Hello Dimitris,
Very interesting and nice to read experiments and web page! Good to see
some experimenters beeing available.
Some questions and ideas:
How do you ground the earth antenna at the end?
Did you try to use the directional antenna to receive DCF39?
On 137 kHz you may get good results with a dipole on the ground if you
have bad soil conductivity. Or you may use a large (earth) loop into the
forest. Here you can hang up the wire 10m above ground and no one cares.
It would be very interesting to have a RX/TX antenna pointing to EU.
Will you use a 400m wire next? .-)
How much place do you have out there?
I would like to participate in the experiments. We would be a good team!
Maybe we can be a team together here. I am the TX side, you are the RX
side (opposite is no good idea i think ;-) ). Would be interesting to
compare the S/N levels of DCF39 when using the same S/N settings as at
home. Then you can compare the hopefully improved performance of the /p
system. If you can gain say 10 dB, maybe we will have a chance then!
You title your grabber as a "urban" grabber. It has a omnidirectional
antenna, right? So if you can use a directional antenna and be outside
the city... You know :-)
Would all be very exciting!!!
It would be interesting to compare different wire length at the same
orientation regarding S/N on the RX side, i.e. VK2DDI. Who is the next
farer distant station, say 400 or 800 km? :-)
Good luck and fun with your experiments!!
How much wire do you have now?
I think the 450 Ohm you get is mostly caused by the earth electrode
resistance. So if you spend e.g. 2 instead of one earth rod, maybe you
can get a 3 dB improvement?
Vy 73 from EU
Stefan/DK7FC
Am 15.10.2011 09:34, schrieb Dimitrios Tsifakis:
Hi Stefan,
I followed up your suggestion of elevating the wire off the ground and
it seems that there is some benefit in doing that:
http://people.physics.anu.edu.au/~dxt103/136/earth/3/
However, it's not convenient as I can no longer drive over it :-)
Overall, I am happy with what I see. The signal was received very
clearly at a distance of 140 km, which is nice for a 25W/QRSS3 setup
that can be further improved.
Anyway, I will continue my tests with comparing the earth dipoles to a
"typical" amateur inverted-L LF antenna comparison (9 m up, 20 m
across).
73, Dimitris VK1SV
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