Module/Xtal Question - RC Groups
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Apr 28, 2012, 05:51 PM
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PyroMan's Avatar

Module/Xtal Question

So I've had a JR XF421 radio ever since I got into this hobby and I think it is about time for me to upgrade. I am looking at getting a JR 8103. I realize that the JR 8103 uses modules, but does it also use xtals.

My current planes are on channel 41, but if I get a 8103 and it has let's say a channel 45 module in it, do I have to buy or new module or can I keep the module in the radio and just swap the xtal with my ch.41 xtal.

I hope that makes sense

My goal is after I get a better radio (like the 8103) I will start lookjing for a cheap synthesized module and not have to worry about xtals. Later on down the road, I'll get a 2.4ghz module but right now all my planes are 72mhz]

Thanks in advance,
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Apr 28, 2012, 06:12 PM
Registered User
Yes the 8103 module requires a crystal and yes, it is the same crystal used in the 421 so it should work, particularly if you're not jumping too many channels.

OTOH whether the FCC regs allow you to change crystals legally without sending the module away to be retuned is a whole other question .

Apr 28, 2012, 06:13 PM
60 years of RC flying
Daedalus66's Avatar
It is illegal in the United States to change crystals. So technically the answer is that you should not do it. Those of us in other countries do it all the time, or did until 2.4 came along.

My advice would be to skip the intermediate stages and go straight to a reasonably advanced 2.4 radio. The DX7, for example, is a solid radio with good programming and 20 model memories. It's discontinued but there are lots available used. It opens up access not only to Spektrum receivers but to the low cost ($6-18) compatible receivers.

Going to 2.4 from 72 is like going to a digital camera from film. You think you will still use the old radio but as soon as you get used to the newer one you forget 72.
Last edited by Daedalus66; Apr 28, 2012 at 06:23 PM.
Apr 28, 2012, 08:47 PM
Registered User
PyroMan's Avatar
Okay first, I'm only going from a ch. 45-ish to a ch.41 -- so it should work with a ch. 45 module, but with a ch.41 Xtal, right?

Second - Illegal!? If that's an actual rule, I guess I've been doing wrong for a long time. So are you saying that the FCC says that I can't put in a ch.41 xtal into my JR421 to fly one plane, then switch to a ch.48 to fly another plane?? The only way to switch channels on my current rx is by swapping the xtal.

Apr 29, 2012, 03:39 AM
Registered User
Originally Posted by PyroMan
So are you saying that the FCC says that I can't put in a ch.41 xtal into my JR421 to fly one plane, then switch to a ch.48 to fly another plane??
Yep, that's what the FCC regs say. And you could in theory be fined quite a lot of money for doing it....but I've never heard of anyone actually getting caught or fined. Nor have I heard of anyone having any technical problems either, at least not with fairly modern equipment.

But bear in mind that these days I fly in the UK where it's normal and perfectly legal to change crystals .


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