21-05-2017, 08:06 AM
(This post was last modified: 21-05-2017, 08:18 AM by Old Sparky.)
A BFO (Beat Frequency Oscillator) sometimes known as a CIO (Carrier Insertion Oscillator) is only needed fro the reception of SSB (Single Sideband) sinnals, and possibly CW (Continuous Wave - or should that be Carrier Wave?) i.e. Morse Code. It should be disabled for AM reception. BFOs were often used in conjuction with Product Detectors in Receivers covering Amateur Bands, etc., where many, if not most, transmissions are SSB. The BFO is set to about + or - 1kHz of the IF, and tuned through a limited range to recover the modulation i.e. audio content. SSB can be Upper or Lower sideband with suppressed or reduced Carrier, hence the need to be able to tune above or below the IF.
