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
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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