[W4HM Spaceweather] W4HM Daily HF Radio Wave Propagation Forecast #259

Sat Sep 16 11:14:08 EDT 2017

Hello to my fellow hamateur radio and SWL radio enthusiasts around the world. 

Welcome to my “not for profit” W4HM daily HF radio wave propagation forecast.

If you find this "not for profit" daily HF radio wave propagation forecast useful to your hamateur and SWL radio activities, feel free to drop me a line and let me know that at

thomasfgiella at gmail.com .

Feel free without prior permission to redistribute this "not for profit" 

daily HF radio wave propagation forecast, as long as you redistribute it in its entirety and give me credit for it.

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#259 Issued Saturday September 16, 2017 at 1500 UTC

Global Daily HF Radio Wave Propagation Forecast- 

We are now entering the fall/spring equinox type of HF radio wave propagation conditions. Globally HF radio wave propagation conditions are most evenly balanced across the equator during the fall and spring equinox.

HF radio wave propagation conditions change hourly, daily, weekly, monthly, yearly and by decade, as the sun rises and sets at different times and at different angles from the ecliptic, as well as by radio wave frequency. This is due to changes in the maximum usable frequency (MUF), lowest usable frequency (LUF) and F layer critical frequency (FoF2).

HF radio wave propagation conditions trend- steady state, which means neither improving nor deteriorating.

Northern Hemisphere Radio Wave Propagation Forecast-

80-60 (75-60) meters- fair at night and poor at day, 

40-30 (41-25) meters- fair at night and fair at day,

20-17 (22-16) meters- very poor at night and fair at day, 

15 (13) meters- very poor at night and poor at day,

12-10 (11) meters- very poor at night and very poor at day.

And before you know it the winter solstice will be here. During the northern hemisphere winter season the higher HF bands of 10-20 meters (11-19 meters) close sooner due to less sun light illuminating the ionosphere than in the northern hemisphere. But the maximum useable frequency (MUF) is higher than in the northern hemisphere as the F layer of the ionosphere is lower in height and is more dense.

Southern Hemisphere Radio Wave Propagation Forecast-

80-60 (75-60) meters- fair at night and poor at day, 

40-30 (41-25) meters- fair at night and fair at day,

20-17 (22-16) meters- very poor at night and fair at day, 

15 (13) meters- very poor at night and poor at day,

12-10 (11) meters- very poor at night and very poor at day.

And before you know it the summer solstice will be here. Keep in mind that almost daily during the southern hemisphere summer season you will find that the 10 (11) meter bands will open via short north-south and east-west propagation paths via sporadic E (Es). Also when multiple sporadic E (Es) clouds form and line up favorably much longer propagation paths open up on east-west paths. And last but not least north-south propagation paths occur across the equator via trans equatorial propagation (TEP).

Received RF signal strength scale-

Very Good- +1 over S9 Or Greater

Good- S7-9

Fair- S4-6

Poor- S1-3

Very Poor- S0

Meter Band Equivalents

Ham & SWL

160->   90

80->     75

60->     60

40->     49, 41

30->     31, 25

20->     22, 19

17->    16, 15

15->    13

12,10-> 11

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This HF Radio wave propagation forecast is produced based on the SIGINT_CAP HF radio wave propagation prediction software. I wrote it beginning in the late 1980’s but I’m sorry to say that it can’t be distributed to the general public.

And though this HF radio wave propagation forecast is produced based on the SIGINT_CAP, I do check the actual band conditions at my location in the USA and tweak the forecast manually where and when necessary. I also check global HF radio wave propagation conditions via remoted radio receivers around on every continent of the globe and tweak the forecast manually if and when necessary.

The hamateur radio JT65A mode RF signal levels received are based on 5 watts and ½ wave dipole up at 40 feet.

The hamateur radio PSK31 mode RF signal levels received are based on 25 watts and ½ wave dipole up at 40 feet.

The hamateur radio CW mode RF signal levels received are based on 50 watts and ½ wave dipole up at 40 feet.

The hamateur radio SSB RF mode signal levels received are based on 100 watts and ½ wave dipole up at 40 feet.

