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Hi Bob,
Regarding a possible advantage for shorter modes, I
still believe that "slower is better". During the first hour, your
signal was consistently short by ~ 3 dB here, and would have likely
been detected in opds-64 already. The CFH plot http://dl.dropboxusercontent.com/u/26404526/plot_131222_0835.png shows some
gentle signal variation on the Halifax path, but no indication
of sharp peaks.
It is mostly the
total signal energy which decides upon a detection. If a short
peak is strong enough for opds-16, it will quite
likely also be detected as part of a one
hour transmission. In practice there's of course a lower limit to this:
With "true decoders" (WSPR and Opera) and forward error
correction, with a sufficiently strong signal about 50% of
the whole data set is required for valid output. On the other hand,
opds contents itself with the much simpler task of only
identifying an entry from a relatively short list, and can often
do so in about 20% of total time.
Best 73,
Markus (DF6NM)
Sent: Sunday, December 22, 2013 5:32 PM
Subject: RE: LF: OP/OPDS 16 tonight on 72.7 dial 2200
start...
Markus; I was very pleasantly surprised at your decodes as we
had bad ice here starting around 0200. I tried to keep retuning but by
0300 couldn't load much power-was down to 200 TX output! By 0730
whan I closed was on exciter at 50 watts! Band kept getting better
but ice kept getting worse-great going on receive and the OPDS16 seems
worth running on this long wave band. It's short duration seems to take
advantage of the peaks as the sigs comes up out of those
fades???Bob
From: [email protected]To: [email protected]Date: Sun, 22
Dec 2013 14:08:29 +0100 Subject: Re: LF: OP/OPDS 16 tonight on 72.7 dial 2200
start...
Well, maybe dim but not completely dark... got a
few opds-16 detections here but not far above the threshold:
2013-12-22 04:56:17 WG4XRS 6448km
74322.200Hz 5mHz -46.2dBOp 93% 15.3dB
2013-12-22 04:39:43
WG4XRS 6448km 74322.200Hz 5mHz -44.2dBOp 100%
15.7dB
2013-12-22 04:23:10 WG4XRS 6448km 74322.200Hz
4mHz -47.1dBOp 94% 16.4dB
2013-12-22 02:10:43 WG4XRS 6448km
74322.199Hz 3mHz -47.0dBOp 97% 15.4dB
73, Markus
(DF6NM)
Sent: Sunday, December 22, 2013 1:30 PM
Subject: Re: LF: OP/OPDS 16 tonight on 72.7 dial 2200
start...
Looks like the shutters where down last
nigh Bob ?
G,
...
Sent: Saturday, December 21, 2013 9:46 PM
Subject: LF: OP/OPDS 16 tonight on 72.7 dial 2200
start...
WG2XRS/4 [WG4XRS opera modes] NY 74.3222 TX freq. On till
0700 weather co-operating. Hopefully Dex and John joining in also.
All
decodes appreciated-Bob
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