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[TowerTalk] trees verticals modeling results

To: towertalk <>
Subject: [TowerTalk] trees verticals modeling results
From: Jim Lux <>
Date: Thu, 29 Dec 2011 10:28:50 -0800
List-post: <">>
Short NEC4 model of a 10m tall vertical at 7.1MHz
tree modeled as wire with resistive loading, also 10m tall. both have 21 
segments.  Real ground 5mS/m, 13, Sommerfeld-Norton, etc

At 1m, 2m, and 5m away.
with 1k/meter and 10k/meter resistance for the tree (bracketing numbers 
from literature)

Loss with 100W feed to antenna

          1m       2m       5m
  1k/m   834mW   232mW    26.9mW
10k/m    99mW    25mW     2.8mW

Current flow in "tree" corresponds to power losses
(e.g. for 1k/m, 1m away, with 1V excitation antenna has 3.73mA, tree has 

Take home message...

Hanging the vertical wire next to the tree isn't a big deal (1% loss), 
and the effect drops off rapidly as you move away.

I wouldn't go stapling the wire to the side of the trunk, but even that 
might not be all that bad.

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