This topic will start with the basic frequency generator that Stan talks about.
The generator can be devided up into two sections.
Primary and gated.This most people know.
The primary generator is actually in and a part of the scanning circuit.There is a means for manual adjustment,but for the most part, it was in the scanner.This scanner is set up to scan through a given range of frequencies.Stan talks about the range being from 0-10khz.This scanner will start at 0 and go up to 10khz,then back down to 0.As the scanning goes on,there is a phase lock loop that will detect and lock onto resonance.
Now this primary generator must have a 50% duty cycle.This doesn't need to be duty cycle adjustable.Just a clean square wave is all that is needed.Stans scanner did just that.
I got to see a video of Stans scanner doing just that.The video is among Stans belongings.I don't have this video,so don't ask.
If you are trying to use a Dave Lawton circuit,it's not going to work.It doesn't have a fixed 50% duty cycle.But don't worry,you can still make it work.You will need to just run the output signal of the 555 pin 3 through a decade counter wired up as a devide by 2.This will get you a good 50% all the time.
I'll go into the gated signal next then the scanning circuit after that.
To come soon.
Don