ÕÍÍÍÍÍÍÍÍÍÍÍÍÍ͸ 
                              ³   CRYSTALS   ³ 
                              ÔÍÍÍÍÍÍÍÍÍÍÍÍÍ; 
                        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 results.
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
approx. 1 Mhz wide.  Experiment.

A crystal rated at a given  frequency should give you reception on the bands
of that frequency plus and minus 455 Khz (the car   radio's or AM radio's IF
frequency). Read the technical specs of the  NE602 and  the theory of oscil-
lators and superhet  radios (see  ITWORKS.HOW, AMRADIO.TXT,  and BIBLIO.TXT)
for an explanation. Additional discussion of  theory is obviously beyond the
scope of this brief introduction.

Crystals over 17 Mhz  or so generally do not give good results.  Sometimes a
high frequency crystal (50 or so Mhz) gives reception on the lesser overtone
frequencies, but this is chancy. If you have a couple of HF crystals around,
give them a try, but I do not recommend buying them for this project.

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  different crystals to a DIP Header and plug them in
one at a time for every  different band you want to  tune.   Perhaps you can
come up with an even more convenient method  of  installing and removing the
various crystals, such as crystal sockets.

There are various sources  for cheap crystals. Ham  shows and computer  flea
markets are best (obtain them there for as cheaply as 10c ea.,  or at most a
dollar or so).   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.