"Tim Wescott" wrote in message
...
It would be easier by far to build (or buy) your own external
oscillator.
This will not only work with your S-108 but with anything else you
might buy
down the road, and you won't have to hack holes in your radio. The
basic
one is just a crystal oscillator with a 100kHz crystal. Fancier ones
will
allow you to switch in a 1MHz crystal. I have an old Heathkit one
that I
hopped up by adding a divider to get marks at 100, 50 and 25kHz for
aligning
narrow-spread QRP receivers.

I know that any ARRL Handbook from 1930 to 1976 will have such a
circuit --
I'd be mildly surprised to find out that a later one lacked it, but
I'm too
lazy to get up right now and check. The 100kHz crystals are still
available
from places like JAN Crystals and International Radio
(http://www.qth.com/inrad/). You can pretty much decide what you want
the
thing to look like, select the appropriate date handbook and start
cutting
metal.

There's also plans for crystal calibrators on the net. Here's one:

http://www.rason.org/Projects/calibrat/calibrat.htm

Frank Dresser