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EI7GL....A diary of amateur radio activity

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Some local tropo on the FM band (88-108 MHz) - 17th Nov 2021

Posted: 17 Nov 2021 11:29 AM PST https://ei7gl.blogspot.com/2021/11/some-local-tropo-on-fm-band-88-108-mhz.html



Wednesday 17th November 2021: I noticed some tropo signals on Band 2
(88-108 MHz) this afternoon and I spent a while doing a scan of the band.
The biggest problem is that I can hear around 75 signals on the band under
flat conditions and that doesn't leave many gaps on the band for distant signals to come through.
I did hear four stations that were certainly via tropo propagation with distances ranging from 167 to 281 kms.
Under flat conditions, I can hear some of the main network FM stations on mountains that are about 130kms away.
While this reception report isn't all that unusual, it was still nice to
catch these signals by just using the telescopic whip antenna of my TecSun PL-380 standing at a north facing window of my house.

It always impresses me how well this little radio works with just its own antenna.

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Analysis of Sporadic-E propagation with WSPR reports by KN6DAD

Posted: 16 Nov 2021 11:16 PM PST https://ei7gl.blogspot.com/2021/11/analysis-of-sporadic-e-propagation-with.html



In a recent article titled 'Detecting Putative Sporadic E Propagation in WSPRNet Spot Records ' for TAPR, Jeanette Zhou, KN6DAD outlined how she
used data from the WSPRnet website to investigate Sporadic-E propagation.
She writes... "WSPRNet propagation data were downloaded from http://wsprnet.org/drupal/downloads and solar indices were from the German Research Centre for Geosciences (GFZ) (gfz-potsdam.de) in February, 2021. WSPRNet spot records of 28, 50, and 144 MHz transmissions during 2020 were
then used for the analysis, combining related spot records with the same timestamp and sender call sign to remove duplicates.
Putative sporadic E propagations were identified as when a transmission’s distance was about 1200 km in the above identified bands; the total number
of records used for the analysis was 1,118,989. "
She then used the data to general the chart above which clearly shows the Summer peak of the Sporadic-E season although I suspect that many of the reports on 144 MHz in July, August & October were due to tropospheric propagation. The 144 MHz data may also be skewed from the fact that there aren't that many people using WSPR on 144 MHz in Europe or North America.
It was interesting that she found that a high Kp index resulted in poor Sporadic-E conditions.
"In conclusion, the putative sporadic E propagation in the WSPRNet spot
records seems to be consistent with known seasonal variations of sporadic E propagation and corresponding geographic distribution, which suggests that these records provide a large number of observations that could be used to study sporadic E formation.
Exploratory data analysis also suggests that Kp index may be negatively correlated with recorded sporadic E propagation."

This corelates with the theory that quiet geomagnetic conditions are better
for Sp-E formation.
In summary... I found this article interesting not only because it shows
the Sporadic-E season but also it shows the perils of using WSPR spots for analysis.
For example, look at how poor the numbers are for April on 28 MHz and yet
we know that there are always plenty of Sporadic-E openings at the end of April.
The reason there are so few WSPR spots for April is because there are so
few people using it on the 10m band. Once the propagation starts getting
better in May then a lot more people start using WSPR on the band.
In other words, a lot of the data is due to human activity rather than
actual conditions. If a band looks dead then people are less likely to have WSPR transmitters active which means many openings generate no reports.
A million plus WSPR records sounds impressive but a lot of the data in
there will be skewed by assumptions about the propagation mode, a lack of
WSPR stations on the higher VHF bands and human behaviour.
WSPR reports can probably be used for propagation analysis but you would
need to be very careful about what data you select to use.
The full article can be seen on Page 7 of the PDF document HERE

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