>> I have a Trimble Terra unit. It receives perfectly but transmissions >>
are variable. Sometimes fine; sometimes OK , sometimes useless; all >> at
about the same range. My headsets are OK and the antenna is >> the standard
fin tape. I am thinking the latter may be the problem ; >>any views or
suggestions.
>> Ben G-BXGG
Maybe, maybe not the antenna. Electrically, the antenna is clueless whether
you're transmitting or receiving. Although, if the comm has excellent
receive sensitivity, the antenna can degrade it by 50% and you might not
notice it, since ATC facilities generally put out more watts than we do. But,
degrade a 5-watt comm (I think the Terra is such) by 50% and you're down
toward the output of a handheld comm.
If you know someone with an RF wattmeter, VSWR meter, and field strength
meter (some are all in one box), you can check everything. Short of that,
one trick is to try a cheapie AM radio. It will have to be fairly close to
the antenna to "receive" anything (and twiddle the tuning to find a good
sub-sub-sub-harmonic frequency), but that's the idea. You can thus compare
yours to someone else's (with similar RF output) at the same distance. Can
check radiating pattern too. One difficulty with installation in the fin is
that one end of the dipole can be too close to the pitch torque tube and push
rod, potentially putting a void in the radiating pattern, giving you the
apparent intermittent problem you describe. You can also rough check the
pattern in the air. If you get a squawk that you're weak, try doing a 360
while transmitting some "long counts" (1 - 10; 10 - 1), and see what ATC
hears.
Happy "RF sniffing"
Regards,
Fred Fillinger, A063
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