henry email@example.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.<
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
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
12115 Paine St
Poway, CA 92064
The Natural Philosopher firstname.lastname@example.org wrote in reply
antenna to resonate at the desired frequency. That is taken care of in the
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.
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
Paul McIntosh" email@example.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
The day has barely started, and I have aleady learned something new (what else
can go wrong?).
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
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