Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz

[Markus Vester <markusvester@aol.com>]

Thanks Stefan for the frequency change to 6.48 kHz. It did help, but unfortunately the level of QRM happened to have increased dramatically since Friday morning.

 

Reviewing stored vlf_wide captures reveals that the "noise strip" above 6 kHz shows significant long-term variability: After being fairly strong during until April 22 19:20 UT, there was a relatively quiet period which ended suddenly May 6, 0:40 UT. I do not know what is causing these variations, but I suspect different types of equipment are being used at the railway yard. There are also intense 33.4 Hz spaced lines of similar type around 3 kHz. Maybe we should all lobby for the return of coal-fired steam engines, which were clean (in that sense) :~(  

 

So my 6.48 kHz grabber is currently pretty useless. Stefan says I need a remote receiver, say 20 km from here. Or maybe I should rather consider moving to a different QTH?

 

All the best,

Markus (DF6NM)

 

 

-----Ursprüngliche Mitteilung-----
Von: Markus Vester <markusvester@aol.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Fr, 6 Mai 2016 9:26 am
Betreff: Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz

No chance to see anything on 6470 Hz here due to heavy railway QRM. I noticed that the unstable lines seem to be concentrated on odd multiples of 16.70 Hz. Going 8 to 10 Hz up (e.g. to 6480 Hz) would place the signal in a QRM minimum, gaining at least 5 dB on average.

 

All the best,

Markus (DF6NM)

 

  

From: Paul Nicholson

Sent: Friday, May 06, 2016 2:24 AM

To: rsgb_lf_group@blacksheep.org

Subject: Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz

Stefan,

Your 200mA carrier comes through well here at 6.47 kHz, nice
signal at 0.14 fT during the night.  Daytime is 0.04 fT or
below and might be a bit of a struggle.

I don't need any more carrier.  From the raw recording I can
optimise filters and blankers and look at most of the diurnal.

--
Paul Nicholson
--