[Lowfer] trimmer for pierce oscillator

[Douglas D. Williams]

Years ago I built an LF converter from a design by Doug DeMaw and Jay
Rusgrove that appeared in the June, 1977 issue of QST. It has proven to be
an excellent design, outperforming two different commercial converters that
I have tried out. 

The local oscillator circuit in the converter is a simple Pierce oscillator
designed around a 2N2222A transistor and a 1.7 MHz crystal. The crystal I
have is 290 Hz high and I would like to add a trimmer capacitor to be able
to adjust the frequency dead on so I don't have to do any mental gymnastics
when trying to tune a certain frequency. 

Here is a link to the schematic of the oscillator circuit:

http://i81.photobucket.com/albums/j231/Goranothos/oscillator.jpg


My question is where should I add the trimmer capacitor and what value
should I use? 

Thanks in advance for any help.

-Doug KB4OER