Yesterday I buy a "FUTABA"Flight pack from nearest hobby shop. The crystal that I already have is FM 72.790 CH50. The receiver in the new flight pack is low band, I read on Tower H***** that Futaba make Receiver High Band and Low Band. The people on the Hobby Shop said to me that no difference exist betwing high band and low band receiver only the crystal.....let me know

Some companies make recievers that work accross the full band (Hitec and FMA, for example), while some receivers are only rated for part of the band. I don't know about your specific RX, but I'd certainly trust the label on the RX before the bloke in the local hobby shop.

http://www.rcuniverse.com/showthread...569#post757120]

Something that many people seem to forget (or never knew) is that currently Futaba is the only manufacturer which splits the 72Mhz band into a high and low band. With modern non-Futaba equipment (less than 10 years old) you don't have to worry about the high/low band issue.

Using a Futaba low-band receiver with a high-band crystal will normally result in reduced range. This is Futaba's recommended method of identifying if your receiver is high-band or low-band. www.futabarc.com/faq/service-faq.html#q637

I think all futaba flight packs are packaged with R127DF receivers. That receiver definitely has high/low bands. (I just purchased a Futaba flight pack.)

Based on my incomplete understanding it has something to do with the dual conversion processing. I find this to be a good article about dual conversion:

http://www.torreypinesgulls.org/Radios.htm

I believe the high/low band distinction has to do with the tuning of the second stage of the dual conversion decoder (i.e. the one that operates at 10 MHz in the article above). Perhaps futaba have two slightly different intermediate frequencies, one low band and one high band.

It would be interesting to find out exacty what technical considerations have led Futaba to split the receiver bands.

... shame the hobby shop fed you the wrong info.

the FMA and Hitec RX's that I have (FMA Extreme 4 and 5, and Hitec 555) are both duel converstion.

I'm sure you are right about the different intermediate frequencies in the futaba though.

The FMA website's FAQ is actually an intersting read. They do some intersting things with their RXs. I don't know exactly how, but they are a lot less sensitive to antenna length for example, and you can chop an FMA antenna almost in half and still have plenty of range. I've even tested this (not intentionally, my antenna was dynamically shorted by a passing propeller).

Also, I'm not sure, it's been a long time, but I think my old JR AM single conversion Rx's from way back were high/low band as well. I wouldn't swear to it, and I don't feel like digging around to find them to check

I agree, shame on the hobby shop.

All radio have hi and lo Futaba is the only one that follows tuning specs. As far as I know.

Can we conclude that Futaba do this in the interest of quality?

i.e., Tuning the receiver to operate optimally at the center of the high or low band will give it an edge over a receiver tuned to operate optimally at the center of the entire band.

They allow for change of tolarence of parts. And changes of power from batteries. Hi and LO are tuned to there optimem performance in band width.

Futaba tunes their receivers for the center of either the upper, or lower half of the 72Mhz band. Everyone else tunes their receivers for the center of the entire 72Mhz band.

This means that a Futaba Low band receiver (channels 11-35) is tuned for channel 23, a Futaba High band receiver (channels 36-60) is tuned for channel 48, Everyone else's receivers are tuned for channel 35/36.