The One Tube Transmitter
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Use
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My First Transmitter
My first attempt at building a transmitter
was a kit I purchased from Antique Electronic Supply (AES)
Their kit is based on a 1939 Zenith model
S-7000 Wireless Record Player transmitter. It uses a 12SA7GT output tube.
This transmitter
will give a newby a place to start!
https://www.tubesandmore.com/products/K-488
Original Schematic as delivered.
After building it using the 12SA7GT tube I modified it to use one of 3 different output tubes either a 12BE6, 12CS6 or 12SA7GT
Below you'll see that I installed a pre-amp daughter-board. (Schematic shown further down.)
This was necessary
because most audio sources cannot deliver the 2v peak-to-peak necessary to drive
the oscillator tube.
So placing this between the audio source and the oscillator increased the modulation
to a more reasonable level.
The image below shows my original build using only the 12SA7GT output tube.
To improve the clarity, I tested both the 12BE6 & 12CS6 output tubes. I settled on the 12CS6.
Below, you see a
new 7 pin tube socket for each of the new tubes and the ribbon cable tying the
original socket to the new one.
Of course, I could only use one tube at a time.
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The AES AM Transmitter rebuilt!
Using a single, shielded, 12CS6. Much neater now!
Taking a idea from the current Nixie Tube Clocks, I've placed a green LED at the base on the output tube.
Yes the tube is shielded, so the LED would not be seen normally, but this is what hobbying is all about!
Just a little bit of bling.
2nd generation of the daughter board.
Notice that at this stage I bypassed the power supply diode with a capacitor, which helps reduce hum, noise.
However, this model does not have the full wave bridge capacitively bypassed, on the daughter-board. I change this going forward, look carefully.
