RFC: Can we figure out how much the Sun really affects propagation?

[Onno VK6FLAB]

As you might be aware, I have been publishing a weekly article about amateur radio since 2011. Last week I published the following article and would like to hear your thoughts.

de Onno VK6FLAB

Foundations of Amateur Radio

Recently I saw a social media post featuring a screenshot of some random website with pretty charts and indicators describing "current HF propagation". Aside from lacking a date, it helpfully included notations like "Solar Storm Imminent" and "Band Closed".

It made me wonder, not for the first time, what the reliability of this type of notification is. Does it actually indicate what you might expect when you get on air to make noise, is it globally relevant, is the data valid or real-time? You get the idea.

How do you determine the relationship between this pretty display and reality?

Immediately the WSPR or Weak Signal Propagation Reporter database came to mind. It's a massive collection of signal reports capturing time, band, station and other parameters, one of which is the Signal To Noise ratio or SNR.

If the number of sun spots, or a geomagnetic index change affected propagation, can we see an effect on the SNR?

Although there's close on a million records per day, I'll note in advance that my current approach of taking a daily average across all reports on a specific band, completely ignores the number of reports, the types and direction of antennas, the distance between stations, transmitter power, local noise or any number of other variables.

Using the online "wspr.live" database, looking only at 2024, I linked the daily recorded WSPR SNR average per band to the Sun Spot Numbers and Geomagnetic Index and immediately ran into problems. For starters the daily Sun Spot Number or SSN, from the Royal Observatory in Belgium does not appear to be complete. I'm not yet sure why.

For example, there's only 288 days of SSN data in 2024. Does this mean that the observers were on holiday on the other 78 days, or was the SSN zero? Curiously there's 60 days where there's more than one recording and as a bonus, on New Years Eve 2024, there's three recordings, all with the same time stamp, midnight, with 181, 194 and 194 sun spots, so I took the daily average. Also, I ignored the timezone, since that's not apparent.

Similarly the Geomagnetic Index data from the Helmholtz Centre for Geosciences in Potsdam, Germany has several weird artefacts around 1970's data, but fortunately not within 2024 that I saw. The data is collected every three hours, so I averaged that, too.

After excluding days where the SSN was missing, I ran into the next issue, my database query was too big, understandable, since there are many reports in this database, 2 billion, give or take, for 2024 alone.

Normally I'd be running this type of query on my own hardware, but you might know that I lost my main research computer last year, well, I didn't lose it as such, I can see it from where I am right now, but it won't power up. Money aside, I've been working on it, but being unceremoniously moved from Intel to ARM is not something I'd recommend.

I created a script that extracted the data, one day at a time, with 30 seconds between each query. Three hours later I had preliminary numbers.

The result was 6,239 records across 116 bands, which of course should immediately spark interest, since we don't really have that many bands. I sorted the output by the number of reports per band and discovered that the maximum number of days per band was 276. This in turn should surprise you, since there's 365 days in a year, well technically a smidge more, but for now, 365 is fine, not to mention that 2024 was a leap-year.

So, what happened to the other 90 days? We know that 78 are missing because the SSN wasn't in the database but the other 12 days? I'm going to ignore that too.

I removed all the bands that had less than 276 reports per day, leaving 17 bands, including the well known 13 MHz band, the what, yeah, there's a few others like that.

I removed the obvious weird band, but what's the 430 MHz band, when the 70cm band in WSPR is defined as 432 MHz?

I manually created 15 charts plotting dates against SNR, SSN, Kp and ap indices. Remember, this is a daily average of each of these, just to get a handle on what I'm looking at.

Immediately several things become apparent. There are plenty of bands where the relationship between the average SNR and the other influences appear to be negligible.

We can see the average SNR move up and down across the year, following the seasons - which raises a specific question. If the SNR is averaged across the whole planet from all WSPR stations, why are we seeing seasonal variation, given that while it's Winter here in VK, it's Summer on the other side of the equator?

