The Experimental Radio Project
 

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The schematic.
Not the greatest feat of engineering in the world, but it works well for such a simple radio, and even picks up some shortwave at night!

A technician friend pointed out that it appears the RF Gain control can short out the battery. Not really, there is a 1K resistor ahead of the
control. With the control set to 0 ohms I did not see the battery voltage drop at all. With the volume control set to minimum, the set draws
6 mA of current. Setting the RF gain control to 0 ohms causes the current draw to increase to 12 mA. At full volume the set draws
50+ milliamps. Since the listener would never turn the RF Gain control to 0, this seemed acceptable.


 
So what happened to the cool TANDEM TUNER?
I still have the coils
 
I tore out the TANDEM TUNER before I got the RF amp working. In the future I'll wire it back up with the solderless breadboard and see how it works.

 Now you may ask yourself "Why would anybody want to turn all those knobs to tune in a radio station?"
Well first of all, it's fun! Secondly, radios from the early 1920's actually had a lot of knobs. This factory made one has six. (and no speaker!)
 
 
This American Marconi model 106 from 1918 has seven knobs and two adjustable crystal detectors, just to TUNE the radio.
There is no amplification of any kind. This one is worth over $20,000.

 FYI - The American Marconi Company was controlled by the British Marconi Company. In the interest of national security, a new
U.S. company was formed in 1919 to buy out the British interests. Almost all of the financial, capital, technical and human assets
were transferred from American Marconi Company to the newly formed company, the Radio Corporation of America. (RCA).

 

Parts and kits:

If you're interested in this hobby, try:


Midnight Science
Peebles Originals

- a whole site dedicated to small sets and parts, magnet wire, etc.
- kits and parts.

Resistor and capacitor kits can be found at Amazon.com, and almost anything can be found on ebay.
Stay away from the Chinese knobs on ebay, they are inexpensive, but they don't fit anything.

This concludes our broadcasting day.

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