Wideband Oscillator for Testing Resonant Circuits

This is a wideband oscillator for testing resonant LC circuits that is probably good to 5MHz. It’s actually nothing more than the front end for this PIC based inductance and capacitance meter circuit. (I have built an LC meter along these lines and it has proved to be an extremely handy piece of kit.)

When used in conjunction with a frequency meter (or scope) this circuit is very useful for determining the resonant frequency of an LC tank. Having built it up a few times on a solderless breadboard, I thought it was time to make a more permanent version.

This time around I used the circuit to peak some IF transformers for 455kHz. I’m not sure if this is a valid technique; the circuits that are yet to built around the coils may pull the frequency somewhat. But it will at least get me in the ballpark.

The oscillator is also useful for determining the tuning range of tuning capacitor / ferrite bar antenna combinations.