Radio propagation 101

Our Sun: Good guy or bad guy? Radio Propagation Radio Propagation 101101

As it turns out, the sun is a

mixture of both for Amateur radio.

Lets talk about the sun first!

NASA Solar images NASA Solar images on Jan 23 – 2012on Jan 23 – 2012

Cycle 24 due to peak Cycle 24 due to peak early 2013. There is early 2013. There is

plenty of daily plenty of daily sunspot activity at sunspot activity at

presentpresent

SunspotsSunspots Sunspots are temporary dark spots that appear on the surface of the Sun.

Sunspot temperatures are at 3000–4500 K (2727–4227 °C),while the surrounding sun activity is at about 5,780 K.

Being colder sunspots appear darker. Isolated, they would be brighter than an electric arc.

Sunspots expand and contract as they move across the surface of the Sun and can be as large as 80,000 Km (50,000 mi) in diameter, making the larger ones visible from Earth without the aid of a telescope.

SSN & SSN & SFISFI – They are not the same – They are not the same

Sun Spot Number

Increased sunspot numbers indicate increasing iononizing radiation of our ionosphere. They vary from zero to over 200 during the peak of the 11 year cycle.

Solar Flux Index

This is a measurement taken of radio signals taken from the sun at 2800 Mhz (10.7 Cm)

Solar Flux values range from 60 (No sunspots) to 300

Sunspot Groups

What the Solar Flare Numbers mean

Magnetic & X-Ray Sun RadiationMagnetic & X-Ray Sun Radiation

Geomagnetic Storms can be

your Friend!

What is the “A” Index and “K” Index?What is the “A” Index and “K” Index?

““A” Index A” Index

““K” Index?K” Index?

The A Index describes the Geomagnetic conditions for the past 24 hours.

The K Index describes the Geomagnetic conditions for the past 3 hours.

How do we How do we know what the know what the sunspot sunspot activity is activity is doing daily?doing daily?

These These updated updated charts are on charts are on must amateur must amateur radio websitesradio websites

Realtime Sunspot ChartsRealtime Sunspot Charts

The Indexes can change rapidlyThe Indexes can change rapidly

Geomagnetic Storm WarningIts coming at you!!!

Where are we heading?Where are we heading?

Sunspots were rarely observed during the Maunder Minimum in the second part of the 17th century (approximately from 1645 to 1715). This coincides with part of a period of cooling known as the Little Ice Age.

Sunspots quickly rise and more slowly fall on an irregular cycle of 11 years, For example, from 1900 to the 1960s the solar maximum trend has been upward. From the 1960s to the present is slowly edging downwards.

Sunspot Cycles – Every 11 YearsSunspot Cycles are Notoriously Difficult to Accurately Predict. 

Solar physicists believe that the speed of a massive circulating current of hot plasma within the Sun predicts the amplitudes of sunspot cycles approximately twenty years into the future. In the years prior to 2006 that speed had become lower than ever before observed.

The National Center for Atmospheric Research predicted Cycle 24 would be intense. NASA predicted Cycle 25 will be extraordinarily weak. The NCAR prediction for Cycle 24 is shown above in pink. NASA's Cycle 24 and 25 predictions are shown in red.

Bugger!

The Boffins got it wrong!!!!

Cycle 24Cycle 24

Pathetic Cycle 24 on it’s way to 2020Pathetic Cycle 24 on it’s way to 2020

How Does the Sun Affect our Ionosphere?How Does the Sun Affect our Ionosphere?

Ionospheric D LayerIonospheric D Layer

Ionospheric E LayerIonospheric E Layer

Ionospheric F LayersIonospheric F Layers

Layer HeightsLayer Heights

Ionized Ionospheric LayersIonized Ionospheric Layers

It is all VERY confusing!It is all VERY confusing!

How does Radio Propagation work for How does Radio Propagation work for us during the day and during the night?us during the day and during the night?

Answer: Very well indeed! Answer: Very well indeed!

It all depends on the Sunspot activity It all depends on the Sunspot activity and the time of day or nightand the time of day or night

This is how it works ….........This is how it works ….........

Know How the Layers Work and You will Work DX

Angle of Radiation -Verticals Rule?Angle of Radiation -Verticals Rule?

Angle of radiation is not just a theory… Angle of radiation is not just a theory… It’s real – if you want to work DXIt’s real – if you want to work DX

High angle of radiation – Little or no reflection and High angle of radiation – Little or no reflection and no DXno DX Low angle of radiation – Good reflection and you work Low angle of radiation – Good reflection and you work DX!DX!

Propagation Terms 1 Propagation Terms 1

Ground WaveAre signals that travel on the surface of the earth for short distances

SkywaveAre signals that reflect off the Ionosphere layers. It is the primary mode of long distance communication.

AbsorptionThe D and E layers absorb signals below 4 Mhz during the day

Crit ical FrequencyThe highest frequency at which reflections are returned to earth from a vertical incidence

Propagation Terms 2Propagation Terms 2

Sporadic E SkipWhen the E layer becomes highly charged permitting reflection of signals up to 200 Mhz for a few minutes to a few hours

Tropospheric DuctingWhere waves get trapped between layers and goes long distances. Usually happens over water. Wonderful news for 6M addicts!

Wave Angle The angle at which radio waves leave the earth and reflect off the Ionosphere and back to earth. The angle determines the skip distance

FadingFading happens when signals return to earth by two or more separate paths and cancel each other out. Aircraft, Mountains and ionospheric layers may also reflect part of a signal while the other part of the signal takes a more direct path

Propagation Terms 3Propagation Terms 3

MUF (Maximum Useable Frequency)

The MUF varies with solar activity and time of day and is thehighest frequency that will reflect off the Ionosphere. If the frequency used is too high, it will pass through the layersand disappear into space. e.g The 24Mhz – 28Mhz example

IonizationThe ionization level of the ionosphere reaches it’s minimum just before sunrise

The GraylineThat hour at Sunrise and at Sunset when the DX magic happens!

The Grey line is RealThe Grey line is Real

How the Grey line worksHow the Grey line works

SV3AQR Beacon on 28,123 Mhz. Note the 10Db increase at the beacon's duskNot every band, location or terminator path behaves the same way.

Signal strengths along the Grey LineSignal strengths along the Grey Line

Understanding Radio Propagation is a bit like

A blind man in a dark cellar searching for a black cat that isn't there.

It's a highly nebulous process!

That damned cat is here somewhere!

Software that will help you work the rare ones

W6EL Propagation Prediction program: It’s free and will tell you when there may be a path opening to where you want your signals to go.

DX Atlas: This program will tell you everything about the actually path of your signal. Better still, it will tell you the exact time you will have to work “The Gray Line”

Aids ( No, not those aids! ) Aids ( No, not those aids! )