Changing channel on a 6EXH

[DieHard]

I called Futaba abouy changing channels in my receiver. i have channel 20 and it is a big no no here in my area. they indicated that i need to send it in and have no crystal install and tx tuned. for $20.00=8.95 shipping. do i really really need to do that. or could i just go buy a new crystal and put it in myself. with out the tuning.

[daniel reese]

So long as we're talking 72.???mhz, you can change channels within the band (high or low) by just changing crystals. There's a little rectangular box on the back with the freq printed on it- pull that straight out and you'll see the crystal pressed into it. Pull out the crystal and insert another one (make sure your rx matches the same freq)

I "think" you can even change to a high band without changing anything in the tx other than the crystal...I think. But I'll deferr to others on that. I had the 6EXHP for a long time and swapped out between ch49 & 58 many times with no problems.

[DieHard]

so there is no tuning the tx to be safe as to not bleed over to the next channels over and under your channel

[swatson144]

In your original post you say receiver, but I infer by context you are asking about changing the chan of the transmitter.

It is illegal in the US to change the crystal in the TX by FCC decree. The reason being that you are only changing 1 part of the transmitter circuit so the whole thing needs to be checked/certified. The correct way is to change the RX to match the TX. Having said that one could add that some people do swap crystals as they want (especially in the car races).

What is so no-no about ch20? it's in "our" band and nothing else should be interfering with it.

Steve

[daniel reese]

Tuning is almost a subject unto itself.

You CAN change channels within a band by merely swapping out crystals. That's is how RC clubs/fields manage radio bandwidth useage at events- each pilot is "issued" a channel to operate on so that no one else will interfere with his signals. Each pilot aught to have a number of crystal sets so that he or she can take advantage of open channels at the field. ( I met one guy who had rx & tx crystals for every channel in both bands!) A single channel separation is usually sufficient for two radios on adjacent channels to operate next to eachother with no interference problems

But...if you wish...(not required) you can have your tx tuned to be precisely on channel. Manufacturers generally dont bother to accurately tune the tx- no matter what channel they originally equip it with since most of us dont fly much beyond a few hundred yards so tuning is not so critical. Were you to have your radio tuned, you might notice an increase in range but that only becomes aparrent beyond 1/2mile!

[swatson144]

I standby my original post. It is illegal. I have researched and quoted the code in the past. While it is common at many clubs to do as you say it is also common to be ejected from other clubs if found on a different chan than what the FCC sticker on the TX states. The rule is very specific in that the transmitter RF circuitry be FCC certified in its entirety. This is why many TX have modules which contain the entire RF circuitry. Modules are completely legal to change.


Steve

[swatson144]

http://a257.g.akamaitech.net/7/257/2422/05dec20031700/edocket.access.gpo.gov/cfr_2003/octqtr/pdf/47cfr95.209.pdf for the specifics.

(d) You must not make, or have made, any internal modification to a type-accepted transmitter. (See R/C Rule 22) Any internal modification to a type-accepted transmitted cancels the type-acceptance, and use of such a transmitter voids your authority to operate the station.

Later, in Subpart E transmitter is defined as the portion or module converts electrical energy into RF energy.

Also R/C rule 22

§ 95.222 (R/C Rule 22) May I make any
changes to my R/C station transmitter?
(a) You must not make or have anyone
else make an internal modification
to your R/C transmitter.
(b) Internal modification does not include:
(1) Repair or servicing of an R/C station
transmitter (see R/C Rule 21,
§ 95.221); or
(2) Changing plug-in modules which
were certificated as part of your R/C
transmitter.
(c) You must not operate an R/C
transmitter which has been modified
by anyone in any way, including modification
to operate on unauthorized frequencies
or with illegal power. (See R/
C Rules 9 and 10, §§ 95.209 and 95.210.)
[48 FR 24894, June 3, 1983, as amended at 63
FR 36610, July 7, 1998]

Them is law.

Steve

[DieHard]

Channel 20 here and around St Louis mo is about the same signal as tv station channel 4 and by that when using channel 20 on a RC transmitter it mixes signal so badly that it effects any all channels. don't really understand it but where not aloud to use channel 20 at the feild at all.

[swatson144]

Aah you must have a ch 4(or 5) TV station. That explains that, as it is listed as one of the exceptions our 72 mhz freqs aren't protected from. 95.207 sect g pretty much covers that http://www.access.gpo.gov/nara/cfr/waisidx_03/47cfr95_03.html

I'd ask the heavy hitters at the club what they recommend and go with it, or an alternate plan.

I just don't want anyone to think that jaywalking is legal, even though it is a common practice, and seldom prosecuted ( though I doubt the fine is up to 10,000$ for jaywalking). I'd rather have people think in error that I care if people are jaywalking.;)

Steve