Local & National meteorological and propagation data (+ theory)
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Current Wx for Mid-Suffolk, United Kingdom - Home of GØFEA
Sunrise & sunset for Mid-Suffolk, United Kingdom
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7 Day Forcast for Mid-Suffolk, United Kingdom
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Latest Infa-Red Satellite Images
Latest Visual Satellite Images
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UK Windspeeds
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UK Lightning - refreshed every 60 minutes (hit F5 to refresh)
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UK Tempratures
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UK Weather overview
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METAR Weather Conditions for RAF Wattisham (EGUW) Mid-Suffolk
Check with airfield and AIS prior to using for flight information
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Shipping Forcast / Weather Conditions for UK
Check with the Met Office prior to using for sailing information
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Propagation information- Click dials on or graph for detailed explaination of results
| VHF Aurora : |  |
| 144 MHz Es in EU : |  |
| 144 MHz Es in NA : |  |
| Solar X-rays : |  |
| Geomagnetic Field : |  |
| Estimated Kp : |  |
Updated every 5 minutes
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Modes of radio propagation
The three main modes of propagation of electromagnetic waves are:
(a) ground (or surface) wave
In ground-wave propagation, the radiated wave follows the surface of the earth. It is the major mode of propagation for frequencies up to about 2MHz. Attenuation of the ground wave increases very rapidly above 2MHz and it may extend for only a few kilometres at frequencies of the order of 15- 20MHz. At very low frequencies the attenuation decreases to such an extent that reliable world-wide communication is possible at all times. The ground wave is not so affected by atmospheric effects or time of day as other modes, particularly at frequencies below about 500kHz.
(b) ionospheric wave (sky wave)
Ionospheric propagation is the 'refraction' (ie bending), and hence reflection, of radio waves back to earth by layers of ionised gases. It is the normal mode of propagation over the frequency range of about 1MHz to 30MHz.
(c) tropospheric wave.
This is the major mode of propagation over long distances (ie beyond the line-of-sight range) at frequencies above about 50MHz.
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The Earth's atmosphere & its importance to Ham Radio
The Earth's atmosphere is a layer of gases surrounding the planet Earth that is retained by the Earth's gravity. There is no definite boundary between the atmosphere and outer space. It slowly becomes thinner and fades into space. It is genrally acepted that there are five different atmospheric layers (ordered highest to lowest, the ionosphere is part of the thermosphere):
Exosphere: from 500 – 1000 km (300 – 600 mi) up to 10,000 km (6,000 mi), free-moving particles that may migrate into and out of the magnetosphere or the solar wind.
Ionosphere: the part of the atmosphere that is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. It is located in the thermosphere and is responsible for auroras.
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The Ionosphere & Ham Radio
The ionosphere represents less than 0.1% of the total mass of the Earth's atmosphere. Even though it is such a small part, it is extremely important, especially to the radio ham! The upper atmosphere is ionized by solar radiation. That means the Sun's energy is so strong at this level, that it breaks apart molecules. So there ends up being electrons floating around and molecules which have lost or gained electrons. When the Sun is active, more and more ionization happens. Different regions of the ionosphere make long distance radio communication possible by reflecting the radio waves back to Earth. It is also home to auroras.
The Ionosphere is broken down into the D, E and F regions. The breakdown is based on what wavelength of solar radiation is absorbed in that region most frequently.
The D region is the lowest in altitude, though it absorbs the most energetic radiation, hard x-rays. The D region doesn't have a definite starting and stopping point, but includes the ionization that occurs below about 90km.
The E region peaks at about 105km. It absorbs soft x-rays.
The F region starts around 105km and has a maximum around 600km. It is the highest of all of the regions. Extreme ultra-violet radiation (EUV) is absorbed there.
On a more practical note, the D and E regions reflect radio waves back to Earth. Radio waves with shorter lengths are reflected by the F region.
The highest frequency at which a signal aimed straight up at the ionosphere is reflected back to earth is called the maximum useable frequency (MUF) or critical frequency. Frequencies above this will pass through the ionosphere, except at shallow angles where the wavefront is bent back down towards the earth. The peak value of the MUF generally occurs between 1000 and 1600 hours.generally peak values are much higher at sunspot maximum than at the sunspot minimum. Peak values are much higher in the winter than in the summer. There is a much larger variation in the MUF over the day in the winter than in the summer. Around the sunspot maximum, the MUF may exceed 50MHz for short periods, but at the minimum it rarely exceeds 25MHz.
Sporadic E or Es is an unusual form of radio propagation utilizing characteristics of the earth's ionosphere. Whereas most forms of skywave propagation use the normal and cyclic ionization properties of the ionosphere's F region to refract (or "bounce") radio signals back toward the earth's surface, sporadic E propagation bounces signals off of smaller "clouds" of unusually ionized atmospheric gas in the lower E region (located at altitudes of approx. 90 to 160 km). This occasionally allows for long-distance communication at VHF and UHF frequencies not usually well-suited to such communication.
