ELF: Recent ZEVS activity

[Markus Vester <markusvester@aol.com>]

It looks like ZEVS (aka KPTF) is currently undergoing a period of increased activity. SNR at DL0AO is no 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  

...