A recent message said that JA7NI needed a way to display more
spectrum on his Argo grabber set to QRSS120. I posted a reply
recommending SpecLab.
This raises another issue that has concerned me for some time. There
is a tendency for DX grabbers to be set to QRSS120, and quite a few
beacons use that speed, or even QRSS240. Indeed if the target grabber
is set for QRSS120, the transmit station must use at least this dot
length to be read successfully.
I believe the danger is to regard this as the 'optimum' speed for DX
working, simply because the S/N ratio is good. In practice, there is
another factor in play. There is often rapid and deep fading on a DX
path, often resulting in only parts of letters being received at this
speed, even though the peak signal is quite strong (see many of the
pictures of transatlantic reception regularly posted on this group).
The situation becomes worse if the final aim of experimenting with a
path is to have a two-way DX QSO. Even exchanging minimal
information, a QSO will take several hours, during which time the
conditions must hold up. Take a look at VE7TIL's excellent DCF39
graph to see how short a good DX opening usually is - perhaps an hour
if you are lucky.
The very few who have had transatlantic QSOs have used QRSS30 or at
most QRSS60. I am not aware of a successful two-way involving a
longer dot length.
I would suggest that DX beacons and grabbers use a =maximum= of 60s
dot length (though a second grabber screen could be provided for 120
etc if desired). In my opinion this would be more likely to result in
useful propagation data.
Any thoughts?
Mike, G3XDV
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