What is the diff. between high/low band.

I just got a Futaba FP-R127DF. It had a #16 Crystal but I would like to use a #26 or something in the fortys. will this work. Also I have access to a Futaba tx that had a #42 Crystal but the guy who has it says he thinks it's a high band tx. Will this not work?

Thanks in advance.

Del

11-35 low
36-60 high

If you go to the fourties you'll need to send the Rx in to be retuned. Tx's can work with both high band and low band if its a modular system. if not, you have to send the tx in to be retuned to a new channel as well. Hope this helps.

How can you tell if its a modular system?

Thanks,

Del

Del,

Most manufacturers of receivers tune them to channel 35, the middle of the 72 mHz band. If you put in a channel 11 or 60 crystal, you are 24 or 25 channels away, or "out of tune".

Futaba tried to treat us better. They tuned some receivers to channel 23 and called them "low band" and some receivers to channel 47 and called them "high band". If you put in crystals from 11 to 35 in a "low band" receiver, or from 36 to 60 in a "high band" receiver, you were less than 13 channels "out of tune".

So, if you do the arithmetic, you can see that you could put a crystal for channels up to 46 in a Futaba "low band" receiver and still be as much "in tune" as if you put an 11 or 60 in anyone elses receiver. Same arithmetic says you could go down to 24 in a "High band" receiver.

Futaba has since seen the error of their ways, trying to give us better reception, and has gone to tuning the new receivers just like everyine else does.

After you have had your set a couple of years, and send it in for maintenance ( I likie Radio South) you will get your receiver back, updated and tuned to the channel of the crystal in it. Right on the money.

By FCC edictt, you are not allowed to change crystals in transmitters and mess up the tuning.

And that is what was meant by "high band" and "low band".

Ken Erickson

Del, it is illegal to change crystals in your transmitter yourself. It has to go to either the manufacturer or to a service center like Radio South to get this done. There is more than just a band change. A change in the crystal will require transmitters to be re-tuned to the new crystal. If you do not, you take a chance of cross-intefering with someone on the adjacent channel and causing a real serious problem, let alone liability for causing the problem to begin with.

If you really need to change frequencies, then send it back for re-crystal and re-tuning, or buy another transmitter on the frequency you need to be on.

If you doubt what is being said here, please, go to the AMA web site and look it up for yourself.

Now, the receiver is a different story. It does not transmit so you can do what you want with that, but not the transmitter.

DS.

A "module" is about 2 inches square ( VERY roughly) and plugs into the back of the TX and is black plastic and contains ALL of the critical tuning circuitry. A crystal is just the little 1/2 inch square shiney silver 2 pin silver thingy like you plug into the RX.

Legal to change RX crystals all you want, NOT legal to change TX crystals, OK to swap entire modules, NOT OK to alter modules.

And in defense of the Non-Futaba RX, there is nothing that says their RX are "out-of-tune". It is not established that they are subject to variances due to crystal changes. Perhaps their circuitry accomodates these changes. Just know that MOST Futaba RX have split bands in 72 MHz although their new R168DF RX is NOT a split band RX. You can get one of these if you wish to avoid problems in the future or another after-market RX.

Most of the newer offerings from Futaba no longer split the band and are labeled High<>Low meaning they are center tuned to the band.

The interference issues with crystal swapping in transmitters isn't so much interfereing with other pilots as interfereing with the commercial users that are sandwhiched between the channels we use. Its a 10,000 dollar per occurance fine, just send it in to retune it.

A high band reciever can be retuned to to a low and vice versa and if its a used reciever its best to have it checked over anyways, retuning will show up any potential problems and cost you a whole lot less than most airplanes.

High/Low does not apply to transmitters, only receivers and only Futabas and as I said, not all of them.

The RX is like the radio in your car, you can adjust it to get the channel you like, without creating problems for others. The transmitter is another story. Your agreement on purchase is for the specified channel{unless moduler or synthesised} which are designed to keep in tune as the channel is changed. If you start changing things on your own, you can deal with unhappy fliers at your field and the men in suits, from the FCC. How many of us remember the 70's when pirate radio stations where the rage. Back then it was a hand slap and confescation of your equipment, now it would probably be conscrewed as an act of terriorism.{ this last statement is ment to be humoress, not an act of agression or to be polliticlly volitale}.

Thank you for all the responses. This site and the people here are really great!! It is apparent that this site will continue to be an asset to myself and all people starting in this fun and exciting addiction.

Thanks again,

Del