You beat me to it - there are off the shelf varicaps dimensioned for band II tuning - its possible to get away with common or garden silicon diodes if you can be bothered fiddling about for ones that give the required range.
Years ago I made an oscillator with a 10.7MHz ceramic resonator & an FM IFT - it didn't seem to be doing much, so I strapped an inverse parallel pair of red LEDs across the secondary winding. It blotted out FM reception in my flat and couldn't be tuned out because it was jamming up the IF amp.Also the page about leds as varicaps didnt really explain how to set up and use an LED as a varicap. Just that it worked. Is there a page that has a tutorial? It would be very convenient to use LEDs instead of veriable capacitors or varicaps because I have tons of LEDs.
It would be tricky to bias a varicap - you'd have to stabilise the decoupled collector rail.Here's the schematic.
Voltage variable capacitance in fixed capacitors is an undesirable property that manufacturers do anything they can to avoid.What if i used a potentiometer to increse or decrease the current coming from a non variable capacitor?
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by Jake Hertz
by Jake Hertz