[TowerTalk] Snow and rain attenuation

[Bob Nielsen]

There are frequencies where there is a resonance with water molecules  
which causes a quite high attenuation, even without rain or snow.  I  
can't find any data in a brief search, but recall that 54 GHz is one  
of these.  I did find some information which indicates that rain  
attenuation is somewhat proportional to frequency squared.

73, Bob N7XY

On Oct 31, 2005, at 11:37 AM, Robert Chudek wrote:

> Hi Bill,
>
> The rain and snow attenuation seems to always raise this type of  
> question. At the opposite end of the spectrum (440 MHz) where I ran  
> ATV, snow and rain did not have a perceptible influence on the  
> signals either. What did influence the path was foliage. In the  
> winter we could shoot signals through the trees, but in the summer  
> there was severe attenuation. I suspected the issue was the water  
> or sap rising during the growing season.
>
> But that aside, is there a frequency where rain and snow have a  
> significant attenuation due to its presence in the path?
>
> 73 de Bob - K0RC
>
>
> Message: 9
> Date: Mon, 31 Oct 2005 11:12:08 -0800 (GMT-08:00)
> From: Bill Jackson <k9rz at radiks.net>
> Subject: Re: [TowerTalk] Snow and rain attenuation
> To: Dan Hearn <dhearn at wwnw.net>, "Towertalk at Contesting.Com"
> <towertalk at contesting.com>
> Message-ID:
> <31955333.1130785928919.JavaMail.root at mswamui- 
> backed.atl.sa.earthlink.net>
>
> Content-Type: text/plain; charset=us-ascii
>
> Dan,
>
> I work with 6 GHz point to point microwave systems at the  
> railroad.  We do not use heated antennas or radomes.  However, I  
> would recommend you install a dish antenna that includes a  
> fiberglass radome.  This will keep ice and snow from forming on the  
> feedhorn and reflective surface of the dish and will actually lower  
> the amount of wind loading from the antenna.
>
> At 6 GHz, the amount of additional path attenuation due to falling  
> rain/snow in the air at 6 GHz is negligible and should not be a  
> concern.
>
> 73 de Bill, K9RZ
>
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