Date: Tue, 23 Feb 2010 09:41:35 +0100 (CET)
From: Jacek Lipkowski <sq5bpf@lipkowski.org>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: VLF_8.79 kHz
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On Mon, 22 Feb 2010, Stefan Sch=E4fer wrote:

> Well, perhaps it is not necessary to reach a "DX", DX becomes very=20
> relative in that frequency range. 50km sounds like a really good DX=20
> 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=
=20
microwavers are having great fun trying to span 200m.

> But what about that WSPR mode, everyone was using before some weeks?=20
> 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=
=20
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=
=20
> 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=20
40W and a 4x14m vertical loop.

a ground dipole should be great, especially if you live in an area with=20
low ground conductivity - the "loop" area gets larger this way

the biggest problems in getting your signal out, apart from the antenna=20
size, is getting an electromagnetically quiet location.

in my expierience in a noisy city location, with a 1.5x2.5m vertical=20
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=20
get much further. this is a very practical setup,  if you can find=20
someone 500m away from you to experiment.

> Important is the achieved fascination, isn't it? What would you feel if=
=20
> you would get a contact in QRSS10 to your next VLF interested neighbour,=
=20
> say in 20km? I expect the biggest problem on VLF is to find a person who=
=20
> is fascinated in the same manner than one self ;-) I do not know someone=
=20
> in a radius of 50km who is interested :-( But i will discuss it in our=
=20
> club...

the next person who i know is very interested lives 220km from me :) it's=
=20
a problem to find someone interested in 136kHz, so finding vlf entusiasts=
=20
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=20
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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