Might be kind of tough to pin down. IF they're using H.F. and probably up
into the GHz region and maybe even as low as the L.F. area to transmit, any
one of those transmitters OR a harmonic OR a clashing of all or any - could
be causing the problem. Given he said Crystal control planes work there but
not Synthesized units and given he said the planes operate ok elsewhere,
leads me to believe that the synthesized receiver (all of those he has
tried) is coming unlocked due to RF overload from something. Synthesized
receivers are nice, but they do have their draw backs. I've had battles with
them too in tight RF areas. Some places, a crystal IS better. Antiquated
maybe, but if it works, what the hell........ Just my opinion. I'm not an RF
engineer, but work around RF a lot. I've seen lots of weird stuff.

Lou

"Roger Conroy" wrote in message
...

"P. Venkman" wrote in message
om...
This is somewhat off topic; I apologize, but it seems like the people
that hang out here might actually be able to help me with my problem.

I fly radio control gliders. I recently purchased a new transmitter
(a Royal Evo 9 with synth module, for those that might care). I'm in
the US so this broadcasts on 72MHz.

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.

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.

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.
However, I'm smart enough to know I'm not that smart. That's why I'm
here.

Is it as simple as finding a filter that passes 72 MHz along and
splicing it in to the wire going to the antenna? Is that likely to
cause other problems (transmitting on the wrong frequency, overheating
the RF module due to impedance mismatch, sudden death)? Assuming I
can't find a filter that passes along precisely the frequency I want,
is it OK to put filters in series (like a high-pass plus a low-pass)?
And finally, am I just totally missing the boat here with this idea?
I'm open to other suggestions.

Here's an idea. How about talking to the senior radio technician on the
military base? Just maybe he/she would have the answer.

73
Roger ZR3RC