Re: LF: Re: Recent ZEVS activity

["Alan Melia" <alan.melia@btinternet.com>]



Yes the skin depth is a point. I was thinking of frozen ground compared with (these days) melting perma-frost, or should we call it imperma-frost :-)) Could be less Rouble trouble the price of oil is rising.

Alan

G3NYK

----- Original Message -----

From: Markus Vester

To: rsgb_lf_group@blacksheep.org

Sent: Thursday, January 11, 2018 11:44 PM

Subject: Re: LF: Re: Recent ZEVS activity

Hi Alan,

don't know for sure, but I think the depth of seasonal temperature changes in the ground (a few meters at best) would be much shallower than the ELF skin depth (a kilometer) in the highly resistive rock bed. I rather tend to believe that some energy is being saved by switching to a lower "standby" current during times of less submarine activity.

Best 73,
Markus


-----Ursprüngliche Mitteilung-----
Von: Alan Melia <alan.melia@btinternet.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Fr, 12. Jan 2018 0:31
Betreff: LF: Re: Recent ZEVS activity



Hi Markus is there a possibility that hard frozen ground at the tx site might give an increase in ERP?

Alan

G3NYK

 

----- Original Message -----

From: Markus Vester

To: rsgb_lf_group@blacksheep.org

Sent: Thursday, January 11, 2018 10:30 PM

Subject: ELF: Recent ZEVS activity

It looks like ZEVS (aka KPTF) is currently undergoing a period of increased activity. SNR at DL0AO is now significantly better than it used to be, so I suspect that transmit power might have been increased. In addition, we have now enabled a 20 Hz filter and a noiseblanker, which effectively suppresses local QRM bursts.

We find that in addition to the traditional three-digit repeated telegrams based on 4-minute dashes, there is also a much faster FSK mode with short dashes (about 10 or 12 seconds). These high-datarate sequences are always initiated by a long dash on the highest frequency, 83.2 Hz.

Screenshots:
http://df6nm.bplaced.net/dl0ao/files/zevs_7.63mHz_180111_2114.png
http://df6nm.bplaced.net/dl0ao/files/zevs_183mHz_180108_0914.png

DL0AO Grabber:
http://df6nm.bplaced.net/dl0ao/VLFgrabber/vlfgrabber_dl0ao_test.htm

See also:
G3ZJO 2012-05-12: https://g3zjoradio.wordpress.com/2012/05/12/more-on-82hz-radio-comms-zevs-13669381/
DL4YHF 2008-08-29: http://dl4yhf.darc.de/t/vlf_experiments.htm

Best 73,
Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: Markus Vester <markusvester@aol.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: So, 1. Okt 2017 0:44
Betreff: Re: ELF: ZEVS reception from a small loop

Those ZEVS messages seem to consist of simple three-digit numbers. With 0.2 Hz spacing, the frequency ranges 81 to 81.8 and 82.2 to 83 Hz provide ten possible MFSK symbols. Each message is sent twice, separated by a single 80.8 Hz dash. Consecutive messages are always separated by the 82 Hz idle tone.

Assuming that symbol frequencies are counted upwards from 0 to 4 and 5 to 9, Stefan's screenshot would translate to

..7 486 128   731    941        473   018
 
73, Markus  

...