If you compare the maximum average SNR of a band against the minimum average SNR of the same band, you can get a sense of how much the sun spots and geomagnetic index influences the planet as a whole on that band. The band with the least amount of variation is the 30m band.

Said differently, with all the changes going on around propagation, the 30m band appears to be the most stable, followed by the 12m and 15m bands. The SNR across all of HF varies, on average, no more than 5 dB.

The higher the band, the more variation there is. Of course it's also possible that there's less reports there, so we might be seeing the impact of individual station variables more keenly.

It's too early for conclusions, but I can tell you that this gives us plenty of new questions to ask.

I'm Onno VK6FLAB

--

73, de Onno VK6FLAB

Listen to the Foundations of Amateur Radio Podcast or check out the eBooks.

[Dave Typinski]

Hi Onno,

The SILSO daily total SSN data looks complete to me. 365 rows for 2024 in the
CSV file.

https://www.sidc.be/SILSO/datafiles

Which data file are you looking at, Onno?
--
Dave


On 5/8/25 23:33, Onno VK6FLAB wrote:
> ...For starters the daily Sun Spot Number or

[Onno Benschop]

Hi Dave,

The data came from the online database at db1.wspr.live. I acknowledge that according to an email I received after writing the article from Arne, they were aware of RAID issues on the database and were in the process of dealing with that. I didn't see any database errors during my sunspot or Kp/ap queries - just during access to the wspr.rx table, so I wasn't expecting that my incomplete numbers might be attributable to their issues.

I also didn't have a copy of the SSN data that I now do, thanks to your supplied link, 366 rows for 2024, very cool, much appreciated! Interestingly, when I download that CSV, it stops on 30 April 2025. I'm guessing that the daily numbers are added periodically.

73, de Onno VK6FLAB

--
Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
---
You received this message because you are subscribed to the Google Groups "HamSCI" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/hamsci/681D8C2B.3090408%40typnet.net.

--

Onno Benschop

()/)/)()        ..ASCII for Onno..
|>>?            ..EBCDIC for Onno..
--- -. -. ---   ..Morse for Onno..

If you need to know: "What computer should I buy?" http://goo.gl/spsb66

ITmaze   -   ABN: 56 178 057 063   -  ph: 04 1219 8888   -   on...@itmaze.com.au

[Johnson Francis]

Interesting article. Have you explored K index similarly? I have a feeling that Planetary K index does not always reflect the local HF propagation, especially on 40m on which we have most of the nets. Is there any publicly available live data of regional K index?

de Jon, VU2JO

--

Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
---
You received this message because you are subscribed to the Google Groups "HamSCI" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/hamsci/CACybYRXeUCAb9iryoLs13Q2AZjcSOdDVr8vgm2TN0mg4pLztww%40mail.gmail.com.

[Dave Typinski]

Hi Jon,

Not sure if the plot at the link below qualifies as "regional" and "live," but
at least three individual stations generate their own K index -- and I suppose
those are averaged somehow to obtain K_p. I think the SWPC's 7-day plot below
is updated every three hours.

https://services.swpc.noaa.gov/images/station-k-index.png

Unfortunately, NOAA/SWPC does not keep these plots in its FTP archive. The
underlying data may exist in their archive... somewhere. Never looked for it.

ftp://ftp.swpc.noaa.gov/pub/

I started keeping an archive of the 7-day plots in 2014. It's just a Python
script and cron job to download them once a day, then I upload them to the web
site once a month.

https://www.aj4co.org/AJ4CO%20Data%20Archive/NOAA%20SWPC%20K-Index%207-Day%20Plots/

Hope that helps, Jon.
--
Dave

On 5/9/25 05:27, Johnson Francis wrote:
> Interesting article. Have you explored K index similarly? I have a feeling that
> Planetary K index does not always reflect the local HF propagation, especially
> on 40m on which we have most of the nets. Is there any publicly available live
> data of regional K index?
>

> *de Jon, VU2JO*

>
> On Fri, 9 May, 2025, 9:04 am Onno VK6FLAB, <c...@vk6flab.com

> <mailto:c...@vk6flab.com>> wrote:
>
> As you might be aware, I have been publishing a weekly article about amateur
> radio since 2011. Last week I published the following article and would like
> to hear your thoughts.
>
> de Onno VK6FLAB
>

> *Foundations of Amateur Radio*

> <https://podcasts.vk6flab.com/>or check out the eBooks
> <https://podcasts.vk6flab.com/ebooks>.

