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LF: Re: Recent ZEVS activity

To: <[email protected]>
Subject: LF: Re: Recent ZEVS activity
From: "Alan Melia" <[email protected]>
Date: Thu, 11 Jan 2018 23:28:59 -0000
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Hi Markus is there a possibility that hard frozen ground at the tx site might give an increase in ERP?
Alan
G3NYK
 
----- Original Message -----
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 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 <[email protected]>
An: rsgb_lf_group <[email protected]>
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  

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