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Propagation
What you are looking at below are easy-to-read charts that will tell you at a glance how the bands are doing at a moment's notice. The one with the solid bars displaying directly in a graph how each band is doing. Now, it's up to us to tell you what these these numbers all mean.
Propagation Chart Numbers and Meanings
Propagation Chart Numbers and Meanings
We've all seen the charts. That is, if we're talking about ham or shortwave operators. You look at the graphs and it says that propagation is going to be good, but what do all of those cryptic numbers on the chart mean? You've got questions, we hopefully have answers. Read on, McDuff. :-)
SFI (Solar Flux Index)
SFI (Solar Flux Index)
This is a gauge on the amount of solar particles and magnetic fields that are actually reaching our atmosphere and is indicative on how the solar winds are influencing HF propagation. The higher the number the better for HF communications:
<70 to 79: Very poor
80-89: Low propagation
90-100 : Average
100-149: Reasonably good
>150: Ideal conditions.
High SFI numbers tend not to affect 30-160 meter bands a great deal, however. If you're running a lower powered station, try to take advantage of conditions when it's approaching 150 or more as those events are extremely rare.
SN (Sunspot Numbers)
SN (Sunspot Numbers)
The SN actually counts the number of sunspots seen on the sun's surface. You'll be looking for a big number here. The count can be anywhere from zero to well over two-hundred. If the number is at the very high end, consider switching on your HF radio because these are rare events. The bad news is that if the sun begins to flare, it will substantially reduce propagation. Here are the numbers to look for:
<50: Propagation is likely very poor
50-74: Attenuated
75-99: Average
100-149: Probably better than average
>150: Exceptional propagation
For SN <100, look for the best activity to be centered on 30 to 160 meters and perhaps best at sunset or sunrise.
A further note:
A further note:
Both Solar Flux and Sunspot numbers have to maintain high numbers over a long period to have an effect on propagation. High numbers on a single day will likely not affect propagation very much. A sustained period of high numbers over the course of a week or so will most likely make a difference.
A, Ap, K, and Kp Indexes
A, Ap, K, and Kp Indexes
These numbers are indexes of geomagnetic activity that you should be aware of and can predict where the best bands activity should occur. Instead of going into a long explanation, let's just show the numbers you're look for:
A Index: Propagation on 10, 12, 15, 17, and 20 meter bands. Derived from scaled average of previous 24 hour K-index readings.
1-5: Best propagation
6-9: Average propagation
>10: Poor conditions
Ap Index: Propagation on 30, 40, 80, and 160 meter bands
1-5: Best propagation
6-9: Average propagation
>10: Very poor propagation
K-Index: Propagation on 10, 12, 15, 17, and 20 meter bands. Falling number mean improving conditions and mostly affects northern latitudes and areas of auroral activity. Scale is 1-9.
0-1: Best propagation
2-3: Good propagation
4-5: Average propagation
6-9: Very poor propagation
Kp Index: Propagation on 30, 40, 80, and 160 meter bands.
0-1: Best propagation
2-4: Good propagation
5-9: Very poor propagation
Other Numbers
Other Numbers
X-Ray: NOAA reports these values from A0.0 to X9.9. X-Rays from the sun mostly affects the D-Layer (HF absorption). The letter (A, B, C, M, & X) show the order of magnitude (A is the lowest), and the number defines the level of radiation. This number is updated 8x daily.
304A: This number is loosely correlated to the SFI. It measures the strength of total solar radiation at a wavelength of 30.4 nm (304 angstroms). Updated hourly, it's responsible for about half of the ionization of the ionosphere's F-Layer.
Ptn Fix: The higher the number, the more it primarily affects the ionosphere E-Layer. This measures the density of charged protons in the solar wind. Updated each hour.
Elc Fix: This also affects the E-Layer but instead of charged protons, it detects charged electrons. The higher the numbers (typically over 1000), the more impact it has on the ionosphere. Updated hourly, as well.
N: NOAA reports these values from 0-5. <2-high confidence in auroral measurement, >2 is low confidence. This number is also updated hourly.
VOCAP HF Propagation Tool
VOCAP HF Propagation Tool
Below, we have info from a website generated from a program that has been 50 years in the making from Voice of the World. It's a proven propagation prediction tool for HF. You can find it here: VOACAP HF Online You can also have a look at this live link: VOACAP Quick Guide.
Reverse Beacon Network
Reverse Beacon Network
Below, check out Dave Casler with information about The Reverse Beacon Network. For more info, watch the video below. Then take a quick trip to the Reverse Beacon Network website. The link is under the video.
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