AM Transmitter

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AM Transmitter

Post by harold wright on Thu Dec 13, 2012 9:47 pm

A friend wants me to build a mini AM transmitter that would allow him to play his favorite sounds through his old AM radios. He also likes to see tubes that glow blue, violet, etc.
I am thinking of maybe splitting the audio signal--one to modulate the transmitter and another audio sig. to modulate a VR tube to make it vary in intensity in step with the modulation, just for the visual effect. Any pointers, anyone?

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Re: AM Transmitter

Post by willy3486 on Fri Dec 14, 2012 10:06 am

There is a kit called sstran or something to that effect. I bought the 30 buck special from Ramsey electronics just because I wanted a kit to build and thats the one I thought I could use. It works but isn't the best. The signal will drift then you have to tune it in. There was a record player back in the 30s or 40s that had a transmitter built in to it that would transmit to AM. I don't remember the brand but Antique Electronic Supply sold a kit that had the tube and all parts based on it. I think I saw a diagram for one in my old NRI manuals from the 40s. I will try to look to see if I can find one in it. I am not 100 % certain it was in there.

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Re: AM Transmitter

Post by Bill Cahill on Fri Dec 14, 2012 10:30 am

Actually, a number of mannufacturers made am oscillators to play your records through your radio. I had a 60's NRI kit radio that could also be turned intoan am oscilator using the speaker as a microphone. I had that kit as a teen. It was fun. Wish I had another.
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Re: AM Transmitter

Post by Motorola man on Fri Dec 14, 2012 10:23 pm

I built a transmitter from an AA5. It's really easy to do, only takes a few minutes and sound quality pretty decent. Range is a bit limited but it's enough to cover an average sized room. For those of you who may shutter at the idea of hacking up a perfectly good radio, it's easily reversable. There are written instructions & videos available online.
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Re: AM Transmitter

Post by N7ZAL on Fri Dec 14, 2012 10:48 pm

Where???
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Re: AM Transmitter

Post by samd on Sat Dec 15, 2012 5:09 am

N7ZAL wrote:Where???


Ditto'!

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Re: AM Transmitter

Post by harold wright on Sat Dec 15, 2012 8:22 am

Thanks for info/responses. I have built a few also. What I really want to do is incorporate the "modulated" volt. regulator tube for the visual effect. I have never seen any info about such on a very low power transmitter. I have seen 866/3B28 rectifiers flicker when a 500 watt AM transmitter was on air.

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Re: AM Transmitter

Post by Motorola man on Sat Dec 15, 2012 7:55 pm

N7ZAL & SAMD, do a Google search for "AA5 transmitter".
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Re: AM Transmitter

Post by 35Z5 on Wed Dec 26, 2012 7:42 pm

willy3486 wrote:There is a kit called sstran or something to that effect. I bought the 30 buck special from Ramsey electronics just because I wanted a kit to build and thats the one I thought I could use. It works but isn't the best. The signal will drift then you have to tune it in. There was a record player back in the 30s or 40s that had a transmitter built in to it that would transmit to AM. I don't remember the brand but Antique Electronic Supply sold a kit that had the tube and all parts based on it. I think I saw a diagram for one in my old NRI manuals from the 40s. I will try to look to see if I can find one in it. I am not 100 % certain it was in there.

Wonder if one could use the 1st audio to drive a tube that was fed B+ through a VR75 or similar not using a transformer(only a current limiting resistor)??? Adjusting screen value res would limit total current... I'd think it could be any odd beam power or power pentode... What I dunno if there is enough variance in current to make the regulator "dance"...

For design you'll find I'll po-po anything series string without at least a isolation transformer, especially if you are giving it to a friend... I use this dual control pentode design and have since early 2007... It's on almost 24/7 and is light years ahead of any phono osc or Tx built from a AA5...

http://amradio.freeiz.com/transmitter/6bk76gy6.jpg


Tom
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Re: AM Transmitter

Post by Guest on Wed Dec 26, 2012 7:48 pm

I guess I missed this thread and started this one;

http://www.tuberadioforum.com/t1797-am-transmitter-kits

Now we have all the info together. Smile

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Re: AM Transmitter

Post by N7ZAL on Wed Dec 26, 2012 9:41 pm

N7ZAL & SAMD, do a Google search for "AA5 transmitter".

I have better uses for my time. Wink Wink
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Re: AM Transmitter

Post by harold wright on Wed Dec 26, 2012 10:50 pm

35Z5/Tom
Thanks. That is getting "into the ball park" of what I had in mind.
Will have to do some experimenting.

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Re: AM Transmitter

Post by 35Z5 on Thu Dec 27, 2012 10:23 am

Would be easy to experiment a bit with a VR75 when you're doing a recap on a radio... Basically sub the regulator and current limiting resistor for the output xformer...

If you have a extra eye tube laying around(wild thought eh?), you could build a simple circuit to modulate it like was used in the Eico 147A signal tracer, schematic is on BAMA...
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Re: AM Transmitter

Post by Wildcat445 on Thu Dec 27, 2012 1:33 pm

I built a transmitter from an old Lafayette signal generator. It works "okay" on AM, but is not nearly as good as an SStrans.

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Re: AM Transmitter

Post by Brig on Wed Mar 20, 2013 6:50 pm

I use a Lodestar model 4160B (sold by AES and others) as a home transmitter. As I listen to it rebroadcast FM throughout my house (occasionally all day) I wonder how the SStrans or other commercial devices could perform any better. It does require a small preamp to broadcast CDs with adequate volume, but this is no problem. I'd enjoy hearing from others who can compare the signal generator route with AA5 conversion and other ways.

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Re: AM Transmitter

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