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.