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This is an interesting experiment and my first thought would be that it is behaving like a Beverage antenna.
At 23.4kHz a 25m long wire less than 0.2% of the wavelength.
It would be the same as claiming that a 30cm (1 ft) long wire could act as a beverage antenna on 160m ;-)
73, Rik ON7YD - OR7T
________________________________________
Van: [email protected] [[email protected]] namens mal hamilton [[email protected]]
Verzonden: woensdag 15 december 2010 18:00
Aan: [email protected]
Onderwerp: Re: LF: Re: Earth Antennnas - General question
Hi Tony
Nice to see you join in on the discussion.
This is an interesting experiment and my first thought would be that it is
behaving like a Beverage antenna. Direction might indicate something for
instance rotate it 90 degs and check the signal strength
One experiment I thought might be interesting is to resonate a low long wire
height say 20 ft and 200 ft long earthed by a spike at the far end and feed
the near end with a signal. The signal source sent via coax, the centre pin
to the wire and the earth shield to a ground pin.
then
put an atu between the coax shield and the near ground pin and resonate it
if possible ie a tuned ground as well as a tuned/resonated wire.
This antenna would really be a Grounded quad loop, the 200 ft wire plus 20
ft height x 2== 240 ft total and the earth/ground would be the other half ie
total length 2 x 240 == 480 ft. The theory is that the ground would provide
a mirror image of the wire above it. So for vertical quad loops, delta loops
you only need build one half above ground and the ground provides the other
hal
There was an article years ago in QST magazine by Belrose that explained the
theory for an 80m grounded delta loop.
Natural resonance should be 2 Mcs
Resonate the wire at a frequency of choice
This is all interesting but I prefer to use a more convential antenna system
that I know will work
73 es gl de mal/g3kev
----- Original Message -----
From: "Tony" <[email protected]>
To: <[email protected]>
Sent: Wednesday, December 15, 2010 3:07 PM
Subject: Re: LF: Re: Earth Antennnas - General question
> 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"<[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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