AMD65

Hi new to the Rc world I seem to be getting a lot of unwanted signals that take control of my hi-lo seem to have the same Cristal # as some one els can any one tell me what my cristal are thay are #typeRX type72-12 72.870 rx54 and the transmitter is type72-7 72.870 TX54 ??? what the heck are thay and how can I change them to a different number that will not be interfered with. Thank you Dennis

Rodney

Dennis, it is not legal to change transmitter crystals in the USA unless you have your transmitter recertified by an authorized shop. If your transmitter uses modules though, they can be changed as the all the rf circuitry is contained in the module and already type accepted. You can return the transmitter to an authorized service center and have the frequency (crystal) swapped out.

Toker41

Wait....
why is it illegal for me to swap them out myself? Is it illegal to swap them out in the reciever?

jlingrel

Swapping them in the receiver is normal. Some of the simpler Futaba TX such as the Skysport have a plug in crystal on the front of the unit where you can insert the crystal for the freq you need. I am not familiar with the more expensive Futabas as I use the Hitec TXs with the Spectra module.

John

piper_chuck

My Feedback: (12)

Regardless of their relative accessabilities, it's not legal to change the TX crystal.

Dennis, the reason it's not legal to change the TX crystal in the US is because there are other users within the same band we use for R/C. When a crystal is changed, it's possible that the transmitter will emit signals on other frequencies. Because of this exposure, the FCC mandates that crystals be changed by a technician with the tools and skills to confirm that the TX is transmitting properly, and if not to make the necessary adjustments to bring it back in spec.

Edit: I thought of a question. Are you flying at a proper field with frequency control? If not, it's possible that you're flying near one and your source of interference is other fliers. If this is the case, changing to another frequency won't help. If you are flying at an R/C field, forgive me, I thought it was important to ask.

jlingrel

Someone has to tell Tower to quit selling crystal sets (tx and rx) for 72 Mhz channels. There is no caution about it being illegal for the owner to buy and change the crystal in the TX.

http://www2.towerhobbies.com/cgi-bin...260**&P=3#tech

John

jdb000001

The type 72-12 receiver crystal is a Futaba single-conversion crystal. Your transmitter and receiver are on channel 54, 72.870MHz.
The single-conversion receivers are usually rather short range compared to the dual-conversion ones.
There may be others flying nearly on the same frequency, or you could be getting interference from another source - the 72MHz band is also used in industral/manufacturing radio systems.

As for the transmitter crystal, I don't really know why they sell them, since it is illegal to change them yourself in the US - may be legal in some foreign countries though.

piper_chuck

My Feedback: (12)

You can buy one and send it to the service center along with your TX. The Tx manuals usually say you must send the Tx in for service. These questions have been discussed ad-naseum, plenty of threads here on RCU answering all of these questions.