Hello Mal,
I am not a great technician but even to me it seems clear, that it's an
obsolete discussion. I do not think that on this low frequencies (vlf) it makes
a remarcable difference if the wire is directly on the ground or not. Maybe in
theory but not in practice as you find grass, little bushes, rocks outside.
Also you can not assume equal ground conductivity underneath the antenna over
the whole distance. Regarding the wave length I assume even 6m should not make
a great difference.
In summer I did some local tests on 9kHz at Erpeler Ley near Bonn. No
sensations to talk about, but I have learned a few things about VLF antennas.
I took about 100m of wire, my dds, pa and the line transformer. First I took
the antenna as a Marconi (10m high, 90m top load). After that I connected the
other end with some ground rods. Then I took down the antenna so it was
directly on the ground. And after that I used it as a kite antenna.
Now you can bet on what had the best results regarding the near field with walk
around reception by ear. Of course it was the kite antenna. The ground antenna
did work rqually good or bad with no difference if lying directly on the ground
or elevated a few meters. Mounted Marconi style (10h 90t) was worst.
(Even on 500kHz there must be a point where ratio of height and top load of a
Marconi antenna gives the maximum result. The 10h 90t did work worse than my
10h 20t. I assume that the top load was coupling more hf to the ground than the
higher antenna capacity could result in radiation.)
Horst DO1KHS/DI2AN
-----Ursprüngliche Nachricht-----
Von: "mal hamilton" <[email protected]>
Gesendet: 15.12.2010 00:47:29
An: [email protected]
Betreff: LF: Re: Earth Antennnas - General question
>Gerhard
>Yes the antennas described by Stefan and Roger and others are of the LOSSY
>variety and similar to Beverages.
>I have made this observation before. I cannot see how these elevated
>antennas can be considered Earth Mode since they propagate a signal into the
>ether to be received at a distance by another elevated antenna several
>metres above ground.
>de mal/g3kev
>
>
>----- Original Message -----
>From: "Gerhard Hickl" <[email protected]>
>To: <[email protected]>
>Sent: Tuesday, December 14, 2010 9:06 PM
>Subject: LF: Earth Antennnas - General question
>
>
>> Hi all !
>>
>> I was following the whole discussion about the so called "earth-mode"
>> and the used antennas with interest.
>>
>> Mal told us that he sees those antennas as "lossy dipoles" while others
>> stated they are "true" earth-antennas.
>>
>> I don't have the theoretical background to tell you why but out of my
>> feeling, all those antennas described remind me on the well-known
>> Beverage-Antenna system.
>>
>> Two wires of any layout, diameter, height and length terminated by a
>> "resistor"...the soil.
>>
>> Could that be a way we could look at this kind of antenna?
>> And if so, what would it explain?
>>
>> 73
>> OE3GHB
>> Gerhard
>>
>>
>>
>>
>>
>>
>>
>
>
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