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Author Topic: Eico 720 Crystals 15m Question  (Read 1311 times)
W1AJO
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Posts: 108




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« on: May 17, 2013, 09:50:05 PM »

I'd like to try using crystals for 15m with my Eico 720.  The manual says use 40m xtals 7.0 to 7.150 MHz.  How do I calculate what freq xtal to get a particular freq on 15m?  Is it just 3x the xtal freq?

I'm guessing that if I want 21.06 MHz I would use a 7.020 MHz xtal, correct?

Thanks!
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KE3WD
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Posts: 5694




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« Reply #1 on: May 19, 2013, 06:17:38 AM »

Sounds right.
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N0XE
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Posts: 197




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« Reply #2 on: May 24, 2013, 11:03:50 AM »

That is correct but be aware FT-243 crystals as well as any crystal for that matter  may be off some, crystals age and do change in frequency so your actual frequency may be a KC or 2 down or up.  Not a problem unless your looking for an exact net frequency,  just be aware of the band edges to stay legal and not TX out of band or your allowed operating frequencies per your license class.  Also some will work better with some transmitters then others, some may chirp on one transmitter and not on others,  yet still be a good crystal, Good luck, little Eico is a neat little transmitter, you should have a lot of fun with it,  73 Jim N0XE
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K8AC
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Posts: 1465




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« Reply #3 on: May 24, 2013, 12:31:46 PM »

If you have a spare crystal, it might be interesting to change the frequency slightly by using some old techniques.  You can move the crystal down in frequency by rubbing a #2 lead pencil over one or both surfaces.  And, you can move one up in frequency by grinding it a bit.  We used to use a paste of Ajax cleanser and water on a flat piece of glass.  With some experience, you can hone in on an exact frequency.
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