[TowerTalk] Effective of ground snow on Antenna radiation pattern

[Jim Lux]

At 05:32 AM 1/14/2007, Mike Harris wrote:
>G'day,
>
>| I don't know much about snow properties at HF, but at Ku-band (13.402
>| GHz, to be specific), the dielectric properties change a great deal
>| with temperature and moisture content.  Ice is not particularly lossy
>| or conductive.  Water is very much so.
>
>
>
>As far as I am aware snow and ice is transparent to HF.

Especially if it is very cold.


The AMSR-E instrument on Aqua  (now in orbit as part of the "A-train" 
of earth observing instruments) is also used to evaluate presence of 
ice, but it's a microwave radiometer at frequencies >6 GHz.


The now cancelled Hydros mission was to use an L-band radar (1.26, 
1.41 GHz) to examine the surface water, including freeze-thaw, 
etc.  The radar backscatter varies some 5-7 dB between frozen and 
thawed soil.

A technical paper describing the mission and instrument:
http://hydros.gsfc.nasa.gov/pdf/TGARSHydros.pdf

This paper says that the effect of freeze thaw is greater at L-band 
frequencies than at higher frequencies that have been used before.

Jim, W6RMK