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Author Topic: SFI and SN  (Read 2615 times)
HAMSTUDY
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Posts: 419




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« on: September 04, 2017, 09:22:23 PM »

Just curious... qrz.com has a panel that shows daily/current solar conditions.  Tonight the panel says the SFI is 144 and the SN is 122.  These might be among the highest numbers over the last year, yet band conditions for both 20 meters and 40 meters for both day and night are listed as poor (not even fair, much less good).  Apparently these relatively high numbers (for the last year) for SFI and SN aren't necessarily predictors of good band conditions?  Obviously we are at a relatively low point in a relatively low 11 year solar cycle, or maybe there is something else at play that results in poor band conditions even the SFI and SN seem relatively high for the last year....?  Thanks for any insights.
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AA6YQ
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« Reply #1 on: September 04, 2017, 10:10:03 PM »

The geomagnetic A index is 14, and the K index is 4; these indicate a disturbed geomagnetic field, which interferes with HF propagation. Also, the solar flux has been continuously below 90 until a few days ago; the recent elevated level will take some time to have an impact, if it persists. Propagation prediction programs like VOACAP operate on a "smoothed" sunspot number (SSN) for that reason.
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KM4DYX
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Posts: 63




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« Reply #2 on: September 05, 2017, 03:16:36 AM »

Low SSN + elevated K-index = poor propagation.
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N3QE
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Posts: 4940




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« Reply #3 on: September 05, 2017, 08:45:31 AM »

Not only are conditions poor, there's forecasted radio blackouts for the next 3 days:

Quote
Prepared jointly by the U.S. Dept. of Commerce, NOAA,
Space Weather Prediction Center.
UPDATED 2017 Sept 05 0030 UTC

.Forecast...
Solar activity is expected to be at moderate to high levels over the
next three days (05-07 Sep) mostly due to the flare potential and recent
history of Region 2673. Radio blackouts reaching the R1-R2
(Minor-Moderate) levels are expected for the next three days (05-07
Sep), with a chance for R3 (Strong) radio blackouts.
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KM4DYX
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Posts: 63




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« Reply #4 on: September 05, 2017, 09:22:55 AM »

Look at it as a testing opportunity. I sometimes make it a point to see what I can do during "poor" conditions. I'm QRP only, so sometimes it's a bit of a challenge, but I can always find a Winlink station to connect with. I wonder how bad it would have to get before I couldn't.

73,
Al
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HAMSTUDY
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Posts: 419




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« Reply #5 on: September 05, 2017, 07:49:43 PM »

AA6YQ, KM4DYX, and N3QE - Thanks, all that helps.  I'll stay on the lookout for the A Index and K Index, the SSN, and forecasted radio blackouts.  73
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AA6YQ
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« Reply #6 on: September 05, 2017, 09:54:12 PM »

AA6YQ, KM4DYX, and N3QE - Thanks, all that helps.  I'll stay on the lookout for the A Index and K Index, the SSN, and forecasted radio blackouts.  73

The sun revolves around its axis every 27 days (slightly faster at the solar equator, and slower at the solar poles); it will be interesting to see what we get when these active regions rotate back into "view" next month.

     
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