>>>I have seen designs with a SBL-1 mixer >>>> >>>>SBL-1 is specified for 1-500 MHz on the RF and LO port, so not really >>>>suitable for this band. However, the SBL-3 goes from 25 kHz to 200 >>>>MHz. The SRA-6H goes from 10 kHz to 50 MHz and should be able to >>>>handle up to +10 dBm signals. >>>> >>>>>but also a number with the NE612 >>>>>osc/mixer. >>>> >>>>I have used the Datong LF converter, which uses the Siemens S042 >>>>mixer/osc IC similar to the NE602/612 and it definitively needs a >>>>preselector in front of it to get away with spurious responses all >>>>over the LF band from broadcast stations. >>>> >>> >>> Thanks Paul, and yes....you're correct. Building a conventional >>> converter would still require a passband filter, so little is to be >>> gained, except that perhaps someone else has already done the >>> design:>: >>> >>> Also, this receiver design has no mixer, it is simply a detector and a >>> very linear one to boot. No mixing byproducts are present because >>> there is no non-linear mixer. In effect, this design is already a >>> converter....except that it converts to audio directly from the rf >>> frequency input. >>> >>> The "spurious responses all over the LF band from broadcast stations" >>> probably don't exist in this type of receiver, which is one of the >>> attractions for VLF use of this technology. >>> >>> Take a look at the link to the design in the original message and you >>> will learn how it operates without mixers and without non-linear >>> detectors. >>> >>> It's WHY I so interested in this particular method of reception and >>> WHY I want to make a front end for vlf for it. The concept is >>> explained in a QEX article in greater detail, Im happy to send the url >>> to anyone who wants to learn more about these high performance direct >>> conversion receivers. >>> >>> Regards and again, Thanks, >>> >>> T >> > Article: 94331 of rec.radio.amateur.homebrew From: "W3JDR" References: <1126570392.772936.313960@g47g2000cwa.googlegroups.com> Subject: Re: Butterworth bandpass filter question Message-ID: Date: Tue, 13 Sep 2005 02:43:25 GMT > An all software based receiver shoulnds like a neat idea until you > realize you run out of dynamic range by trying to sample such a wide > bandwidth directly. In another reply to this thread, I mentioned commutating filters. At VLF, one of these ahead of a good ADC would probably also yield very good performance without downconverting to audio baseband first. As to speed of the ADC, using undersampling you theoretically only need enough speed to sample at twice the modulation (information) bandwidth. This is just a few kilohertz sampling rate. I've heard of this technique, but don't recall ever seeing it implemented in a real receiver design. Can anyone comment and shed more light on this?? Joe W3JDR Article: 94332 of rec.radio.amateur.homebrew Date: Mon, 12 Sep 2005 22:47:47 -0400 From: -ex- Subject: Re: Amphenol Microphone Connectors (Heathkit, etc.) References: <1126467283.868773.248440@g47g2000cwa.googlegroups.com> <4324E54D.1B6CA2C7@earthlink.net> <1126565786.017061.212370@o13g2000cwo.googlegroups.com> <1126566794.914242.307060@o13g2000cwo.googlegroups.com> <43261E6B.ED5E8398@earthlink.net> <1126572313.988761.285890@z14g2000cwz.googlegroups.com> <432633B7.8BE8BDD0@earthlink.net> Message-ID: <4548f$43263dd6$4232bd50$30875@COQUI.NET> Michael A. Terrell wrote: > > How do I know what the shipping will be if I don't know the zip > code? 3 or 4 ounces in a first-class mailer is the same cost to all US destinations. 