Date: Wed, 9 Feb 94 04:30:37 PST From: Ham-Homebrew Mailing List and Newsgroup Errors-To: Ham-Homebrew-Errors@UCSD.Edu Reply-To: Ham-Homebrew@UCSD.Edu Precedence: Bulk Subject: Ham-Homebrew Digest V94 #24 To: Ham-Homebrew Ham-Homebrew Digest Wed, 9 Feb 94 Volume 94 : Issue 24 Today's Topics: 100hz tone board 2m/70cm linear - circuit wanted Microphones & motorcycle helmets (2 msgs) QRP shopping list Securing VXO coils, what glue? Send Replies or notes for publication to: Send subscription requests to: Problems you can't solve otherwise to brian@ucsd.edu. Archives of past issues of the Ham-Homebrew Digest are available (by FTP only) from UCSD.Edu in directory "mailarchives/ham-homebrew". We trust that readers are intelligent enough to realize that all text herein consists of personal comments and does not represent the official policies or positions of any party. Your mileage may vary. So there. ---------------------------------------------------------------------- Date: Thu, 3 Feb 1994 19:20:53 GMT From: mvb.saic.com!unogate!news.service.uci.edu!usc!howland.reston.ans.net!vixen.cso.uiuc.edu!moe.ksu.ksu.edu!usenet-feed.umr.edu!n0mgj@network.ucsd.edu Subject: 100hz tone board To: ham-homebrew@ucsd.edu Can anyone help me with the specs on a 100hz tone board. Recently our repeter was forces to use a 100hz ctcss sub audible tone. Dose anyone have the specs on building one. It is for a mobile radio with plenty of space inside so tiny is not a necessity. Thanks in advance for any help. Willie Sandin n0mgj@eeclc.ee.umr.edu n0mgj@umr.edu ------------------------------ Date: Tue, 8 Feb 94 08:07:57 GMT From: mnemosyne.cs.du.edu!nyx!dtock@uunet.uu.net Subject: 2m/70cm linear - circuit wanted To: ham-homebrew@ucsd.edu I use a dual band Icom HT in the car. Having bent longer aerials, I now use a 1/4 wave. I could do with more 'oomph' but find commercial dual band linears excessively pricey - typically between 250 and 400 UK pounds. Can anyone give me pointers to published designs or suitable circuits to build one myself? Other comments or suggestions welcomed. Thanks David (GM0SYA) ------------------------------ Date: Sun, 06 Feb 94 21:52:26 PST From: agate!howland.reston.ans.net!sol.ctr.columbia.edu!destroyer!nntp.cs.ubc.ca!mala.bc.ca!oneb!ham!emd@network.ucsd.edu Subject: Microphones & motorcycle helmets To: ham-homebrew@ucsd.edu timi@mendel.berkeley.edu (Tim Ikeda) writes: > I'm wondering if anyone has a good system for reducing the wind > and engine noise picked up by full-faced helmet microphones. A lot > of the noise seems to come up from under the chin bar. Would it be > feasible to rig a noise-cancelling, two-microphone system such > that one microphone pointed downward is connected 180 degrees out > of phase with one aimed at the mouth? Is there somethind else that > might do the trick? I'd also like to be able to run VOX without > shouting into the mike (Shouting in the helmet seems to cause horrible > sounding audio). > > Anyone out there with some experience at rigging helmet systems? > > Regards, > Tim Ikeda > timi@mendel.berkeley.edu I'd vote for rigging a push to talk switch on the handlebars, preferably close enough to get at it with your thumb. At least, that's what I did, after no amount of fiddling would get a VOX system to work reliably. I used a Bell Star with a microphone element mounted in the chin bar padding (and an 8 ohm headphone speaker near the right ear), and wind noise only became objectionable over 120 kph or so, according to those I was talking with, anyway. A ptt switch was installed with a bracket on one of the bolts holding the front brake lever to the handlebar. Seemed to work alright, but it was distracting. Robert Smits There is *no* idiotproof filter. VE7EMD Idiots are proof against anything! Ladysmith B.C. - Richard Chycoski, VE7CVS e-mail: emd@ham.almanac.bc.ca ------------------------------ Date: 4 Feb 1994 23:22:46 GMT From: nntp.ucsb.edu!library.ucla.edu!europa.eng.gtefsd.com!howland.reston.ans.net!spool.mu.edu!sol.ctr.columbia.edu!news.kei.com!newsstand.cit.cornell.edu!newsstand.cit.cornell.edu!usenet@@.. Subject: Microphones & motorcycle helmets To: ham-homebrew@ucsd.edu In article Tim Ikeda, timi@mendel.berkeley.edu writes: > >Thanks for the post, Kevin. >I'm intrigued with your idea of using dual band HTs as a full-duplex >intercom system between the driver and the passenger. I like