Re: [AMRadio] More on the T-368 exciter
It is my understanding that the heating element that envelops the PTO in all these rigs is designed for operation under extreme temperature conditions, and it is not meant for improving stability at normal ambient temperatures. The drift problem is caused by turning the oscillator stage off during receive periods and starting it back up at every transmission. It takes a few minutes for the components inside the can to come to constant operating temperature. Running the tube filaments all the time won't cure the problem; you need to run the oscillator plate voltage all the time too. My 75A-4 does the same thing when I first turn it on from a cold start. Isolating the oscillator stage well enough that I can keep it running all the time completely cured the problem with mine. Another cause of drift in both my exciter PTO and the 75A-4 is slight variations in oscillator tube filament voltage due to line voltage changes. I found that even a change of only one or two volts from the nominal 115 volt mains voltage was enough to cause noticeable drift. So I run my T-360 PTO unit tube filaments off a regulated 6-volt DC supply that I happened to have on hand. For the 75A-4 I run the whole receiver off a miniature Sola constant voltage transformer that I found at a hamfest. It was probably manufactured sometime in the mid 1980's, and was designed to run a personal computer in an office setting, so it is very quiet, without the loud buzzing noise that most of these transformers are notorious for. It is rated for 75 watts, just about exactly what the 75A-4 draws. The T-368 drift shouldn't be enough to hurt anything when running AM, but it can be a problem with CW on the higher frequency bands, since the oscillator frequency is multiplied for the upper ranges. I once tried connecting up the heater in one of my R-390A's. It actually worsened the frequency wandering as the thermostat tripped on and off. It takes a substantial temperature variation to activate the thermostat. One possibility might be to disconnect the thermostat and run the heater at reduced voltage during stand-by periods, using a relay powered by the station's transmit-receive switching system. Feed the heating element from a variable voltage power supply, perhaps a 24v transformer running off a variac, and experiment to see if there is a voltage setting that exactly compensates for the cool-down while the oscillator is on stand-by. Then a small transformer with the proper output voltage could be wired in permanently. Don k4kyv ___ This message was typed using the DVORAK keyboard layout. http://www.mwbrooks.com/dvorak/ http://gigliwood.com/abcd/ __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Tube Theremin
I went and found the book. I'll get it scanned at school (I'm now a music teacher) by this weekend so we can post it. It's funny to read the old style schematics. ken --- On Thu, 3/26/09, sbjohns...@aol.com wrote: > From: sbjohns...@aol.com > Subject: Re: [AMRadio] Tube Theremin > To: amradio@mailman.qth.net > Date: Thursday, March 26, 2009, 11:02 PM > Ken, that sounds great. We could also post it online for > others. > > Thanks... > > Steve WD8DAS > > sbjohns...@aol.com > http://www.wd8das.net/ > - > Radio is your best entertainment value. > - > > > -Original Message- > From: Ken Zuercher > To: Discussion of AM Radio in the Amateur Service > > Sent: Thu, 26 Mar 2009 8:36 pm > Subject: Re: [AMRadio] Tube Theremin > > > > > Steve, > I have a manual for what I believe is the first > commercially available > Theremin > made by RCA in the 1930's. It uses the same hetrodyning > principal but > uses some > oddball transformers that would give us fits to replicate. > I can try to > scan the > manual with schematic if you're interested. It is > fascinating. > Ken Zuercher KC8QO > > > --- On Fri, 3/20/09, sbjohns...@aol.com > wrote: > > > From: sbjohns...