>
> --
> Please follow the HamSCI Community Participation Guidelines at
> http://hamsci.org/hamsci-community-participation-guidelines.
> ---
> You received this message because you are subscribed to the Google Groups
> "HamSCI" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to hamsci+un...@googlegroups.com

> <mailto:hamsci+un...@googlegroups.com>.

> To view this discussion visit
> https://groups.google.com/d/msgid/hamsci/CACybYRXeUCAb9iryoLs13Q2AZjcSOdDVr8vgm2TN0mg4pLztww%40mail.gmail.com

> <https://groups.google.com/d/msgid/hamsci/CACybYRXeUCAb9iryoLs13Q2AZjcSOdDVr8vgm2TN0mg4pLztww%40mail.gmail.com?utm_medium=email&utm_source=footer>.

>
> --
> Please follow the HamSCI Community Participation Guidelines at
> http://hamsci.org/hamsci-community-participation-guidelines.
> ---
> You received this message because you are subscribed to the Google Groups
> "HamSCI" group.
> To unsubscribe from this group and stop receiving emails from it, send an email

> to hamsci+un...@googlegroups.com <mailto:hamsci+un...@googlegroups.com>.

> To view this discussion visit

> https://groups.google.com/d/msgid/hamsci/CAP9dWxoLTKuDNc%2BHr0pz1%2Ba8yUw_OpzSMne2Jaj1xtovv%3DG5kw%40mail.gmail.com
> <https://groups.google.com/d/msgid/hamsci/CAP9dWxoLTKuDNc%2BHr0pz1%2Ba8yUw_OpzSMne2Jaj1xtovv%3DG5kw%40mail.gmail.com?utm_medium=email&utm_source=footer>.

[Phil Erickson]

Hi Dave,

 Not sure if the plot at the link below qualifies as "regional" and "live," but at least three individual stations generate their own K index -- and I suppose those are averaged somehow to obtain K_p.  I think the SWPC's 7-day plot below 

is updated every three hours.

 Kp shows up enough places as a gauge of geomagnetic storm disturbance that I thought a bit more information on it could be useful for this list.  GFZ Potsdam generates and has archived Kp values.  It is a weighted combination of 13 different individual K index values and indeed has a 3 hour cadence.  From GFZ:

K variations are all irregular disturbances of the geomagnetic field caused by solar particle radiation within the 3-h interval concerned. All other regular and irregular disturbances are non K variations. Geomagnetic activity is the occurrence of K variations.

  It's important to realize that both K and Kp are quasi-logarithmic.  (The "A index" is linear instead.)  The reason is complicated and goes way back to the late 1930s when Jules Bartels derived this index for the first time.

 Since you (didn't) ask, this is the table showing the individual observatory K indexes and their weights which go into the single planetary K index:

  One can always use individual K values from each station if you don't mind missing the planetary averaging that happens by using all stations.  Here's a nice map with Kp example - note heavy bias towards the northern hemisphere:

  FYI, both of those figures are from this open access article:

Matzka, J., Stolle, C., Yamazaki, Y., Bronkalla, O., & Morschhauser, A. (2021). The geomagnetic Kp index and derived indices of geomagnetic activity. Space Weather, 19, e2020SW002641. https://doi.org/10.1029/2020SW002641

