---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 10/25/17: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 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 _____________________________________ Time: 03:48:08 PM PST US From: David Saylor Subject: AeroElectric-List: 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 _____________________________________ Time: 04:09:33 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 04:11:48 PM PST US From: John Cox Subject: Re: AeroElectric-List: 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 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 _____________________________________ Time: 05:11:28 PM PST US From: Subject: AeroElectric-List: 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? 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