@aol.com > > Subject: [AMRadio] Tube Theremin > > To: amradio@mailman.qth.net > > Date: Friday, March 20, 2009, 4:08 PM > > I've got a new sort-of AM project on the bench > here > > now:? a tube Theremin.? This musical instrument > produces > > sound by heterodyning two > > oscillators that run in the low-end of the broadcast > band. > > I'd like to find three Miller 70-OSC coils or > > equivalent for this rig - anyone have some?? > > > > > > > > If you are interested in the circuit, I'm building > upon > > the ideas of Doug Forbes that I found online.? > > > > See > > > > http://www.wd8das.net/theremin.gif > > > > and > > > > http://www.wd8das.net/theremin.txt > > > > > > > > Thanks... > > > > > > > > > > > > > > > > > > > > > > > > Steve WD8DAS > > > > > > > > sbjohns...@aol.com > > > > http://www.wd8das.net/ > > > > > - > > > > Radio is your best entertainment value. > > > > > - > > > > > > > __ > > Our Main Website: http://www.amfone.net > > AMRadio mailing list > > Searchable Archives: > > http://www.mail-archive.com/amradio@mailman.qth.net/ > > List Rules (must read!): > http://w5ami.net/amradiofaq.html > > List Home: > http://mailman.qth.net/mailman/listinfo/amradio > > Post: AMRadio@mailman.qth.net > > To unsubscribe, send an email to > > amradio-requ...@mailman.qth.net with > > the word unsubscribe in the message body. > > > > This list hosted by: http://www.qsl.net > > Please help support this email list: > > http://www.qsl.net/donate.html > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: > http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Post: AMRadio@mailman.qth.net > To unsubscribe, send an email to > amradio-requ...@mailman.qth.net with > the word unsubscribe in the message body. > > This list hosted by: http://www.qsl.net > Please help support this email list: > http://www.qsl.net/donate.html > > > > > > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: > http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Post: AMRadio@mailman.qth.net > To unsubscribe, send an email to > amradio-requ...@mailman.qth.net with > the word unsubscribe in the message body. > > This list hosted by: http://www.qsl.net > Please help support this email list: > http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Tube Theremin
Thats a great idea as I was wondering about it also On Thu, Mar 26, 2009 at 9:02 PM, wrote: > > Ken, that sounds great. We could also post it online for others. > > Thanks... > > Steve WD8DAS > > sbjohns...@aol.com > http://www.wd8das.net/ > - > Radio is your best entertainment value. > - > > > -Original Message- > From: Ken Zuercher > To: Discussion of AM Radio in the Amateur Service > > Sent: Thu, 26 Mar 2009 8:36 pm > Subject: Re: [AMRadio] Tube Theremin > > > > > Steve, > I have a manual for what I believe is the first commercially available > Theremin > made by RCA in the 1930's. It uses the same hetrodyning principal but > uses some > oddball transformers that would give us fits to replicate. I can try to > scan the > manual with schematic if you're interested. It is fascinating. > Ken Zuercher KC8QO > > > --- On Fri, 3/20/09, sbjohns...@aol.com wrote: > >> From: sbjohns...@aol.com >> Subject: [AMRadio] Tube Theremin >> To: amradio@mailman.qth.net >> Date: Friday, March 20, 2009, 4:08 PM >> I've got a new sort-of AM project on the bench here >> now:? a tube Theremin.? This musical instrument produces >> sound by heterodyning two >> oscillators that run in the low-end of the broadcast band. >> I'd like to find three Miller 70-OSC coils or >> equivalent for this rig - anyone have some?? >> >> >> >> If you are interested in the circuit, I'm building upon >> the ideas of Doug Forbes that I found online.? >> >> See >> >> http://www.wd8das.net/theremin.gif >> >> and >> >> http://www.wd8das.net/theremin.txt >> >> >> >> Thanks... >> >> >> >> >> >> >> >> >> >> >> >> Steve WD8DAS >> >> >> >> sbjohns...@aol.com >> >> http://www.wd8das.net/ >> >> - >> >> Radio is your best entertainment value. >> >> - >> >> >> __ >> Our Main Website: http://www.amfone.net >> AMRadio mailing list >> Searchable Archives: >> http://www.mail-archive.com/amradio@mailman.qth.net/ >> List Rules (must read!): http://w5ami.net/amradiofaq.html >> List Home: http://mailman.qth.net/mailman/listinfo/amradio >> Post: AMRadio@mailman.qth.net >> To unsubscribe, send an email to >> amradio-requ...@mailman.qth.net with >> the word unsubscribe in the message body. >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: >> http://www.qsl.net/donate.html > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: > http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Post: AMRadio@mailman.qth.net > To unsubscribe, send an email to amradio-requ...@mailman.qth.net with > the word unsubscribe in the message body. > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > > > > > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Post: AMRadio@mailman.qth.net > To unsubscribe, send an email to amradio-requ...@mailman.qth.net with > the word unsubscribe in the message body. > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > -- Jim Isbell "If you are not living on the edge, well then, you are just taking up too much space." __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Tube Theremin
