Back to your interference problem. Is your operating
channel frequency smack in the middle of the 40 Mhz band?
If so, maybe you could try a different set of crystals, so
that you operate as far away from everyone else as
possible. Or simply just borrow a different set of crystals
in case there is a weird mix going on, just to eliminate
that possibility.

We've recently got wise to that one and I've ordered a pair of xtals
from the *last* channel of the band. That's what we'll be running with
come the last week in August, when we're due up for the next filming.


Not necessarily the solution, I got bitten by that one once some 9 or 10
years ago when I used to fly radio controlled aircraft (in the UK on 35MHz).
It bothered me when someone else at the flying field had the same crystal as
I did and I had to wait for them to finish flying before I could fly. So
bought another pair of crystals, the highest I could find, if I recall that
was channel 83 (35.230MHz). Everything was fine for a while but a few weeks
later I crashed after losing radio contact with my plane.

A little investigation (in between gluing the aircraft bits back together)
found the cause. A channel vs frequency listing, compared with the MHz
printed on the crystal case revealed that the receivers were single
conversion superhets with 110KHz IF. Channel separation was 10KHz. Clearly
with that setup, image rejection is practically negligible. So someone
transmitting on channel 61, 220KHz away, interferes with channel 83. After
that I went back to my crystals on 76 smack in the middle of everyone elses,
learnt to be patient if someone was already using the channel, and had no
more problems ;-)

Hans G0UPL
http://www.HansSummers.com