OTHR on 40 Meters 2339 UTC 29 March 2021

[Traveling Wave]

2339 UTC - Over the Horizon Radar from 7280 to 7290 kHz on 40 Meter amateur band is S7 in WNY tonight. I guess its the Chinese?
0030 UTC - Checked again and the OTHR was gone.

Checked again on 30 March 2021 at 2332 UTC and OTHR was back on 7280 to 7290 kHz with S7 in WNY.

[redhat]

I'm sure you know this, but the 7200--7300 Khz spectrum is only available to amateur radio users in ITU region 2, North and South America.  The rest of the world recognizes this segment as a broadcast band.
...just in case some folks don't know that.

+-RH

[Token]

Would need a bit better description, more information of what it sounded like at least, of the radar to try and narrow down the source.  Maybe a sound clip or a waterfall picture.

However, the Russian 29B6 Konteyner radar is known to hit around those frequencies, often around that time.  The 29B6 can and does hit any frequency it wants, including the middle of ham bands, aviation frequencies, maritime, etc.

T!

[SV1XV]

You may consult the IARU R1 "Radar Systems on Shortwave" guide by DK2OM, August 2013. It contains spectrum plots and other characteristics of the various HF radar systems. The guide was on the old IARU R1 website but I cannot find it after the site upgrade, so I have uploaded a copy here:

http://www.ipernity.com/doc/777361/50694630

[~SIGINT~]

Unfortunately, SV1XV's link requires sign-in / registration to access the file.

The publication was located on the International Amateur Radio Union (IARU) site at the following URL: http://www.iaru-r1.org/wp-content/uploads/2019/12/Radar-Systems-DK2OM-2013.pdf

[Token]

The DK2OM document is a very good primer on HF radars, however there are several issues with it.  The largest is its age.  Because of its age it does not list newer radars such as the Russian 29B6 that is a serious contender for this source, and also at least one signal in it is probably not a radar.

To the OP, confirming that your question was about a radar that was present on ~7285 kHz at 2339 UTC, March 29, 2021, and terminated sometime before 0030 UTC on 30 March.  The same radar was again seen on ~7285 kHz at 2332 UTC on 30 March?  And also, you are relatively certain this was a radar, and not DRM?

The reason I ask if you are sure it was not DRM, on the nights of 24 to 31 March, from 2330z to 0000z each day, there is a signal that looks very similar to DRM that can be seen on the Twente WebSDR full day page ( http://websdr.ewi.utwente.nl:8901/fullday/ it defaults to the last 24 hours, but at the top you can enter the date you want to see ).  Unfortunately, because of the relatively low resolution of that page it can be difficult to tell DRM from certain narrow radars, such as the 29B6.  But the start and stop times across a weak+ worth of time are suspiciously regular to be a radar, such timing is more consistent with other kinds of signals.  While radars which change frequency to chase propagation conditions (most radars that change frequency through the day do it for this reason) often do approximately the same thing every day for days in a row, they don't typically do exactly the same thing for several days in a row.

Here is a crop from the Twente Fullday plot of the 29th of March, showing the time and frequency in question:


If you are fairly certain it was not DRM then the 29B6 is my leading suggestion as a candidate.

T