Ken, that sounds great. We could also post it online for others. Thanks... Steve WD8DAS sbjohns...@aol.com http://www.wd8das.net/ - Radio is your best entertainment value. - -Original Message- From: Ken Zuercher To: Discussion of AM Radio in the Amateur Service Sent: Thu, 26 Mar 2009 8:36 pm Subject: Re: [AMRadio] Tube Theremin Steve, I have a manual for what I believe is the first commercially available Theremin made by RCA in the 1930's. It uses the same hetrodyning principal but uses some oddball transformers that would give us fits to replicate. I can try to scan the manual with schematic if you're interested. It is fascinating. Ken Zuercher KC8QO --- On Fri, 3/20/09, sbjohns...@aol.com wrote: > From: sbjohns...@aol.com > Subject: [AMRadio] Tube Theremin > To: amradio@mailman.qth.net > Date: Friday, March 20, 2009, 4:08 PM > I've got a new sort-of AM project on the bench here > now:? a tube Theremin.? This musical instrument produces > sound by heterodyning two > oscillators that run in the low-end of the broadcast band. > I'd like to find three Miller 70-OSC coils or > equivalent for this rig - anyone have some?? > > > > If you are interested in the circuit, I'm building upon > the ideas of Doug Forbes that I found online.? > > See > > http://www.wd8das.net/theremin.gif > > and > > http://www.wd8das.net/theremin.txt > > > > Thanks... > > > > > > > > > > > > Steve WD8DAS > > > > sbjohns...@aol.com > > http://www.wd8das.net/ > > - > > Radio is your best entertainment value. > > - > > > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: > http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Post: AMRadio@mailman.qth.net > To unsubscribe, send an email to > amradio-requ...@mailman.qth.net with > the word unsubscribe in the message body. > > This list hosted by: http://www.qsl.net > Please help support this email list: > http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [AMRadio] Tube Theremin
Steve, I have a manual for what I believe is the first commercially available Theremin made by RCA in the 1930's. It uses the same hetrodyning principal but uses some oddball transformers that would give us fits to replicate. I can try to scan the manual with schematic if you're interested. It is fascinating. Ken Zuercher KC8QO --- On Fri, 3/20/09, sbjohns...@aol.com wrote: > From: sbjohns...@aol.com > Subject: [AMRadio] Tube Theremin > To: amradio@mailman.qth.net > Date: Friday, March 20, 2009, 4:08 PM > I've got a new sort-of AM project on the bench here > now:? a tube Theremin.? This musical instrument produces > sound by heterodyning two > oscillators that run in the low-end of the broadcast band. > I'd like to find three Miller 70-OSC coils or > equivalent for this rig - anyone have some?? > > > > If you are interested in the circuit, I'm building upon > the ideas of Doug Forbes that I found online.? > > See > > http://www.wd8das.net/theremin.gif > > and > > http://www.wd8das.net/theremin.txt > > > > Thanks... > > > > > > > > > > > > Steve WD8DAS > > > > sbjohns...@aol.com > > http://www.wd8das.net/ > > - > > Radio is your best entertainment value. > > - > > > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: > http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Post: AMRadio@mailman.qth.net > To unsubscribe, send an email to > amradio-requ...@mailman.qth.net with > the word unsubscribe in the message body. > > This list hosted by: http://www.qsl.net > Please help support this email list: > http://www.qsl.net/donate.html __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: AMRadio@mailman.qth.net To unsubscribe, send an email to amradio-requ...@mailman.qth.net with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
