Moving to US 72MHz - will my Hitec eclipse 40MHz Tx work?

Yes, it works. I brought over my Prizm 7X and just switched modules. Since the module is certified for that control box, you should have no problems.

henry snipped-for-privacy@hotmail.com (Henry) asks:

transmitter module which at present is 40MHz. I saw 72MHz transmitter module for hitec eclipse on towerhobbies and I wonder if I can just plug the module in to convert my Tx to 72MHz. Of course I will be switching Rx to match as well.<

Henry

Since the transmitter uses a module you probably can change the module to switch to the 72mhz band. As you stated you will also have to purchase a new

To get the transmitter functioning properly, you will most likely also have to change the transmitter antenna since its required length is a function of the transmitter frequency.

I would recommend that you have the transmitter changed over by Hitec-RCD's U.S. service facilities. They will know exactly what has to be done to the transmitter, and can make sure that the transmitter is functioning as required by FCC regulations.

If you switch the transmitter from 40mhz to 72mhz yourself there is a possibility your insurer and/or the AMA might use the modifications as a reason to deny coverage if you are ever involved in an accident while using this transmitter. I would imagine that in case of an accident an injured parties lawyer would love to hear how you modified your transmitter yourself.

I can (and have) changed my transmitters module (within the 72mhz band), I can (and have) changed my transmitters antenna, I can (and have) changed my transmitters back-up battery. I would NOT change my transmitter from the 72mhz band to any other band myself, I would have the manufacturer do it for safety and liability reasons.

You can contact Hitec in the U.S. at the following (taken from the U.S. Eclipse manual) Hitec-RCD Inc.

Tel: 858-748-6948 Fax: 858-748-1767 Web:

Ken Barnes

You can.

You don't. Transmitter antennas are mostly all bottom loaded to allow the same antenna to resonate at the desired frequency. That is taken care of in the tranmsitter module.

Thats your problem.

Actually, swapping an externally-accessible RF module is perfectly legal and allowed under FCC regulations. Replacing the antenna is not an internal modification to the RF section, either.

Certainly. Get the Spectra module, and you will be able to choose any of the 50 72MHz. band channels to match any 72MHz. FM receiver just by changing a dial on the module.

Jim - AMA 501383

Henry wrote:

The Natural Philosopher snipped-for-privacy@b.c wrote in reply

antenna to resonate at the desired frequency. That is taken care of in the tranmsitter module.<

That may be true in the US R/C market. Assuming the manufacturer is using a quarter wavelenght antenna the difference between the antenna for the 72mhz (air) and 75mhz (ground) bands is only a little over 1.5 inches (39" (air) vs

The difference between a quarter wavelength antenna for the 72mhz and 40 mhz bands is over 31 inches (39" (72mhz) vs. 70.1999" (40mhz)).

At the very least Henry should compare the length of the antenna installed on his transmitter with a U.S. spec Eclipse 7 transmitter. If the lengths are different the cost of a replacement antenna is only 10 or 15 bucks. However I still stand by my recommendation that he have Hitec (or a reputable R/C transmitter repair facility) do the switch to 72mhz.

Ken Barnes

He isn't.

The antenna lengths for most transmitters are the same length irresepective of 27mhz, 35mhz, 49 mhz 72 mhz or 75mhz.

They are all tuned to the output stage to make em resonate.

the difference between the antenna for the 72mhz

That is correct! My Hitec Prizm 7X uses exactly the same antenna part number whether US or UK. I haven't seen any 70" antennas over here yet!

Paul McIntosh" snipped-for-privacy@mcintoshcentral.com wrote in reply:

whether US or UK. I haven't seen any 70" antennas over here yet!<

Not having access to part numbers from outside of the U.S. I based my opinion on my limited (and 30 years out of date) knowledge of antenna theory. I suspected that the antenna used for 40mhz probably would have been an eighth wavelength, which would be a few inches shorter than a quarter wavelength 72mhz antenna.

Ken Barnes The day has barely started, and I have aleady learned something new (what else can go wrong?).

Thanks all for your input. I will keep you posted once the gears arrive

Go and do a google search on 'bottom loading antenna' or 'center loading antenna' and get your theory updated.