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