The Experimental Radio Project

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Andrea Havens
My girlfriend Andrea bought me a nice piece of plywood at Home Depot to use as a base.
The components were placed on the plywood to get a sense of the size, then she cut it to size.
A front panel was made using a 1/8" thick piece of Luan floor underlayment. This proved to be very difficult to
drill into without splitting the wood. Making the front panel and mounting the parts took a whole afternoon.
To wire the coil switch the front had to come off.
The coil switch.
The TANDEM TUNER was built next, along with connections for antenna and ground.

Now it was time to see how well the TANDEM TUNER worked. I had never seen this circuit before and I was sure I had "rediscovered" some long lost circuit that would be interesting to crystal set fans everywhere. I connected an antenna and ground, then put a crystal diode and high impedance headphones across the secondary winding of the second coil. I expected to hear several local radio stations, but instead only a single one could barely be heard.

 I checked all the connections and tried every combination of controls but the TANDEM TUNER wasn't working the way I expected it would.
Well if it doesn't work, it must be because it needs an RF amp.
In this photo one is being assembled.
The completed RF amp, Version 1.
A Field Effect Transistor (FET) replaces the vacuum tube.
LM386 circuit
Before any testing was done I built the audio amplifier using an LM386.  I wouldn't need the headphones for the next test, the rig now had a speaker. (or "reproducer" as they called it in 1929)
The audio amp, built on two terminal strips. I do NOT recommend
this method but it gave a certain "look" to the radio.