For every day during the month of April 2021, I listened from about 08:00 to 22:00 UTC every day for FT8 signals on the 28 MHz band. For the first few days, I heard only a few countries every day. The chart below shows from the 7th to the 30th of April.
As can be seen from the chart, the second week of April continued at a low level with just a few countries heard every day. The 10th was one of those exceptions in that I didn't hear a single signal despite listening all day.
The chart clearly shows that the Sporadic-E season started on the 15th of April with the third week being in marked contrast to the second week.
Lyrid Meteor Shower: For Sporadic-E to occur, there needs to be a supply of metallic dust from the residue of meteors burning up in the atmosphere at a height of about 100kms. The first real meteor shower of the Spring is the Lyrids which goes from the 18th to the 25th of April and peaks on the 22nd.
Was the early arrival of the Lyrids responsible for the Sporadic-E season starting on the 15th and 16th. The exact start and finish of the shower seems to be different depending on what source you look at.
The 23rd of April is for me always a main date for Sporadic-E. I just noticed every year from my logbook that it was a date that stood out. It's probably no accident that it comes just a day after the peak of the Lyrids.
Methodology & shortcomings: In hindsight, I probably should have recorded the number of stations and countries on a day by day basis but I wasn't really planning to record the start of the season. The chart was just an idea I had once the month was over.
I was able to extract the number of countries heard on FT8 from my previous blog posts but the exact number of stations heard wasn't good enough that I would have confidence in the data for a chart.
As we are still near the bottom of the solar cycle, most of the signals that were heard were via Sporadic-E. It might be more difficult to repeat this test near the sunspot peak as there could be a F2 propagation in the mix as well.
I'll make a note in my calendar and I might repeat the exercise in 2022 and see if the results are the same.
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