hello,
I recently bought a used 9CHP (with the module) from a club member since I needed to move up from my 6EX. Needless to say it is not on the same channel as all my receivers. He said, just swap the crystal in the module to whatever you want and fly. Reading through the directions, it says you absolutely cannot do this. Called the hobby shop and they said, yes, you can do it. Hm. Apparently the FCC has made it illegal to change the channel on your TX unless your a qualified technician. Does anyone have any advice on this and where can I get the x-tal if it is indeed common practice. Thanks.

First of all, if you are dealing with a crystal in a transmitter it is absolutely illegal for the end user to change the crystal. Many do get confused when a radio uses a frequency module. The end user can change the entire frequency module, but they may not change the crystal inside of that module. Any changes of a crystal (whether it's directly in a radio or in a frquency module) must be done by a cerified shop. These rules apply in the US and are not applicable in other countries. If your hobby shop told you that you can change the crystal yourself then they are incorrect.

If you are interested in the full text of the regulations concerning this matter they can be found at:

[link=http://www.access.gpo.gov/nara/cfr/waisidx_04/47cfr95_04.html]FCC Title 47, Part 95 - Personal Radio Services[/link]

Copied from Futaba's website

Copied from FCC regulations concerning this issue




Ken

That hobby shop is not only wrong but should hold no further creditbility with you. Its irresponsible acts like that telling the customers what they want to hear contrary to federal regulation that puts our free and unlisensed use of all the bands avaliable to us at risk. It has nothing to do with whether or not it just works in your radio but has everything to do with the posibility of us stepping on the toes of 'Paid up to six figures' primary users interspersed beween each of the 72 Mhz hobby channels and we are lowly secondary users which means quite simply if we are a problem to primary user we are 'out of there' according to FCC protocol.

Your Tx is a module type. They were developed precisely for this reason to allow very simple tx frequency changes by replacing the single frequency module with one of another frequency or a synth type. This requires no tuning. Its a no brainer do the right thing purchase a module on your desired freqency.

Don't become the known crystal swapper at you field, the one who will always be suspect because he insist on flying a Dirty Tx.

John

If I remember correctly, Futaba had a "Dial-A-Channel" module for module type tx's. If they are still available you may want to consider that. I have a 9CAP and really like it. Hitec also has a "Dial-A-Channel" module that will fit the Futaba but it also falls under them same as changing the tx crystal, a BIG NO-NO. Also watch changing crystals in Futaba 72mhz rx's as they have a low and high channel numbers. Rx's are tuned for ch 10 to 34(?) and 35 to 60. I think that's the change point. Check around your area, lots of Futaba tx's had these modules. You just may be able to find the one you need at a really good price.

This comes up every six months or so. As Ken pointed out, it is illegal to swap out your TX crystal yourself. This has to be done by a qualified service organization (Radio South, or the radio manufacturer) and then tested to insure that the TX is tuned to the center frequency. If you swap it out yourself, you can almost guarantee that you will be operating over someone else on an adjacent frequency and will be the cause of a crash.. or worse.

If you want to avoid this, either leave it alone or go to Spread Spectrum like a DX7/DX9?Airtronics RDS8000, FASST and forget about it.

Now Dick, some of just don't want to change! We like having 40 radio's stacked all over the place and fighting over the pin! Just having fun.

Brian

You might consider switching to 2.4 since you're going to have to buy a module anyway. It's a simple switch just like changing frequencies.

OK guys, he says he bought a radio WITH a module. All he needs to do is buy an appropriate module. http://www3.towerhobbies.com/cgi-bin...EARCH=futl8910 is the synthesized version. The 2.4 GHz conversion is also an option but would require all new RX's.

Illegal is nothing more then A sick bird!! I'm sure the person at the hobby shop thought you meant the module because it's often called the radio crystal depending on who is speaking. Common error. We also found out early that the Hitec Spectra fit right into the Futaba radios so you then had it all, sort of. Then the AMA came out with the statement about that sick bird thing again when using the Dialacrash in any radio except the Hitec. Changing your module to change your channel is nothing new, done all the time.
Jester brought up A great point though, if you are starting from scratch then you may want to give the 2.4 switch A thought. In my case I have so many RXs and planes I'm priced out of the change. If I was just starting out then I would switch over right now.

