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From: pat <g4gvw@aol.com>
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Date: Sat, 19 Sep 2015 21:36:54 +0100
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Subject: Re: LF: Re: Ground
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Status: O

I would tend to agree with Alan. My limited experience has tended to 
suggest that treating the 'sky-borne' wires of an antenna system as one 
'plate' of a capacitor of which the other 'plate' is the Earth and the 
rest of the universe has made a certain amount of sense.

73

On 19/09/15 12:26, Graham wrote:
> In saying that ,   I have the  idea  capacity to ground, may be  more 
> important than  'resonant' length , besides ,  in the  ground , the 
> effective length must be  longer , as the Vfactor of the  ground , is 
> not the  same as  free  space ?
>
> There  are some , huge signals rolling  Down under , where the 
> stations are located  in the  outback, 100's of miles from water , 
> with  nothing  but 'dry land'  A circular  perimeter fence some miles 
> long seems to  do  the trick
>
> Bob  over in NY State  , uses  wire  mesh to  cover  his  front lawn  
> , granted bigger than the  average , but  again , capacity as opposed 
> to resonance ?
>
> May be , just  make a  large  ground  'mat' and  tune against that ?   
> loop couple  the  ATU  as the  tuner earth and the equipment will  not 
> be  the same
>
> Or -If there is the height , use a  Loop  ?
>
> 73-Graham
> G0NBD
>
>
> NB  -   Steel tape  ?
>
> --------------------------------------------------
> From: "Alan Melia" <alan.melia@btinternet.com>
> Sent: Saturday, September 19, 2015 11:24 AM
> To: <rsgb_lf_group@blacksheep.org>
> Subject: LF: Re: Ground
>
>> 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
>>>
>>>
>>
>>
>

-- 
73 de Pat G4GVW
QTH Nr. FELIXSTOWE
EAST COAST UK