Sideband Switching of BFO
From HF Signals
Note: the sidebands in the Minima are inverted
- When the upper sideband is selected, the left hand side trimmer is not connected. You set the proper USB frequency with the right-hand side trimmer.
- The Minima is, then, tuned below 10 MHz and the diodes short the left side trimmer to be parallel of the USB trimmer. Now you can set the LSB frequency.
This sequence is important as the USB frequency is set as an offset from the LSB frequency.
The three diodes are necessary to prevent the RF peaks from turning on the diodes.