[TowerTalk] trees verticals modeling results

[David Jordan]

Bravo Jim... finally the answer... it don't make enough difference to type 
two sentences about it.  Move that wire away from the tree trunk and hang it 
from a limb and BINGO... you got an antenna that works good enough for most 
folks; sure beats no antenna doesn't it;(?)!

73,
Dave
wa3gin
----- Original Message ----- 
From: "Jim Lux" <jimlux at earthlink.net>
To: "towertalk" <towertalk at contesting.com>
Sent: Thursday, December 29, 2011 1:28 PM
Subject: [TowerTalk] trees verticals modeling results


> 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
> 6.95uA)
>
>
> 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.
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk