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From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <1843908200.20151104162925@chriswilson.tv>, <CAA8k23QB1RxnKaYXrYq0YVscvzEsNstciTwTkW=D6Dvt2fLUYQ@mail.gmail.com>, <8E31BC8EB75546E59F99E35AFAAA0DEE@AGB> <563DD93A.22662.37C4EA@mike.dennison.ntlworld.com> <514333482.20151107111905@chriswilson.tv> <79AAC450664E4A62AE4F7F72331E43BC@gnat> <AC8A5CA3A2DB4EDBA6E3FE8CB9B23A7B@AGB> <9E37EAD7DC7A43E08EFF3EAF82788F58@gnat> <957601B31AB3407BB82F82515E15A9F1@AGB> <676EC95B2D174FF79B59FC2718AE9C5F@gnat>
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Date: Sat, 7 Nov 2015 21:16:41 -0000
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Subject: Re: Re[2]: LF: Capacitive top hat question
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Status: O

'elevated coil merely reduces the voltage in the section below it'.

'load the best point for the ground rods was under the remote end'

Quite so , what go's up  must come down, lower voltage  at the  tuner , more 
amps in the  vertical ,  higher voltage
at the  top/end .. same  capacity ,  but more voltage , more  power transfer 
to ground

Which was my point ,  adding   additional top wires, more capacity , has the 
same  effect  as  adding a  top loading  coil, which in turn  increases  the 
apparent  capacity to  ground , same  result ?

 G, ..

--------------------------------------------------
From: "Alan Melia" <alan.melia@btinternet.com>
Sent: Saturday, November 07, 2015 4:23 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: Re: Re[2]: LF: Capacitive top hat question