  Finally, I'll point out that the K scale saturates at 9 as you can guess from the table above ("K9 limit in nT" for each station), making it hard to tell relative disturbance strength of the largest superstorms.  For that, there are newer indices that both give values on faster time cadence and also have a higher maximum value.  In particular, the Hp30 (30-minute resolution) and Hp60 (60-minute resolution) are calibrated to be on about the same numerical scale as Kp up to a value of 9.  They are beginning to make headway in the community and are sometimes used for recent studies.  Those newer indices are found again at GFZ Potsdam:

https://kp.gfz.de/en/hp30-hp60

  "The geomagnetic Hpo index is a Kp-like index with a time resolution of half an hour, called Hp30, and one hour, called Hp60. besides that, the Hpo index is not capped at 9 like Kp, but is an open ended index that describes the strongest geomagnetic storms more nuanced than the three-hourly Kp, which is limited to the maximum value of 9. Next to the Hpo we also provide the linear apo index (ap30 and ap60). The Hpo index was developed in the H2020 project SWAMI and is described in Yamazaki et al (2022). The newest version Hpo V3.0 is described in this preprint.  It is based on an improved algorithm for very high Hpo values and extends the time series back to January 1985"

 We still use Kp because its calibration is uniform going back decades.  But in the great May 2024 superstorm, I recall Hp30 reaching over 12 for a short interval.

73

Phil W1PJE

To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/hamsci/681E7E62.7020004%40typnet.net.

--

----
Phil Erickson
phil.e...@gmail.com

[Johnson Francis]

Thanks a lot Dave.

73

de Jon, VU2JO

To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/hamsci/681E7E62.7020004%40typnet.net.

[Dave Typinski]

Hi Phil,

That's outstanding information and a great summary, thank you so much!
--
Dave

On 5/9/25 19:04, Phil Erickson wrote:
> Hi Dave,
>
> Not sure if the plot at the link below qualifies as "regional" and "live,"
> but at least three individual stations generate their own K index -- and I
> suppose those are averaged somehow to obtain K_p. I think the SWPC's 7-day
> plot below
>
> is updated every three hours.
>
> Kp shows up enough places as a gauge of geomagnetic storm disturbance that I
> thought a bit more information on it could be useful for this list. GFZ Potsdam
> generates and has archived Kp values. It is a weighted combination of 13
> different individual K index values and indeed has a 3 hour cadence. From GFZ:
>
> K variations are all irregular disturbances of the geomagnetic field caused
> by solar particle radiation within the 3-h interval concerned. All other
> regular and irregular disturbances are non K variations. Geomagnetic
> activity is the occurrence of K variations.
>
>
> It's important to realize that both K and Kp are quasi-logarithmic. (The "A
> index" is linear instead.) The reason is complicated and goes way back to the
> late 1930s when Jules Bartels derived this index for the first time.
>
> Since you (didn't) ask, this is the table showing the individual observatory K
> indexes and their weights which go into the single planetary K index:
>

> Screenshot 2025-05-09 at 6.51.07 PM.png
>
> One can always use individual K values from each station if you don't mind
> missing the planetary averaging that happens by using all stations. Here's a
> nice map with Kp example - note heavy bias towards the northern hemisphere:
>

> <mailto:hamsci%2Bunsu...@googlegroups.com>
> > <mailto:hamsci+un...@googlegroups.com
> <mailto:hamsci%2Bunsu...@googlegroups.com>>.

> > To view this discussion visit
> >
> https://groups.google.com/d/msgid/hamsci/CACybYRXeUCAb9iryoLs13Q2AZjcSOdDVr8vgm2TN0mg4pLztww%40mail.gmail.com
> >
> <https://groups.google.com/d/msgid/hamsci/CACybYRXeUCAb9iryoLs13Q2AZjcSOdDVr8vgm2TN0mg4pLztww%40mail.gmail.com?utm_medium=email&utm_source=footer>.
> >
> > --
> > Please follow the HamSCI Community Participation Guidelines at
> > http://hamsci.org/hamsci-community-participation-guidelines.
> > ---
> > You received this message because you are subscribed to the Google Groups
> > "HamSCI" group.
> > To unsubscribe from this group and stop receiving emails from it, send an
> email
> > to hamsci+un...@googlegroups.com

> <mailto:hamsci%2Bunsu...@googlegroups.com>
> <mailto:hamsci+un...@googlegroups.com
> <mailto:hamsci%2Bunsu...@googlegroups.com>>.

