CO8TW radio propagation page

Solar activity and HF/VHF propagation page.

CO8TW

Information about radio propagation on HF and VHF for Hams and SWL.

(This page will automatically update every 15 minutes.)

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30 days solar cycle activity. Solar activity forecast for next 27 days. Estimated planetary K-index.

Understanding solar indices by Ian P., G3YWX PDF document.(538 kbyte)

http://www.sec.noaa.gov/ftpdir/latest/wwv.txt Actual solar-terrestrial indices.; http://dxcluster.ham-radio.ch/top_50_WWV.html Actual solar-terrestrial indices.; http://www.swpc.noaa.gov/ftpdir/weekly/27DO.txt Predicted Sunspot Numbers and Radio Flux for next 27 days.; http://www.swpc.noaa.gov/ftpdir/weekly/Predict.txt Predicted Sunspot Numbers and Radio Flux for next years.; http://www.swpc.noaa.gov/ftpdir/weekly/RecentIndices.txt Recent Solar Indices of Observed Monthly Mean Values.
http://www.voacap.com/prediction.html VOACAP Online, propagation predictions.

GOES Solar X-ray Flux.

Click here to see the most recent image of the far side of the sun at http://gong.nso.edu/data/farside/

Click here to see the most recent image of the far side of the sun http://soi.stanford.edu/data/full_farside/latest.syn.gif

Click here to see the most recent spherical map of the Sun as it currently appears.

                                   This movie shows a spherical map of the Sun as it currently appears,
                                   formed from a combination of the latest STEREO Ahead and Behind beacon
                                   images. The movie starts with the view of the Sun as seen from Earth, with
                                   the 0 degree meridian line in the middle. The map then rotates through 360
                                   degrees to show the part of the Sun not visible from Earth. The black wedge
                                   shows the part of the Sun not yet visible to the STEREO spacecraft.

Solar X-Rays

Geomagnetic Field

VHF Aurora

144 MHz E-Skip

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K index.

Current solar images.

http://www.swpc.noaa.gov/ftpdir/latest/SRS.txt Solar Region Summary.

Real time solar wind.

Solar wind velocity. Solar wind density.

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Putting it all together

* Higher solar flux levels are generally good for HF
* High K and A indices are generally bad – result in absorption and breakdown of the F region.
* Solar Flux / K index / Solar wind speed and Bz will give you a real-time indication of what bands you should concentrate on.
* Bz going south(-) and an increased solar wind speed (450km/s+) are generally bad news for HF.
* If your signals follow a polar path that cuts through the auroral zone(s) and the K index is high you will have problems.
* Spring/Autumn/Winter are better than Summer as the ionosphere is cooler, denser and MUF is higher during the day. Ionic composition is different in Winter too. But night time MUFs are higher in summer.
* The opposite is true in the southern hemisphere.
* Spring/Autumn good for trans-equatorial contacts.
* As the sun gets higher D layer absorption grows, but the MUF rises, so follow the MUF up during the day and down at night.; * The center of the visible solar disk is the region that has maximum effect on Earth.
: Flares.
: * Check the higher bands for openings for several hours following a solar flare, or a ten-flare event, due to the enhanced E/F layer ionization, possibly temporarily raising the MUF.
* If you’re in a QSO when a major flare causes an HF blackout, it seldom lasts more than an hour. If you’re working a contest, this hint could be useful. Take a break, but don’t QRT!
* X-rays do provide extra ionization to the E/F layers for improved reflectivity and a higher MUF. Exploit the benefits of a solar flare.
* The most damaging effects of a solar flare is actually the arrival of the shockwave 2-3 days later, triggering a geomagnetic storm.
* Often our magnetic field gets very quiet following a strong geomagnetic storm for 12–24 hours. This is an excellent time to work 40–160M due to very low noise levels.
* Use the current K-Index from WWV or the internet to determine the current geomagnetic conditions. The A-Index is actually yesterday’s geomagnetic condition, and does not represent present conditions.
* As soon as the solar storm ceases, HF noise levels become quiet with an elevated MUF, lasting until sundown. Night time conditions on 80-40M can be excellent. The daytime MUF the next day may be elevated as well.
* when the geomagnetic storm subsides. Night time noise levels on 40-80M can be very low.
* The x-rays from flares (class M5.0 or larger) can be intense enough to have a considerable impact on ionospheric radio communications. In some cases, the absorption can be strong enough to completely blackout all radio communications between points more than 3,000 to 4,000 km up to frequencies as high as 10 MHz for a period of between 15 to 30 minutes. Minor absorption can maintain weaker than normal signal strengths for an additional 20 to 30 minutes. These types of major flares are much less frequent than minor M-class flares.

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Aurora (also known as "aurora borealis" or "northern lights") is caused by interaction between the Earth's magnetic field and the solar wind (a mix of charged particles blowing away from the sun). During solar storms, enough of these charged particles make it through to the Earth's upper atmosphere that they interact with the earths natural magnetic field lines. When enough of these particles collide, energy is released in the form of auroral light. In addition to creating a pretty light show (mostly in upper latitudes), radio signals scatter off of these particles and can greatly enhance propagation on 6 meters and above. High levels of aurora can also make HF propagation via polar routes difficult.

Real Time Real Time

Northern Hemisphere Southern Hemisphere

Auroral Activity. Auroral Activity.

Northern hemisphere auroral potential.

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Grey line map - One (click here)

Grey line map - Two (click here)

The grey line is a band around the Earth that separates the daylight from darkness. Radio 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 area as it moves around the globe. This map shows the current position of the grey line terminator.

