Cool new feature on TwenteSDR

TwenteSDR is a web-controlled shortwave receiver located at the University of Twente in the Netherlands. Unlike many other remotely controlled receivers, it can be tuned by multiple users simultaneously by leveraging Software Defined Radio (SDR) technology. It is a popular online destination for shortwave radio enthusiasts when they are away from their listening posts. For readers unfamiliar with the service, below is a short demo showing TwenteSDR tuned into Radio New Zealand International on January 19, 2014.

Yesterday they added a new feature where it is possible to see what the entire shortwave spectrum looked like in the last 24 hours. I had a quick look and noticed an interesting pattern: it seems that there is almost a perfect inverse linear correlation between band openings (measured in kHz) and the time of the day.

24 hour view of the shortwave spectrum between 49 meters and 16 meters, taken from TwenteSDR on 07/10/2015. Download the full cached copy.

I wonder how propagation conditions (rather dismal in the last few days!) and the time of the year affect this relationship. I'll keep checking this plot on TwenteSDR to try to understand this better.

Propagation on 07/10/2015

Daylight map on 07/10/2015 courtesy of solarsystemscope.com