HFU HF Underground

Loggings => HF Mystery Signals => Topic started by: alleycat on March 24, 2021, 0047 UTC

Title: Very short pips (mostly double; some single), 4 second interval, numerous freqs
Post by: alleycat on March 24, 2021, 0047 UTC
I'm currently (24 March @ 0030z) monitoring 4300 kHz and hearing a series of very short pips at a 4-second interval. Folks on the UDXF discussion group at groups.io have reported this phenomenon on a large number of HF frequencies being audible around the world (including SDRs in North America, Austria and China). Audio clip at https://www.lutins.org/temp/radio/pips.mp3 (https://www.lutins.org/temp/radio/pips.mp3); waterfall as follows:
(https://www.lutins.org/temp/radio/pips.jpg)
Title: Re: Very short pips (mostly double; some single), 4 second interval, numerous freqs
Post by: ~SIGINT~ on March 24, 2021, 0127 UTC
01:06 UTC - I can confirm that I as well am receiving that UNID signal from Toronto, Ontario Canada. It is faint, but audible and visual on the spectrum and waterfall displays. The signal appears to have additional characteristics, 2 kHz high and 2 kHz low from the centre frequency. Unfortunately the signal level is currently too low and short in duration for a proper analysis.

(http://www.milspec.ca/board/img/2021-03-23_210633.png)


RSPduo | End-fed longwire antenna | Toronto, Ontario Canada
Title: Re: Very short pips (mostly double; some single), 4 second interval, numerous freqs
Post by: Token on March 24, 2021, 0322 UTC
If you search "pips network" on these forums you will see they have been discussed here off and on for 10 years or so.

The transmission consists of a dit or dash and a pause some multiple of that dit or dash.  In the case of this transmission it is a 40 millisecond long dit, with a 4.000 second long pause (many different combinations of pulse length and pause have been seen).  The signal starts at some low frequency, makes a pulse, steps up to the next higher frequency, makes another pulse, etc, to the highest frequency, after which it starts over at the low frequency.  So you see it allows, in this specific case, for up to 100 different frequencies to be in each sequence.

Based on past receptions, this network appears to be sourced in the US, from 2 different locations.  Some frequencies are shared between both networks / locations, and so those frequencies show double dits.

I have never been able to confirm the purpose (or exact sources) of this signal, but my supposition is that it is some kind of ionospheric tool.

T!
Title: Re: Very short pips (mostly double; some single), 4 second interval, numerous freqs
Post by: Dag on April 02, 2021, 0014 UTC
I am hearing double and occasional single pips about every 4 seconds on 8825 kHz USB.
Dag