crystals
 

Is there a difference between a reciever crystal and a trasmitter crystal, or are they interchangeable?

RE: crystals
 

For Airtronics and JR there is a difference, they are not interchangeable.

RE: crystals
 

Yes there is. No, they aren't.

Dr.1

RE: crystals
 

What brand of Transmitter you using?

RE: crystals
 

They are different. Not only that, different receivers use different crystals. A dual conversion receiver uses a different crystal than a single conversion receiver on the same frequency. Different brands of receivers also require different crystal; i.e. don't try to put an Airtronics crystal in a Futaba etc.

RE: crystals
 

To be a spoil-sport, a reminder that it is illegal to change TX crystals unless you are properly licensed by the FCC to do so. If you have a synthesizer TX or one with plug-in freq modules then you can change freqs yourself. RX crystals can be changed by anyone as they do not control any broadcasted signals.
You do want to make sure to get RX crystals that match your system.

RE: crystals
 

Bruce, I believe TX crystals that plug-in are changable by the unlicensed consumer. I have never seen any cautions about changing crystals in RC equipment other than cautions about ensuring that the TX is intended for Upper or lower band for the 72 Mhz aircraft range or the entire 75Mhz surface vehicle range.
I agree that if you start unsoldering parts in a TX you need to be licensed AND know what you are doing.
If I am wrong then the entire industry is in violation.

RE: crystals
 

I sure hope this thread does not turn into the type or argument that usually starts when it comes up on the radio forum. There's always a few lawyer wannabes who think they found a loophole in the FCC regs, or some outlaws who say just go for it, you'll never get caught.

Basically in the US, the end user CAN NOT change the tx crystal on their own. It doesn't matter whether it's soldered in or not, they are NOT supposed to do it. The reason is it's possible that the transmitter will no longer be on spec with the new crystal. This creates a risk of interfering with other channels or other (non-RC) users in nearby radio bands. Only someone with the proper equipment to test and retune the tx, if necessary, is supposed to change crystals. Exceptions to this are the already noted swappable frequency modules or synthesized frequency transmitters.

So, this is a good excuse for you guys to go out and buy a couple more boat radios for when they've got you swapping frequencies during the weekend! ;) BTW, did you check out the results of the [link=http://www.rmhalliday.com/CMBTC2.html]CMB Tunnel Champs[/link] yet? A lowly TS2 with a bone stock OS won the Open Offshore and also managed to place pretty high up in both sport and modified B tunnel. [X(]

RE: crystals
 

From Futaba's web site:

--------------------------------------------------------------------------------
How do I change the frequency of my transmitter?
For a module unit: to change the frequency you simply remove the module and replace it with a module on the new channel. You can even change 'bands' (IE 72MHz to 75MHz). All radio frequency circuitry is in the module so there is no need to 'retune' after a module change. (However, the receiver cannot be similarly changed to change bands. If you go to a new band you MUST buy a new receiver on that band. Please see the note below regarding crystal changes, which is valid for ANY receiver where you are changing within one frequency band.) DO NOT attempt to change transmitter frequency by changing the crystal within the module. You must use a module which is properly tuned to the frequency desired.

For a unit with crystals: We CANNOT recommend changing crystals to a different frequency. Changing the crystal on your transmitter is illegal unless you have the proper license. The FCC has established guidelines for the modeler's safety and for the safety of spectators. For safety and FCC reasons we must request that both TX and RX be sent to the service center to ensure proper crystal change and retuning to the new frequency. Crystal based radios cannot be converted to another band without parts replacement, and may not be able to be converted at all.


BTW - I have the correct license and equipment to do this here where I work. I still send mine in so that the mfg can give the system a good going over.

RE: crystals
 

Skoda450,
It doesn't matter if the crystal is soldered in, or is a plug in type, it's illegal in the US for a end user to change the frequency of their transmitter. This doesn't apply to units that have a frequency module in them. But units that have crystals in them need to be sent into a shop to have the frequency changed.

Ken

RE: crystals
 

Ditto, you cannot legally change the TX crystal on certified TXs. The 72MHz TXs for aircraft are certified. Other bands may or may not be certified. I believe the 75MHz band does not used certified TXs, so XTAL swap may be OK there, but don't take my word on this until you do your own research. But back to 72MHz, This has been beat to death, and as pointed out previously, there are always some who think they have found a loop hole. I have personal "Ins" to the FCC as both my parents work for FCC field monitoring offices, i.e they enforce the regulations. I've been thru this with them. There is no loop hole. The law is clear.

The industry is not in violation. The Hi/Lo band issue, which I believe only applies to Futaba gear, is on the RX, not the TX. TX will ship preconfigured for a certain freq, which is marked on the TX and the box; or it can use modules. You can change XTALs on your RX all you want.

Cheers.

RE: crystals
 

In Australia you can change your crystals however you like although you must stay within the frequency range afaik.
36Mhz for planes.

No need for a license as far as I am aware.

Any Aussie's confirm or deny this?

RE: crystals
 

Just a note, in the Rx, it is recommended that you use the same brand crystal as Rx. Ie: futaba crystal in futaba rx, don't mix brands. i know people do it and will tell you all day long there is nothing wrong with it, but thats the recommendation by the factory.