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Old Sep 11, 2001, 01:10 AM
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ETKing's Avatar
Southern California, USA
Joined Sep 2001
388 Posts
Crystal swap didn't work

I swapped a 555 RX in for a Feather RX in my Zagi tonight. I swapped crystals in RXs so that I could continue to use the TX that I modified with dual rate elevator, but the 555 won't work with the crystal from the Feather. They look the same, but is there a difference? HELP!
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Old Sep 11, 2001, 01:21 AM
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Daren's Avatar
Los Alamos, NM, USofA
Joined Nov 2000
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Dual or Single?

I know the 555 takes a dual conversion crystal. What's in the Feather? If it's a single, you've discovered the source of your problem.

Daren
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Old Sep 11, 2001, 01:24 AM
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Vernon, BC, Canada
Joined Dec 2000
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Doesn't work. I think I read somewhere that the feather uses an AM crystal which I thought was strange tor an FM Rx. Why don't you ask "MIKE at Hitec" He has a thread running.
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Old Sep 11, 2001, 03:05 AM
Yoe
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Skellefteċ, Sweden
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The feather reciever has single conversion while the 555 has dual conversion. The crystals are different for the different types of Hitec recievers.
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Old Sep 11, 2001, 07:05 AM
aka: A.Roger Wilfong
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Novi, Michigan, United States
Joined Jan 2001
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The problem is that the Feather is a single conversion (SC) Rx. The xtal is offset from the receive frequency by 455kHz. The 555 is dual conversion (DC) and the crystal offset is 10.7mHz.
There is no difference between an AM and an FM xtal that is related to the modulation scheme. There may be designe differences in the Rx's local oscillator that require a different "cut" to the crystal, but this has nothing to do with AM/FM. Usually, the difference between AM and FM crystals from the same manufacturer is that the AM Rx's are SC and the FM are DC, but both AM and FM could be either SC of DC - it's purely a marketing/feature/engineering trade off.
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Old Sep 11, 2001, 10:47 AM
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Southern California, USA
Joined Sep 2001
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Thanks for the input. Now I have read

http://www.torreypinesgulls.org/Radio%20Article.htm

I guess I shouldn't just go around changing stuff I don't understand!
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