SSB receiver ?

Hi all I have a question about the SSB receiver (Single sideband).

Does one have to know the carrier frequency a priori, or is there a way to recover the carrier frequency even if it is not sent ? (Cannot be the case, forget it.)

But what does the so called Beat frequency oscillator do ?

Kindest regards,
StoppTidigare

There is no simple way to know the exact frequency. You can manually tune it close enough that your very powerful signal processing capability of your ears and brain can extract the information.

There are two complex ways to have specialized circuitry do the tuning. One is if there is an intentionally inserted spectral line at some know frequency relative to the suppressed carrier. An even more complex way is to know that voice signals have overtones and the automatic analysis circuit tunes the radio so that these are harmonically related relative to the carrier.


The BFO term comes from the old days of manual morse code. It was adjustable relative to the bandpass filter so the operator could make whatever tone he liked. In effect the CW signal was converted to almost baseband. (that is an audio tone and not a DC level)


This same function is in SSB receivers. It is the local oscillator for the last down conversion to base band.