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Radio Wave Propagation. Ionosphere Layers. Radio Waves are Bent by the Ionosphere. F1 and F2 Ionosphere Layers Combine at Night. Critical Angle. Ground Wave, Sky Wave and Skip Zone. Great Circle Route. MUF is the highest frequency that allows a radio wave to reach the desired destination.

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Radio wave propagation

Radio Wave Propagation








MUF is the highest frequency that allows a radio wave to reach the desired destination.

Stay below the Maximum Usable Frequency for the best chance for a successful contact.

MUF is affected by all of these:

Path, distance and locations

Time of day and seasons

Solar

MUF: Maximum Usable Frequency


LUF: The lower limit to the range of frequencies that provide useful communications between two stations.

All signals below LUF are absorbed.

When LUF exceeds MUF – No HF radio frequency will support communications along an ionosphere signal path.

LUF: Lowest Usable Frequency


Propagation prediction software 40 meters
Propagation Prediction Software provide useful communications between two stations. (40 Meters)


Propagation prediction software 20 meters
Propagation Prediction Software provide useful communications between two stations. (20 Meters)


Propagation prediction software 10 meters
Propagation Prediction Software provide useful communications between two stations. (10 Meters)


11 Year Cycle – Variation in the sunspot number. provide useful communications between two stations.

We are at the bottom of Cycle 23.

Higher bands like 15 meters and 10 meters are not very good.

Sunspot Number: Daily index of sunspot activity.

SolarActivity


Solar Activity provide useful communications between two stations.

Higher Sunspot Numbers = Better HF Propagation

Above 100 is good


Solar Flux provide useful communications between two stations.

  • SFI (the Solar Flux Index) is radio energy emitted by the Sun.

  • The higher the SFI, the better the propagation.


Three Numbers: provide useful communications between two stations.

SFI= Solar Flux Index .

“A” Index = A daily measurement of the state of activity of the Earth’s magnetic field. Based on yesterday’s K Index.

“K” Index = Readings of the Earth’s geomagnetic field updated every 3 hours.

Solar Flux


Sudden ionosphere disturbance

Caused by a solar flare – ionizes the D Layer. provide useful communications between two stations.

Disrupts lower HF frequencies first.

Most sensitive above 45° latitude.

So, try a higher frequency.

It takes about 8 minutes for UV and X radiation (traveling at speed of light) to reach Earth.

Sudden Ionosphere Disturbance


Geomagnetic disturbance

A dramatic change in the Earth’s magnetic field that occurs over a short time.

Sometimes caused by a coronal mass ejection. These particles can take 20 to 40 hours to reach Earth.

Geomagnetic Disturbance


Geomagnetic disturbance1

Degrades high latitude HF propagation, particularly those latitudes greater than 45 degrees.

Sometimes creates a visible aurora.

Coronal holes also disrupt HF communication.

Geomagnetic Disturbance


Scatter – Forward Scatter and latitudes greater than 45 degrees.Back Scatter


Scatter – Forward Scatter and latitudes greater than 45 degrees.Back Scatter

  • Scatter signals fall between ground wave and skip zone.

  • HF Scatter signals have a wavering sound.

  • Occur most often above the MUF.

  • (Also used on 6 meters with meteors!)


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