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Date: Sat, 15 Oct 2011 14:14:11 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: noise on VK and earth dipole tests
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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
>