the >idea of a comm system that might still work even after the passenger >falls off. ;^) Well, that gets pretty expensive for a system (2 times $300 per HT plus headset) that mostly just needs a $20 intercom. :-) Fortunately I haven't lost the passenger too often. The couples that have two riders with radios do it mostly because she is a ham too and doesn't want to miss out on the conversation. Plus it cuts the entangling wiring down. > >Ultimately I'd like to rig a system (like below) for my bike. I'd >like to also find a source of good mike elements (salvaged or new) >that I could use. I've been scanning some books on op-amps for >circuits I might try, but this project could easily overwhelm my >poor circuit design abilities. So any pointers would be greatly >appreciated. > > > headset #1 headset #2 > > mic----------------------` '----------------mic > [in] > preamp/mix > | [out] | > | | (attenuation needed?) > amp mic > | >HT unit< (switching needed) > | /--- spkr > mix > phones----vol-------' `--------------vol---phones > >- Tim Ikeda (timi@mendel.berkeley.edu) Hmmm, not sure what is going on there with the ascii art (I'm not very good at that myself, and I don't read it well) but I've thought of a system where I could basically mate a radio system to an intercom system with perhaps an enhanced vox system. Features I wanted were the ability to put audio to both riders on the intercom, route my audio to the radio normally, and the 2nd person on the intercom on demand. Have full duplex intercom running all the time. At least touch on touch off control, with good sidetone so I could tell for sure when I was transmitting (maybe with a tone in my ear - or just my voice gotten louder) Havent' come up with anything yet, but I have been thinking about it. Most of the intercoms are just LM386's with a resistive divider on the input and the output paralleled to both headsets. That would work with a tap in to the mic line from the radio speaker through an attenuator, and another attenuator to take the speaker output to the helmet speakers down to mike input levels. I've definately thought about this at times, but sort of ran out of impetus to continue on the project last summer. Maybe this year... For vox, I think I'd want a good sidetone so I could tell when I was keyed up, a timer to kill it after 30 seonds or so anyway, a quick 'kill ptt' button to lock off the transmitter when I don't want to vox, and probably some fancy differential filtering circuit to compare road noise to voiceband levels and only key if the voiceband to noise ratio goes up, not if they both go up (to keep it from keying by a general rise in noise from a truck or increased wind. You might ride into a headwind you know :-) Could you give me a text description of your desired circuit so I can maybe make better comments? Kevin ------------------------------ Date: Tue, 8 Feb 1994 19:50:03 GMT From: crl.dec.com!crl.dec.com!nntpd.lkg.dec.com!ryn.mro.dec.com!est.enet.dec.com!randolph@decwrl.dec.com Subject: QRP shopping list To: ham-homebrew@ucsd.edu With flea market season rapidly approaching here in the NE, I sat down with W1FB's QRP Notebook and went through all the schematics to compile this parts list. This is everything that appears 3 or more times in the book, except for important stuff like chips. Buy lots of it if it has a + next to it. So now you all can fill up your QRP junk boxes... Transistors Amidon cores Diodes Chokes Enamel Hardware 2N2222A+ T24-43 ? 1N914+ 1mH+ Wire 6-32 2N3553 T37-6+ 22uH+ #18 4-40 2N3866 T50-2+ Zeners 15uH #20 2N3904+ T50-6+ 6.8V 10uH #24 2N4400+ T68-2+ 9.1V #26 2N4401+ T68-6 15V #28 2N4403+ FT37-43+ 33V #30 2N4416+ FT50-43+ 56V (0.4 & 1W) 2N5179+ FT50-63 MPF102+ BLN43-202 40673 (NTE222) Bead, 850mu Chips Op Amps Pots Mini Air Ceramic or CA3028 (RCA) 741 100k+ Variable Mica Trimmer CA3046 747 10k+ 15 5 50 LM386 (Natl) TL081 (TI) 1k 25 10 60+ LM723 50 15 100+ MC1350P (Moto) 100+ 25 300 MC1496G 150 MC3346P MWA110 NE555 (Sig) NE602 uPC1651G (NEC) Disk Ceramic NP0 Electrolytic Polystyrene 22 100+ 0.001++ (102) 22 100+ or Tantulum 220 27 130 0.005 (502) 27 130 1+ 560 33 150+ 0.01++ (103) 47+ 150 2.2+ 1000 47+ 220 0.1++ (104) 56+ 220 4.7 1500 56+ 470 68 10+ 2000 68+ 680 22+ (16 & 25V) 2200+ 220 10000 15000 Resistors (1/4 & 1/2w, comp or film) 10+ 100++ 1.0k++ 10k++ 100k++ Silver Mica 15 150 1.5k+ 12k 220k+ 130 390 22 180+ 