Message-ID: <3AB29F5D.A3AF00FA@ns.sympatico.ca>
Date: Fri, 16 Mar 2001 15:18:54 -0800
From: "John Currie" <john.currie@ns.sympatico.ca>
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: "Wolf" BPSK tests anyone?
References: <5337.200103161327@gemini>
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Hi all, I haven't said I have quit transatlantic testing.  In fact I would
like to continue looking for stations in the 0.1 to 0.5 watt erp range. I
consider the reception of G3XDV at "O" copy this week to be an
encouragement to continue.  If anyone wants to continue please let me know
by E-mail
    Also I will be setting up an antenna for transmitting at summer QTH in
may if anyone wants to try for summer QSO. I will be looking for dfcw or
qrss 30 second dots
    73 de John VE1ZJ

James Moritz wrote:

> Dear LF Group,
>
> Since transatlantic QRSS activity seems to have ceased for the
> time being, I thought I would give KK7KA's "Wolf" a try. This is
> essentially BPSK, but the encoding and decoding scheme is
> designed so that a weak signal can be effectively integrated over a
> long period. The current version of the software operates with a
> fixed-length 15 character message; with good SNR, this will
> decode in 24 seconds, but with a weak signal, the software will
> operate on up to about 25 minutes of received signal, hopefully
> leading to a significant improvement in performance. The US
> Lowfers seem to have been doing quite well with it. There is quite
> a bit of info on http://www.scgroup.com/ham/wolf.html, and also
> http://www.highnoonfilm.com/xmgr/updates/wolf.htm .
>
> I have now tested my Decca TX with a specially built BPSK keyer
> which has the accurate timing required by Wolf. I am able to
> receive my own signals, and decode them successfully, so I know
> it works! Both the carrier frequency, and the timing of the data
> should be within 1 part in 10^7, which seems to be more than
> adequate.
>
> The requirements for receiving this mode are basically just
> receiver plus soundcard/PC, but great care is needed in initially
> calibrating both the system frequency offsets, and the errors in the
> soundcard sampling rate, in order to successfully decode weak
> signals. This is critical for successful operation. The software
> includes some utilities to help do this. The signal processing is "off
> line"; first you record a period of received signal at 8k samples/sec
> using the software of you choice (I used DL4YHF's Spectrum Lab,
> which conveniently allows you to display a spectrogram at the
> same time). Then, you run the recorded .wav file through the Wolf
> program, together with the appropriate calibration factors. The
> program prints the decoded message. This can be repeated if
> neccessary, until you are happy with the results.
>
> I gather VA3LK is also nearly ready to start trials using this mode,
> so if anyone is interested in trying some tests, I would be happy to
> oblige. The most important thing seems to be which frequency to
> use; from this end, the obvious choice seems to be either in the
> 135.9 - 136.0kHz, or 137.4 - 137.6kHz ranges. I can vary ERP
> from about 1W down to 1mW, or less if you like, and set frequency
> in 0.1Hz steps.  Let me know what signal would best suit your
> needs. I should be able to be QRV most evenings over the next
> couple of weeks.
>
> Cheers, Jim Moritz
> 73 de M0BMU