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brainy
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12dB Signal decrease because of snow?

Sat Jan 21, 2012 2:24 pm

Hi there,

we have a 2.5km link with a OmniTIK and a SXT (5GHz, both chains, long guard interval). Everything is working well, signal strenght is -69db. LOS is ok, fresnel is not 100% free (there are trees).

Since yesterday it's snowing and the signal is -81db now ... is it normal that the signal will decrease 12dB just because of snow?

Someone has expirience with that?

Thanks for your answers.

Regards
Joerg
 
rodolfo
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Re: 12dB Signal decrease because of snow?

Sat Jan 21, 2012 2:29 pm

it depends how much it snows.
more probabiliy you have snow or ice in front of one antenna.
rodolfo
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tjc
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Re: 12dB Signal decrease because of snow?

Sat Jan 21, 2012 6:55 pm

If you think about it, weather radar works by getting reflections from rain and snow. The heavier it is the more reflection and absorption there is. So you have to expect some signal loss from precipitation.

Also as rodolfo points out, unlike rain, snow accumulates, on your antennas, on the trees that are in your line of sight, ... I'm sure that there are tables for this somewhere, in a radio engineering handbook or the like, that will give you the attenuation factor for a km of forest (brush, light forest, heavy forest, snow covered forest, ...).
 
InoX
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Re: 12dB Signal decrease because of snow?

Sat Jan 21, 2012 7:43 pm

15-25dbi loss from the snow today, lucky me most of them have better than -50
 
syadnom
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Re: 12dB Signal decrease because of snow?

Sun Jan 22, 2012 7:43 pm

I had a significant storm in my area and I lost just 1-2dBm *BUT* the snow blocked a lot of noise and my SNR gain 10dBm+ on many of my sectors!

My shortest link is 1/3 mile (2 nanobridges ptp) and it got 4dBm improvement in signal
My average link is about 1.5 miles. Performance on this 1ft+ snowfall day was excellent.
 
bac522
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Re: 12dB Signal decrease because of snow?

Mon Jan 23, 2012 9:03 pm

Snow itself will not attenuate the signal for the frequencies beings used. My guess is snow collecting on the trees is interfering with your signal. I bet you could correlate a continual drop in signal as snow depths increased.

Also, have you been able to look at the antenna's to ensure no buildup of ice/snow?

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