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Click here to see the total Electron Content. *** 1 TECU = 10E+16 electrons per square meter _____________________________________________________________________________________________________________

Near real time MUF map.

The following map shows Maximum Usable Frequencies (MUFs) for 3000 kilometer radio signal paths. More importantly, the current sunspot number (SSN) and Planetary A-index are updated every 30 minutes on the bottom of this image. Additionally, the grey line position, auroral ovals, and sun position are provided.

Near real time MUF map.

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Near-Real-Time F2-Layer Critical Frequency Map.

The following image is a recent high-resolution global map of F2-layer critical frequencies. This corresponds to the maximum radio frequency that can be reflected by the F2-region of the ionosphere at vertical incidence (that is, when the signal is transmitted straight up into the ionosphere). It is also a map showing the current location of the auroral ovals, the sunrise/sunset terminator and the regions of the world where the sun is 12 degrees below the horizon (which estimates the gray-line corridor where HF propagation is usually enhanced).

This map can be used to determine the frequencies that will always be returned to the Earth. Transmitted frequencies higher than the indicated contours (which are given in MHz) may penetrate the ionosphere, resulting in lost power to space. Frequencies lower than the indicated contours will never penetrate the ionosphere. Lower foF2 values indicate a weaker ionosphere and correspond to regions with lower Maximum Usable Frequencies (MUFs). Higher foF2 values indicate a stronger ionosphere and correspond to regions with higher MUFs.

It is important to remember that these contours refer to the transmitted signals that are vertically incident on the ionosphere. All long-distance communications use signals that are obliquely incident on the ionosphere (that is, the radio signals are passing through the ionosphere at an angle instead of head-on).

Near-Real-Time F2-Layer Critical Frequency Map.

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Near-Real-Time Map of the F2-Layer Height Maximum.

The following image is a recent global map indicating the altitude above the surface of the Earth where the ionospheric electron density reaches a maximum. It is known as the height maximum of the F2 layer (or hmF2) and is given in kilometers above the surface of the Earth. It is also a map showing the current location of the auroral ovals, the sunrise/sunset terminator and the regions of the world where the sun is 12 degrees below the horizon (which estimates the gray-line corridor where HF propagation is usually enhanced).

Near-Real-Time Map of the F2-Layer Height Maximum

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Near real time E layer critical frequency map.

The following image is a recent high-resolution global map of E-layer critical frequencies. This corresponds to the maximum radio frequency that can be reflected by E-region of the ionosphere at vertical incidence (that is, when the signal is transmitted straight up into the ionosphere). It is also a map showing the current location of the auroral ovals, the sunrise/sunset terminator and the regions of the world where the sun is 12 degrees below the horizon (which estimates the gray-line corridor where HF propagation is usually enhanced)

Radio communicators most often do not want their signals to spend very much time in this region of the ionosphere. Signals which are reflected within the E-region spend the greatest time in the E-region and are accordingly attenuated the most.

Signals that exceed the E-layer critical frequency (and are vertically incident) will penetrate the E-region and travel toward the F-regions. Signals that are below the critical E-layer frequency will always be reflected back to the Earth.

Near real time E layer critical frequency map.

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Near-Real-Time Maps of Ionospheric X-Ray Absorption

The following are near-realtime maps of ionospheric absorption produced by solar x-ray activity (solar flares). Enhanced x-ray activity increases absorption on HF radio signal passing through the daylit ionosphere. These maps depict real-time absorption of radio signals (based on current x-rays) on frequencies between 5 MHZ and 30 MHz.

Click on the realtime maps you desire:

5 MHz Absorption Map
10 MHz Absorption Map
15 MHz Absorption Map
20 MHz Absorption Map
25 MHz Absorption Map
30 MHz Absorption Map

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Click here ( http://www.voacap.com/prediction.html ) Professional-grade high-frequency (3-30 MHz) propagation predictions

Click here ( http://www.vhfdx.info/spots/map.php ) to see DX Sherlock 2.0 - QSO real time maps

Click here ( http://www.swpc.noaa.gov/dregion/ ) to see D-Region Absorption Prediction

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Cycle 21, 22, 23 and 24.

Cycle 24 Prediction.

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Click to see 400 year of sunspot observation. _________________________________________________________________________________________________________________________

Also you most to see.

HF propagation: The basics by Dennis J., W1LJ/DL PDF document ( 976 kbyte); Introduction to HF propagation by IPS Radio and space services PDF document (1.28 mbyte); Solar activity and HF propagation PDF document (987 kbyte); Transequatorial propagation PDF document (181 kbyte); http://www.arrl.org/w1aw-bulletins-archive-propagation ARRL propagation bulletin.; http://www.vhfdx.net/spots/map.php VHF/UHF qso real time maps.; http://www.mmmonvhf.de/ Make more miles on VHF.; http://mysite.verizon.net/k9la K9LA propagation tutorial.; http://www.keele.ac.uk/depts/por/28.htm Worldwide list of HF beacons by G3USF.; http://www.keele.ac.uk/depts/por/50.htm Worldwide list of 50 mhz beacons by G3USF.
http://www.ncdxf.org/beacons.html NCDXF beacons.: http://www.qsl.net/w6elprop Propagation software, V2.70 (479 kbytes); http://www.g4ilo.com/ Propagation software. (1.0 mbyte); http://dxfile.free.fr/propag.htm Propagation software. (two programs 2.7 mbyte)

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