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-   RC Radios, Transmitters, Receivers, Servos, gyros (https://www.rcuniverse.com/forum/rc-radios-transmitters-receivers-servos-gyros-157/)
-   -   JR CRYSTAL (https://www.rcuniverse.com/forum/rc-radios-transmitters-receivers-servos-gyros-157/1635563-jr-crystal.html)

juance 03-17-2004 10:16 PM

I purchased a RX crystal for JR 649 PCM rx. The old crystal has the dot on the left most of the group of three and the new one has the dot on the right most one.

Question: What does it mean ?
Although, my TX crystal does not have any dots at all, and the tx crystal is black, while the rx one is gray. I checked it and it works.

Any explanation and recomendations would be appreciated.


AMA-69405 03-18-2004 10:51 AM

The dots on JR receiver crystals, in simplest terms, tell you where the crystal is "tuned", based on factory test, relative to the marked frequency. I don't know about other (outside USA) distributors, but I believe that Horizon has a shipment policy for complete systems that keeps the transmitter and receiver crystals within one "dot" of each other. In other words, if the Tx crystal is left-dot, they do not ship it with a receiver that is right-dot. If the Tx crystal is center-dot, it can be shipped with any Rx crystal. etc. As I understand it, this is all simply an effort to maximize range and interference rejection.

In your case, if there are no dots on the Tx crystal, I suppose you could consider it a center-dot crystal, but that's a guess... not a statement of fact. I've personally never seen a modern JR Tx crystal without dots... where was this purchased, and how long ago?

Gary L.

juance 03-19-2004 10:45 AM

Hi Gary:
Thanks for your kind reply. Its true, my transmitter is an old 388S which has a black crystal. The best, though is to by a TX crystal to be safe.

Thanks again.


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