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'm just now getting into J

Old 08-11-2005, 03:12 AM
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justahobbie
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Default 'm just now getting into J

Hello

I'm just now getting into JR from Futaba and started using a 8103 I got from a buddy. I just found out that most receivers are single conversion, and just as a curiousity, how do they differ from Futaba's Single Conversion (or Great Planes/Hitec) as far as range. The Futaba/Great Planes/Hitec have very little range.

My real question is what do the 3 little round circles and the black dot mean on the crystals and what crystal do I use for my new PCM R770 receiver? Is there a different crystal for FM/PCM?

Thanks
Ryan
Old 08-11-2005, 08:58 AM
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dsnyder
 
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Default RE: 'm just now getting into J

The reason JR can use single conversion systems and still have excellent performance is ABC&W technology that is used in JR receivers. ABC&W acts like automatic gain control on the antenna circuit which filters out unwanted noise and only accepts input on the frequency it is supposed to accept.

The dot indicates the cut of the crystal in relation to its true frequency, either centered exactly on the frequency or just to the left or right of the frequency when viewed on a scope. Generally it is recommended to avoid opposite dots in the transmitter and receiver for the best possible reception, however I regularly use systems with opposite dot s without any problems. It was more critical in years past than it is now, but JR chose to continue the dot system to allow users to optimize their system for top performance.

It does make very little difference in overall performance, but for top performance avoid using oposite dot s in the transmitter and receiver, such as a left dot in the transmitter and a right dot in the receiver. For top performance they should be next to each other, a center and a right or left, or the same.
Old 08-11-2005, 12:05 PM
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justahobbie
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Default RE: 'm just now getting into J

Thanks Danny

Answers a lot of questions, but just one more.

Is the JRPXFR** crystal the correct one to use in the PCM R770 receiver, or is there a special PCM crystal. I noticed the receiver worked with this crystal but am not sure if it is truely the correct crystal.

Thanks
Ryan
Old 08-12-2005, 09:00 AM
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dsnyder
 
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Default RE: 'm just now getting into J

Yes, that is the correct crystal. PCM vs FM makes no change in the crystal required.

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