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Re: VLF: Opera frequency range

To: <[email protected]>
Subject: Re: VLF: Opera frequency range
From: "Graham" <[email protected]>
Date: Fri, 27 Dec 2013 19:37:17 -0000
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There  was a  change  to the  top  qrg of the  band a  while  back  , which is why the  mid band  was  moved  , not  sure  its a  while  back , who  was testing  at the  time ? , was it the  USA that  changed ?  other than  that , the  decoder only  needs  the  signal from a sound card inside the  pass  band to  give -50 dB  Op -55/6 wspr  decode levels
G,

Sent: Friday, December 27, 2013 6:46 PM
Subject: VLF: Opera frequency range

Hi Graham, Peter, VLF,
 
there seems to be conflict in the VLF frequency selection: Somewhat arbitrarily, EA5HVK hardcoded Opera-VLF to ~ 8910 Hz, while I would rather stick close to 8970 Hz. Direct Opera-4H audio generation from Opera software won't work well with the deep search, because 
 
- most transmitters and grabbers are currently set up for 8970 Hz, and we can easily reuse "6000" and "60000" SpecLab instances for opds data export,
- frequency instability from a raw soundcard (ie without continuous samplerate correction) is typically a ppm or so. This is not really sufficient to produce a coherent peak in about 60 uHz,
- searching a wide frequency range (yes, 22 Hz is vast!) for with uHz resolution would be unnecessary and inefficient with the SpecLab / opds combo.
If one would like to try decoding 8970 Hz signals with standard Opera software, one solution would be audio frequency conversion through SpecLab and VAC. Or we could ask José for a software version with user definable frequency assignments.  
 
Best 73,
Markus (DF6NM)
 
From: Graham
Sent: Friday, December 27, 2013 5:27 PM
Subject: Re: LF: Opera RX active 24/7 - de PA1SDB

The Op decoder  limits are  8900 Hz > 8922  Hz
 
mid band  8911 Hz 
 
There  was  a change  of band  some  time  back , the  Op software  is  correct  tx/rx  soundcard SDR
 
73-G,
 
 

Sent: Friday, December 27, 2013 2:57 PM
Subject: Re: LF: Opera RX active 24/7 - de PA1SDB

Hi Peter, all,
 
Blacksheep seems to be responding again...
 
Hmm, 8.925 kHz would be way out of range of my SpecLab instances. I am currently looking for Opera signals near 8.97 kHz:
 
 opds-32: 8968.5 - 8971.5 Hz (Stefan?)
 opds-4H: 8969.8 - 8970.2 Hz (Uwe?)
 
Best 73,
Markus (DF6NM)
 
 

Sent: Friday, December 27, 2013 1:57 PM
Subject: LF: Opera RX active 24/7 - de PA1SDB

Hello VLF,
Opera RX on 8KC, 24/7 now.
Also Spectogram available.
 
The frequency band is 8895 - 8925 Hz,  right ?
 
 
 
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