Hi Roger,
Have you already checked how your earth antenna acts as a RX antenna?
Maybe you have read my last mails in which i have discussed
measurements of the effictive area of my earth antenna. Most probably
there are some military VLF transmitters that you can receive! That
could become a way for you as well, checking the RX performance on VLF
or LF. This might help you to improve your system.
Is there a way for you to cross the road with a small wire? You could
install a ground electrode in some 100m distance and take a walk each
evening rolling out a tiny wire.
Indeed this are inspiring experiments and i like the effort as well,
knowing that it will never be so effective as a high vertical antenna.
For tomorrow i have prepared 3 grabber windows on my inofficial 2nd
grabber site at
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
First you see the standard 8,97 kHz window, the 2nd window is for 7,97
kHz and the 3rd is for 6,97 kHz. Tomorrow to the time of minimum QRN
(arround 7...10 UTC) i will transmit there with about 50...70 watts,
trying to reach my grabber in 5 km distance. You know it worked on 8,97
but i want to check how the earth antenna behaves on lower frequencies.
Therefore, i have taken my big 600W PA that works without a transformer
(and thus no saturation of any ferrite cores when going down to DC ;-)
) down to wavelengths up to infinity ;-) I plan just to send a "A" in
DFCW-600 to need a minimum of time but secure ID since the QRN changes
rapidly as we know.
One day we will have a earth mode QSO, Roger, isn't it? ;-)
73, Stefan/DK7FC
Am 19.07.2010 16:53, schrieb Roger Lapthorn:
Today I tried some more experiments with my 20m spaced
earth electrode "antenna" and small beacon TX on 136.93kHz (I think
this is a more accurate frequency). I switched over to QRSS3 and took
the (deaf on 136kHz) FT817, E-field probe and PC out for a ride in the
car to see where copy stopped. Firstly, I stopped in a National Trust
car park 1.5km from home - solid copy on QRSS3 when holding the E-field
probe box as high as possible above the car roof. Then I drove on to a
spot 4.6km from home (Swaffham Bulbeck) and copy was again
achieved, albeit not as strongly. I was prevented from doing further
tests as the coax inner from the E-field probe to the FT817 came apart,
so I had to return home.
So, I'm certainly getting a signal radiated beyond the near field. I've
no other LF-HF antennas up (just the VHF/UHF vertical which was
disconnected), so there is no coupling into other antennas. In the
coming days I'd like to see the directionality of the "antenna" by
looking for signal levels with the QRSS3 beacon at all compass points
some 4-5kms away from the QTH.
In the meantime, if anyone near Burwell, Cambs wants to look for the
QRSS3 signal near 136.93kHz I'll leave it running until about 8pm
tonight when I have to switch off as my grandson is sleeping in the
shack bedroom. Any reports would be amazing.
73s
Roger G3XBM
--
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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