Understanding propagation numbers

How To Read Propagation Numbers
The A index [ LOW is GOOD ]

  • 1 to 6 is BEST
  • 7 to 9 is OK
  • 11 or more is BAD

Represents
the overall geomagnetic condition of the ionosphere (“Ap” if
averaged from the Kp-Index) (an average of the eight 3-hour K-Indices)
(‘A’ referring to amplitude) over a given 24 hour period, ranging
(linearly) typically from 1-100 but theoretically up to 400.

A lower A-Index generally suggests better propagation on the 10,
12, 15, 17, & 20 Meter Bands; a low & steady Ap-Index
generally suggest good propagation on the 30, 40, 60, 80, & 160
Meter Bands.

 
SFI index [ HIGH is GOOD ]

  • 70 NOT GOOD
  • 80 GOOD
  • 90 BETTER
  • 100+ BEST

The
measure of total radio emissions from the sun at 10.7cm (2800 MHz),
on a scale of 60 (no sunspots) to 300, generally corresponding to the
sunspot level, but being too low in energy to cause ionization, not
related to the ionization level of the Ionosphere.

Higher
Solar Flux generally suggests better propagation on the 10, 12, 15,
17, & 20 Meter Bands; Solar Flux rarely affects the 30, 40, 60,
80, & 160 Meter Bands.

K index [ LOW is GOOD ]

  • 0 or 1 is BEST
  • 2 is OK
  • 3 or more is BAD
  • 5 is VERY VERY BAD

The
overall geomagnetic condition of the ionosphere (“Kp” if averaged
over the planet) over the past 3 hours, measured by 13 magnetometers
between 46 & 63 degrees of latitude, and ranging
quasi-logarithmically from 0-9. Designed to detect solar particle
radiation by its magnetic effect. A higher K-index generally means
worse HF conditions.
A
lower K-Index generally suggests better propagation on the 10, 12,
15, 17, & 20 Meter Bands; a low & steady Kp-Index generally
suggest good propagation on the 30, 40, 60, 80, & 160 Meter
Bands.

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