ELT antenna in composite planes.

"Vaughn Simon" wrote in message
...

Yes, but in this case, we are comparing a shortened (ducky) antenna to a
1/4 wave antenna, not a gain antenna. A 1/4 wave antenna has a pretty
high angle of radiation. I raised my eyebrow at Jim's estimate of 15 db,
but when you start adding factors, (eliminate the loss of the stubby
antenna, antenna in the clear outside of airframe, elevated antenna) you
could end up with more difference than you think.

Jim's wasn't an estimate. Jim got up onto the top of a mountain (not
difficult in Northern California) with a calibrated spectrum analyzer and a
lab standard ground plane antenna and did a test for the local Search &
Rescue group on 2 meters. Using the best engineering practices and
measurement techniques I could muster, I had about twenty of the S&R folks
use first their ducky and then a regular old brazing rod - SO239 mickey
mouse ground plane.

THe spectrum analyzer showed somewhere between 10 and 20 dB of difference
between the duck and the ground plane. The average was very close to a 15
dB difference between the two.

I've since repeated that same test with us both at the same level (like
across a flat meadow about four football fields long) and with THEM on the
mountain and me in the valley.

Same same.

Jim