The variability in distance depends on a number of factors, including cloud height and density. Maximum Usable Frequency (MUF) also varies widely, but most commonly falls in the 27–110 MHz range, which includes the FM broadcast band (87.5–108 MHz), and the amateur radio 10 and 6 metre bands. As its name suggests, sporadic E can happen at almost any time, but it does display seasonal patterns. Sporadic E activity peaks predictably in the summertime in both hemispheres. As my log shows sporadic E has been most noticeable in mid-to-late June, trailing off though July and into August.
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Global maps of ionospheric total electron content (TEC) are produced in real-time (RT) by mapping GPS observables collected from ground stations. These maps are produced to test real-time data acquisition, monitoring facilities, and mapping techniques. The RT TEC mapping can provide accurate ionospheric calibrations to navigation systems.
These maps are also used to monitor ionospheric weather,and to nowcast ionospheric storms that often occur responding to activities in solar wind and Earth's magnetosphere as well as thermosphere.
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Tropospheric Ducting
The speed of a radio wave in the atmosphere is determined by the dielectric property of the air. This property depends on the pressure, tempertaure and humidity of the air. In general as we move upwards through the atmosphere the pressure decreases and temperature falls. This means that the dielectric property changes with height and allows a slight increase in the speed of a radio wave as we move upwards through the atmosphere. This in turn means that if a radio wave moves away from the earth at an angle less than 90 degrees, then the upper part of the wave travels faster than the lower part. Therefore even under normal conditions this can in effect bend, or refract, the wave back down to earth. The normal rate of change of dielectric constant with height refracts the wave so that it follows a curved path of about 1.3 times the radius of the earth. Therefore, we typically can receive signals which are 1.3 times further than we can see by line of sight.
Tropospheric ducting occurs when we get a sharp rate of change in the dielectric constant as we move upwards through the atmosphere. This occurs when we get a rapid increase of temperature and arapid decrease in humidity (dew-point) with height.
Under these conditions we now have the radio wave bent back towards the earth. However, the radio wave can then reflect back of the earth and become refracted again to return earthwards once more. This can sometimes occur a number of times with little attenuation but some fading. The result can be long distance reception of radio waves that would normally have been far beyond the radio horizon.This is not to be confused with skip these signals are not bouncing of the ionosphere but rather traveling in ducts several hundred feet above the ground.
Typical conditions required for a good duct to occur are:
- An increase in temperature by 3C or more per 100ft.
- A rapid decrease of RH (dew-point) with height.
The depth of the duct required for varying wave-lengths is:
- 50ft for wavelengths around 3cm (approx. 1000MHz)
- 600ft for wavelengths around 1m (approx. 300MHz)
Typical meteorological conditions which can be favourable for ducting are:
- Warm dry air over a cooler surface, especially a cool sea
- Surface cooling under clear skies overland
- Anticyclone (high pressure) or developing high pressure ridges with a cold surface
- Sea breezes undercutting warm air overland
- At fronts with a strong thermal contrast
- In cold downdraughts associated with cumulonimbus clouds (indicated by heavy showers or thunderstorms)
To decide wether there may be potential for ducting then first consult the Met Office forecast or the data on this site. If they are showing hints of high pressure building or a weak ridge crossing the area then there could well be potential.
________________________________________________________________________________The Sun and Ham Radio
The Sun exhibits sudden releases of energy, most frequently observed events include solar flares. Solar flares are essentially huge explosions on the Sun. Solar flares emit huge bursts of electromagnetic radiation, including X-rays, ultraviolet radiation, visible light, and radio waves. Solar flares are most common during times of peak solar activity, the "solar max" years of the sunspot cycle.
The number of sunspots seen on the "surface" of the Sun changes from year to year. This rise and fall in sunspot counts is a cycle with the length of a cycle at about eleven years, on average.
A peak in the sunspot count is called "solar maximum" (or "solar max"). The time when few sunspots appear is called a "solar minimum" (or "solar min"). An example of a recent sunspot cycle spans the years from the solar min in 1986, when 13 sunspots were seen, through the solar max in 1989 when more than 157 sunspots appeared, on to the next solar min in 1996 (ten years after the 1986 solar min) when the sunspot count had fallen back down to fewer than 9.
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Grey Line Map
To update map press "F5"
The "grey line" is a band around the Earth that separates daylight from darkness. Propagation along the grey line is very efficient. One major reason for this is that the D layer, which absorbs HF signals, disappears rapidly on the sunset side of the grey line, and it has not yet built upon the sunrise side. Ham radio operators and shortwave listeners can optimize long distance communications to various areas of the world by monitoring this band as it moves around the globe.
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