Solar Cycle Sunspots & Radio Flux - Impact on Propagation
From: mediumwavedx
Date: Wed, 01 Dec 2021 19:45:14 UTC
Concerning medium wave, sunspots and the increasing solar flux are relevant to skywave signal strength and are accounted for in most modern (nighttime) skywave prediction methods. In general, medium wave skywave signal strength is slightly better during low or zero sunspot periods, at the bottom of the solar cycle. The calculation of the additional path loss in dB is dependent on location.
Greater consideration is given to paths within North America and Europe (nearer to the north geomagnetic pole), and Australia (nearer to the south geomagnetic pole). The North American loss factor is 4 times that of Europe and Australia, and rises for all as we get to the higher latitudes. Longer paths, those between North America and Europe are usually interpolated.
The ITU skywave prediction method is one such method which incorporates these added loss factors due to sunspots and solar flux.
Below are single hop skywave loss factors in dB as the sunspot count goes up.
Paths within North America:
Sunspot count = 0 0 dB added loss
Sunspot count = 7 an additional loss of 0.28 dB
Sunspot count = 25 an additional loss of 1 dB
Sunspot count = 50 an additional loss of 2 dB
Sunspot count = 100 an additional loss of 4 dB
Paths within Europe:
Sunspot count = 0 0 dB added loss
Sunspot count = 7 an additional loss of 0.07 dB
Sunspot count = 25 an additional loss of 0.25 dB
Sunspot count = 50 an additional loss of 0.5 dB
Sunspot count = 100 an additional loss of 1 dB
Paths between North America and Europe:
Sunspot count = 0 0 dB added loss
Sunspot count = 7 an additional loss of 0.175 dB
Sunspot count = 25 an additional loss of 0.625 dB
Sunspot count = 50 an additional loss of 1.25 dB
Sunspot count = 100 an additional loss of 2.5 dB
Admittedly, these extra losses are small but important enough that they are factored in for skywave calculations. However, 3 or 4 dB can make a difference logging a station or not.
--
Bill, WE7W
https://radio-timetraveller.blogspot.com
(MWCircle iog via wor iog)
