Model Forum / Radio Controlled / Air Models / January 2009

Oh.

Futaba early sets, some sets could be reprogrammed to be on logical
channel '0' so they all interfered with each other. Just switching on
long enough to read the battery voltage and then switching off would do it.

This was never formally admitted as a problem by Futaba,..

Futaba chipsets are only rated to about 55-65C. In hot sun in a closed
fuselage some sets have packed up completely. This has been
independently tested by a modeller and established beyond my reasonable
doubt. Futaba don't admit to the problem.

Early spektrum receivers would, if a servo drew enough power to drop the
avionics voltage below 3v, take up to 30 seconds to reboot, which is
handy if you have just pulled up the undercarriage and lose control.
Later sets will reboot in a couple of seconds. After JR held their hands
up to that one... `With a 72Mhz set if ou lost control for half a second
due to a low voltage, you would be fine immediately the voltage
rose..just a short glitch maybe.

What else? Mmm. *Some* chipsets draw about 50-70mA. A typical HF set is
5-10mA. Doesn't sound like a lot, but its CONTINUOUS and has been a
possible cause of BEC overheating in electric aircraft, and somewhat
shorter pack  duration in people using them with separate batteries.

XPS sets have been shown to simply not do what is claimed, and have been
associated with several shootdowns..no one ever really go to the bottom
of that one. Some people have had trouble free operation with them too.

Simpler cheap sets like Assan, which we have used, definitely slow down
when used in a 'busy' 2.4Ghz environment. Their response to interference
is to discard frames so only the odd one gets through. This is not
fatal, but its a tad unnerving 'My plane just felt sluggish: I dont
think I wanted to fly it' was the comment from my friend on that one...

2.4Ghz antenna are very short. This is wonderful if you have a small
balsa or glass fuselage - no more dangly antennae hanging out the back
like its the wrong time of the month for the model, In a CARBON fuselage
is an utter disaster. Carbon is opaque to 2.4Ghz. So you need a receiver
that has  the capability - or you have to concoct - a way of mounting a
remote dipole (or two if the set is twin RF like Spektrum). You cant
just tape the antenna on the outside of the fuselage (that actually
isn't a good idea even on 72Mhz).

So whilst shootdowns*, and glitches are gone forever, a whole new set of
issues to do with voltage stability, heat, and the issues of antenna
placement have occurred instead.

I want 2.4Ghz like mad. But its costly..no 3rd party receivers since
every manufacturer uses a different modulation system. And there are
still issues with ALL of the sets currently o the market.

If I were coming back into the hobby, as a solo or remote site flyer,
i'd pickup a dirt cheap 72Mhz set, especially if it had an RF module..
because its cheap, its good enough, receivers are cheap, and 3rd party
are avaialable. THEN  you maybe can think about slotting a 2.4GHz module
in the back later on.

But I wouldn't be in a hurry.

There are more sets coming out from different manufacturers, who have
waited, and looked at the problems of the early sets, and solved them.

* except the Futaba ZGUID issue, and some anecdotal XPS issues. Don't
buy XPS..there are better sets at the money.