Here are some general guidelines concerning correlation of propagation indices
to actual expected HF/MF propagation conditions. Courtesy of KN4LF.
1.) Dropping indices numbers are better.
2.) For "medium frequencies" a solar flux under 150, under 100 better, 70 is
best for E layer multi hop.
Keep in mind though that the 10.7 cm (2800 mhz) solar flux index is not a
"reliable" gauge of ionization in our atmosphere for F layer HF frequency
refractions, as the energy of photons at this frequency is to low on the order
of one million times. However most are used to solar flux and sunspot number
and it's a hard habit to break. A better indicator is the background x-ray
flux. See #7 below.
3.) Solar flux of at least 100 for E valley-F layer ducting mechanism.
4.) Previous 24 hour Ap index under 10, under 7 for several days consecutively
is best.
5.) Previous 3 hour Kp index under 3 for mid latitude paths, under 2 for high
latitude paths, 0-1 for several days consecutively is best.
6.) Energetic protons no greater then 10 MeV (10+0) for 160/120 meters and no
greater then (10-1) on MF broadcast band.
7.) Background x-ray flux levels less than C1 for several days consecutively
for 160/120 meters and less then B9 for MF broadcast band but A9 or less best.
8.) No current STRATWARM alert.
9.) IMF Bz with a (positive number) sign, indicates a lesser chance of high
latitude path auroral absorption/unpredictable refraction or scattering of MF
RF signals, when the Kp is above 3.
10.) A 0 (zero) or better (positive number) Dst index as related to the
Equatorial Ring Current.
73,
Thomas F. Giella, KN4LF
Plant City, FL, USA
Grid Square EL87WX
Lat & Long 27 58 31 44N 82 09 51 98W
NWS Tampa Bay, FL SKYWARN Observer # HIL-249
SWFWMD Rainfall Network Observer #574 Thackery
CWOP Weather Station #CW2111
PODXS 070 PSK31 Club Member #349
KN4LF Solar Space Weather & Geomagnetic Data Archive:
http://www.kn4lf.com/kn4lf5.htm
KN4LF Daily HF/MF Radio Propagation Outlook: http://www.kn4lf.com/kn4lf6.htm
KN4LF HF/MF Radio Propagation Theory Notes: http://www.kn4lf.com/kn4lf8.htm
KN4LF Amateur & SWL Radio History: http://www.kn4lf.com
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