RadioBanter - View Single Post - Radio control transmitter

April 26th 04, 06:29 PM

See answers in line:

(Doug McLaren) wrote in message ...
In article ,
P. Venkman wrote:

| I have problems with this transmitter at one particular flying site
| that's right next to a military base. The xmitter is fine at other
| locations, and all the gliders respond just fine to my 'old' xmitter
| at this site. I've done a bunch of things and it really is just the
| new xmitter at this particular flying site.

You haven't actually told us what the problem is.

Is the computer in your transmitter crashing? (interfering with the transmitter)
Are the servos in your plane jittering? (interfering with the receiver)
Are you seeing reduced range or something? (interfering with the receiver)

The computer doesn't crash; the servos jitter badly; range is reduced
to zero, as the jittering starts immediately.

I know reading this you're going to think it's the reciever, but
please read through my other posts. It's not. I've tried 5 different
recievers (4 brands) on different frequencies, and with my old
transmitter all are fine and with the new transmitter they all glitch.
However, it's only at this particular site - anyplace else all the
receivers are glitch-free with the new transmitter.

| It seems like there must be an interference problem with some signal
| being broadcast from the military base. I've tried to shield the
| transmitter without much improvement. That makes me think the
| offending signal may be coming in through the antenna.

We'll need to know what the actual problem is. Shielding your
transmitter isn't going to do much unless the interference is actually
affecting your transmitter (possible, but unlikely) rather than your
receiver.

| Being relatively naive electronically, it seems like I could simply
| insert a filter between the antenna and the rest of the transmitter
| that passes through the 72 MHz signal but blocks everything else.

If the problem is interference to your receiver, doing this at your
transmitter won't help at all. You'd need to do it at the receiver.

Some people have had good luck simply wrapping their receiver (just
the receiver, not the antenna) in tin foil. Twisting the servo and
power wires round and round can also help reduce interference to the
receiver as well, and you can get chokes to wrap your servo wires
around as well.

Tried all of this; no help.

Very very few people put additional filters on their R/C receivers.

Are there any pager towers nearby? Pager companies use the spaces
between the R/C channels to talk to pagers, and can use hundreds of
watts -- this has definately been known to overload R/C receivers and
crash planes. (In that case, the fix would be to 1) do the tin
foil/choke thing and 2) try a different frequency. (Your transmitter
is synthesized, so all you need is a new receive crystal.)

No pager towers, at least that I'm aware of. However the military
base has a large number of antennas and who knows what they're
broadcasting.

| However, I'm smart enough to know I'm not that smart.

That's a pretty good sort of smart to be!

| Is it as simple as finding a filter that passes 72 MHz along and
| splicing it in to the wire going to the antenna?

Probably not, unless your problem really is with the transmitter
computer crashing.

Well, the computer doesn't crash. I finally ran into another guy at
this site flying with an Evo; he had the crystal instead of the synth
version, and he had no trouble at all. I'm working on getting a
crystal module to try.

Which receiver are you using? The cheap park flier ones don't handle
interference well at all.

I've tried two Airtronics, an old RCD (they're Hitec now), a JR, and
an FMA M5. With the old transmitter (an Airtronics) they're all fine;
anyplace but that site they're all fine with the new transmitter too.
Try the new transmitter at that site, and they ALL glitch.

Do other people fly at this site? Your radio should be able to talk
to any plane, so try switching frequencies and picking the proper
shift and see if you can do a proper range check with their plane.
(Or another plane if you have more.)

This is a pretty popular site. I've seen lots of people flying lots
of different types of equipement at this site with no problems. I've
flown four different planes there with the old transmitter with no
problem.

You might also try asking in rec.models.rc.air, though they'll
probably tell you the same things I did.

I've asked a variety of places without much luck. Mostly it's been a
pattern of demonstrating I've tried all the reasonable things and it's
not a problem with the reciever, followed by suggestions that I either
just get another radio or fly at a different site. Neither of those
'solutions' are appealing, so I was hoping someone on this site (being
more technically knowledgable) might have a better idea.

BTW, I completely understand why people think it's the receiver to
start with. It practically always is. I tried three different
recievers myself before I finally started to think just maybe it was
the transmitter.

(And yes, I fly R/C too.)