4oz would be $1.06. -Bill Article: 94333 of rec.radio.amateur.homebrew Message-ID: <432648F0.33AC8128@earthlink.net> From: "Michael A. Terrell" Subject: Re: Amphenol Microphone Connectors (Heathkit, etc.) References: <1126467283.868773.248440@g47g2000cwa.googlegroups.com> <4324E54D.1B6CA2C7@earthlink.net> <1126565786.017061.212370@o13g2000cwo.googlegroups.com> <1126566794.914242.307060@o13g2000cwo.googlegroups.com> <43261E6B.ED5E8398@earthlink.net> <1126572313.988761.285890@z14g2000cwz.googlegroups.com> <432633B7.8BE8BDD0@earthlink.net> <4548f$43263dd6$4232bd50$30875@COQUI.NET> Date: Tue, 13 Sep 2005 03:34:33 GMT -ex- wrote: > > Michael A. Terrell wrote: > > > > > How do I know what the shipping will be if I don't know the zip > > code? > > 3 or 4 ounces in a first-class mailer is the same cost to all US > destinations. 4oz would be $1.06. > > -Bill Thanks, Bill. I haven't shipped anything in about two years, so I had no what the rate was. I don't know for sure what the connector weighs, off hand, but should be about the right range after its packed. My digital postal scale only measures in quarter pounds so its only useful on heavier items. -- ? Michael A. Terrell Central Florida Article: 94334 of rec.radio.amateur.homebrew From: mcalhoun@ksu.edu Subject: Use microwave oven chassis for a radio? Date: 12 Sep 2005 23:01:40 -0500 Message-ID: I recently tore another microwave oven apart for the two really-strong magnets that are in the tube (they are fun to stack alternate-polarity on a wooden dowel so they seem to "float" in the air; kids of all ages just love to play that that "toy") (I kept the transformer, diode, capacitor, and misc. microswitches, too), and as I carried the rather bare chassis out to the garbage-can area, I wondered if anyone had ever tried built an amplifier in such a chassis -- maybe even using some of its many interlocks? -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) Article: 94335 of rec.radio.amateur.homebrew From: "Paul P" References: Subject: Re: Help identify tower manufacturer Message-ID: Date: Tue, 13 Sep 2005 05:31:31 GMT Thank you Rick for contributing. I think we have it identified. Lots of good information was received and it will help prepare to move and re-erect the tower. Several hams that have look at it commented on its good condition. It should be an easy move thanks to the guys at my club http://www.skyviewradio.net/ Any information that was send to me can be found at the page below. Thanks again, Paul. "Paul P" wrote in message news:v5fUe.214720$5N3.62635@bgtnsc05-news.ops.worldnet.att.net... > Gentlemen, > > I am attempting to identify the tower manufacture of the tower pictured > at: > http://www.ppinyot.com/antenna.htm. I would like to properly design a > base for it given the manufacturers specs plus perhaps pick up additional > sections. > > The tower seems to be of a stamped steel design (not tubular) with stamped > steel cross members. It has been well maintained by the silent key's son. > I gather it is about 10 to 15 years old. There is an unpainted ladder > chained to one side for storage. Please do not confuse this as part of the > tower. > > Also if you happen to recognize the beam please Identify it too. > > Unfortunately some one discarded all the paper work not knowing it's > value. > > Thanks Paul > > paul at ppinyot dot com > > KB3LZP > Article: 94336 of rec.radio.amateur.homebrew From: Paul Keinanen Subject: Re: Butterworth bandpass filter question Message-ID: References: <6vKdnb33bpFiL7neRVnysw@pipex.net> <2k2ai15p86rraoqt11sgl72fu1cpo7om8o@4ax.com> <1126557596.768317.288480@g14g2000cwa.googlegroups.com> Date: Tue, 13 Sep 2005 13:10:57 +0300 On Mon, 12 Sep 2005 21:31:52 -0400, TRABEM <> wrote: >It has occurred to me that the antenna itself has a great deal of >selectivity, yet some loop users still report front end overload from >AM broadcast band and other megawatt LF rf sources. Look for "antenna effect". Most likely the broadcast signals are connected directly to the pickup wiring, which works then as an ordinary "electric" antenna. One way would be to make the pickup loop of coaxial cable. Bend the end of the cable back to a convenient place on the cable to form a loop, solder the end (both centre