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Dave Saylor
Joined: 11 Jan 2015
Posts: 209
Location: GILROY, CA
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 Posted: Wed Oct 25, 2017 2:48 pm Post subject: 406 ground plane |
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I'm planning to install a new ELT. It comes with a "shark fin" antenna that incorporates the 406 antenna and the antenna for the internal GPS. It has no 121.5 capability. It has a metal base plate, which I thought was sufficient for higher frequencies.
However, the installation instructions call for a ground plane of at least 120 square inches, and preferably 300 square inches.
Am I missing something? Why would an antenna operating at such high frequencies need such a large ground plane? Isn't the rule that the radius of the ground plane should match the length of the antenna?
--Dave
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--Dave
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nuckolls.bob(at)aeroelect
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| Posted: Wed Oct 25, 2017 3:09 pm Post subject: 406 ground plane |
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At 05:46 PM 10/25/2017, you wrote:
| Quote: | I'm planning to install a new ELT. It comes with a "shark fin" antenna that incorporates the 406 antenna and the antenna for the internal GPS. It has no 121.5 capability. It has a metal base plate, which I thought was sufficient for higher frequencies.
However, the installation instructions call for a ground plane of at least 120 square inches, and preferably 300 square inches.
Am I missing something? Why would an antenna operating at such high frequencies need such a large ground plane? Isn't the rule that the radius of the ground plane should match the length of the antenna?
--Dave |
The 1/4 wave ground plane at the lowest frequency of
interest is 300/406 meters = 0.74M x 39.36 in/M x 0.25
yields a radius of 7.25"
7.25 (squared) x 3.1416 = 166 square inches . . . which
meets the "120 mininum".
Bob . . .
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rv10pro(at)gmail.com
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| Posted: Wed Oct 25, 2017 3:11 pm Post subject: 406 ground plane |
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300 sq. in. would be 17.5 x 17.5 and using six radials of 1" wide copper adhesive tape is commonly used to propagate a solid ground plane. 0/60/120/180/240/300 degrees as the line of longitude runs.
John
On Wed, Oct 25, 2017 at 3:46 PM, David Saylor <saylor.dave(at)gmail.com (saylor.dave(at)gmail.com)> wrote:
| Quote: | I'm planning to install a new ELT. It comes with a "shark fin" antenna that incorporates the 406 antenna and the antenna for the internal GPS. It has no 121.5 capability. It has a metal base plate, which I thought was sufficient for higher frequencies.
However, the installation instructions call for a ground plane of at least 120 square inches, and preferably 300 square inches.
Am I missing something? Why would an antenna operating at such high frequencies need such a large ground plane? Isn't the rule that the radius of the ground plane should match the length of the antenna?
--Dave
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http://www.matronics.com/Navigator?AeroElectric-List |
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Dave Saylor
Joined: 11 Jan 2015
Posts: 209
Location: GILROY, CA
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| Posted: Thu Oct 26, 2017 5:24 am Post subject: 406 ground plane |
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OK, 120 it is. Thanks again Aeroelectricians!
On Wed, Oct 25, 2017 at 4:08 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 05:46 PM 10/25/2017, you wrote:
| Quote: | I'm planning to install a new ELT. It comes with a "shark fin" antenna that incorporates the 406 antenna and the antenna for the internal GPS. It has no 121.5 capability. It has a metal base plate, which I thought was sufficient for higher frequencies.
However, the installation instructions call for a ground plane of at least 120 square inches, and preferably 300 square inches.
Am I missing something? Why would an antenna operating at such high frequencies need such a large ground plane? Isn't the rule that the radius of the ground plane should match the length of the antenna?
--Dave |
 The 1/4 wave ground plane at the lowest frequency of
 interest is 300/406 meters = 0.74M x 39.36 in/M x 0.25
 yields a radius of 7.25"
 7.25 (squared) x 3.1416 = 166 square inches . . . which
 meets the "120 mininum".
Â
 Bob . . .
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| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
--Dave
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