Progressive Receiver Preselector designed by W3TS, Dana Michael
I chose to use this circuit replacing the broadband filters in the original Progressive Receiver design.
Advantages: 1) Lower parts count, 2) Operating frequencies can be peaked individually for optimum performance.
Disadvantages: 1) Bands need to be manually tuned, 2) One more knob on the front panel, 3) The dual gang capacitor may be difficult to find.
For best performance:
1. The preselector should peak 40 meters near maximum capacitance.
2. The transformers will need to be squeezed to "balance" the circuit. (Perhaps adding another turn to the primary -- 16T -- would make this easier.
3. On 10 meters, listen for a "double peak." If found, the circuit is not balanced and more "squeezing" is required. Try to squeeze the turns to eliminate one of the peaks. I tried using trimmer capacitors to make peaking the circuit easier, but I discovered that I had too much capacitance to peak 10 meters with them installed.
4. In my Progressive, 10 meters peaks at about 5% capacitance.
5. I use a 4:1 Jackson Ball vernier on the preselector to make it easier to peak the higher frequencies.