Ham Radio

Friday, March 20, 2009
Spring equinox and its effect on propagation
For all of you living in the Northern Hemisphere today is a great day. Today the Spring Equinox (or Vernal Equinox) is upon us, this is great as it hails goodbye to winter and officially means the start of Spring.

At 11:44 UTC the sun crossed over the Earth’s equator which means longer hours of sunlight for all of us up North! Thanks to the Earth’s tilt 23.4 degree tilt we will now be getting more of the Sun’s rays increasing the temperature (hopefully) and signalling the start of Summer.

The Spring equinox also has a marked effect on propagation. We will now be having longer hours of sunlight. These longer hours mean the sun will be increasing the energy in the ionosphere more than during the winter.

You may have noticed propagation improving over the last few weeks, this is due to the Spring equinox. The Vernal equinox is a particularly good time for HF propagation as on the first day of spring the length of the day and night in both the Northern and Southern hemispheres will be 12 hours each. During both the Spring and the Autumn equinoxes the northern and southern hemispheres both have an even distribution of solar radiation making it the optimum time for DX. As a result of the equinox bands should be more likely to stay open and there should be more reliable propagation paths between the Northern and Southern hemispheres.

Equinoxes are also the time when auroras are most likely to occur (so keep an eye out for Aurora Borealis in the night sky). Caused by solar flares colliding with nitrogen and oxygen atoms in the atmosphere they usually take place in the E and D layers of the atmosphere. Auroras affect both HF and VHF propagation, decreasing the quality of HF signals but opening up interesting possibilities for VHF operators.

For those of you wanting some light entertainment on the subject of auroras and amateur radio you might want to try the 2000 Dennis Quaid film Frequency I’m not sure you’ll be lucky enough to get the kind of propagation found in this film, but at least with Summer now officially on the way propagation might start to improve.

Fingers crossed for some decent solar activity!

de M3TLL
posted by Simon Davison @ 4:52 pm  
4 Comments:
  • At 4:01 pm, Blogger Phaze58 said…

    Seen That film Lou
    of to chase DX se ya

     
  • At 3:48 pm, Blogger The Elusive Loo said…

    It is a good film!

    Good DX

     
  • At 6:25 am, Blogger myles said…

    the bands have been open as usual.
    The Equinox won't change anything.
    WSPR stations are being spotted as normal.
    If a change happens I will be surprised.
    http://wsprnet.org/drupal/

     
  • At 10:05 am, Blogger 2E0HTS Simon said…

    Myles, thanks for the comment, however this post is over a year old (March 09. I would have to say that the bands have most definitely improved since then!

    thanks for the wsprnet link

     
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