💾 Archived View for spam.works › mirrors › textfiles › hamradio › xtal.ham captured on 2023-06-14 at 17:04:49.
-=-=-=-=-=-=-
CRYSTALS
for your shortwave converter
The original project instructions specify a 5 Mhz and/or 8 Mhz crystal be
installed in the kit at the "xtal" location on the schematic. You would need
to use one of the optional capacitors (150 pF with 5 Mhz, or 47 pF with 8
Mhz) at C1. I have tried crystals of other frequencies with varied success.
A 14.31818 Mhz crystal pulled in more signals than any others I tried (it
gives access to the 19 and 22 meter bands). 11.111 Mhz also works well.
Even a commonly available 3.579 Mhz color burst crystal works o.k. (use a 220
pF cap for C1 with this one). Every different crystal gives you a new band 1
Mhz wide. Experiment.
I strongly suggest mounting a 14 or 16-pin wire-wrap DIP socket where the
crystal would be, instead of hard-wiring in one particular crystal. This way
you can solder each one of your different crystals to a DIP header and plug
them in one at a time for each different band you want to tune. Perhaps you
can come up with an even more convenient method of installing and removing
the various crystals.
There are various sources for cheap crystals. Ham shows and computer flea
markets are best (you can obtain them there for as cheaply as 50c ea., or at
most a dollar or two). Ads in electronics magazines feature them for a
dollar or two each. They can sometimes be found on old CPU boards, plug-in
cards, or other circuit boards. As a last resort, order them from Jameco,
Digikey, JDR Microdevices or even Radio Shack at $2 - $8 each.