> > To view this discussion visit
> >
> https://groups.google.com/d/msgid/hamsci/CAP9dWxoLTKuDNc%2BHr0pz1%2Ba8yUw_OpzSMne2Jaj1xtovv%3DG5kw%40mail.gmail.com
> >
> <https://groups.google.com/d/msgid/hamsci/CAP9dWxoLTKuDNc%2BHr0pz1%2Ba8yUw_OpzSMne2Jaj1xtovv%3DG5kw%40mail.gmail.com?utm_medium=email&utm_source=footer>.
>
> --
> Please follow the HamSCI Community Participation Guidelines at
> http://hamsci.org/hamsci-community-participation-guidelines.
> ---
> You received this message because you are subscribed to the Google Groups
> "HamSCI" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to hamsci+un...@googlegroups.com

> <mailto:hamsci%2Bunsu...@googlegroups.com>.

> To view this discussion visit

> https://groups.google.com/d/msgid/hamsci/681E7E62.7020004%40typnet.net.
>
>
>
> --
> ----
> Phil Erickson

> phil.e...@gmail.com <mailto:phil.e...@gmail.com>

>
> --
> Please follow the HamSCI Community Participation Guidelines at
> http://hamsci.org/hamsci-community-participation-guidelines.
> ---
> You received this message because you are subscribed to the Google Groups
> "HamSCI" group.
> To unsubscribe from this group and stop receiving emails from it, send an email
> to hamsci+un...@googlegroups.com <mailto:hamsci+un...@googlegroups.com>.
> To view this discussion visit

> https://groups.google.com/d/msgid/hamsci/CAAZaqEt1d-9BBG50NwgTh0miCBfH_76BQp1yBrg4Xn4OU0eMPg%40mail.gmail.com
> <https://groups.google.com/d/msgid/hamsci/CAAZaqEt1d-9BBG50NwgTh0miCBfH_76BQp1yBrg4Xn4OU0eMPg%40mail.gmail.com?utm_medium=email&utm_source=footer>.

[David Eckhardt]

I still much prefer the ionosonde data ! ! ! !

There is a whole lot to be gained by monitoring the scatter from the WWV signals.  At present, I have the DC receiver set up for the 5 MHz transmissions:

Time along the bottom is in UTC.  I am 6-hours behind UTC here in N. Colorado, USA (40 16 36.80 N    105 13 0.16 W). 

The D-Layer influence is obvious.

D-Layer:  5 MHz gone during daytime, present during dark hours.

F-Layers:  5 MHz gone during dark hours, present during daytime.

I'm located some 25 miles south of the WWV installation so I receive both the GW and SW.  The GW is clearly visibly throughout the screen capture as a thin red line centered on the image.  ionospheric scatter is obvious. 

Dave - WØLEV

To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/hamsci/681E7E62.7020004%40typnet.net.

--

Dave - WØLEV

[David Eckhardt]

Thanks for the update on your email address.  I have it, but didn't know which one to use.

I haven't heard you on the air for ages.  But, I guess you are still around.  Maybe the solar photography has supplanted ham radio?

Dave - WØLEV

Virus-free.www.avg.com

On Sun, May 11, 2025 at 4:40 AM Phil Burk <philli...@comcast.net> wrote:

Dave, I pulled away from Comcast and mostly using my Gmail account.  I dumped Comcast (Xfinity) and we now get the Internet through Pulse . . . so much better, and 1/3 the monthly cost.

phil....@gmail.com

Phil

On May 10, 2025, at 12:35, David Eckhardt <davea...@gmail.com> wrote:



I still much prefer the ionosonde data ! ! ! !

There is a whole lot to be gained by monitoring the scatter from the WWV signals.  At present, I have the DC receiver set up for the 5 MHz transmissions:

--

Dave - WØLEV