DenverJayhawk

First, I'm sorry if this has been asked before. I did a search on Crystal Replacement and didn't find anything relevant.

I own an old Airtronics 4 ch FM 72mh radio. I've confirmed with Airtronics that it meets the narrow band requirements that came into effect in the early 90s. I haven't used the TX in many years but would like to put it into a new model. The cystal on the receiver is CH 28. I'd like to replace the crystal in the receiver because it looks beat up. Sorry for the noob question, but how does the TX synch up with the receiver if I put a new crystal into the receiver?

BuschBarber

My Feedback: (2)

Just make sure that you purchase the crystal for the correct channel and that it is the correct crystal type for your Rx. There are Single Conversion and Dual Conversion crystals. You need to check to see if your Rx is Single or Dual Conversion. With the correct crystals in the Tx and Rx, the two will communicate without any other steps. Some radios have both PPM and PCM modes. If your Tx is PPM/PCM switchable, be sure what mode your Rx is designed for and set the Tx mode accordingly. In your case, it is probably FM, which is also referred to as PPM.

DenverJayhawk

Thanks, Rich.

Do I / Should I also replace the cyrstal in the TX? I don't see where I can easily access the cyrstal in the TX. Also, how can I tell if I'm running PPM/PCM and Single/Dual conversion?

DenverJayhawk

ok, I just saw the rx says dual conversion. So that answers that. It is a FM TX, so I'm assuming that means PPM?

BuschBarber

My Feedback: (2)

You don't need to replace the crystal in the Tx unless it was damaged. You can look up the specs on your radio from the Airtronics site or do a Google search on that model Tx. From your description, it sounds like an FM or more commonly known now as PPM. Technically speaking, PCM is also FM, so they use PPM to differentiate from PCM. This happened when the first PCM computer radios came out.

As for the Rx, if it is Dual Conversion, it should be marked on the case. If not sure, you can always Google the Rx model or look it up on the Airtronics site. If you order the crystal recommended for your model Rx, you should have no problems.

Over time, and sometimes, after a crash, your Rx can get out of tune. Periodically, you may have to send in your Tx and Rx to have them ReTuned.

Do a good Range Check, according to the Tx manual, and if you are getting good range, you should be OK. If your range is marginal, then you may have to send it in.

I have never had Airtronics radios, but I have friends who do.

Skarn

It's actually illegal in the US to replace the transmitter crystal. It's an FCC rule.

You can do a search for threads discussing this.

Skarn

Sport_Pilot

That is arguable, however in this case he is replacing with the same frequency so it is not a factor.