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Old 02-03-2011, 05:50 PM
JoelW JoelW is offline
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Join Date: Apr 2008
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Default K Factors above 1.33?

I have been repeatedly told that K Factor tends to vary between 0.66 (2/3) and 1.33 (4/3) due to changes in air density. But the K Factor variable calculation creates a chart with a K value rising beyond 10.

Can anyone explain to me what would cause a higher K factor? Presumably very low air density? Under what circumstances would this happen?

If I run a Variable test and see that the diffraction loss is highest with a K Factor of (eg) 5 or 10, should I use that? I have presumed in the past that this is for some very strange conditions that are not likely to occur.

Would a very high K Factor be something that would only be used in system design under very specific circumstances? Eg in a desert environment?

I normally do paths for 400 & 900 MHz, occasionally 2.4 GHz. No microwave PTP links. These designs are for SCADA systems. Our company does work world-wide, so hard to say where the next one will be.

I have not yet found a book that really discusses this topic well. If you have any recommendations I'd love to hear them!
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Old 02-08-2011, 10:14 AM
BobH BobH is offline
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Default

One book that does go into propagation in some depth is "Microwave Transmission Design Guide" by Trevor Manning and is a book that I find tends to become a "bible". A very readable tome.
I think you will find that under normal circumstances, K factors vary between the 0.66 and 1.33 but anomolies outside this range do occur but I think planning for them would not do a great deal of good and would probably make any link non cost effective by doing so.

BobH
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