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Author Topic: Effects of extreme Cold air on VHF/UHF transmissions?  (Read 9174 times)
EI4HQ
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« on: February 04, 2014, 07:17:04 AM »

Hi,

Somewhat unusual request; I'm doing some research into radio communications in the Arctic. I've a vague recollection of reading somewhere that the range of VHF/UHF communications can be impacted in conditions of extreme cold air. It is perhaps more likely that such a phenomenon may be the result of extreme temperature inversions that can occur in very cold weather... 

Does anyone have any observations/experiences/pointers to reading on such phenomena?

Thanks
Cormac, EI4HQ
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KB4QAA
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« Reply #1 on: February 07, 2014, 05:57:42 PM »

A temperature inversion, cold low, warmer higher will form a duct extending distances.

Uniform cold temperatures with standard adiabatic lapse rates will have essentially no difference in propagation.

Absolute temperature, whether hot or cold is not the a factor.  The important factor is the lapse rate (temp change with altitude).  Standard atmospheres have an essentially straight slope which presents a uniform density of the air that decrease evenly with increased height.  

Non standard lapse rates (temp changes) will cause air density to vary, causing refraction of the RF, in the same way glass or lenses of different shapes/density refract light.  Example the difference in looking through a window vs. looking thru the bottom of a coke bottle.
« Last Edit: February 07, 2014, 06:05:07 PM by KB4QAA » Logged
EI4HQ
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« Reply #2 on: June 08, 2014, 06:35:07 AM »

Many thanks KB4QAA...
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K9MHZ
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« Reply #3 on: June 11, 2014, 07:43:03 PM »

You know, the guy to contact would be Eric Nichols, KL7AJ.  He lives up there, and knows more about that stuff than the rest of us put together.  Great person too....I'm certain he'd be glad to help.

Good luck.

Brad, K9MHZ

 
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