Message-ID: <4D08D9C8.50607@o2.ie>
Date: Wed, 15 Dec 2010 15:07:52 +0000
From: Tony <ei8jk@o2.ie>
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References: <1292360809.3356.74.camel@gerhard-desktop> <003701cb9be9$46bb5b00$0401a8c0@xphd97xgq27nyf>
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Subject: Re: LF: Re: Earth Antennnas - General question
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Hi Mal & LF

Your comments prompted me to carry out some simple tests today.
I layed out a 25m length of Thompson RG 214/U double screened coax on 
the lawn and connected the centre conductor at the far end to a 
stainless steel rod abt 300mm long pressed into moist soil.
In the shack I measured the signal strength of DHO-38 at -51 dB with the 
coax screen connected to the station earth.
I then disconnected the station earth and still measured -51 db and then 
I strapped screen and conductor together and still measured -51dB
Then I added an extra 10m of coax and elevated it all to an average of 
2m above the ground and carried out all the above again with absolutely 
no difference in signal strength.
Finally I pulled the earth rod out of the ground and the signal dropped 
to -94 dB and then I disconnected the coax totally from the earth rod 
and the signal dropped to -102 dB.
Make of that what you will.

I also out of interest connected my MFJ antenna analyser and found that 
the SWR was fairly flat across the whole spectrum (between 2:1 and 8:1) 
from 1.8 MHz to 150 MHz, although I don't think I will hear much on 2m

73, Tony, EI8JK.

.
On 14/12/2010 23:47, mal hamilton wrote:
> 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"<gerhard.hickl@aon.at>
> To:<rsgb_lf_group@blacksheep.org>
> 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
>>
>>
>>
>>
>>
>>
>>
>
>