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Re: LF: Wolf Tests

To: [email protected]
Subject: Re: LF: Wolf Tests
From: "Mike Dennison" <[email protected]>
Date: Tue, 1 May 2001 09:21:59 +0100
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M0BMU wrote:
Have not been very active lately due to visiting relatives, but I have been making regular recordings on 137.79kHz in an attempt to receive VA3LK's Wolf-mode beacon sigs. So far, however, nothing to report - solar activity has been mostly high since I started, so perhaps this is to be expected.
Nothing positive identified here either. I did get two consecutive lines ending in
'LK', but could not tweak things to get any closer. I suspect that coincidence is
the culprit, not Larry.
...................I think there may be more problems due to the various carriers that exist within the bandwidth occupied by the Wolf signals - as far as I can tell, these effectively increase the noise level, and the Wolf signal is too wide to avoid them in the same way as can be done with QRSS. So it might be worth looking for a quieter part of the band relatively free from carriers.
I certainly received what appeared to be a valid signal as the 'f' reading went
gradually down to zero and the 'jm' reading gradually went up, but perhaps this
was just a carrier it found. I certainly did not get any valid data.
Can WOLF be run slower, and hence narrower, to get between the carriers?
Or does this make it just as slow as 3s QRSS, and hence defeat the object?
The thing to remember about the figures generated by Wolf is that they don't mean very much unless a signal really is being decoded. It is instructive to make a recording of some noise, and run it through Wolf - as often as not, strings of identical -f and -jm figures will appear, as they do for a real signal. This means that trying to optimise Wolf parameters using the numbers generated by Wolf is unlikely to be helpful unless a signal has already decoded successfully.
As I note above, it is usually a good sign when the 'f' reduces and the 'jm'
I will run my Wolf-mode beacon again over the next few days if anyone is interested; the frequency and bit rate of this is accurate enough to use as a calibration reference for setting up a Wolf receiving system.
This would be useful, Jim. I am running Cool Edit at 11025 sample rate now
and this does seem to be less fiddly. It would help to have a known WOLF
signal to work on, though.

Mike, G3XDV (IO91VT)

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