Message-ID: <20090911145105.H80AG.5132880.root@mp19>
Date: Fri, 11 Sep 2009 11:51:05 -0700
From:  <w1tag@charter.net>
To: rsgb_lf_group@blacksheep.org
Cc: Chris <c.ashby435@btinternet.com>
MIME-Version: 1.0
Sensitivity: Normal
Subject: Re: LF: WOLF
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


Chris, Jim, all,

Remember that despite the fancy signal coding, the end result with WOLF is a simple BPSK signal sent at 10 bits/second, i.e., the phase is flipped 0/180 degrees as fast as 10 times a second. In that sense, it's the same modulation scheme as the familiar PSK31, but at a slower rate and with less shaped keying. PSK31 has a highly shaped amplitude envelope - slow rise and fall times, easily noted on an oscilloscope connected to your transmitter output. There's a signal to noise tradeoff in doing that, however, as the transmitter is at full power for only a portion of each bit. But the reduced keying clicks are important in a high-power narrow environment, such as the PSK31 section of 20 meters.

WOLF keying has a faster rise and fall time, giving some s/n improvement, but creating the sidebands you see in the waterfall display with a strong signal. Remember that each of those sidebands is flipping in phase right in step with the main carrier, and you can center one on the waterfall and get a decode assuming the signal is strong enough. 

WOLF is unnecessarily complex for communication where the signal is audible, and is of real value only for very weak signals. At 137 kHz, it can be copied under conditions that support only QRSS30 or 60 rates, and it can offer much better data throughput. But for weak signals that require build-up of copy over many minutes, the accuracy of the audio tone and the sound card sampling rate can become issues. With strong signals, the frames of data can slew all over the place, and you will still get decodes.

I have done a number of WOLF QSO's, and they are not difficult. You only need to work out the concept of time slots in advance, and what sort of response will be given in case of good/no copy. There are articles on my web site describing some of these QSO's. The most amazing one was a 1000 km 2-way with 1 watt TRANSMITTER output in the early afternoon. Think about that one...

My results on copying Jim last night were the worst of the week, and I don't know why! Part of the problem was that I was out of the house for most of the evening, and am not sure about noise levels, which may have been higher due to an approaching coastal storm. 

John, W1TAG


---- Chris <c.ashby435@btinternet.com> wrote: 
> Hi All,
> I don't understand some of these comments about critical set up, frequency etc. I just downloaded the program, connected to the RX and it worked. Could it be because Jim is extremely strong here? I can tune +/- 200Hz off and it still decodes. I haven't worked out if/how it 'locks' to the signal. Maybe it would not be possible to receive a nearby weaker signal??
> I find some of the documentation a bit daunting, has anybody written a simple explanation of how to set the system up properly?
> Not sure how useful it would be in reality for a QSO, inclined to think CW would be the best bet. Seems very limited as is.
> Vy 73, Chris, G4AYT, Whitstable, Kent, JO01MI.