Re: LF: VLF - G3XIZ - QRT

[Andy Talbot <andy.g4jnt@gmail.com>]

Yes.   There are a couple of possible other lines too, and if it wasn't for the fact that the line shown very definitely wasn't there when I restarted the Rx after Chris had announced he was QRT, I wouldn't have been nearly so confident.  Its a great pity the Rx wasn't actually doing its job as the signal went off.   WHY does saving a screen grab stop the Rx - that's just mad.   I'll use a [ctl]-[prt scn} next time.

 

The correct freq was read off on the cursor, so I know the frequency cal was OK. 

 

The SDR-IQ driver software (Spectravue) can go to much lower bandwidths, but playing about with it a few dys ago to check calibration issues, if the decimated sampling rate is set to one of the values lower than 55kHz then frequency accuracy is not brilliant - I was seeing 0.4Hz readout error on the cursor against known frequencies so need to work out why that is.    Keeping to a 55kHz rate, readout error was to within a bin's accuracy.    Presumably 55kHz is the highest single - decimation allowed by the digital downconverter (Fclock / 1200)  and going lower introduces a double decimation process.      Max FFT size is 2Meg, so at 55kHz, BW is then restricted to 0.03Hz.

 

It will go to 5kHz sampling, so theoretically the software can get get down to .003Hz bin size, but testing it all out at the resulting 6 minute update rate would be more than a bit tedious - and would need at least  QRSS600 signalling.

 

Andy

www.g4jnt.com

 

On 27 December 2010 13:57, Markus Vester <markusvester@aol.com> wrote:

Hi Andy, Chris,

 

there is certainly a good looking trace at 8972 in your screenshot. What is a bit suspicious is that the calibration dash would place it about 1 Hz up, and also that there is another dash appearing at 8998 Hz at the same time.

 

Wishing you all success for this fasinating work,

 

Markus (DF6NM)

From: Andy Talbot

Sent: Monday, December 27, 2010 2:10 PM

To: rsgb_lf_group@blacksheep.org

Subject: Re: LF: VLF - G3XIZ - QRT

Unfortunately taking that screen grab stopped teh SDR-IQ and I didn't notice for a while.  Anyway, after eventually restarting there is not even the faintest indication of a line at the appropriate spot, which does suggest a possibility your QRSS 3600 signal  was detected.

 

Look forward to your next transmission - with slower dot period please.

 

Andy

www.g4jnt.com

 

 

On 27 December 2010 12:28, Andy Talbot <andy.g4jnt@gmail.com> wrote:

At what time  did you turn off?

 

Take a look at http://www.g4jnt.com/DownLoad/XIZ_1.jpg  where there is just the faintest line at the right frequency - looking in a bandwidth of 0.05Hz.

 

(The other point labelled is wher ei inject a frequency 10Hz higher at the start to check frequency cal)

 

If it is genuine, and not just a spuron, then QRSS 60 would probably show results.

 

Its still running to see if that just-possible line has now clearly gone.

 

Andy

www.g4jnt.com

 

 

On 27 December 2010 12:20, Chris Osborn <g3xiz@yahoo.co.uk> wrote:

Thanks for your efforts chaps.

I had definite QRSS-3 confirmation from Dennis M0JXM at 1.5 km but Pete M0FMT at 11 km
had no copy.

I have developed an intermittent short-circuit problem with the loading coil and will QRT now.

I'll notify via the reflector when transmitting again.

73 Chris XIZ

---

From: James Moritz <james.moritz@btopenworld.com>
To: rsgb_lf_group@blacksheep.org
Sent: Mon, 27 December, 2010 11:44:17
Subject: LF: Re: VLF - G3XIZ

Dear Chris, LF Group,

The VLF RX has been running since 1130 - Nothing seen yet.

Cheers, Jim Moritz
73 de M0BMU