Re: LF: 8.97kHz antennas

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Thanks Alan. 

Yes I can understand that poor ground conductivity would result in a larger loop within the ground and that with high conductivity the loop would be very small. With regard to piping and cables, I'm thinking that any such tests would have to be done well away from buildings and property ideally in the middle of a large field out in the country or on a stretch of moorland perhaps well away from cables and pipes. In an urban area cables and pipes are everywhere and anything could be happening. 

73s
Roger G3XBM

On 16 March 2010 19:36, ALAN MELIA <alan.melia@btinternet.com> wrote:

I think the answer to this Roger is "you will have to try it" The ground antenna is dependent on the actual parameters of the ground below you. It can be considered as a vertical loop .....the connection being the "top" or the loop. Over conductive soil it won't work too well, but over poor ground it can be quite effective. The problem with these variables (what is the real skin depth ?) is calculating the ERP, and so knowing what power you will need. Then what about underground cables and pipes?? Verticals are a doddle to calculate by comparion.

As with previousl experiments, the trials can be easier than the calculations.

Alan

--- On Tue, 16/3/10, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:

> From: Roger Lapthorn <rogerlapthorn@gmail.com>
> Subject: LF: 8.97kHz antennas
> To: rsgb_lf_group@blacksheep.org
> Date: Tuesday, 16 March, 2010, 13:59

> Getting a Marconi vertical up in the sky is
> no mean task when 100m long and carrying a decent antenna
> current so I was wondering whether there is any merit in
> using grounded electrode pairs (as used for
> through-the-ground "earth mode" conduction tests)
> possibly fed with elevated feed wires as an alternative?
>
>
> Not being much of a theory man I've little idea how
> this would perform and what amount of the 8.97kHz energy
> injected into the loop thus formed would actually be
> radiated. Clearly stringing out a 200m long grounded
> electrode pair "antenna" in a big field would be
> considerably easier than raising a kite mounted vertical.
> This arrangement on a much larger scalle was used at 76Hz
> for Project Sanguine (to radiate a signal to submarines,
> deeply submerged) and papers I've read on "earth
> mode" caution that for military applications the
> through-ground path may not be secure because of the amount
> of energy radiated. I also recall that G0AKN used this
> arrangement with some success on 73kHz.
>
>
> Anyone know the answer?
>
> 73s
> Roger G3XBM
> --
>
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>
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> G3XBM    GQRP 1678      ISWL G11088
>
>

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