ELT antenna in composite planes.

Ok. I don' t actually use a short "stuby" ducky. There are some 9-12"
long duckys with pretty decent gain which is still small enough to
directly mount on the ELT. Check http://smileyantenna.com/ choices.
The disadvantage of inside mounted ducky depends where it is - the
composite material by itself does not attenuate the signal
significantly. In fact my wing mounted VHF aircraft regular antennas
are mounted "inside" composite winglets ( see http://www.abri.com/sq2000
)

A quarter wave with ground plane has a donut pattern with a hole on
top. Also, my logic tells me (gain reciprocity notwithstanding) that a
ducky radiates better than receives - there is simply not enough
antenna surface to collect signal like in a larger antenna. But for
ELT transmission is what counts.

Paul (KC0WIF)

On Oct 31, 6:19 pm, "Vaughn Simon"
wrote:
wrote in message

ups.com...

The radiation gain in larger
antennas comes from directionality and not from nothing

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.

You are correct that a long antenna gets its gain from decreasing the angle of
radiation and concentrating more of the signal at (or even below) the horizon,
but I have never seen a gain antenna used for an ELT, have you?

Vaughn (WB4UHB)