At 2.4 GHz, the reflections are such that I can watch the antenna impedance=
 change while I'm sitting 2 feet away, just breathing.
There used to be 915 MHz alarms that work that way.  A short monopole on to=
p of a box, and since pretty much everything has a different dielectric con=
stant than air, motions in "stuff" cause changes in the antenna impedance t=
hat trip the alarm.  "Stuff" can include stratified air in a closed room.

It will be problematic at most (all?) frequencies, just different problems.=
 =20
At 457kHz, reflections aren't much of a problem, and almost nothing attenua=
tes the signal, but the path loss is some 60dB per decade distance inside 1=
00m (radiansphere) but local noise produced by your drone will deafen you e=
xcept at short ranges.

10m and shorter distances are easy.

The book by Joe Moell on transmitter hunting is a classic, though somewhat =
dated now.   I've hunted with him, and N6JSX who is an evil genius at hidin=
g a transmitter.  =20

Pseudo-Doppler rigs tend to be rather deaf, and reflections drive them nuts=
..

The "Double Ducky" direction finder might work for you, since it switches q=
uickly enough that you shouldn't get much change in RSSI over that time per=
iod.

When I was in Wisconsin, I helped Bill with the "Foxcopter", a continuously=
 rotating 5 el VHF beam mounted in the back of his pickup truck, using RSSI=
 and a storage scope to plot the antenna pattern in the direction of the si=
gnal.  Reflections were easy to see and ignore.
http://www.homingin.com/hmgindx.html

--
David VanHorn
Lead Hardware Engineer

Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO =A080301 USA
phone:=A0303-417-1345 =A0x110
email:=A0david.vanhorn@backcountryaccess.com=A0



--=20
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