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Re: LF: OP/OPDS 16 tonight on 72.7 dial 2200 start...

To: <[email protected]>
Subject: Re: LF: OP/OPDS 16 tonight on 72.7 dial 2200 start...
From: "Markus Vester" <[email protected]>
Date: Sun, 22 Dec 2013 21:56:43 +0100
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Hi Bob,
 
looking at last night's opds-16 spectrogram http://dl.dropboxusercontent.com/u/26404526/opds16_131222_0800.png, your signal was low level but steady from 22:30, but had vanished completely around 0:15 before I went to bed. Finding the hits this morning was a pleasant surprise for me as well!
 
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)
 

From: Bob Raide
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)
 

From: Graham
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,
 
WG4XRS KA9CFD 4000m OPERA 725 miles 02:43:50
WG4XRS K3SIW-1 4000m OPERA 580 miles 01:54:10
WG4XRS K3SIW-2 4000m OPERA 580 miles 07:41:53
WG4XRS W3NF 4000m OPERA 233 miles 23:25:09
 
 ... 

From: Bob Raide
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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