sammyd

I am trying to get the real answer about changing frequencies with a JR radio. I have spoken to many people at the field I fly at and it is a mixed response. Some say you must change the module in the radio and others say that you need only change the crystal in the tx and rx. When I ask the local hobby store they say crystal only on both ends. When I tried to purchase crystals online they told me I needed a module for the radio and crystal for the rx. What is the deal. Does it vary with radio's or is there an across the board answer.
Thanks in advance

dsnyder

It is against FCC regulations to change the crystal in a transmitter, except when performed by an authorized service center. You can change the module if you have another module or purchase another module, but you cannot change the crystal in the module per the FCC. You can change the crystal in a receiver.

R J Graul

Danny,
What is the reason for this FCC reg that an RC transmitter crystal can only be changed by an authorized service center? I bet you have been to contest's where flyer's have changed transmitter and reciever crystals to eleminate channel conflicts, I know I have. It does not take a whole lot of smarts to swap a crystal in todays transmitters! Can you shed a little more light on this subject?

Is there any retrictions or problems in a wide spred of channel changes from (hi to low channels etc.) in TX, or SPCM, PCM or FM recievers?

Thanks For the Help,
Ralph Graul

dsnyder

Changing the crystal in the TX can alter the tuning/output of the system, and can cause "splattering" on neighboring frequencies. Yes, I have seen it done, but that doesn't make it legal.

In receivers, they are tuned to the center of the band, so as long as you stay within the operating band of the receiver, they will work fine.

bretthan

SammyD, I have also encountered the same problem, and after reading this, and the thing I find interesting how the recievers are tuned to the center of the band. dsnyder, how come radio manufacturers don't do this to the transmitters as well, wouldn't that make this whole issue go away (as long as people doing it have a radio equipped like this), and make life at the field a hell of a lot easier.

dsnyder

No, it wouldn't change the FCC regulations and would still be against the law to change the frequency of a TX except when performed by an authorized service center.