> I think you are waving your arms around G  :-)) There is no 
> "transformation" the elevated coil merely reduces the voltage in the 
> section below it. This reduces the current forced into lossy environment 
> near the feed and verticle (as Mike found) The top section has a remote 
> end with is the high voltage point, that point drives most displacement 
> current through the "load capacitance" to ground. The capacitance is a 
> physical thing.....two plates....it does not vary with frequency !! At the 
> feed point the elevated coil cancels some of the capacitance so the 
> capacitance must be measured well below the resonant frequuency, or the 
> inductance allowed for. This can all be calculated easily. This is why I 
> always recommend measring the parameters of an untuned aerial . You dont 
> then get confused by the tuning elements, it is a simple capacitance in 
> series with a resistance (which is predominantly loss)
>
> If you have a copy of the old Peter Dodd LF experimenters Sourcebook there 
> is an interesting reprint of an article from 1926 about the Nauen VLF 
> aerial system.. Short of money they couldnt afford unlimited amounts of 
> copper so they had to use what they could afford efficiently. The found 
> with a top load the best point for the ground rods was under the remote 
> end not under the feed point!!
>
> Alan
> G3NYK
>
> ----- Original Message ----- 
> From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Saturday, November 07, 2015 3:53 PM
> Subject: Re: Re[2]: LF: Capacitive top hat question
>
>
>> Im thinking of  transformation, caused by  a top loading  coil . That 
>> would appear to  offer a  higher  ground capacity  from the  top  wires , 
>> after the  coil , lowering the  feed  z at one side and  higher at the 
>> other ?
>>
>> G,
>>
>> --------------------------------------------------
>> From: "Alan Melia" <alan.melia@btinternet.com>
>> Sent: Saturday, November 07, 2015 3:24 PM
>> To: <rsgb_lf_group@blacksheep.org>
>> Subject: Re: Re[2]: LF: Capacitive top hat question
>>
>>> Measured ....the only type that matters :-))
>>> Alan
>>> ----- Original Message ----- 
>>> From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
>>> To: <rsgb_lf_group@blacksheep.org>
>>> Sent: Saturday, November 07, 2015 2:31 PM
>>> Subject: Re: Re[2]: LF: Capacitive top hat question
>>>
>>>
>>>> doubling the capacity ofan aerial halves the ground loss
>>>>
>>>> Actual or  effective  capacity  ?
>>>>
>>>> G,
>>>>
>>>> --------------------------------------------------
>>>> From: "Alan Melia" <alan.melia@btinternet.com>
>>>> Sent: Saturday, November 07, 2015 12:32 PM
>>>> To: <rsgb_lf_group@blacksheep.org>
>>>> Subject: Re: Re[2]: LF: Capacitive top hat question
>>>>
>>>>> I think that maybe too much emphasis is placed on specific structures. 
>>>>> At these frequencies any structure of conductors can be resolved into 
>>>>> an equivalent vertical and horizontal arrangement......even a 
>>>>> continuously sloping wire!. As Mike says the horizonal portion does 
>>>>> not radiate appreciably because of the reflection in the close-by 
>>>>> ground.
>>>>>
>>>>> Predominantly horizontal conductors will inrease the capacitance of 
>>>>> the aerial to ground and an extra run of wire will have most effect if 
>>>>> separated by around a metre to reduce interaction between to two. 
>>>>> Ball-park figure an extra 6pF per metre. The actual configuration of 
>>>>> connection is unimportant for the horizonals form a "skeleton" plate. 
>>>>> Note whereas Rugby LF station had originally caged wires between the 
>>>>> 850 foot masts to increase the capacity, after the rebuild the 
>>>>> internal area with the masts was "laced" with straight single wires. 
>>>>> This produced more capacity and was easier to maintain the the high 
>>>>> windage cages.
>>>>>
>>>>> Then the more horizontal wire the higher the aerial capacity, so the 
>>>>> smaller the inductance needed to resonate it ......and lower coil 
>>>>> loss. However another effect not well modelledin aerial synthesis 
>>>>> programs isthat doubling the capacity ofan aerial halves the ground 
>>>>> loss. There are mesurements on my web site confirming this, under 
>>>>> spiral aerials. Halving ground loss is very difficult to achieve with 
>>>>> extra groundrods or "radials" at LF/MF unless it is poor to start 
>>>>> with. The only casewhere this is not useful is over very good ground, 
>>>>> a high water-table or possibly sea water.
>>>>>
>>>>> As to feeding Chris's loop as a loop..... the size is much less than a 
>>>>> wavelength and is too low compared with the wavelenth to radiate 
>>>>> efficiently. Any uncancelled radiation will probably be vertically 
>>>>> upwards, much of which will escape the ionosphere never to return.
>>>>> Its performance at HF where distance above ground is of  the same 
>>>>> order as a wavelength will be totally different.  Phase difference 
>>>>> round the loop will lead to a totally different pattern of radiation.
>>>>>
>>>>> Alan
>>>>> G3NYK
>>>>>
>>>>>
>>>>> ----- Original Message ----- 
>>>>> From: "Chris Wilson" <chris@chriswilson.tv>
>>>>> To: "Mike Dennison" <rsgb_lf_group@blacksheep.org>
>>>>> Sent: Saturday, November 07, 2015 11:19 AM
>>>>> Subject: Re[2]: LF: Capacitive top hat question
>>>>>
>>>>>
>>>>>> Hello Mike,
>>>>>>
>>>>>> Saturday, November 7, 2015
>>>>>>
>>>>>>
>>>>>> Thanks for the info Mike, as always! Is there any real benefit in
>>>>>> having the vertical section centralised within the top hat capacitive
>>>>>> array, be it a horizontal loop, random horizontal wires, or a plain
>>>>>> single wire?
>>>>>>
>>>>>> And is there much point in struggling to get one corner or side of a
>>>>>> horizontal top hat loop higher than the rest, or the same for a 
>>>>>> single
>>>>>> wire? I have some tall trees, but unfortunately not two tall trees
>>>>>> opposite one another a