Varactor tripler

An interesting circuit I recently discovered is a frequency tripler with varicap
diode. A 70 cm input signal (e.g. 432 MHz) results in a 23 cm outputsignal (1296 MHz).
Efficiency is about 50%.

The circuit I found did not contain a description. Component values were given, though. It looks like a simple and straight forward way to generate some RF power in the L-band (1.2 GHz). Of course you need a suitable 70 cm transmitter for this experiment.

It looks like as if tube trimmers are used. The varactor and capacitor of 0,5 pF look
as if that are hard-to-get components. One can make small capacitors with values less
than 1 pF by twisting to pieces of wire.


Principle frequency tripler;

.