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changing TX crystal

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Old 07-31-2006, 10:24 AM
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skylane42
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Default changing TX crystal

OK, I have a JR transmitter I want to change to a different channel. I have heard I can do this but it is illegal in the US. Now, the new crystals are for sale from various vendors so if it is really illegal why do they sell them? Any suggestions would be appreciated.
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Old 07-31-2006, 11:27 AM
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carrellh
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Default RE: changing TX crystal

Unless you have the equipment, and skills, to test (and adjust) the transmitter for output and accuracy after the change; you're not allowed to change the crystal yourself. They sell crystals because there are people who do have the equipment and skills to do the testing and adjusting. I'm not one of those people.
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Old 07-31-2006, 11:45 AM
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Default RE: changing TX crystal

Unfortnately ... you are in the US.....
In the rest of the world you can purchase and change Tx and Rx crystals without any problems whatsoever. AMA and the FCA made the rule not the manufacturers...(of course they Want you to send the equipment in $$$). Except for Futaba who has high and low restriction on older equipment.
This ruling maybe a bit outdated with the advent of Spectra-like modules wher you have a module (instead of a crystal) and you can change channels at will... which makes me wonder... what is the spectra but a super-crystal???? all the other parts of the radio remain the same (as they do with changing crystals)....
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Old 07-31-2006, 11:50 AM
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Default RE: changing TX crystal

Your car will do over 65mph on the highway, that doesn't make it legal to do so.

You also risk shooting down your fellow pilots if the transmitter is out of tune.
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Old 07-31-2006, 11:53 AM
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Default RE: changing TX crystal

ORIGINAL: SwampFlier-RCU

Unfortnately ... you are in the US.....
In the rest of the world you can purchase and change Tx and Rx crystals without any problems whatsoever.
Actually, this same restriction exists in more than just the US. I saw the same thing in Canada and I believe Australia. As for no problems, other countries don't have the same frequency allocations we do here. The recent death of two spectators, which appears to have been caused by government permitted interferance, is enough to convince me that much of the rest of the world is NOT the place to look for a good example on radio frequency control.
AMA and the FCA made the rule not the manufacturers...(of course they Want you to send the equipment in $$$).
Considering how little it costs to have this service done, nobody's getting rich on it.
Except for Futaba who has high and low restriction on older equipment.
Futaba's high/low has nothing to do with transmitters.
This ruling maybe a bit outdated with the advent of Spectra-like modules wher you have a module (instead of a crystal) and you can change channels at will...
Actually, the FCC rule allows for modules.
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Old 07-31-2006, 11:59 AM
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Default RE: changing TX crystal

Just a follow up.. what is the difference between a single conversion and dual conversion crystal?
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Old 07-31-2006, 12:12 PM
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carrellh
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Default RE: changing TX crystal

ORIGINAL: skylane42
Just a follow up.. what is the difference between a single conversion and dual conversion crystal?
This applies only to receivers, not transmitters. It is related to the way they filter the signal. You have to use the right crystal for the receiver. I don't know if one method is superior to the other. I doubt that it is; it's probably just what the manufacturer decided to use.
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Old 07-31-2006, 12:14 PM
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Default RE: changing TX crystal

ORIGINAL: SwampFlier-RCU

what is the spectra but a super-crystal???? all the other parts of the radio remain the same (as they do with changing crystals)....
The plug-in modules contain the entire radio transmitter section - they are certified by the FCC to be interchangeable (note that it is still illegal to change the crystal in a module without having it retuned). You can change frequency on the synthesized modules because they are designed and FCC certified to produce the proper output on all of the selectable channels.

Changing a plug-in module is different than changing just the crystal - the module contains all the RF circuitry, the rest of the radio just produces the PPM or PCM signal that is fed into the transmit section (basically, its just a trainer box, with the module being the transmitter). Thats also why you can use the same transmitter (an 8UAFS in my case) with a 50Mhz module, a 72Mhz module, or a 75Mhz module - something you could never do just by changing the crystal.
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Old 07-31-2006, 12:35 PM
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Default RE: changing TX crystal

It's simple, easy to do, and done a lot here in the US. It's also ILLEGAL, as has been pointed out.

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