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ZL3AI > APRDIG 19.09.06 22:13l 109 Lines 3741 Bytes #999 (0) @ WW
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Subj: [APRSSIG] Vol 27 #16, 2/2
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From: ZL3AI@ZL2BAU.#87.NZL.OC
To : APRDIG@WW
Message: 13
Date: Sat, 16 Sep 2006 11:20:46 -0500
From: Glenn Wiebe <ve4gn_at_mts.net>
Subject: [aprssig] APRS antenna for an airplane
Would mounting a 1/4w vertical or similar antenna on the belly of an
aircraft not create a null area directly underneath the plane? I remember
the pilot of a Jet Ranger under contract to the company I worked for at the
time telling me that they would not install it there for use with our
company 179 mhz radio for that reason.
73 de Glenn...VE4GN
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Message: 14
Date: Sat, 16 Sep 2006 11:29:33 -0500
From: Glenn Wiebe <ve4gn_at_mts.net>
Subject: Re: [aprssig] APRS antenna for an airplane
Glenn Wiebe wrote:
>Would mounting a 1/4w vertical or similar antenna on the belly of an
>aircraft not create a null area directly underneath the plane? I
>remember the pilot of a Jet Ranger under contract to the company I
>worked for at the time telling me that they would not install it there
>for use with our company 179 mhz radio for that reason.
>
>73 de Glenn...VE4GN
That's 170 mhz.
------------------------------
Message: 15
Date: Sat, 16 Sep 2006 10:30:36 -0600
From: Earl Needham <needhame1_at_plateautel.net>
Subject: Re: [aprssig] APRS antenna for an airplane
At 10:20 AM 9/16/2006, Glenn Wiebe wrote:
>Would mounting a 1/4w vertical or similar antenna on the belly of an
>aircraft not create a null area directly underneath the plane? I remember
>the pilot of a Jet Ranger under contract to the company I worked for at
>the time telling me that they would not install it there for use with our
>company 179 mhz radio for that reason.
Yes it would, but at 100+ MPH, the null isn't in any particular place for
very long. I suspect you would never notice it.
Earl
Earl Needham, KD5XB, Clovis, New Mexico DM84jk
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Message: 16
Date: Sat, 16 Sep 2006 12:52:34 -0400
From: "Wes Johnston, AI4PX" <wes_at_kd4rdb.com>
Subject: Re: [aprssig] APRS antenna for an airplane
As a flying repeater, we have to "racetrack" the area we want to provide
coverage for. That means we are not directly over the top of who we are
talking to.... we circle around them.
On a pretty slick note... I once mounted a 15db 2.4gig yagi inside the
plane on a small tripod bungee corded down to the rear seat. We then
circled about a point (yagi pointed perpendicular to the travel of plane)
with the wingtip pointing at my parent's house. We were able to use their
wifi access point as long as the wing tip was pointed toward them. 1500'
AGL.
Wes
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Message: 17
Date: Sat, 16 Sep 2006 11:58:37 -0500
From: "Dave Kaplan" <davek_at_cloverleaf.com>
Subject: RE: [aprssig] APRS antenna for an airplane
Below is a quote to give you something to think about if you are doing a
clean install. This quote is taken from an excellent article that can be
found at: http://www.hamtv.com/pdffiles/ATVinAcft.pdf
"... I realized that the braid of the RG58 coax to the antenna would
vibrate enough to change contact resistance between the strands and that
would show up as an AM modulation from SWR change. The solution is to use
Teflon double shielded coax with tight braid or aluminum foil. I suggest
RG400, which you can possibly get from companies that do mobile cellular
phone installations, or RG162."
I use to run APRS while flying a Tubine Commander and later a King Air 200
but now I am flying a Citation (and going 100 MPH faster) I don't have the
down time anymore in the cockpit.
Dave
WB0WNX
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End of aprssig Digest, Vol 27, Issue 16
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