novice
Posts: 90
Joined: Tue Aug 07, 2012 2:55 pm

What Factors Affect The Range Of HF Communications

Sun Jan 20, 2013 12:03 am

"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
 
rfields5421
Posts: 5638
Joined: Thu Jul 19, 2007 12:45 am

RE: What Factors Affect The Range Of HF Communications

Sun Jan 20, 2013 1:57 am

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

This is a good basic discussion

http://ecjones.org/propag.html

Some of these images can help understand how it works.

http://www.google.com/search?q=hf+ra...HgBw&ved=0CFMQsAQ&biw=1193&bih=639

This video is also pretty good

http://www.youtube.com/watch?v=YgmvPWRYw3I

This PDF of a presentation is also pretty good

http://www.google.com/url?sa=t&rct=j...QNjxch0G_90A&bvm=bv.41248874,d.b2I
 
Woodreau
Posts: 1197
Joined: Mon Sep 24, 2001 6:44 am

RE: What Factors Affect The Range Of HF Communications

Sun Jan 20, 2013 12:42 pm

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

http://msi.nga.mil/MSISiteContent/St...ticFiles/NAV_PUBS/APN/Chapt-10.pdf

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.
 
novice
Posts: 90
Joined: Tue Aug 07, 2012 2:55 pm

RE: What Factors Affect The Range Of HF Communications

Tue Jan 22, 2013 4:43 pm

Thanks for the links guys a lot of helpful information in them
 
apodino
Posts: 3030
Joined: Mon Apr 04, 2005 2:11 am

RE: What Factors Affect The Range Of HF Communications

Wed Jan 23, 2013 4:37 pm

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.
 
txjim
Posts: 179
Joined: Fri May 16, 2008 1:44 pm

RE: What Factors Affect The Range Of HF Communications

Thu Jan 24, 2013 4:51 pm

I would also refer you to an old Collins Radio publication, "The Fundamentals of Single Sideband" available here:
http://www.collinsradio.org/cca-coll...s/fundamentals-of-single-side-band

Chapter 11 specifically discuss radio wave propagation

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