Message-ID: <2264.200105021203@gemini>
From: "James Moritz" <j.r.moritz@herts.ac.uk>
Organization: University of Hertfordshire
To: rsgb_lf_group@blacksheep.org
Date: Wed, 2 May 2001 13:03:28 +0000
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Subject: LF: Re: Wolf tests
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Dear LF Group,

Thanks for the reports on the Wolf-mode signals - I hope this was 
useful. I put in the 3 minute bursts of carrier partly so that people 
who can receive the signal at relatively good strength could use 
the Wolf -m option to calibrate the frequency offset in their 
receivers. The frequency should have been correct within 0.01Hz. 
Also, it enables the more DX stations to check the signal is present 
using a spectrogram type program as I2PHD has done.

As Mike says, it is useful to have a spectrogram of the signal 
available when recording the .wav files, which is one reason why I 
use Spectrum Lab to make the recordings. I find that if the BPSK 
signal is visible on the spectrogram at all, it will usually decode 
within the first 1 or 2 frames.

I have done some rough comparative tests of the relative 
sensitivity of Wolf and QRSS - A signal level that Wolf reliably 
decodes in 15 - 20 minutes requires about 60 second dots to be 
readable in QRSS mode. Obviously, a stronger signal can use 
shorter dots, and Wolf will decode it more quickly. It should be 
pointed out that the nature of the noise may make a significant 
difference to the relative performance of the two modes. However, 
it looks like Wolf offers a significant saving in time, which is why I 
am interested in it.

A QRSS signal gives a visible trace when it is several dB too weak 
to be actually copied, while with Wolf, you can only sure a signal is 
being received by being able to copy it correctly. In my opinion, 
this makes the QRSS modes better for beacon operation, where it 
is only neccessary to identify and assess the strength of the 
signal, and very little actual information has to be transmitted. This 
means there is no great disadvantage in the slow speed of QRSS, 
and it has the advantages of flexibility and simpler equipment. 
However, for 2 way communications, the slow speed of QRSS is 
an extreme limitation, and a development of Wolf might be a 
solution.

I also tried to copy VA3LK's beacon signals last night, but no 
results - the QRN level was very high, so not suprising.

Cheers, Jim Moritz
73 de M0BMU