The HF shortwave broadcast band AM Mode RF signal levels are based on 100,000 watts (100 kw) and a typical high gain VOA type curtain array antenna.

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Please keep in mind that this is a relatively simplified HF radio wave 

propagation forecast, so as to keep it easily understandable and applicable by the average radio enthusiast.

Globally HF radio wave propagation conditions are most evenly balanced 

during the fall and spring equinoxes and most diametrically opposed during 

the summer and winter solstices.

Conditions change daily, weekly, monthly, yearly and by decade, as the 

sun rises and sets at different times and at different angles from the 

ecliptic, as well as by radio wave frequency. This is due to changes in the 

maximum usable frequency (MUF), lowest usable frequency (LUF) and F layer 

critical frequency (FoF2).

The D and E layers also come into play through RF radio wave signal 

absorption and refraction. And then there is sporadic E (Es) radio wave 

propagation that can really throw a wrench into the gears so to speak.

Things like sporadic E (Es) radio wave propagation and lightning storm 

static can impact HF radio wave propagation in an unpredictable manner and 

mostly bad.

Ongoing solar, space and geomagnetic weather goings on also impact HF radio 

wave propagation conditions in a negative manner.

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GENERAL GUIDELINES CONCERNING CORRELATION OF PROPAGATION INDICES TO ACTUAL HF PROPAGATION CONDITIONS-

NOTE!!! The propagation indices "interpretations" are my personal 

intellectual property. Therefore the radio wave propagation indices 

allowed without permission in advance as long as proper credit is given.

All 14 of the following indices have to occur as described below in order to 

see the best global high frequency radio wave propagation possible,

something that happens rarely.

1.) Dropping geomagnetic field indices numbers are better, Kp of 0 best.

2.) A daily sunspot number of 150 or higher, 200 or higher best.

3.) A daily sunspot number of greater than 100 for routine stable formation 

of the E Valley/F Layer ducting mechanism.

4.) Previous 24 hour Ap index under 10, fewer than 7 for several days 

consecutively are best.

5.) Previous 3 hours Kp index fewer than 3 for mid latitude paths, fewer 

than 2 for high latitude paths, 0 for several days consecutively is best.

6.) Energetic protons no greater than 10 MeV (10+0).

7.) Background x-ray flux levels greater than B1 for several days 

consecutively, greater than C1 best.

8.) No current STRATWARM alert.

9.) Interplanetary magnetic field (IMF) Bz with a (positive number) sign, 

indicates a lesser chance of high latitude path aurora 

absorption/unpredictable refraction or scattering of medium frequency RF 

signals, when the Kp is above 3.

10.) A -10 or better towards a positive number Dst index during the recovery 

time after a geomagnetic storm, as related to the equatorial ring current. A 

positive number is best.

11.) Rising positive T index number. The T Index tracks with the F2 layer 

critical frequency (foF2) and sunspot number (SSN) and indicates the 

capability of the F2 layer to refract RF signals.

12.) Galactic cosmic rays decrease to -3 units below zero and trending 

towards zero.

13.) Energetic electron flux levels no greater than 2 MeV (2+0).

14. A solar wind speed of less than 300 km/s for several days consecutively.

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Standard Disclaimer-

Note! I use error prone RAW public domain data from the NOAA Space 

Environment Center, other U.S. government entities and educational 

institutions, to produce my comprehensive HF radio wave propagation 

forecast. This data is gathered and made public by the U.S. Government using 

taxpayer $$$ (including mine).

However the solar, space and geomagnetic discussions as well as the HF propagation forecast that I produce from the RAW public domain 

data is my personal intellectual property. Therefore the solar, space and geomagnetic weather discussions and HF radio wave 

propagation forecast contained herein is copyrighted © 1988-2017 by Thomas 

F. Giella, W4HM.

Feel free without advanced permission to redistribute this "not for profit" 

solar, space and geomagnetic weather discussion and HF radio wave propagation forecast, as long as you redistribute it in its entirety and 

give me credit for it.

Also solar, space and geomagnetic weather forecasting is still an inexact 

science. The forecasts are not official but for educational and hobby 

related purposes only and are subject to human error and acts of God, 

therefore no guarantee or warranty implied. 