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Date: Wed, 25 Jul 2012 11:05:45 +1000
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From: Dimitrios Tsifakis <dtsifakis@gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Re: Pretests for the 630m band dipole
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Hi Mike,

I would like to share my web page which described a few very simple
experiments I did a few months ago:

http://people.physics.anu.edu.au/~dxt103/136/earth/

There sure is a lot to explore, especially for those that cannot use a
conventional LF/MF aerial.

73, Dimitris


2012/7/25 Mike Underhill <mike@underhill.co.uk>:
> Hello Stefan, and thanks for interesting reply.
>
> But a few more comments before I go back to lurking. As yet I am not signed
> up to lurk also on the yahoo reflector.  Perhaps I will when a bit less busy
> and if persuaded  of the benefits of doing so.
>
>
>> I want to try to get a antenna orientation beaming to G and PA, where the
>> most RX stations are present
>
> My point is that you might have to orientate the antenna at right angles to
> what is normally expected if the loop mode is stronger than the dipole mode.
> It indeed may depend on ground conductivity?
>
>
>> I will also try different heights above ground, starting from 0 to maybe
>> 2m or 5m AGL.
>
> This will be very interesting.  Over dry ground  on 160m amd 80m I have
> found that differences with similar height differences to these are quite
> small, less than 6dB or so.  It is not until you approach the critical
> height that the height gain becomes very significant.
>
>>> Occasionally broadcast signals in the 31m and 25m bands were found to be
>>> be stronger on the underground antenna than on the reference antenna.
>>
>> A stronger S/N or a stronger signal level?
>
> The signals were definitely stronger but the noise level was usually a bit
> higher, perhaps by 6 to 10dB.
>
>
>> BTW it is not at all easy to evaluate the differences of such different
>> antenna arrangements. I have never seen such a QSB on any band. Probably it
>> is the best to have a local RX station and do the tests on groundwave
>> distance. Probably the antenna radiates in a very high angle But the
>> difference (of the simulation) between 90 deg and 20 deg is just 5 dB while
>> the antenna gain is stated to be -5 dBi..
>
> Good points. But it is measurements that confirm the veracity of simulations
> and never the other way round.
>
> Looking forward to seeing your results.  And now back to lurking!
>
> 73 - Mike - G3LHZ
> .
>
>