Re: LF: Would slower QRSS help?

[Markus Vester <markusvester@aol.com>]

Bob,

 

nothing at all in Nuernberg last night. There seemed to be no diurnal change in the background noise level, showing that my receiving setup is not sensitive enough yet. Apparently the current LF-VLF diplexer arrangement is too lossy for direct connection to the soundcard, and in addition the ADC noisefloor is a bit higher above 24 kHz (Sigma-Delta noise shaping?). Will try to redesign the circuit and insert a simple preamp tonight.

 

I have also slowed the grabber window to 424uHz bins, hoping for more long carrier transmissions tonight.

 

Best 73,

Markus (DF6NM)

-----Ursprüngliche Mitteilung----- 
Von: Markus Vester <markusvester@aol.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: So, 2 Mrz 2014 7:57 pm
Betreff: Re: LF: Would slower QRSS help?

Just added a 3.8 mHz (aka "600") window for 29.499 khz to the bottom of my grabber:

 http://www.df6nm.de/vlf/vlfgrabber.htm.

Don't have much hope of seeing anything here. But if a miracle should happen, very slow qrss (like five minute dots) might become readable.

 

Bob, could you give some details about your antenna capacitance, voltage, current etc?

 

Dex, are you intending to add some turns to your coil to come close to Bob's QRG?

 

Best 73,

Markus (DF6NM)

 

From: Bob Raide

Sent: Sunday, March 02, 2014 6:35 PM

To: rsgb_lf_group@blacksheep.org

Subject: RE: LF: Would slower QRSS help?

Paul;
It appears to me that your 60 second bins has it!  I see A and B very plainly.  Your RX capability is phenomenal!!!
Warren Zeigler told me of your history of VLF receptions. 
I will be running in QRSS 180 tonight.  If it isn't enough I can go slower yet and then carrier for an hour with slight freq switch if nothing else works.
Please during transmission send me e mail for any changes you might like me to implement.  Not sure if you can or want to stay up that late but I will do whatever it takes to see your optimum results.
This is only second night on and transmitter still not optimum.  Have tuned input to make and install.  Would like a few more DB before corona takes over-Bob
 

> Date: Sun, 2 Mar 2014 17:16:42 +0000
> From: vlf0403@abelian.org
> To: rsgb_lf_group@blacksheep.org
> Subject: Re: LF: Would slower QRSS help?
>
> > ... QRSS 60 last night.
>
> I guessed wrong and Markus suggests a faster
> spectrogram. This one is in 60 second bins
>
> http://abelian.org/vlf/tmp/29499_140302h.gif
>
> And in 30 second bins
>
> http://abelian.org/vlf/tmp/29499_140302i.gif
>
> I don't know if it's any more readable but many
> dots are clear in the 30 second one.
>
> > Would slower be of any help for tonight's transmission?
>
> Much. For detection at the max possible range send pure
> carrier. To confirm ID, change frequency at some point,
> 10 mHz or so, on the hour.
>
> For the slow Morse each doubling of dot length would double
> the brightness of your trace on the spectrogram. 120 should
> put you in the red and 240 would be well into the yellow.
>
> Background noise subsided here from about 04:30 so the S/N
> improved for the final 2.5 hours of transmission. That
> appears to be the European window to aim for.
>
> --
> Paul Nicholson
> --
>