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From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <CAKvcm2dpuftdtK6OdQv8fOfiw+4yQrPBQBHJ-FN2gDbT4P_oMQ@mail.gmail.com> <51D498BD.3050007@iup.uni-heidelberg.de> <op.wzq2tgvnyzqh0k@pc-roelof>
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Date: Fri, 5 Jul 2013 14:48:48 +0100
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Subject: Re: LF: VK1OD's analysis of the MiniWhip antenna
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Status: O

What happens  if its  a  small  'ball'  and  not  a  flat plate ?

G..

--------------------------------------------------
From: "Roelof Bakker" <roelof@ndb.demon.nl>
Sent: Friday, July 05, 2013 2:09 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: VK1OD's analysis of the MiniWhip antenna

> Hello all,
>
> Further to this discussion, I have done the ultimate test to demonstrate 
> that an active whip antenna with a 1 meter long whip behaves as a 
> capacitance at LF.
>
> For the test I used the ground wave carrier of semi local NDB ONO at 399.5 
> kHz.
> As it is the only station at that frequency the carrier level is very 
> stable at daytime.
> The distance is 59 km, which excludes probably all skywave propagation.
>
> The antenna was mounted vertical and the carrier of ONO produced a signal 
> level of -69.1 dBm as received with a PERSEUS SDR.
>
> Next the antenna was mounted horizontal at the same height as the bottom 
> of the vertical mount.
> This produce a signal level of -72.0 dBm.
>
> I reasoned that the mean height of the 1 meter long antenna when mounted 
> vertical is 50 cm higher. So the antenna was then mounted horizontal 50 cm 
> higher from its previous position. This produced a signal level of -69.9 
> dBm, close to the value measured when mounted vertical.
>
> The main point however, is that a horizontal polarized antenna should NOT 
> receive a vertical polarized ground wave signal at (almost) the same 
> strength.
>
> So at LF, there is nothing gained in using a whip instead of a small piece 
> of copper clad PCB.
>
> Comments are much appreciated!
>
> Best regards,
> Roelof Bakker, pa0rdt
>