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Author Topic: Possible Ionosonde?  (Read 641 times)

Offline markolinux

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Possible Ionosonde?
« on: December 02, 2020, 0142 UTC »
2 Dec 2020, @ 0105 UTC tune/in.

I'm hearing / seeing a signal that is sweeping the HF bands from 2025.5 kHz up through around 6500 - 6600 kHz or so. The higher it goes, the weaker it gets.

It sweeps quickly through that range in 2 seconds, then repeats.

It's not a constant carrier though, like the normal ionosondes - there's only a signal every so often. There are carrier signal on these frequencies as it sweeps:

2025.5
2098.0
2165.5
2231.0
2297.0
...etc

Not a constant difference between signals either. As it gets higher in the frequency range, the signals seem to turn into a "double beep" whereas at the bottom of the range, it sounds like a single beep.

Here's a video recording of my waterfall, using HDSDR:

https://spacetubes.com/DX/2020.12.02_0015UTC_UNID.Sweeper.mp4

Can't recall seeing anything like this before. I left it zoomed all the way out so you could see the sweeper going from left to right across the bands.

Location: N. Indiana
Radio used: RX888 SDR, 8 MHz bandwidth setting
Mode: SSB to hear the carrier as it "passes by", but AM detects it too, just like a normal ionosonde
Antenna:  south-aimed DKAZ loop

Mark Pettifor
Goshen, IN
KC9DOC
SDRs:  Perseus -- HF+ Discovery -- RSPdx
Antennas:  DKAZ -- Superloop (Conti) -- Belar loop
                  -- Vertical wire -- BOG/LOG (sometimes)
SW - MW; Listening and DXing.

Offline ion_op

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Re: Possible Ionosonde?
« Reply #1 on: March 05, 2021, 0428 UTC »
Sounds like the high frequency trading(financial) intruder that used to be in the ham bands.
« Last Edit: March 05, 2021, 0430 UTC by ion_op »

Offline Token

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Re: Possible Ionosonde?
« Reply #2 on: March 05, 2021, 1506 UTC »
Sounds like the high frequency trading(financial) intruder that used to be in the ham bands.

This does not appear to be the same signal as what you are talking about.  That one did not step from low to high so clearly in frequency as this one, nor was it ever seen to sweep so wide in frequency in a single sweep cycle.  Some kind of ionosonde or ionospheric testing is a good guess for this one.


The HFT signal you are talking about was never proven to be HFT.  HFT was suggested, early on, as a source based on possible location and a few spot frequencies, and that guess stuck.  No one seriously looked at other possible sources to try and eliminate anything.  Some of the frequencies used matched licencing for HFT, others did not.  No one explained why it should be entertained as a source on the basis of some frequencies matching licence data, but not eliminated based on other frequencies not matching licence data.  I had and still have serious doubts that it was related to HFT.  And no one ever gave a compelling definition (that I saw) of how such a signal, used the way it was, would benefit HFT.

T!
T!
Mojave Desert, California USA

Offline Token

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Re: Possible Ionosonde?
« Reply #3 on: March 05, 2021, 1619 UTC »
2 Dec 2020, @ 0105 UTC tune/in.

I'm hearing / seeing a signal that is sweeping the HF bands from 2025.5 kHz up through around 6500 - 6600 kHz or so. The higher it goes, the weaker it gets.

It sweeps quickly through that range in 2 seconds, then repeats.

It's not a constant carrier though, like the normal ionosondes - there's only a signal every so often. There are carrier signal on these frequencies as it sweeps:

2025.5
2098.0
2165.5
2231.0
2297.0
...etc

Not a constant difference between signals either. As it gets higher in the frequency range, the signals seem to turn into a "double beep" whereas at the bottom of the range, it sounds like a single beep.

Here's a video recording of my waterfall, using HDSDR:

https://spacetubes.com/DX/2020.12.02_0015UTC_UNID.Sweeper.mp4

Can't recall seeing anything like this before. I left it zoomed all the way out so you could see the sweeper going from left to right across the bands.

Location: N. Indiana
Radio used: RX888 SDR, 8 MHz bandwidth setting
Mode: SSB to hear the carrier as it "passes by", but AM detects it too, just like a normal ionosonde
Antenna:  south-aimed DKAZ loop

First, I do not know exactly what this is, but my thoughts on it:

When i see a signal like this (and I have seen essentially identical signals, if different frequency steps) my first thoughts are either some type of system test (antenna and / or transmitter) or ionospheric testing.

For system testing, someone may have installed a new wideband transmitter and antenna, or possibly they are pulling maintenance on an older, existing one.  And they are stepping up across all of their authorized frequencies or spot frequencies across their authorized bands of operation.  I have done the same thing myself and seen others do it also.

And while chirped / compressed pulses are more common for ionospheric testing, this kind of transmission absolutely could be used for such testing.

Observing its habits may help narrow things down.  If this was a hardware test of some kind it will probably not be seen very often, maybe only active a few minutes / hours / days.  But if it is some kind of atmospheric / ionospheric test it is more likely to be seen about the same time every day for an extended period.

For a first guess this is some kind of ionospheric test.

(edit below)
DOH!  This is probably (almost certainly) the Pips Network.  I did not recognize it at first because the pulse length and timing is different from what I have normally observed in the past.  Typically you see it with some multiple of about 62.5 msec pulse duration, instead of the ~40 msec duration in this example.  And typically the cycle time is longer, often 3 seconds or some multiple of 3 seconds.

With that in mind, there are probably about 50 frequencies involved in each set, with two sets, and propagation is killing the higher frequency ones for you.

Note the pulse duration, about 40 msec.  Note the repetition time, about 2 seconds.  It steps up in freq, from one to the next, with no significant delay between each step.  In 2 seconds that allows for 50 different 40 msec dwells.

Typically this is two different networks of frequencies, with some frequencies shared, meaning some frequencies have 2 Pips on them, while others are single Pips per frequency.

This network has been seen off and on for many years now.  If you search for "Pips Network" on these forums you will probably find several threads concerning it.  No one has come up with a solid explanation of what it is, but ionospheric testing / measurement of some kind is a front runner.

T!
« Last Edit: March 05, 2021, 1758 UTC by Token »
T!
Mojave Desert, California USA