On 12/31/14 8:34 PM, n0tt1@juno.com wrote:
Guys, just curious....what's "inside" one of these aircraft
glide slope antennas and how are they matched
to say, a 50-ohm coax.
Basically half of a folded dipole: a folded monopole. Narrow band
matching: Glide slope is a bit above 300 MHz with a span of about 5 MHz,
so about 1-2% BW
http://en.wikipedia.org/wiki/Instrument_landing_system
One ham has one of these
mounted on his car and he uses it for RFI
location....the one with the "tap" on the upside-down U.
Kinda looks like a dual loop antenna.
There is another antenna with a single loop in
the upper right of the screen...looks like an insulator
in the middle of the loop.
Aerodynamic design, basic conservativeness in the aviation biz, avoiding
patents from other companies. There's only so many ways to make an omni
300 MHz antenna.
Actually, you might want a pattern that's sort of fore/aft, since you
generally don't start looking at the GS until you're on final and lined
up with the localizer.
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