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)

| 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.

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.)

| 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.

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

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.)

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

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

--
Doug McLaren, Reserve your bear to right arms.