The AMA should have been following the FCC regarding the Hitec Spectra module. Hitec did not receive FCC approval for use of their Spectra module in ANY tx other then their own. Futaba of course did not get FCC approval for the Hitec unit because they have their own. Been down this road along time ago. Looked at this for my 8 Futaba module tx's.

You are right in your interpretation of the info from Futaba. You are not supposed to change the crystal in a transmitter module without having it checked for frequency accuracy and output power.

You can send the module to Hobby Services and they will change the frequency for $25 plus $9.99 shipping
http://www.hobbyservices.com/futaba-rates.html
There are independent service centers who can do the same job. Radio South is well known.

If you choose to buy a new module:

This is the fixed frequency module. Price is about $50
http://www3.towerhobbies.com/cgi-bin...I=LXH256**&P=0
If Tower does not have your channel in stock, check http://www.servocity.com

There is also a synthesized module that does not use crystals. You turn little dials to put it onany channel from 11 to 60. Price is about $100
http://www3.towerhobbies.com/cgi-bin...?&I=LXHKB1&P=0

<<EDIT >> If your 6EX still works, having the existing 9C module changed to your channel makes the most sense to me.

Hi Brian.. yeah, you are so right!!

I have, what, four of them now? After the OC Airshow, I saw that you had a few more than that!!

Dick.

Sec. 95.645 Control accessibility.
(a) No control, switch or other type of adjustment which, when manipulated, can result in a violation of the rules shall be accessible
from the transmitter operating panel or from exterior of the transmitter enclosure.
(b) An R/C transmitter which incorporates plug-in frequency determining modules which are changed by the user must be certificated
with the modules. Each module must contain all of the frequency determining circuitry including the oscillator. Plug-in crystals are not
considered modules and must not be accessible to the user.

So, is Futaba manufacturing illegal radios by making their crystals removable? I don't think so. The FCC is talking about changing the "72 MHZ" freq to say "35 MHZ" etc., not changing legitimate crystals in the RC band with which the transmitter was certified. With regards to Futaba, I have always stayed in the upper or lower band as they recommend with no issues with both AM and FM.

Sec. 95.645 Control accessibility.
(a) No control, switch or other type of adjustment which, when manipulated, can result in a violation of the rules shall be accessible
from the transmitter operating panel or from exterior of the transmitter enclosure.

This tells me Futaba and other's, removable freq crystals are within the rules of the FCC or they would not have been certified.

So, are you saying an Illegal is not A sick bird????

The transmitter portion of the tx is designed to transmit in a specific frequency "range" and that range is 72mhz. Anything outside that and perfomance drops drasticly. Changing to even "Ham" band at 50mhz would require radio rework. I will not get into the specifics of rf transmision but will leave it at this: changing the crystal in ANY RC Tx by someone other than a certified facility is currently illegal according to the FCC. The certified facility will tune the tx to the new frequency and verify that the Tx in "on" frequency and not drifting. This is usually done with a spectrum anilyzer. Just because the FCC set a 25 watt limit on marine vhf radios does not mean they weren't cranked up or had amps put on them. I won't tell you where mine are at! With most tx's you need some tool (hemostats, screwdriver) to get at the crystal some you don't. Sure you can pull the tx crystal and change it, no one would ever know, but let's see now, rx crystal $15 or less and is legal. I know what I do and it aint screwing with the tx.

chris6414,

The crystal caps on both of my Futaba transmitters, and my one Hitec transmitter, were glued to the transmitter case.

The glue dot is very tiny and was easy to break, but, I assume the Futaba and Hitec legal teams decided they can defend themselves in court by saying they try to keep people from doing the wrong thing.

To remove the crystals I had to "break" the radio.

This is so much simpler than everyone is trying to make it. You're simply not supposed to change a crystal in a TX yourself. If your radio is module based, buy the proper module. If your radio isn't module based, contact your brand's service center and send the radio in to them. This isn't rocket science.

quick question. i know changing the transmitter channel is bad bad bad.
but if it is so bad then why can i simply remove my tx crystal on my futaba 4yf. you would think they would at least solder it in the circuitry if they did not want you to change it.
so my 43 ch 72 mhz tx crystal can not be changed to a 44 ch 72 mhz (by me a unlicenced dude). 1. because it is illegal 2. because it could interfear with someone elses?
the next question is what would a manufacture do differently? crystals are inscribed with a "code" so doesnt a transmitter read the code and transmit it.? i understand how a change from a 72mhz to a 50mhz could mess up the signal but a 72mhz to a 72mhz conversion confuses me. someone please explain.

some say it is illegal ^ some not^ .which is it? i would like to do a 72 to 72 conversion (bought something from th scratch and dent)

Legalities aside there is an even BIGGER problem in TX swaping crystals...

