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Old 06-06-2018, 8:39 AM
Token Token is offline
Join Date: Jun 2010
Location: Mojave Desert, California, USA
Posts: 1,960

That video you linked is one of my videos.

But note that the sounder in that video does not come up and down on one frequency, rather it hits a freq for short period and then moves to a higher frequency. That is what the sounder does, it starts at a frequency just below the lowest operating freq for 29B6 (6000 kHz) and steps up through the spectrum to just above the highest operating freq for 29B6. And a short while later it repeats the cycle. But it does not hit a single frequency repeatedly in a short period of time.

Think of it this way, a sounder, be it backscatter or forward scatter (bistatic), is a radar. I don’t like to call them that, but it is a fact. Radars are designed with a specific set of target parameters in mind, and those parameters drive how the radar operates. In the case of a sounder the target (the ionosphere) changes slowly, and so it does not have to look at the target very often to have a complete set of data. Hitting a given frequency or specific narrow frequency range every 10 to 50 minutes provides ample data on how the ionosphere is changing.

Radars (as opposed to sounders) are designed for targets that move / change more rapidly, missiles, aircraft, ships, etc. And so they must look at the target more often to keep track of what is going on.

As I said, sounders are radars, just specialized to look at the ionosphere. As such they can end up using basic waveforms that may be very similar to other radars. One way to tell a probable sounder from a probable radar is its revisit or dwell rate and time. If it looks at a given frequency / area rapidly it is likely looking for a target that changes quickly, and so it is probably a “radar” looking for man made targets. If it looks at a given frequency / area a few times an hour it is likely a sounder, since the ionosphere typically does not change rapidly.

So the activity you describe, coming up and down every minute or so on a given frequency, sounds much more like a radar than a sounder. And it is quite possible that it was a frequency hopping radar, and while you heard it as “off” it was actually still on, but on a different frequency, and it hopped back to the frequency you were monitoring every minute or two. So that it may have been “on” all the time, but monitoring a single frequency you would not have heard it until it jumped back to the freq you were monitoring.

As for “more parties” doing this stuff, HF radar is quite common, and has been since the first days of radar, in the late 1930’s. There has basically never been a time, since radar became a real thing, when HF radar was not used, although people outside the field sometimes don’t realize that.

Australia, France, Iran, UK, US, Canada, China, and Russia all have very active HF OTHR programs, and have for years. Other countries, such as Germany, India, South Africa, etc, also have HF radars, although typically less well known or less active.


Last edited by Token; 06-06-2018 at 8:44 AM..
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