On Mon, 22 Feb 2010, Stefan Schäfer wrote:
Well, perhaps it is not necessary to reach a "DX", DX becomes very
relative in that frequency range. 50km sounds like a really good DX
here.
50km would be real dx, because this is not near-field anymore.
it is interesting to compare this with the other end of the spectrum. the
microwavers are having great fun trying to span 200m.
But what about that WSPR mode, everyone was using before some weeks?
Wouldn't that be a nice tool to try what's possible, for a first step?
qrss cw is much easier to generate (eg. via a microcontroller) and doesn't
need a linear PA. the whole setup is much easier do debug.
If 750m is possible with 2W TX power and 4m*14m loop then it should be
possible to reach some km with a grounded dipole of abt 2x500m.
for the 750m test i used a different antenna. but i did reach 930m with
40W and a 4x14m vertical loop.
a ground dipole should be great, especially if you live in an area with
low ground conductivity - the "loop" area gets larger this way
the biggest problems in getting your signal out, apart from the antenna
size, is getting an electromagnetically quiet location.
in my expierience in a noisy city location, with a 1.5x2.5m vertical
3-turn loop on a balcony, with 40W and qrss3:
100m - easy, i can hear the beacon by ear, even when it's 9kHz
300m - easy copy with spectrum lab
450m - still fine copy
550m - very weak signal, marginal copy
the near field falls with the third power of distance, so it is hard to
get much further. this is a very practical setup, if you can find
someone 500m away from you to experiment.
Important is the achieved fascination, isn't it? What would you feel if
you would get a contact in QRSS10 to your next VLF interested neighbour,
say in 20km? I expect the biggest problem on VLF is to find a person who
is fascinated in the same manner than one self ;-) I do not know someone
in a radius of 50km who is interested :-( But i will discuss it in our
club...
the next person who i know is very interested lives 220km from me :) it's
a problem to find someone interested in 136kHz, so finding vlf entusiasts
in your area might be a problem.
BTW, why exactly choosing 8,79 kHz (Horst?)?, why not 8,9 kHz?
going lower in frequency avoids problems with key clicks and oscillator
drift going past the 9kHz barrier
We all have a great hobby, really!
i'll drink to that! :)
VY 73
Jacek / SQ5BPF
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