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 Post subject: AM Transmitter schematic
PostPosted: Apr Sun 21, 2019 7:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1244
Location: Knoxville TN
Hello, I want to build a household tube transmitter for the fun of it. I have an SS Tran 3000 but I want to challenge myself and make one with tubes. This will be for local broadcast (as in my house) 25-30 YARDS would be plenty.


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 Post subject: Re: AM Transmitter schematic
PostPosted: Apr Sun 21, 2019 9:53 pm 
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Joined: Feb Sat 06, 2016 1:47 am
Posts: 2907
Location: La Mesa Califonia
Will this do ?


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 Post subject: Re: AM Transmitter schematic
PostPosted: Apr Sun 21, 2019 11:01 pm 
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Joined: Dec Sun 29, 2013 10:11 pm
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Location: Richmond, Va.
T'bird - What are the specs on the coil, and what type of antenna does it require? CharlesD


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 Post subject: Re: AM Transmitter schematic
PostPosted: Apr Mon 22, 2019 1:17 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 12549
Location: Mpls, Minnesota
There are much better performing transmitters than the one posted by T bird. Do a search in this section and you will come up with a couple of very good designs.

Dave


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 Post subject: Re: AM Transmitter schematic
PostPosted: Apr Mon 22, 2019 11:43 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3220
Location: Nr London, England, SS1 3PT
Hello Jim

https://www.vintage-radio.net/forum/sho ... hp?t=26009

Have a read here. I built mine maybe a dozen years ago and its worked fine all that time. Usual problems with Hum from intermodulation. If you feel like making it then give me an e-mail and I will send you my tips on minimising this.

Heres some comparison to an SStran that a friend had . Radio in use was a top quality HMV radiogram.

Once I had sorted the MATE out for mains hum / intermodulation it sounds fine to me, I'm not convinced a little FM will produce objectionable distortion.

Side by side comparisons are never easy, and the MATE takes time to warm up, but changing from one to the other I think you would have to be very discerning to tell whether you were listening to it or the SStran in a blind test.


Gary


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 Post subject: Re: AM Transmitter schematic
PostPosted: Apr Mon 22, 2019 12:57 pm 
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Location: La Mesa Califonia
Antenna is a wire around 4 to five feet. Coil is here.

https://www.tubesandmore.com/products/coil-oscillator


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 Post subject: Re: AM Transmitter schematic
PostPosted: Apr Mon 22, 2019 2:06 pm 
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Location: Hebron, Ky
Rick McWhorter has a schematic and instructions that can be found at this site for what looks like a pretty awesome transmitter:

http://www.richardmcwhorter.com/AM_Transmitter/

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 Post subject: Re: AM Transmitter schematic
PostPosted: Apr Mon 22, 2019 9:09 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2284
Location: Saskatoon
Doubtful that any of the transmitters at those posted links could hold a candle to Norm's simple 6888 transmitter:
viewtopic.php?f=12&t=63310
Also, check out 35Z5's 6GY6 transmitters:
viewtopic.php?t=68236


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 Post subject: Re: AM Transmitter schematic
PostPosted: Apr Tue 23, 2019 1:25 am 
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mugginsjr wrote:
Rick McWhorter has a schematic and instructions that can be found at this site for what looks like a pretty awesome transmitter:

http://www.richardmcwhorter.com/AM_Transmitter/

LOL, that thing's mostly for looks & has a hot tuning cap to boot.

The 6888, 6GY6 and other dual control pentodes modulate with far more depth than anything with a remote cutoff pentagrid amp.

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 Post subject: Re: AM Transmitter schematic
PostPosted: Apr Wed 24, 2019 1:14 am 
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Joined: Apr Thu 14, 2016 8:25 pm
Posts: 462
Location: pensacola fl
There is also the 12CS6 version.


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 Post subject: Re: AM Transmitter schematic
PostPosted: Apr Sat 27, 2019 7:59 pm 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 2978
Location: Lexington, KY USA
Don't even consider building one like this without modifications for safety:


Image

Note that the audio input jack is connected directly to the AC line.

If you want to use this circuit, add a proper power transformer, or an AC line isolation transformer.

Yes, 120V usually won't kill you, but sometimes it does. There are quite a few such circuits floating around; this isn't the only one. Some have capacitors in series with the audio input common connection. This may keep you alive, but introduces a good chance for lots of hum.

The remote cutoff 6SA7 is not your best choice for an oscillator / modulator tube, either. The remote cutoff signal grid characteristic introduces audio distortion. There's a good selection of $1.00 tubes that will do better. If you do use a pentagrid tube, it might be worthwhile to separate the oscillator and modulator functions, using a second tuned circuit to couple the plate to your antenna.

Study the linked threads for lots of ideas.

Ted


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 Post subject: Re: AM Transmitter schematic
PostPosted: May Fri 10, 2019 1:16 pm 
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Location: Hebron, Ky
Just wondering Tim, did you build one? If so, which one?

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 Post subject: Re: AM Transmitter schematic
PostPosted: May Thu 16, 2019 7:44 pm 
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mugginsjr wrote:
Just wondering Tim, did you build one? If so, which one?

Tim, Ted or Tom?

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