Friday, November 26, 2010

Lesson 12: General Class Exam Course G3A

This is lesson 12 and the G3A questions.  Here we are dealing with sunspots and geomagnetic disturbances as well as there impact on radio wave propagation.  Especially in dealing with HF frequencies, the solar cycle and the rest of the sun's behavior has a big impact on propagation, both good and bad.  It is part of the environment that you will need a fairly good understanding of if you are hoping work the HF frequencies.  The lesson is fairly straight forward, but there are a few things you will need to know.

-The average sunspot cycle is 11 years.
-The sun's rotation is 27 days long.  If you are having good propagation on 10m, then you might need to wait until the sun does a complete rotation before you find that sweet spot again.
-It takes 8 minutes for X-ray and ultraviolet radiation to reach the earth from the sun.
-It takes 20-40 hours for the impact of charged particles expelled by coronal Mass ejections to impact the earth's magnetic field.  These are carried in the solar winds.
-Sunspots are good for HF propagation especially above 20 MHz.
-Geomagnetic disturbances are bad for HF propagation, especially in regions closer to the poles where you can usually see the northern and southern lights.  This does not necessarily mean they are bad for VHF propagation.
-The K-index in a short term prediction of the stability of the earth's magnetic field.
-The A-index is a long term prediction of the stability of the earth's magnetic field.

Focus on the above and this lesson will be easy.



  1. So far this is the worst test to study for, and try to memorize. The only way I can describe this chapter is to say the info is choppy. It does not flow well. But I do appreciate that you have the study guide for the tests. It would be much worse trying to study with just the book. With your help this whole thing is much more palatable. Thank you

  2. This is one of those subjects that I had a tough time with because I had nothing to relate it to. I still had more issue with the RF circuit sections, but there is a lot of memorization in this lesson. Good luck! let me know how it goes. 73! -Andy

  3. um... Andy? when r u going to update this?

    Thank You
    T. H.