[Lowfer] WG2XRS/4 [WG4XRS for short] will start at 2200 withWSPR15...
JD
listread at lwca.org
Thu Dec 12 22:41:05 EST 2013
Continuing to get excellent copy in Kansas tonight, Bob, even though the
noise level went from consistently under S1 before sunset to a median value
of S3 with lots of crashes to S7 or S9 after dark (in my normal 250 Hz CW
bandwidth). Comparing with the Argo 10 second captures, it appears there
was a little sunset fade beginning at 2300, followed during the next hour by
an increase in noise from the thunderstorms in Arizona and New Mexico that
seem to be the herald of our next winter storm. SNRr had deteriorated by a
good 17 dB by the 2345 slot, to -20. The signal itself started recovering
after that, but SN values remained around -17 and -18 on WSPRX. (Argo
continued to get adequate detection at QRSS3 and splendid results in 10
second mode, but the NDB mode trace was considerably broken up, and hearing
the CW ID was now out of the question.)
It had been my intention to continue my experiment of trying different
filter configurations within the receiver tonight. However, having been
delayed getting to the field, I didn't have all my presets the way they
needed to be. And, when I saw all that lovely noise we didn't have to the
same extent last night, I took that as an opportunity to answer a question
I'd been wondering about: how would hard limiting affect WSPR-15's
perception of SNR? Turns out, the answer is "quite favorably."
I raised the drive to my clipper by about 6 dB at the start of the next time
slot, and 15 minutes later saw a 5 dB improvement in the reported ratio.
The next slot was a further dB better. Then I noticed that my AGC speed had
been set to slow all evening. Would letting it recover faster have any
effect? Yes, as it turned out 15 minutes later, there was another 3 dB
improvement! (Argo showed a substantial improvement with the 6 dB increase,
too, but hardly any change with the faster AGC.) I don't know if that will
hold true when we eventually start seeing springtime noise levels again, but
I'm very encouraged. I know when I was observing HF with WSPR-2 last
summer, clipping did not seem to help much, but I expect that may have had
to do with all the non-random signals that were being picked up at the same
time. For now I'll only venture to say that for a single signal in the
detection band, WSPR-15 responds at least as favorably to aggressive
clipping as Argo does. You can see the improvement on the waterfall and in
the panadapter view.
I'm heading back to the field shortly and will continue to look at XRS4
until at least 0500. I'd like to get one comparison between this particular
CW filter configuration I'm using now and the SSB configuration I was using
for the latter part of last night's session; but as I say, I don't have my
memory settings preset the way I'd like, and we know how well my mental
arithmetic works in the cold. <g> So, I'll probably defer that comparison
to another day.
At 0500 I'll probably switch to looking for XNI, so I can be headed back to
town by midnight. It's about 10 degrees warmer than this time last night,
but it's still below freezing, and breezy. The moon is nice and bright, for
the most part, but a few clouds are starting to move in. Freezing rain and
sleet are expected by daybreak, so I want to be home and warm well before
that. More later...
John
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