2.2k+ 15k 470k+ 150+ 470 33+ 220 2.7k 22k+ 180+ 560 47+ 270+ 3.3k+ 27k+ 220 750 56+ 390 3.9k 33k 240 1000 470+ 4.7k+ 47k+ 270+ 1200 560+ 5.6k+ 56k+ 330 -Tom R. N1OOQ randolph@est.enet.dec.com ------------------------------ Date: 3 Feb 94 20:56:42 GMT From: sdd.hp.com!col.hp.com!srgenprp!alanb@hplabs.hp.com Subject: Securing VXO coils, what glue? To: ham-homebrew@ucsd.edu asirene@ntuvax.ntu.ac.sg (asirene@ntuvax.ntu.ac.sg) wrote: : Hi, : I am winding some coils for a VXO and want to know if : the "glue-gun" melted plastic is suitable for securing the coil : or if it is too lossy? Most of the low-temperature thermoplastics like polyethelene, polystyrene, etc have low loss at RF frequencies. My guess is that hot-melt glue would probably work fine, especially if you don't use huge gobs of it. AL N1AL ------------------------------ Date: Fri, 04 Feb 1994 18:18:57 -0800 From: munnari.oz.au!metro!dmssyd.syd.dms.CSIRO.AU!dmsperth.per.dms.CSIRO.AU!uniwa!harbinger.cc.monash.edu.au!yeshua.marcam.com!news.kei.com!eff!usenet.ins.cwru.edu!agate!NewsWatcher!user@@. To: ham-homebrew@ucsd.edu References , , <2iulc6INNgak@newsstand.cit.cornell.edu>.marcam. Subject : Re: Microphones & motorcycle helmets In article <2iulc6INNgak@newsstand.cit.cornell.edu>, F. Kevin Feeney wrote: [...] >For vox, I think I'd want a good sidetone so I could tell when I was >keyed up, a timer to kill it after 30 seonds or so anyway, a quick 'kill >ptt' button to lock off the transmitter when I don't want to vox, [...] Would it be possible to detect transmission from the antenna? Something that would detect a voltage potential in the line and also have high impedance? That signal could be used to gate a tone or start a timer. >Could you give me a text description of your desired circuit so I can >maybe make better comments? It's is very similar to what you've described. Ok, here goes. Starting from the input - Signals from both the driver's and passenger's microphones are put through a preamplifier and mixed. Part of this amplified signal is sent to the microphone input of the radio. If there's a preamp before the radio input, I think I'll need to bring the signal back down again before putting into the radio. Or maybe I'd better skip the pre-amp step? Output: Output from the microphone preamp is boosted to a level needed to drive headset speakers. I don't know whether I need the preamp/amp combination or if a single-step amplifier will do the trick. I recently tried and failed to build a stable, single-step microphone- to-speaker amp so that's why I'm considering a preamp. (Oddly enough, my "custom amp" worked just fine as a broadband AM receiver - my first homebrewed radio in ten years!). The audio signal is also mixed with the speaker output from the radio and the mixed audio is finally sent out to the headphones; each with their own volume control pots. Switches: To be announced. I'm not sure yet. As Ted kennedy says, "I'll drive off that bridge when I come to it." Basically, it looks like a three-person intercom with a radio plugged in as the third party. Neither rider will be left out of a conversation. Because the helmets and earplugs reduce hearing, each rider gets their voice fed back into their earpieces to compensate. That should prevent the mistake of screaming into the microphone because you can't hear your own voice. Of course, all of this would be a lot simpler if I knew what the heck I was doing. Regards, Tim Ikeda timi@mendel.berkeley.edu PS - Thanks for all those who sent me ideas via email. ------------------------------ Date: 3 Feb 1994 15:37:15 GMT From: news.cstar.andersen.com!news.acns.nwu.edu!casbah.acns.nwu.edu!rdewan@uunet.uu.net To: ham-homebrew@ucsd.edu References <1994Jan25.191202.1@ntuvax.ntu.ac.sg>, <1994Jan26.001852.3038@ke4zv.atl.ga.us>, ews Subject : Re: Antenna pre-amp design. Help! In article , Masahiro KITAGAWA wrote: >asirene@ntuvax.ntu.ac.sg writes: >9V Daniel>> Can anyone here give me some advice on building an antenna >9V Daniel>> pre-amp for working 4 - 24 mHz? Should I go broadband or >9V Daniel>> switched bands? What about pre-filtering? > >Please use MHz if you mean 1,000,000 Hz. mHz is 0.0001 Hz. ^^^^^^^^^^^^^ Gosh. If you must nit-pick, at least get it right. Rajiv aa9ch r-dewan@nwu.edu ------------------------------ End of Ham-Homebrew Digest V94 #24 ****************************** ******************************