The TX coils and chokes need to be tuned for your frequency. If this is not done for you and you swap crystals several things happen.

- Your TX puts out far LESS power than it should on the frequency you are trying to use.

- Your TX puts out spikes on other adjacent channels, and you could be responsible for someone else's plane ( and it's expense! ).

- Your RX sees more noise than it would normally.

-

I was flying a plane on 72mhz last year, and I noticed that it took a noticible "hit" when it went by one pilot who was at the other end of the field from me.
I didn't think about it for a while after that day... and I had no further problems.

A couple of months later I was flying another plane on the same frequency I used before... I was bringing it in for a landing, when the same guy walks up to the pits to prepare for takeoff. My plane glitches and crashes at the time he turned his TX.

A couple other club members saw this and they asked me what frequency I was on.

They walked up to him and asked him the same thing. He was supposidly ten channels off from mine...

Someone had the presence of mind to ask him if he had changed the crystal on his TX himself... he said yes, that it was originally on another channel.

They told him that he owed me a new plane.

He left mad and never showed up again. He is no longer a club member too.

The guy still owes me a plane.

Don't be him! You CAN be sued for this!

k thanks

The laws governing this issue are in place, and were posted earlier. It is very illegal to make this change. Opjose has listed some of what could happen in regards to RC planes if you make this change. But here are more things that could happen. The frequencies that we use (for free) are very close to other frequecies that are in use in which the owners have payed for use of those frequencies. One that comes to mind quickly is television channel #4, but there are others as well. If you change the crystal on your radio and interfere with their broadcast the FCC will more than likely be looking for who is causing the interference. The fines for this are $10,000 per incident.

Ken

What may not be obvious to users that are not necessarily "trained" in electronics is this: The crystal is the generator for a signal that is transmitted by the radio. But, it is not the direct generator. What happens is that the crystal generates a signal that is both amplified (increased in strength) and fed to a circuit within the radio that will multiply or divide the frequency, depending on the application, to the required CENTER frequency.

Crystals are "cut" to a specific frequency, however, it is not cut exactly to that frequency. So, electronic circuitry is in the radio transmitter that will "tune" that frequency to exactly where it has to be. That is now fixed for the crystal that was originally installed in the radio transmitter.

Changing the crystal to another channel caused this "center frequency" to be de-tuned because it, the radio, was never re-tuned to center up that frequency to where it has to be. When this happens, it will "bleed" over to another adjacent channel, or even worse, could generate sporatic harmonics (multiples of the original crystal frequency) that could be amplified and transmitted. This is where the problem comes in. Bleeding over on adjacent frequencies is problematic for reasons that I hope you understand. It is not good to have two transmitters operating on the same frequency (channel) at the same time at the same field. Bad.. very bad. The same goes for harmonics. And, as Opjose pointed out, spikes can also occur on other channel frequencies because of de-tuning caused by inadvertent changing of transmitter crystals.

Thus, the FCC has deemed this to be illegal when done at home. It must be done by a qualified radio technician that will install the crystal, tune it to the correct center frequency, then using a "spectrum analyzer", will examine the transmitter output to make sure that it does not: 1. Generate a signal that it is not supposed to (Harmonics), 2. Bleed over to an adjacent channel (could do that based on a mis-match of the crystal to the circuitry, even though it may be the right one, and 3. cause spikes elsewhere that could cause problems with other radio receivers in the local area.

So, take heed. Send them in to be done right. When you get it back, it will be operating at peak performance and will not cause problems with other pilots.

CGr.

Good point guys. I was just lucky for the past decade flying in the AM mode when everyone else was FM I will be picking up some new crystals. I don't fly at a field currently. Thanks for the insight. I did find that glue dot on my 7C last night. I had been flying a ch 46 transmitter with a channel 36 crystal. Same lower band but not the right one.

High band/ low band has nothing to do with transmitters.

It does when your matching a Futaba receiver to it.