[Lowfer] Re: 600MRG> WOLF Copy from last night

[John Andrews]

OK, as promised, a few comments on last night's reports.

As we all know, the fading way up here at 505 kHz is more rapid than at 
185 or 137 kHz, and deep fades seem to be common. XGR/3 creates a lot of 
those by using the vertical loop, which has quite a bit of high-angle 
radiation. Fading of my signal at Jay's QTH (70 miles) is definitely 
worse than his fading here. So /3 provides a good test of what these 
various modes can do!

The fades were mostly apparent in the q: (signal to noise) values. Big 
fades at 10-12 minute intervals were common. The reports that were the 
most useful were ones with stable jm: values, indicating steady timing 
of the signal framing. As I mentioned in the last message, having your 
sound card's actual sampling rate nailed down is a big help with any 
weak signal digital mode work, particularly at low data rates. With 
WOLF, it's absolutely necessary, as successive lines don't sum up 
properly to build up weak signal property if the timing keeps slipping. 
There are a bunch of ways to get that calibration, and Loran-C signals 
may be of some use. See these articles for suggestions:
http://www.lwca.org/library/articles/w1tag/R75cal.htm
http://www.w1tag.com/SpecLabsamp.htm

If the f: (frequency) readings keep changing even though you're getting 
good copy, you'll also see those jm: (framing) numbers jumping around. 
The cause is likely to be receiver instability. That's not as big an 
issue with modern receivers as with boat anchors. The latter are just 
not suited for this kind of thing, and should be reserved for CW work. 
You may find that warming the receiver up in advance is enough to make 
it stable. My Icom R75 is on 24/7, and is quite steady unless the shack 
temperature swings widely.

Take a look at Hartmut's results from last night, temporarily available at:
http://www.h-wolff.de/Latest500kHz.htm
He's been through the sound card cal business for LF, so these results 
are almost classic. The frequency readings are dead steady, the pm: 
(signal strength buildup) grows slowly and steadily, the jm: (framing 
values) are the same for each run, and the q: (signal to noise) numbers 
show steady growth from negative to positive. Note the much lower q: 
values than in the eastern U.S. reports, which comes from the much 
weaker signal. The surprise is that there is much less evidence of 
fading on the T/A path than on any of the U.S. reports. That indicates 
that multipath interference was low, which would be the hallmark of 
excellent conditions. Of course, my excess high-angle radiation would 
not be a factor at 3700 miles!

Anyway, thanks to all for the reports, and a chance to try this mode up 
here at 600m. More goofing around will follow as the winter progresses...

John Andrews, W1TAG / WE2XGR/3