Hi Kriss,

Most likely some type of military OTH radar, but something else to consider might be stock exchange transmissions that are starting to gain a foothold in the HF frequency spectrum.  Here are a couple of links discussing the practice:

http://ka7oei.blogspot.com/2020/12/intruder-at-top-of-20-meter-amateur-band.html

https://sniperinmahwah.wordpress.com/2018/05/07/shortwave-trading-part-i-the-west-chicago-tower-mystery/

https://sniperinmahwah.wordpress.com/2018/06/07/shortwave-trading-part-ii-faq-and-other-chicago-area-sites/

https://sniperinmahwah.wordpress.com/2018/07/13/shortwave-trading-part-iii-fourth-chicago-site-east-coast-patent-regulation-and-farmer-kevin-mystery/

http://www.arrl.org/news/experiments-look-to-leverage-low-latency-hf-to-shave-microseconds-off-trade-times

https://forums.qrz.com/index.php?threads/ham-radio-mentioned-prominently-in-high-frequency-trading-story.617581/

https://www.metafilter.com/190005/High-Frequency-Trading-on-Shortwave-Radio

https://spectrum.ieee.org/wall-street-tries-shortwave-radio-to-make-highfrequency-trades-across-the-atlantic

I remember running across some YouTube videos a year or so ago, that showed how wide-spectrum (several tens to hundreds of kHz wide), but haven’t been able to locate them.  If I find links, I’ll provide them to the group.  I suspect we are going to see more such interference in the HF band in the future.

Ken --  WBØOCV