Hello Tony,
Show us your RX earth terminal side and whether AC voltage supply or
DC battery did you use for the experiment. AC line can be a good long
antenna for receiving.
7L1RLL Rick
On Wed, 2010-08-11 at 16:16 +0200, Rik Strobbe wrote:
> Hello Tony,
>
> measuring voltages on untuned antennas is "tricky", in particular with
> small electrical antennas (compared to the wavelength) as these tend
> to have large reactive components.
> On 60kHz the L-antenna you described has a reactive component of about
> 10000 Ohm while the resistive part will be some 10's to some 100's Ohm
> (mostly loss resistance). So properly tuning the antenna will increase
> the RX voltage by several S-points.
> Ground loop antennas on the other hand seem more broadband.
> Maybe that explains why they perform better at lower frequencies
> ( compared to the untuned L-antenna).
>
> Anyway, your L-antenna should perform well on 500kHz.
>
> 73, Rik ON7YD
>
>
> ______________________________________________________________________
> Van: [email protected]
> [[email protected]] namens Tony [[email protected]]
> Verzonden: woensdag 11 augustus 2010 14:05
> Aan: [email protected]
> Onderwerp: Re: LF: Earth antenna
>
>
>
> Hi Roger.
>
> The soil here is well drained peaty topsoil about 400mm - 500mm deep
> on a mixture of slate and shale and although I am 500m from the sea, I
> am 75m above the water.
> I have no idea what the electrical conductivity is but I imagine it's
> probably lower in the winter when my windows get a covering of salt
> during storms. It would be interesting to pick on one reliable ground
> wave transmission and monitor it through various weather conditions.
> It would also be interesting to see how it works lower in frequency
> (sub 50 KHz), which is something that I will definitely look into.
>
> 73,
> Tony, EI8JK
>
>
> On 11/08/2010 11:32, Roger Lapthorn wrote:
> > Thanks for this Tony.
> >
> > Do you know what sort of soil/rock you have beneath you there? Here
> > I am on relatively low conductivity chalk/clunch with clay a few
> > miles to the north west under fenland peat.
> >
> > If the earth electrode antenna is behaving as a loop (a debated
> > theory) then it is most effective is the "loop in the ground" is as
> > large as possible, which would be the case with low conductivity
> > soil/rocks underneath: the return path between electrodes would be
> > forced to take a longer route deeper into the ground. If the soil
> > between the electrodes has good conductivity then the return current
> > would flow directly making the effective loop size small.
> >
> > In the last few days we've had a lot of rain here and the results on
> > 500kHz last night with the earth electrode antenna suggest the rain
> > made little difference to performance with reception several times
> > by PA0A. This is counter-intuitive to me, as I would have expected
> > levels to be weaker if the soil was wet (loop formed being smaller
> > etc.). Of course it could have been that the contact resistance of
> > the earth probes was lower and overall the two effects cancelled?
> >
> > Whatever the theory says, the earth electrode "antenna" has some
> > mileage especially when, like me, there is little space for large
> > "in the air" antennas. Sure, a big vertical or large loop in the air
> > would be better (I think), but this is about experimenting and
> > discovering the limits of possibilities.
> >
> > Good luck and keep everyone posted if you do further tests.
> >
> > 73s
> > Roger G3XBM
> >
> >
> >
> > On 11 August 2010 10:34, Tony <[email protected]> wrote:
> > I have finally found the time to get some (radio) work done
> > here and got my 2nd tower finished and I erected an inverted
> > L, 10m vertical and 30m top rising to 15m at the far end. I
> > still have the "earth antenna" which is just a length of
> > wire laying on the ground 80m long and terminated directly
> > to an earth stake and laying roughly in the same direction
> > as the top wire of the L .
> > Comparing the two gave some very interesting results.
> >
> > 10 MHz CW L = S7 earth = S1
> > 7 MHz CW L = S9 earth = S3
> > R. Bristol 1566 KHz L = 0 earth = S2
> > Donebach 153 KHz L = S6 earth = S8
> > DCF77 77.5 KHz L = S3 earth = S5
> > MSF 60 KHz L = S4 earth = S8
> >
> > All very non-technical I know, neither antenna was matched
> > or tuned in any way and was all done about 13:00z.
> > There was no noticeable difference in the noise level but
> > when I tried it before the earth antenna was very much
> > quieter after dark. I will try and repeat this tonight and
> > see what the difference is then.
> >
> > Tony, EI8JK.
> >
> >
> >
> >
> > --
> > http://g3xbm-qrp.blogspot.com/
> > http://www.g3xbm.co.uk
> > http://www.youtube.com/user/g3xbm
> > G3XBM GQRP 1678 ISWL G11088
>
>
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