nuckolls.bob(at)aeroelect
Guest
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 Posted: Sun Feb 15, 2009 10:04 am Post subject: Anyway to test VOR antenna location on ground? |
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At 11:33 PM 2/14/2009, you wrote:
| Quote: | I have an AAE antenna for my panel mounted Vertex VX-700 handheld. I
made a 1/4" thick balsa 90 degree bracket where half the antenna is
horizontal, and half vertical so it will kinda work for both nav and
com (supposedly ~ 70% as well for each as compared to mounting with
antenna straight in proper orientation)
Anyway had strobes going today (Kunzleman that drives two wingtip
heads with position LEDs) and found a location where the strobes
don't antagonize too much. This places the horizontal portion of the
antenna at the top of the fuse going fore and aft parallel with the
pitch torque tube ( large OD thin wall aluminium) about 16" away.
Any ideas on how I could perhaps test VOR on ground to see if
location works reasonable?
I tuned to a VOR and was just about able to hear identifier with
volume all the way up. No change to reception with antenna out of
plane or in position I like with strobe going, I spun plane 360
degrees while listening and there was no change.
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Antennas for frequencies below that of transponders
and GPS are almost always a compromise from "ideal".
Ideal being a 1/4 wave radiator sitting in the center
of an infinite ground plane and no metallic obstructions
closer than say 10 wavelengths.
Fortunately, the vast majority of our communications
and navigation is line of sight limited and ground
based transmitters in both services tend to be robust.
Only a flight test in the situations YOU plan to use
the antennas will let you know if "more study is
needed". I've had builders report 100% satisfactory
performance and others report "piece of (at)#$(at)#" performance
on the same antenna. Problem was that one guy never
talked to anyone outside a traffic pattern and
the other guy was hoping for "loud and clear" from
an RCO out on his 10,000 foot horizon.
Every antenna installation on a $high$ TC aircraft
where optimum performance is expected gets an in-flight
pattern test. This takes a bunch of test equipment
and a cooperating ground station.
Our Mid-Continent airport is 10.5 miles from the VOR
and I can recall very few radios that would get
a signal strong enough on the ground but EVERY
radio would come alive seconds after you broke ground.
These were antennas and radios that are presumably
holy-watered. So without a lot of $time$ and test
equipment expense, your next best bet is go fly
it.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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