connector and shield) to the shield at that point. At the opposite end of the loop cut the shield and now you have a nice electrostatic shield around the centre conductor. Paul OH3LWR Article: 94337 of rec.radio.amateur.homebrew From: Paul Keinanen Subject: Re: Butterworth bandpass filter question Message-ID: <6h4di1tpjl6hs71vl61fgjacgcessaf2s3@4ax.com> References: <1126570392.772936.313960@g47g2000cwa.googlegroups.com> Date: Tue, 13 Sep 2005 13:11:00 +0300 On Mon, 12 Sep 2005 21:52:01 -0400, TRABEM <> wrote: >But, if the switch is anywhere near linear, you would not want your >gain stage before the switch, would you?? I can't see using an rf amp >at the antenna that just creates non linearity when you could use a >nice quiet audio amp op amp on the far side of the analog switch. If you use a huge amplification on a single frequency, you can end up with stability problems, due to unexpected feedback paths, such as a direct conversion receiver with a lot of audio gain started to oscillate, when the loudspeaker sound vibration was connected back to some front end component that was microphonic. Putting a (possibly switchable) preamplifier between the selective loop and the mixer would allow some gain to be done at non-audio frequencies, thus, reducing the risk for stability problems. Paul OH3LWR Article: 94338 of rec.radio.amateur.homebrew Date: Tue, 13 Sep 2005 17:16:44 +0200 From: thegreatmontezuma Subject: The easiest way to get free cash! Message-ID: <4326ec6d$9$17316$756600cd@cachenews.cambrium.nl>

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Article: 94340 of rec.radio.amateur.homebrew From: nospam@nouce.bellatlantic.net Subject: Re: switching power mosfet as RF amplifiers Message-ID: <1dvdi1lqodbfnqvsvk7oh34vqgo8offr55@4ax.com> References: <1126622313.323612.14380@g44g2000cwa.googlegroups.com> Date: Tue, 13 Sep 2005 16:52:48 GMT On 13 Sep 2005 07:38:33 -0700, francesco.messineo@gmail.com wrote: >Hello, >I have lots of power mosfet (IRF640, 740, 840 and similars), I'd like >to try >to build a power amplifier for 50 MHz (even 100W CW is ok), what >parameters >of these mosfet can tell how high they can go in frequency? I've only >seen >some projects for HF bands with these kind of mosfets, so probably >there is >a good reason not to try to go higher. I think fall and rise time give >the >limit, but what else? Also, the datasheet of these devices don't have a >table of Zin and Zout, so how one is supposed to calculate them? >Thanks in advance for any hint. > >73 de > >IS0FKQ Good luck. Most of those devices will exhibit gain to amazing frequencies due the fact that fets have no real limits like junction transistors. What they do have that limits them is real world things like lead inductance, Input capacitance, output capacitance and Drain to Gate Miller capacitance all of which make it difficult to get power in and out of them as frequency increases. The input capacitance for the IRF510 is 135pf, the higher power parts can easily be upwards of 1275pf for the IFR640 (Xc of around 2ohms). Output capacitance around 400pf and feedback capacitance of 100PF also for the 640. I have driven an IRF510 at 50mhz and gotten 4.5W out of it. To do so I had to drive it as a 5 to 10ohm very reactive input, use a 24V supply and load the output to around 10ohms, and bias it for 100ma minimum. It was unstable thermally(tended to runaway toward device burnout). The output spectrum (harmonics) and IMD were poor. At 12V power out was nearly RF power input. It was more effort than driving a 2SC1307 (old cb final) at 12V, more gain and the IMD was better. At 12V the 1306 gave 6W carrier power with good stability. A pair of 2sc1971 driven pushpull easily give 10-11W carrier at 12V and are fairly clean. There are FETs characterized for RF power but they are not inexpensive and corosponding bipolar devices are fairly cheap. Allison KB1GMX