Tnx Roger,
Today i have prepared further 9 rods for each pole, so 20 rods for each pole in
sum now. Tomorrow in the morning i will drive again on the hill and try to even
reduce the losses. When DHO38 comes back after its break arround 7...8 UTC i
will try to transmit a message to my grabber using about 50 watts. I have
already an idea what to transmit ;-)
I have thought about the losses problem: First we say that it is important to
have a low ground conductance so that we achieve a big loop in the ground. But
next we say that we need a very low local earth resistance at the poles. There
on the mountain the earth conductivity seems to be very low and THUS it is not
easy for me to get a low losses at the poles. It is the same dependency! Thus i
have to do more effort to come down with the losses but it is better than
taking just one 20cm rod and achieve 100 Ohm since it would mean that the loop
area is small as well! Preparing those small earth rods is no problem. Even if
i would need 100 for each pole i would do it (not worth to mention, compared to
the work to wind such a coil ;-) ).
Today in the morning the QRN was pretty low but in the afternoon it rained. I
hope for good conds tmw. :-)
In further tests i plan to study the influence of rain and temperature and so.
This can be done by using QRP (e.g. 1W TX power, supported by a solar cell and
a battery) and my DFCW-6000 window or even the DFCW-60000 window that will
cover about 7 weeks!
The 60000' window is running since about 2 weeks and is available here:
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
DFCW-60000 is not really suited for a QSO of course but it gives a good
overview of the QRN dependency during the summer time. And it is suitable for
transmitter tests if one can run a transmitter for some days or a week. Even
slower, i have added a "Annual overview" window but it will take some months to
have a real information there...
73 es gl,
Stefan/DK7FC
________________________________
Von: [email protected] im Auftrag von Roger Lapthorn
Gesendet: Fr 25.06.2010 09:44
An: [email protected]
Betreff: Re: VLF: 5,2 km distance on 8,97 kHz with an earth antenna
This is excellent Stefan.
In your case it is much more probable you are seeing true earth mode
propagation not aided by utilities in the ground, although it is hard to avoid
them. It will certainly be worth trying reception on a loop antenna with the
loop orientated both (a) in alignment with the earth electrode loop and (b)
flat on the ground. Also it is worth trying a lower frequency like 838Hz where
I've been doing my recent tests.
In all, I am VERY excited about your tests and results. Thanks for sharing them
here.
Last night I managed to get 5.25km (my best DX yet), but this was definitely
aided by utilities. Tests at many other locations out as far as 6km to the west
and north totally failed to produce even a faint trace on the Spectran screen
using QRSS3 on 838Hz. Information on my website as usual. See
http://sites.google.com/site/g3xbmqrp/Home/earthmode .
73s and good luck
Roger G3XBM
2010/6/25 Stefan Schäfer <[email protected]>
Dear LF/VLF,
Today i spent more than 8 hours in the forest on a hill 520m ASL, improving
and experimenting with my VLF earth antenna. It was a fantastic and very
successful day that gave a lot of fun and motivation. BTW, just spending time
in this wonderful nature with all its beauty cannot be wasted time even if all
the experiments would fail :-)))) That is what i thought many times this day.
If you live in a city with much noise (on the band and audible) you may
understand what i mean when i say that all you can hear there is the wind and
some birds!
Since there are a lot of photos and things to tell i set up a pdf document
with my report that is available at
http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF_5km_with_an_earth_antenna.pdf
, for the VLF enthusiasts (Dreamers!) and those who want to become one! :-)
Best 73, Stefan/DK7FC
--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk <http://www.g3xbm.co.uk/>
http://www.youtube.com/user/g3xbm
G3XBM GQRP 1678 ISWL G11088
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