Posts: 2148
Joined: 1/18/2003 From: Pella,
IA, USA Status: offline
you change them with no problems like range or anything right. someone told me that the transmitter is tuned to the channel at the factory is this true? I know you can change RX. this is probably the dumbest question ive posted. Im 99.9 percent sure just needed to have confirmation.
Posts: 1157
Joined: 10/31/2002 From: San Jose,
CA, USA Status: offline
Yes you can change the crystals to a different channel. I believe FCC dictates that the set shipped with the radio set are tuned. We (I) do it all the time most especially in a racing event.
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i have heard that the tx is tuned to the specific channel but the rx is not, so changing rx crystals wont affect anything. However, if you change a tx crystal you are suposed to change the modual or get it retuned. I always change tx crystals and have never had any glitching or other problems, so i think this is bs
Posts: 1575
Joined: 2/7/2002 From: South Bound Brook,
NJ, USA Status: offline
[QUOTE]Originally posted by someguy i have heard that the tx is tuned to the specific channel but the rx is not, so changing rx crystals wont affect anything. However, if you change a tx crystal you are suposed to change the modual or get it retuned. I always change tx crystals and have never had any glitching or other problems, so i think this is bs [/QUOTE]
nope.. its not BS.
here is a really badly drawn graph showing two TX signals
the one on CH62 is tuned by the factory, the other on ch64 is from a crystal swap.
you notice that the TX doesnt just transmit on one frequency but drifts a bit at lower power. this is the way all TXs transmit, from a CB to a wireless phone to a RC TX.
the proper one is "peaking" right at the proper frequency the other is "peaking" somewhere else but is still giving a signal on ch 64 enough to drive the RX.
now if someone is on that frequency that TX #2 is on then they will be getting alot of noise.... and if this is a critical system, like communications for emergancy personel. well someone is going to try and find you.
thats interesting to know. I just knew that you can change frequencies and your car will work fine. Some of the manufacturers lead you to think otherwise, probably cause they want to sell you more moduals.
Posts: 1670
Joined: 8/14/2002 From: Jacksonville, NC, USA Status: offline
Because people do it anyway, and no one is going to stop selling them minus the TX module cause it is profitable, go to a local race and you will see 10.000 people on shannels they were not "tuned" too.
Posts: 2148
Joined: 1/18/2003 From: Pella,
IA, USA Status: offline
Yes It is illegal to change 72 and 75. a module is a small box that comes on and off the transmitter. If the radio does not have a module then legally you cannot change the TX cystals unless you send it into someone authorized to do so. The authorized personal will then somehow tune your transmitter so that it does no bleed into commercial channels, It is hassle but its the legal way. Now if your Tx has a module you can just buy a module with a different channel. I was confused at first but now I understand
Posts: 4390
Joined: 7/6/2005 From: behind my 'puter, USA Status: offline
With modern radios, like the Futaba 3PK or JR's Hitecs, Airtronics, etc. how often have these radios seep or bleed into other channels from a crystal change? I was under the impression that modern ground RC radios do not have that problem anymore, even if one illegally changes the cystals.
Posts: 4390
Joined: 7/6/2005 From: behind my 'puter, USA Status: offline
quote:
ORIGINAL: slodsm
Because people do it anyway, and no one is going to stop selling them minus the TX module cause it is profitable, go to a local race and you will see 10.000 people on shannels they were not "tuned" too.
I have done this on many occasions too. I have yet to receive any citations for changing my own crystals. How is the FCC going to enforce such a law? They cannot. They can only tell radio makers to tell their customers that it is illegal to change their own crystals.
Anyway, I do not even use 75Mhz anymore. I chunked my 75Mhz TX module and slapped on the Spectrum 2.4Ghz DSM module. No more glitches and crystals. I don't even have to switch synth channels!
Posts: 311
Joined: 3/16/2004 From: Soulsbyville,
CA, USA Status: offline
This question always kills me! The tuning of the oscillator curcuit of the transmitter will always accept a wide range of different channels between 61 and 90 (Same for channels 11 - 60 for 72MHz, etc). Think about it. Would you believe that any radio manufcaturer would have 45 different circuit designs for each 75MHz radio model they sell? NOT!
JR sells TX-RX sets for their 72MHz radios and I'm sure they have thought about this! Spending your time and money to send your radio back to the factory to have the transmitter 'tuned' is a joke and a waste of money! For further information on this, please read the FAQ and white paper at www.performancedevice.com.
PS: Don't forget to visit www.buyrccrystals.com for the BEST crystal prices (Yes, we are a sponsor on RCU!).
Posts: 4390
Joined: 7/6/2005 From: behind my 'puter, USA Status: offline
quote:
ORIGINAL: SportCrystals Spending your time and money to send your radio back to the factory to have the transmitter 'tuned' is a joke and a waste of money! For further information on this, please read the FAQ and white paper at www.performancedevice.com.
Thanks for the info.
In my personal opinion, I think if the FCC lobbied to get the retarded law that prohibits crystal changes, then we the citizens should lobby to pass a law that requires the FCC to pay for the shipping, handling, and labor charges for crystal swaps. Also, under this law, the FCC must buy each and every RC enthusiast a duplicate radio to fill in for the one that must be sent in!
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you can change tx crystals in FM? - 
RE: you can change tx crystals in FM? - 