Before revision: BFOs are sometimes included in communications receivers designed for short wave listeners; they are almost always fitted to amateur radiostation receivers , which often receive CW and SSB signals.Larry Wolfgang, Charles Hutchinson (ed), The ARRL Handbook for Radio Amateurs Sixty Eighth Edition, ARRL, -9, pages 12-29,12-30 The beat frequency oscillator was invented in 1901 by Canadian engineer Reginald Fessenden.
After revision: BFOs are sometimes included in communications receivers designed for short wave listeners; they are almost always found in communication receivers for amateur radio , which often receive CW and SSB signals.Larry Wolfgang, Charles Hutchinson (ed), The ARRL Handbook for Radio Amateurs Sixty Eighth Edition, ARRL, -9, pages 12-29,12-30 The beat frequency oscillator was invented in 1901 by Canadian engineer Reginald Fessenden.