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Re: [TowerTalk] Antenna modeling

To: Jim Lux <>,"R. Kevin Stover" <>,TowerTalk <>
Subject: Re: [TowerTalk] Antenna modeling
From: Pete Smith <>
Date: Wed, 08 Dec 2004 13:18:32 -0500
List-post: <>
At 12:07 PM 12/8/2004, Jim Lux wrote:
#3. When modeling an antenna with traps how do you know what values to plug in as loads for the traps?

Measurement? Ask mfr? Ask other hams who have one? Model it from physical dimensions, and adjust trap values until the SWR curves look like the ones in the spec sheet.

This what I have done with linear loading, as well. Simulating it with a lumped inductance and the right length elements gives me what I choose to believe is a sufficiently high-fidelity model for interaction and similar large-scale phenomena. Some modern antennas -- the F-12 C'3s come to mind -- probably won't give you believable feedpoint impedances anyway -- but the patterns seem to be pretty credible.

Some very effective tri-bander stacks have been designed using single-band monotaper models of antennas like TH-7s, bypassing the whole tra\sp exercise altogether

Modeling antennas with LC traps could be a real pain in cut and try mode, given all the possible combinations that will resonate at a particular frequency. In that connection, AC6LA's MultiNEC is a really neat tool, because it will let you automatically alter multiple parameters in a design singly or all at once, producing hundreds of runs from which you can select.

73, Pete N4ZR


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