KQ6XA on How To Read HF Propagation Numbers

In my General Class license course, when I cover propagation, I often joke that the only index I use is the E-index. When I get a puzzled look, I explain that E stands for “ear,” and if I can hear stations that means propagation is good. If I can’t hear any stations, it means propagation is bad.

Seriously, though, it’s good to know what the various indexes mean. Here’s KQ6XA’s rules of thumb when it comes to interpreting the numbers.

  • K index: LOW is GOOD.
    • 0 or 1 is BEST
    • 2 is OK
    • 3 or more is BAD
    • 5 is VERY VERY BAD
  • A index: LOW is GOOD.
    • 1 to 6 is BEST
    • 7 to 9 is OK
    • 11 or more is BAD
  • Solar Flux Index: HIGH is GOOD.
    • 70 NOT GOOD
    • 80 GOOD
    • 90 BETTER
    • 100+ BEST

By the way, the Space Environment Center, a department of the NOAA, publishes the Radio User’s Page. This page provides links to space weather info specifically of interest to radio operators. Very cool.


  1. Of course, for those of us who enjoy weak signal stuff on VHF, a K index of 4 or 5 can be very good news.

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