Re: VLF: 8970 Hz Op-4H

["Markus Vester" <markusvester@aol.com>]

Thanks Jim for the positive comments!

 

The SNR measured by opds was -58.3 dB on the Opera average power scale, equivalent to -54.3 dB carrier power ("PEP") in 2.5 kHz. This would scale to -20.3 dB in 1 Hz or +21.7 dB in 64 µHz (inverse of Op-4H sequence duration). Please note that the SNR measurement in opds is not completely robust and could be pessimistic by a couple of dB. The last figure 17.0 dB is for the SNR (peak-to-average power) of the time-domain cross-correlation between the waveform and the callsign template, stating the significance of the identification. In theory the correlation result should be 6 dB below the PEP SNR, but it saturates at about 22 dB for strong signals.

 

Stefan also managed to detect my second run last night:

 

DK7FC JN49IK VLF OPDS-4H correlation     Range: 8969.87 ... 8970.23 Hz
   date      time   call   distance  frequency bandwidth  snr    correlation
2013-12-31 22:30:04 DF6NM    175km   8970.000Hz   0mHz -60.3dBOp  82% 14.2dB
2013-12-31 18:07:58 DF6NM    175km   8970.000Hz   0mHz -58.3dBOp 100% 17.0dB

 

The catch between Stefan and myself is that for the ~ 180 km distance, on 9 kHz there is normally a midday minimum due to skywave-groundwave cancellation, so the lowest noise coincides with a low signal level. On the other hand, OK2BVG at ~ 400 km gets both high signal and low noise at noon. Looking at Lubos' grabber, the modulation sidebands are weakly visible in the "6000" window, and it might even be possible to detect one another using opds-32! 

 

Anyhow I have now started a third Op-4H sequence at 9:55 today, which should end around 14:16. Let's see what comes out...

 

Happy new year to all in the group,

 

73, Markus

From: hvanesce

Sent: Wednesday, January 01, 2014 10:58 AM

To: rsgb_lf_group@blacksheep.org

Subject: RE: VLF: 8970 Hz Op-4H

Congrats Markus and Stefan!

Great news, well done.

 

Am I interpreting correctly in the following?

17dB SNR with FFT bin width of ~ 69uHz, from ~~20uW ERP (9 meter antenna) at 175km?

 

I will be celebrating VLF Opera tonight.

 

Happy New Year,

 

Jim AA5BW

 

From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Joe
Sent: Tuesday, December 31, 2013 12:06 PM
To: rsgb_lf_group@blacksheep.org
Subject: AW: VLF: 8970 Hz Op-4H

 

Hi Markus, Stefan,

 

congrats to you, well done!

 

73 Joe

 

 

Von: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] Im Auftrag von Markus Vester
Gesendet: Dienstag, 31. Dezember 2013 19:15
An: rsgb_lf_group@blacksheep.org
Cc: Paul
Betreff: Re: VLF: 8970 Hz Op-4H

 

Stefan, we made it ;-))

 

DK7FC JN49IK VLF OPDS-4H correlation     Range: 8969.87 ... 8970.23 Hz
   date      time   call   distance  frequency bandwidth  snr    correlation
2013-12-31 18:07:58 DF6NM    175km   8970.000Hz   0mHz -58.3dBOp 100% 17.0dB

Wishing you all a very good start into 2014!

 

73, Markus (DF6NM)

 

From: Markus Vester

Sent: Tuesday, December 31, 2013 3:17 PM

To: rsgb_lf_group@blacksheep.org

Cc: Paul

Subject: VLF: 8970 Hz Op-4H

 

This morning I have reconnected the VLF amplifier and coil to the antenna, and started to transmit on 8970.000 Hz (Rb controlled). Sent a more or less uninterrupted carrier between 12:30 and 13:30, and have started an Opera-4H sequence at 13:41.

 

With 0.33 amps up to 9 m my estimated ERP would be around 20 uW. The carrier seems to be well visible on the OK2BVG grabber (up to 10 dB in "600"). I'm now trying to reach opds-4H at DK7FC but the SNR (10 dB for the carrier in "6000") may be just a bit marginal.   

 

Best 73,

Markus (DF6NM)