On 16/10/2018 09:14, Jeff wrote:

A common way of generating both usb and lsb was to have 2 switched
crystals with frequencies just above and below 9MHz in the oscillator,
feeding a balanced mixer, before the xtal filter, and switch depending
on which sideband you required.

Is there a mathematician on here that can explain the maths of sideband
inversion/retention?

No inversion is required with this method.

If you feed a ~9MHz signal and audio into a balanced mixer the output
will be both sidebands plus a suppressed carrier.

Your xtal filter is ~2.4kHz wide centred on 9MHz, so if you move the
frequency of the ~9Mhz signal (switch a crystal) going into the balanced
mixer either above or below 9MHz you can select which side band goes
through your filter.

Simples.

Wasn't a similar system used in the Yaesu FT-200 (9MHz IF, 5 MHz VFO)?

IIRC the set had a NORM/INV sideband switch.


--
Spike

"Nearly all men can stand adversity,
but if you want to test a man's character,
give him an internet group to manage"