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Re: LF: 136 Dial freq for OP-OPDS 32 for tonight...,

To: <[email protected]>
Subject: Re: LF: 136 Dial freq for OP-OPDS 32 for tonight...,
From: "Markus Vester" <[email protected]>
Date: Wed, 18 Dec 2013 01:08:55 +0100
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Ah there's one detail I forgot to mention, which may better answers your question: The software procedure which estimates the carrier bandwidth first applies some variable smoothing to the power spectrum. The smallest used smoothing window is 5 FFT bins, which then translates into different mHz bandwidths (1.2 mHz at Op-64,  2.5 mHz at Op-32, 5 mHz at Op-16). Even when the carrier has been ideally narrow in reality, the display can hardly be less than that.
 
73, Markus
 
 
Sent: Wednesday, December 18, 2013 12:50 AM
Subject: Re: LF: 136 Dial freq for OP-OPDS 32 for tonight...,

Bob,
 
the bandwidth displayed by opds is supposed to tell you the width of the central carrier, it's ideally zero and not related to the modulation speed. A stable and coherent signal like yours usually shows 1 or 2 mHz, but the figure surely won't be good to the last digit. The carrier is only present when the transmitter is being keyed with phase continuity from dash to dash, and it can then be used by opds as a phase-reference for synchroneous AM demodulation.
 
On the other hand, the conveyed keying information resides in the AM sidebands around the carrier, with a width proportional to the inverse dot length. In Hartmut's Op-16 (4 second dots) capture, we find about 0.2 Hz wide main lobes on each side of the carrier. Due to the "unspreading" effect of the correlation, opds can still retrieve the most likely callsign even when the power density of the sidebands is well below the noise.
 
Best 73,
Markus (DF6NM)
 

From: Bob Raide
Sent: Wednesday, December 18, 2013 12:13 AM
Subject: RE: LF: 136 Dial freq for OP-OPDS 32 for tonight...,

Markus;
Was wondering why my bandwidth was over twice as high as usual last night on 73 band OP16? Must have something to do with faster OPERA mode?  And looking at my signal on Hartmut's grabber was what appeared to be digital data on each side of the carrier.  Wonder what would cause those sidebands as I understand OPERA is nothing but keyed CW with no modulation-unless it was hum on my carrier?  Bob
 

From: [email protected]
To: [email protected]
Date: Tue, 17 Dec 2013 23:59:41 +0100
Subject: Re: LF: 136 Dial freq for OP-OPDS 32 for tonight...,

Bob, Alex,
 
welcome again!
 
2013-12-17 23:03:34 WE2XEB  6448km 137540.999Hz   2mHz -47.7dBOp  76% 15.5dB
2013-12-17 23:03:07 R7NT    2060km 137590.028Hz   4mHz -42.4dBOp  77% 17.0dB
 
73, Markus (DF6NM)

From: Bob Raide
Sent: Tuesday, December 17, 2013 6:53 PM
Subject: LF: 136 Dial freq for OP-OPDS 32 for tonight...,

WE2XEB NY will be on at 2200 or so with OP/OPDS 32 tonight at 136 dial freq 137.541 TX freq as of now-all decodes appreciated-Bob
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