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 Post subject: whats a good and simple audio transmitter design?
PostPosted: Jul Thu 12, 2012 2:24 am 
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Joined: Jan Tue 25, 2011 4:40 am
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Location: washington state
So ive just gotten my three tube regen receiver working nicely. Id like to build a simple audio transmitter to match it. Simple as in low parts and tube count and hopefully using the older style tubes, 4 or 5 pins. Being underpowered isnt much of a problem, as my main goal is to have it transmit across the room to my receiver.

Can anyone recommend a design for me? Ive looked at a ton and now im just confused.

My radio uses plug in coils. During the night im getting excellent reception on AM and poor reception on SW. My antenna isnt designed for SW, so i blame it on that. But if i was just going to transmit to such a short distance, wouldnt it be best to build the transmitter for SW then, as it would be uncrowded?

Well im sitting here unsure what to do and which design to choose, any help is appreciated.

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 Post subject: Re: whats a good and simple audio transmitter design?
PostPosted: Jul Thu 12, 2012 3:08 am 
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Fixed frequency 1000kHz
Under $5
http://www.instructables.com/id/Make-a- ... ansmitter/
Click Download PDF


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 Post subject: Re: whats a good and simple audio transmitter design?
PostPosted: Jul Thu 12, 2012 3:25 am 
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Joined: May Tue 30, 2006 4:46 pm
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Location: Santa Rosa, CA
Quote:
During the night im getting excellent reception on AM and poor reception on SW. My antenna isnt designed for SW, so i blame it on that.


Depending on the SW frequency, there is little propagation at night... this is especially true if you are listening at 12 MHz and above. The antenna is probably not the culprit.

Quote:
But if i was just going to transmit to such a short distance, wouldnt it be best to build the transmitter for SW then, as it would be uncrowded?


Transmitting on SW requires an FCC license. You can build simple transmitters for the AM broadcast band (very low power and short antenna). These are covered under FCC rules Part 15 and you will find lots of ideas in the Homebrew Radio section of this Forum.

Rich


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 Post subject: Re: whats a good and simple audio transmitter design?
PostPosted: Jul Fri 13, 2012 2:10 am 
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Joined: Jan Tue 31, 2012 2:17 am
Posts: 30
The book titled "The Boy's Second Book of Radio and Electronics" by Alfred Morgan, publ. Scribners 1957, SBN# 684-13154-4, pp.254-268 contains a complete design, schematic, parts list and instructions for building a low powered audio (phono) transmitter of limited range using two vacuum tubes. It operates in the broadcast band. Its a nice project and it will do exactly what you're looking to do, and all the parts should be available. Although the tank circuit might be the only challenge to find, you can probably fabricate one yourself from modifying an AM broadcast band RF circuit tuning coil. The tubes are 6F7 and 25Z5 rectifier. Not 4 or 5 pin but close, still ST tubes.

Alternatively, if you're looking for something a little more period and challenging you may want to check out an ARRL "The Radio Amateur's Handbook" from the early 20's through about 1930 for tube transmitter design, circuits and construction with part lists. Several simple designs available for CW but more complex for radiophone. You'll need to hunt down the parts, alot more challenging and seriously depower it so as not to broadcast over more than a few tens of feet.

I'd recommend the former as its readymade and an open breadboard type so should look really cool alongside the radio. Most early amateur transmitters were homebrew. BTW whats the 3 tube radio?


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 Post subject: Re: whats a good and simple audio transmitter design?
PostPosted: Jul Fri 13, 2012 2:20 am 
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Location: Lehighton, PA.
http://antiqueradios.com/forums/viewtopic.php?f=12&t=193042

http://antiqueradios.com/forums/viewtopic.php?f=12&t=186658

http://antiqueradios.com/forums/viewtopic.php?f=12&t=132867

Larry

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 Post subject: Re: whats a good and simple audio transmitter design?
PostPosted: Jul Sat 14, 2012 12:40 am 
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Joined: Jan Tue 25, 2011 4:40 am
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Location: washington state
radiomania wrote:
BTW whats the 3 tube radio?


Its just a homebrew i tinkered together with junk shop and ebay parts. Basically i copied the westinghouse aeriola sr circuit, well i used a cx-301-a (i tried several types of four pin tubes and this was the most sensitive. I just changed it to plug in coils, added an rf choke and changed the filament and plate voltages. Then added two 201a rf stages onto it. Works pretty decent during the day and darned if it doesnt work as good as a real radio at night. Im surprised i could build a well functioning receiver, thats why i want to build a small transmitter now. I guess i got bit by the homebrew bug and now want to try something different.

As I currently cannot find an audio transmitter design that uses 4 or 5 pin tubes, im going to placate myself with building a little morse transmitter. Though im still looking for an early tube audio transmitter design.

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 Post subject: Re: whats a good and simple audio transmitter design?
PostPosted: Jul Sat 14, 2012 3:50 am 
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jbivy wrote:
radiomania wrote:
BTW whats the 3 tube radio?


"As I currently cannot find an audio transmitter design that uses 4 or 5 pin tubes, im going to placate myself with building a little morse transmitter. Though im still looking for an early tube audio transmitter design."


OK. Well you'll certainly find what you're looking for in the early ARRL Amateur Radio Handbooks. The design for the morse transmitter, which you've shown above, a single tube Armstrong oscillator, should work just fine. Best of luck with your project.


Last edited by radiomania on Jul Sat 14, 2012 4:28 am, edited 1 time in total.

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 Post subject: Re: whats a good and simple audio transmitter design?
PostPosted: Jul Sat 14, 2012 4:20 am 
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"What's a good and simple audio transmitter design?"

Decent bandwith, but you'll only be able to transmit a couple hundred feet with it... :mrgreen:

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 Post subject: Re: whats a good and simple audio transmitter design?
PostPosted: Jul Sat 14, 2012 5:04 am 
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Joined: Jan Tue 25, 2011 4:40 am
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Location: washington state
Nick D. wrote:
"What's a good and simple audio transmitter design?"

Decent bandwith, but you'll only be able to transmit a couple hundred feet with it... :mrgreen:


No worries there, as my goal is to transmit..... all the way from one end of my house to the other!

Im bored and like tinkering, thats it. Maybe an audio transmitter is out of my skill range anyhow, at least for now. But as ive near every piece for this little armstrong oscillator, i cant see a reason not to build it.

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 Post subject: Re: whats a good and simple audio transmitter design?
PostPosted: Jul Sat 14, 2012 11:25 am 
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Check the Home Brew area of this forum. There used to be several schematics and there is one for a TNT transmitter, 1929 vintage.

Yes the old Handbooks have a lot of great projects, in fact I'm currently working on one from 1944.

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