Mailing List lml@lancaironline.net Message #5742
From: Brent Regan <brent@regandesigns.com>
Subject: re: 36" dia ELT ground plane
Date: Thu, 08 Jun 2000 06:57:35 -0500
To: Lancair List <lancair.list@olsusa.com>
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Walter asks:
"What will I loose using only a 12" ground plane on my ELT antenna?"

You loose the ability to be compliant to the TSO without testing. In the
strict sense of the regs, in order to be compliant to the TSO you must
install the ELT per the instructions provided with the ELT. The instructions
for my ELT specify a 36" diameter ground plane for installations in non
conductive airframes. Per those instructions " Other .. antennas may be used
provided they meet the minimum VSWR requirements". My understand of this is
that unless you install the provided antenna exactly per the instructions,
you must test the VSWR to verify it is within the required limits.

Testing the VSWR is not difficult. It involves connecting a VSWR meter in
series with your antenna feed and turning on the ELT. You can likely borrow
or rent a VSWR meter from your local avionics shop. It's probably a good
idea to test all your antennas for performance.

Regards
Brent Regan


[You can also rent a VSWR meter from Bob Nuckolls on the AeroElectric
Connection website, I think he charges about $25 for a week's use of
it.  Go to http://www.aeroelectric.com/ for more info.     <Marv>    ]

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