Vacuum Tube PLL

Thread Starter


Joined Dec 13, 2006
I am looking in to building a phase locked loop out of vacuum tubes. Can anyone recommend any tube models that would be good for making VCO's and phase detectors?

John Luciani

Joined Apr 3, 2007
You didn't mention the frequency of the VCO. You could check out some of the
early Theremin schematics. The RCA Theremins were made with tubes.
The Theremin VCOs are in the 100-300KHz range.

Try for some schematics.

(* jcl *)