18-03-2017, 12:51 AM
The explanation in ARRL is better than that diagram above. ARRL shows a primary at the IF frequency. The secondary is centre tapped and voltage introduced from primary to the tap by a 100 picofarad capacitor. It then says the phases at the resonant carrier frequency lag and lead by the same phase angle. So, I assume that's the ratio. The out of phase voltages each side of the tap pass to a double diode. They're rectified as two DC voltages of opposite polarity. Then it says changes of frequency in the circuit will cause the amplitudes of the two DC voltages to increase and decrease relatively. By that I deduce deviation in the carrier through the original modulating signal will be converted to amplitudes. That is about my best effort towards understanding. If correct it's better than two weeks ago when I was clueless.
