Record Player to FM Receiver with 6C5 Tube

This sends the record player side to side needle movement signal to FM receiver.  Left lower is Sappire record needle grounded with stationary plate mounted on tone arm close enough (about 1/32 inch from needle) to send a capacitor like signal to vary the FM radio frequency oscillator frequency. Keep all ocsillator leads as short and as rigid as possible. It tested with range of 25 feet with no antenna. Hartly Oscillator type circuit to oscillate 6C5 tube. One source $7.95 USD for 6C5 tube. 6 volts DC to tube heater or 6.3 volts if AC power is used. Parts information.  Where 5 nF capacitor is located is an adjustable 5 plate variable capacitor 5nF to 50 nF.  The 200 nF grid capacitor is fixed mica capacitor. The 200 nF (maximun value) above battery ground is an adjustable ceramic base trimmer capacitor.  Grid resistor is 50 K ohm 1/4 watt resistor. Inductor coil is 8 turns of #20 enameled copper wire closewound over bakelite case of stypic pencil.   To operate.  Start record player playing with transmitter turned on. Tune FM receiver to quit spot on FM Band. Adjust capacitor above negative battery a little then turn adjustable 5nF beside coil until a "plop" is heard on FM receiver.  If "plop"sound is missing, add or remove one turn from grid end of coil to find FM band then try again.

published 8 years ago