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Hi Roger,
WSPR should decode from about -29 dB SNR in 2.5 kHz
(ie. 0 dB in 3.2 Hz). On the other hand, a
clearly discernible carrier in a 0.42 mHz FFT ("DFCW-6000") would
require about 6 dB SNR in the 0.63 mHz noise bandwidth (ie. 0 dB in 2.5
mHz).
The difference in sensitivity would thus be around
31 dB. Of course the data rate will be different as
well...
Best 73,
Markus
Sent: Wednesday, April 27, 2011 10:45 PM
Subject: Re: LF: More 8.97kHz WSPR decodes - changed PC
here
Dear Eddie (et al)
In the context of the very very
weak signals experienced at VLF I don't think WSPR is a serious contender except
for localised tests. No doubt someone here far more knowledgeable than me can
tell us the "dB advantage" of say, QRSS600 or 6000 versus WSPR, but the
difference must be enormous.
Where WSPR scores, in my view, is the
automatic reporting via the internet database. This has proved a real boon at
137 and 500kHz. Even here though very slow QRSS would beat WSPR every
time. I am a great believer in WSPR, but do not believe it will be that
much use at VLF.
Andy (G4JNT) are you able to comment on
please?
73s
Roger G3XBM
On 27 April 2011 20:51, qrss <[email protected]> wrote:
Just a further thought. WSPR doesn't of
course spread its power over 6Hz it actually transmits full carrier on each of
the four frequencies for 0.682 mS and sometimes several of the same element
follow without a break in carrier, which accounts for some of the bright spots
and lines we see when things are marginal. One element is a longer dot time
than 2WPM Morse, and that is SLOW Morse. Long integration times are out of
course. 73 Eddie G3ZJO
On 27/04/2011 18:58, Roger Lapthorn wrote:
Hi Eddie (et al)
It is highly unlikely you'd
copy Andrew on VLF remembering that the WSPR signal spreads around 6Hz in
the transmission burst, so the energy in any narrow FFT bin would be tiny.
Also, this is earth mode (I hope, as G6ALB does not hold an NoV to radiate
at VLF), so signals are propagating through the ground by conduction and no
significant amount of signal is radiated.
I'm still intrigued why
the best reception here today was with my 80sq m vertical loop. This
outperformed several earth electrode set-ups here at the RX end, an E-field
probe and a 30t loop laying close to copper pipe work in the house! If
the signals are coming down the pipes then why don't these more direct means
of coupling to them work as well as (or better than) a vertical loop
outside? Odd.
73s
Roger G3XBM
On 27 April 2011 18:33, qrss <[email protected]> wrote:
Great
stuff Roger and Andrew
If you are RX'ing on an 80m dipole it may be
worth a look here, I would never say can't until I have tried. Bearing in
mind I should be able to observe signals which would not be decode able on
WSPR
I would appreciate a prior notification of times and exact
frequency of the WSPR signal of any further tests.
Keep it
up.
73 Eddie G3ZJO
On 27/04/2011 15:19, Roger Lapthorn wrote:
As
an experiment I changed over to my wife's laptop and got immediate
decodes of G6ALB's VLF earth mode signal (3km) at -17dB S/N, suggesting
the issue with lack of decodes may be with my soundcard and not
Andrew's.
1408 -17 -0.6 0.008986 0 G6ALB JO02
47
1410 -17 -0.6 0.008986 0 G6ALB JO02 47
1412 -17
-1.2 0.008986 0 G6ALB JO02 47
1414 -17 -0.8
0.008986 0 G6ALB JO02 47
1416 -17 -0.8 0.008986 0
G6ALB JO02 47
This is a very solid signal on the 80m square
single turn vertical wire loop antenna. Andrew is using 44W to an earth
electrode antenna.
73s
Roger G3XBM
--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/
--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/
--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/
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