Message-ID: <21D465C632E748AEB1B44B29D0A538CA@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <001301d0f2ae$fa2eb260$6401a8c0@ehnebrcdvojcgn>
Date: Sat, 19 Sep 2015 11:24:24 +0100
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Subject: LF: Re: Ground
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Status: O

Sadly Marcin there is probably no answer to your question. Over the early 
years of LF activity I tried to make sense of the various "recipes" that 
were floating around. I found that in general they don't necessarily work 
for you. The reason being that the local ground condition varies widely at 
different locations and in various weather patterns. The commercial site 
designs bear little relation to amateur dimensions.

Eventually I came to the conclusion that the only way to proceed was to do 
measurements at your site and see what strategy is the best. The "best" 
solution will depend very much on the type of antenna you intend to erect 
above it. The idea that quantities radials are necessary by comparision with 
160m and commercial systems is a myth. To be reasonably effective radials 
need to me of the order of 1/8th wavelength long at least. This is way 
beyond practical amateur site dimensions. Running one conductor along the 
ground under a top-wire (of say an inv L) has a positive effect, but often 
running out more can be a waste of effort and money. Again it depens on your 
local conditions. These measurements proved that after you reach the 
diminishing returns point of ground stakes and counterpoises, then 
increasing the antenna capacity has most effect. It seems counter-intuitive 
but putting more horizonal wire in the air reduces the "ground loss" !! In 
my case doubling the capacity halved the "ground loss".

At LF in amateur situations the loss resistance is very often not due to 
grounding but to the effect of the surrounding environment. Commercial 
station chose open land and do not try to install antenna in the middle of a 
forest. Amateurs have to deal with building and foliage with the near field 
range of the radiator. There is no advice in the manuals about this and the 
condition is not modelled well (or at all !) in simulator packages.

Alan
G3NYK


----- Original Message ----- 
From: "Marcin" <bxi@go2.pl>
To: <rsgb_lf_group@blacksheep.org>
Sent: Saturday, September 19, 2015 8:44 AM
Subject: LF: Ground


> Hello,
>
> I'd like to design a ground for 136kHz/472kHz. I have a few hundred metres
> of steel tape at my disposal for this. I'd like to find out how deep into
> ground 136kHz and 472kHz respectively can go?
> How deep do I have to dig the tape for 136kHz and for 472kHz, or what 
> would
> suit both frequencies?
>
> Thanks in advance.
> 73! Marcin SQ2BXI
>
>