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What Factors Affect The Range Of HF Communications  
User currently offlineNovice From United Kingdom, joined Aug 2012, 90 posts, RR: 0
Posted (3 years 4 months 1 week 8 hours ago) and read 5093 times:

"The following factors affect the range of HF communication:
1. Transmitter power
2. Frequency
3. Time of the day
4. Season
5. Location
6. Disturbance of the ionosphere"

Why is it the lower the frequency the further they travel, is are am i right here?

'Location'? would that be to do with the ionospheres lengths being different i.e. getting smaller towards the poles?

As with 'disturbance of the ionosphere' i take it the following wiki abstract is what they it is referring to;
"A sudden ionospheric disturbance (SID) is an abnormally high ionization/plasma density in the D region of the ionosphere caused by a solar flare. The SID results in a sudden increase in radio-wave absorption that is most severe in the upper medium frequency (MF) and lower high frequency (HF) ranges, and as a result often interrupts or interferes with telecommunications systems."

From that i don't understand why an increase causes it to absorb the radio wave? as i thought it was this increase in the ions that created the D region, which enabled radio waves or sky waves to reflect from

5 replies: All unread, jump to last
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7884 posts, RR: 32
Reply 1, posted (3 years 4 months 1 week 6 hours ago) and read 5063 times:

You are really going beyond the scope of an aviation forum.

This is a good basic discussion


Some of these images can help understand how it works.


This video is also pretty good


This PDF of a presentation is also pretty good


User currently offlinewoodreau From United States of America, joined Sep 2001, 1190 posts, RR: 7
Reply 2, posted (3 years 4 months 6 days 19 hours ago) and read 5012 times:

Here's another document discussing radio wave propagation. It's what I used in my former career as a navigator.


If the link doesn't work, you can google Pub 9 American Practical Navigator then select Chapter 10 or the whole manual.

[Edited 2013-01-20 04:44:04]

Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
User currently offlineNovice From United Kingdom, joined Aug 2012, 90 posts, RR: 0
Reply 3, posted (3 years 4 months 4 days 15 hours ago) and read 4864 times:

Thanks for the links guys a lot of helpful information in them

User currently offlineapodino From United States of America, joined Apr 2005, 4500 posts, RR: 5
Reply 4, posted (3 years 4 months 3 days 15 hours ago) and read 4788 times:

As an Amateur Radio Operator, I have had to learn a lot about this because we do a lot of stuff on HF in the hobby. I could be here all day writing, but I encourage you to check out ARRL.ORG, which is one of the national associations that deals with Amateur Radio. There are a lot of good resources there that should help answer your questions.

User currently offlinetxjim From United States of America, joined May 2008, 282 posts, RR: 0
Reply 5, posted (3 years 4 months 2 days 15 hours ago) and read 4732 times:

I would also refer you to an old Collins Radio publication, "The Fundamentals of Single Sideband" available here:

Chapter 11 specifically discuss radio wave propagation

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