Today's Message Index:
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1. 03:48 PM - 406 ground plane (David Saylor)
2. 04:09 PM - Re: 406 ground plane (Robert L. Nuckolls, III)
3. 04:11 PM - Re: 406 ground plane (John Cox)
4. 05:11 PM - LOM Magneto and Shower of Sparks on Z-18 ()
Message 1
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| Subject: | 406 ground plane |
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
Message 2
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| Subject: | Re: 406 ground plane |
At 05:46 PM 10/25/2017, you wrote:
>I'm planning to install a new ELT.=C2 It comes
>with a "shark fin" antenna that incorporates the
>406 antenna and the antenna for the internal
>GPS.=C2 It has no 121.5 capability.=C2 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?=C2 Why would an antenna
>operating at such high frequencies need such a
>large ground plane?=C2 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 . . .
Message 3
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| Subject: | Re: 406 ground plane |
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@gmail.com> wrote:
> 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
>
Message 4
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| Subject: | LOM Magneto and Shower of Sparks on Z-18 |
I have LOM engine and have a few questions regarding Z-18
What purpose does the filter F526.910-03 serve, is there anything else
available that will serve the same purpose if it is an essential item?
The Magneto's that are on my engine do not have a retard terminal as shown
in the Shower of sparks article, is the LOM magneto different?
I have the starting vibrator LUN 2231 as described on Z-18, should I wire it
into the single terminal on the Magneto?
Thanks
Mike
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