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nuckollsr(at)cox.net
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 Posted: Fri Feb 23, 2007 9:10 pm Post subject: Converting Old Cat Whisker Antenna To VOR/LOC/GS |
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At 11:51 AM 2/23/2007 -0600, you wrote:
| Quote: |
Bob ...
I have an old never installed cat whisker vor antenna. The whiskers are
24" stainless molded into what looks to be bakelite. Two stainless #4
studs protruding and go through a 1" diameter phenolic disk with nuts,
check nuts and fiber lock nuts. The old, I mean old paper work,
describes the antenna as vor 108-117.8 Mhz dated 1/76. It describes how
not to drill holes where it says "DO NOT DRILL HOLES IN THIS AREA" (a
rectangle molded into the bakelite). Mfd by The Antenna Specialists Co.
My fondest hope is to modify the reception so as to receive vor/loc/gs ...
can this be done and how? I have an antenna splitter from Ant to G/S and
Nav. I can solder, follow directions, links and pointing if the lights
are turned up bright.
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A comm antenna is generally mounted vertically out the top or bottom of
the airplane
to most closely match the polarization of comm facilities both ground
based and
airborne (vertical). VOR/LOC/GS signals are horizontally polarized which
is why
you see the dual cat whiskers mounted in a horizontal plane on older
airplanes.
You can use the antenna you've described but with degrade performance.
The optimum
length for the VOR/LOC reception is LONGER than for a Comm antenna . . .
about 26".
So using this antenna as is will further degrade performance due to not
being centered
at the frequency band of interest.
Now, I can't quantify 'degraded' . . . you can give it a try, go fly it and
see if it does what you need to have done. If you find that you're not
hearing
VOR stations as far out as you'd like, you'll have to do something
different.
LOC/GS signals are so strong that a wet string hung out the window would
probably work okay so I suspect you'll find the antenna is reasonably
useful off the approach end of a runway. Let us know what you discover.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
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Jerry Grimmonpre'
Joined: 09 Jan 2006
Posts: 144
Location: Huntley, Illinois 60142
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| Posted: Sat Feb 24, 2007 9:41 am Post subject: Converting Old Cat Whisker Antenna To VOR/LOC/GS |
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For 'lectric Bob
and
Reply to Old Bob ... Good Morning Mentors!
Yes ... information does get tangled at times.
This older, never installed V cat whisker antenna, is going on the belly of my RV4. The airplane was never equipped with a VOR/LOC/GS receiver so I am retrofitting. ACS wants within a breath of $400 for their V shaped cat whisker NAV/LOC/GS antenna. I believe the difference in the ACS V shaped antenna and my V shaped cat whisker lies within the balun design and maybe a bit of electronics soldered together. The difference easily qualifies this conversion as $time$ well spent ... saving over $300.
What I need is info from Bob N on what to do with a plain VOR/NAV V shaped cat whisker antenna to convert it a NAV/LOC/GS receiver fed through a AV-570 Diplexer.
Hope this helps ...
Jerry
Old Bob ... the PBGC debacle didn't touch me ... I'm blessed. The RV8A project continues but temporarily on the back burner, deferred by the RV4 mods. I got the 4 to keep the skills up, have some fun and to witness good/bad build practices for the 8.
[quote][b]
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