Solar activity and HF/VHF propagation page
Information about radio propagation on HF and VHF for Hams and SWL.
(This page will automatically update every 15 minutes.)
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Understanding HF Propagation VE2XIP PDF document.(694 kbyte)
Understanding solar indices by Ian P., G3YWX PDF document.(538 kbyte)
Fundamentals of Ionospheric Propagation.
Actual solar-terrestrial indices.
At 18 minutes past the hour, radio stations WWV and WWVH
broadcast the latest solar flux number, the average planetary A-Index and the latest mid latitude K-Index. In addition, they broadcast a
descriptive account of the condition of the geomagnetic field and a
forecast for the next three hours. You should keep in mind that the
A-Index is a description of what happened yesterday. Strictly speaking, the K-Index is valid only for mid latitudes.
http://www.swpc.noaa.gov/products/3-day-forecast 3 day forecast.
ftp://ftp.swpc.noaa.gov/pub/weekly/27DO.txt Predicted Sunspot Numbers and Radio Flux for next 27 days.
http://spawx.nwra.com/spawx/list27do.html Predicted Sunspot Numbers and Radio Flux for next 27 days.
activity forecast for next 27 days..
http://cluster.f5len.org/sun/dsd.png Last 30
days daily solar data.
ftp://ftp.swpc.noaa.gov/pub/weekly/Predict.txt Predicted Sunspot Numbers and Radio Flux for next years.
Recent Solar Indices of Observed Monthly Mean
Online, propagation predictions.
Pass solar cycles.
Click here to see the most recent
image of the far side of the sun at http://gong.nso.edu/data/farside/
|| VHF Aurora |
144 MHz E-Skip
Current solar images.
Solar wind velocity. Solar wind density.
Putting it all together
* Higher solar flux levels are generally good
* 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.
- * 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
* 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
* 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.
line map - One (click here)
Grey line map - Two (click here)
Grey line map - Three (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.
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.
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.
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
____________________________________________________________________________________________________________ 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.
Near-Real-Time Maps of Ionospheric
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
Tropospheric Propagation Forecast
Worldwide refractive index forecasts
Click here (
http://www.voacap.com/prediction.html ) Professional-grade
high-frequency (3-30 MHz) propagation predictions
https://www.n5pa.com/ham.vhfuhf.php ) VHF/UHF qso real time maps. Click here (
https://www.dxmaps.com/spots/mapg.php?Lan=E&Frec=TI2&HF=S ) to see DX Sherlock 2.0 - QSO
real time maps
Click here (
https://www.swpc.noaa.gov/products/d-region-absorption-predictions-d-rap ) to see D-Region Absorption Prediction
21, 22, 23 and 24.
Solar Cycle radio flux progression. _________________________________________________________________________________________________________________________
Click to see 400 year of sunspot observation.
Click to get an Azimutal map.
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
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.
Propagation real time.
VHF/UHF qso real time maps.
more miles on VHF.
- http://mysite.verizon.net/k9la K9LA propagation tutorial.
https://www.qsl.net/wj5o/bcn.htm 28 Mhz beacon list.
- 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.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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