Shortwave oddity, ionospheric Digisonde, 17 February, 2024, 1504 UTC

This is a recording of a signal I call the "Grinder" in my log books. It is a digitally modulated ionosonde, or sounder, called a digisonde. An ionosonde is a tool that makes measurements of the RF responses of the ionosphere. A digisonde is an ionsonde using digital modulation techniques.
I believe this particular digisonde is the Lowell Digisonde International DPS-4D, however it could be another make / model.
Because the signal is stepped, I am stepping the receiver audio to catch every 3rd or 4th frequency step. This provides an idea of what the signal sounds like on any single frequency. The center frequency for my 1600 kHz sampled width is 16740 kHz, but these signals step across very wide frequency ranges, often the entire HF spectrum. It is common to see these signals from 3000 to 30000 kHz.
The diagonal lines running left to right are a different kind of ionosonde, called a chirpsonde or chirpsounder.
Recorded on my local receiver at my location in the Mojave Desert of California, USA, 17 February, 2024, 1504 UTC.
Disclaimer: Many of the radio reception recordings on this KZbin channel pertain to unusual, uncommon, unknown, or mystery signals that might be found on radio, both shortwave and VHF/UHF. Among the subjects covered are numbers stations, utility stations, military transmissions (both in the clear and encrypted / encoded), aviation, maritime, ham radio, CB radio, radars, ionosodes, propagation beacons, ditters, dashers, whistlers, and just about anything else that might transmit, in any mode, USB, LSB, CW, Morse Code, FM, AM,FMCW, LFMCW, etc. Think of it as SIGINT (signals intelligence) / COMINT (communications intelligence) / ELINT (electronic intelligence) lite, the hobby version. All the recordings are made by me, most often at my home. Although there are a few mysterious things to be found here, you will not find anything paranormal, extraterrestrial, spiritual, or mystic. However, everyone can have their own interpretations of the sounds heard, make of it what you will.

[@afnDavid]

The Good RadioKeeping Seal of Approval.

[@thes764]

Interesting catch! Never saw/noticed this here in Europe, unlike the normal ionosondes. Thanks for sharing & 73!

[@midoedo]

u really got a great bunch of videos I wonder if u can help me identifying and decoding a mysterious signal ?

[@Psybeam60]

if you don't mind, may i ask how you find these oddity events to record? do you just scan the waterfall for interesting signals? i just got into the hobby recently so i'm curious : )

[@FirstToken]

It is a bit of a combination of all of the above. Understanding how propagation works can help you to target frequency ranges at specific times of the day for greater probability of hearing things. Recognizing patterns on wideband waterfalls helps you find signals while looking at very wide ranges of frequencies. However, in this case, I went looking for this specific signal to record.

[@Antenna101]

Good video!

[@FirstToken]

Glad you enjoyed it

[@Antenna101]

@@FirstToken :D

[@afnDavid]

WUNclub approves this video.

[@SnivillusLupin]

What is it?

[@FirstToken]

@SnivillusLupin, as described in the in-video annotation and in the description below, this is a digitally modulated ionosonde, or a digisonde. These are tools that measure ionospheric response in regards to radio waves.