Ok, I have searched Hi and low for the answer to prevent asking an stupid question…
Is it possible to make one 27 mhz transmitter work on all 6 frequencies by swapping a crystal… like in a 72 mhz transmitter… If so which transmitter would have the most output for controlling multiple rc devices.. IE one controller in the house for all rc needs.. versus what I have now 15 27 mhz spectrum transmitters….

It is illegal to swap crystals in the US in a transmitter, it must be done by a shop. It is OK in the receivers with certain limitations depending upon the brand. If you can fine a transmitter with a synthesizer module in the 27 Mhz band that would do what you want. Check the various manufacturers for this option, I don't know of any off the top of my head.

Like Bruce said it is illegal in the US to switch crystals in a Tx without a retune. Now there are options and it depends exactly what type of uses you are talking about. Your question cannot be properly answered untill you state the various uses you intend. There are bands for mixed aircraft and surface, aircraft only and surface use only. There are synthesized Tx's avaliable or single frequency module's that make changing instant and legal but it all depends on what cha ya got in mind?

John

It's my understanding that that restriction does not apply to the 27mhz band.

nope, sec 95.222 makes no mention of any frequency, only to RC control devices.

http://www.nsea.com/PART95/95.222.txt

Jim this is the curious statement that would require more explination to get a good answer. Are we talking RC models, garage door openers What?

I’m sorry I was not more specific.. But seriously, thanks for the timely responses… I have 3 f-27 strykers… 10 or so firebird scouts… 2 firebird commanders.. 1 freedom flyer… and a glider… all on the 27mhz freq…. I use a lot of these to teach kids at my church but I just wanted to “Slim” down the number of controllers I use…. So to answer the question, they are all Air RC’s… and yes I know I could use better planes to teach but we are sometimes talking about 8yr olds… As they get older I get them using my gas 72mhz planes.. Witch I use a Hitec Eclipes 7 w/ spectia to use all the Freqs... So hay, a spectria in 27 Mhz is what I need... Sometimes you just got to trip over it...

Cool Richard that makes a lot more sense now. I don,t think anyone is doing a 27Htz synth probably just not the market for it. With. only six channels on 27 and shared surface/air, makes 27 the poor stepchild even for the car guys. Most of them eventually go to the 75Htz. Hitec does make a Spectra synth module for 75 but apparently not 27. Sorry I could not be of more help.

John

Well .... if there are only six 27 MHz frequencies then wouldn't you need, at the most, just six transmitters, one on each frequency?

See the problem is some work with the others on that channel and some don't... I purchased a set of 6 Tx & Rx chips at radio shack... But alas it was unsuccessful... I thought it might be a number of channels or a synchronization issue but was unsure… Was wondering if You guys new of a "one size fits all kit" like one 4 channel with plenty of Tx Power that the chip can be swapped in..

you may run into other problems with those planes also, they do not neccessarily use any standard encoding, and could be entirely different from everything else. basically, you are stuck with the tx you have for the plane already.

i never new that u could change frequenceys.....well u learn sommin new every day

OK, I know this subject has been absolutely flogged to death. I wish we could get simple, clear, non confusion-causing answers from the FCC but I doubt that it will ever happen. I remember following a thread similar to this a year or more ago, with many people far more knowledgeable than I contributing, and the conclusion was that the modification (I'm not advocating swapping crystals) ban did not apply to 27 MHz. A quick search of the FCC site shows that the ban (95.222) applies to type-accepted transmitters(95.209 refers to 95.222 and specifically mentions type accepted transmitters), and the 27MHz band, is non type-accepted as per 95.209. This rule does refer to technical specifications I did not look up. I'll just stick to 72 & 75MHz with synthesized transmitters and receivers to solve my problem. I guess that since the park flyers tend to be lower cost, manufacturers just don't pay attention to 27MHz with regards to more sophisticated transmitters.

Jim I beleve your assesment is reasonably accurate and for whats it worth the 1991 narrow banding in the US did not apply to our six channels on the 27Mhz band either. This has allowed a flouishing market in very old systems on the band that predate the middleaged wideband systems on 72 that are illegal. This for the challange flying vintage RC airplanes (not RC assist old timer free flights) as it once was. Of course great care is taken in when and where they are operated due to shareing with surface RC and garage doors.

John