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Date: Tue, 12 Sep 2006 22:23:50 +0200
From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: top loaded vertical and trees??
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Hello Dick,

my 136 kHz antenna (in the period 1997-2001) was completely surrounded =20
by trees and actually I use 4 of this green lossy capacitors to =20
support the antenna.
My experiences:
1. Loss is very high. I never got it below 130 Ohm in winter and 160 =20
Ohm in summer.
2. Keep the wires as far as possible from the greenery.
3. An elevated loading coil works miracles. Putting about 50% of the =20
needed inductance at the top of the vertical wire improved my ERP by 6 =20
dB. More than 50 % would be even better, but that was to heavy in my =20
case.
4. Even with an elevated loading coil measured ERP was at least 5 dB =20
below the theoretical value.
5. Due to the losses the antenna Q is that low that re-tuning within a =20
1 kHz range is not required (at least one advantage).
6. Due to friction nylon ropes do not last very long in a tree. I used =20
steel cables at the friction points.
7. The combination of wind and Murphy's law will make the trees that =20
support the antenna always moving in opposite directions. Even with =20
moderate wind 3 mm flexible Cu-wire easily snaps at 15 meter height =20
(when it is streched 1-2 meter). An easy and cheap cure is to include =20
so-called "bicycle strechers" (the rubber things used to fix something =20
at the rear of a bicycle) in the supporting ropes.
8. The easiest way to get wires 15-20 meter up in a tree is a =20
slingshot or bow/arrow (the later is more accurate).

To end with a positive note: all the above didn't stop me from working =20
almost all stations that were active at that time. Best DX was OH1TN =20
(+/- 1700 km) in normal CW. My DFCW30 signal was captured in the US at =20
least once but I cannot remind when and by who.

73, Rik  ON7YD


Quoting Dick <knaap159@zonnet.nl>:

> I think this question has been around a while ago, but can't  =20
> remember exactly.
>
> What about running an toploaded vertical in the middle of an wood?
>
> It will be a 12m vertical wire, with an flat, pancake shaped coil on =20
>  top, and additional at least 4 toploading wires
> each 20m long, supported by trees.......
>
> So, nearest tree will be over 25m away from antenna.
>
> What about negative influence (attentuation) caused by the trees?
>
> I'm asking this because it might be rather difficult to find a free  =20
> place for the antenna in LX.
>
> (We will be QRV 136kHz upto 10m, so lot of antennas, masts around ,hi)
>
> Dick, pa4vhf


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