Winstar Comm. (WCII) Message Board

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Technology Stocks : Winstar Comm. (WCII)

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To: Trey McAtee who wrote (3089)	12/9/1997 5:23:00 PM
From: David Krafcsik	Read Replies (4) of 12468

I just dug out my Intro to Radar Systems handbook and pawed through until I found the Atmospheric Attenuation of Microwave signals chart. It turns out that 38 GHz is right in a transmission window between an H20 absorption band at ~23 GHz and an oxygen absorption band at 60 GHz. The one at 24 GHz isn't too bad, maybe 0.2 dB/km attenuation, but the 60 GHz is horrid, with around 10 dB/km atten. Anyways the upshot is that if they went higher in frequency they would have two problems. First if they went much higher than 38 GHz, they would have to skip up past the Oxygen absorption @ 60 GHz up to the 80-110 GHz band. Even then, the attenuation of the atmosphere has still increased from approx. .05 dB/km at 38 GHz to about .1 dB/km. Then, they have the additional problem that it is much harder to generate signals up at the 94 GHz area, which would be an additional expense. The plus side is that the attennas would be smaller, but they are already fairly small, so that doesn't matter. Interestingly, the 28 GHz band that some wireless companies are using are on the trailing edge of the water absorption band, so I would expect them to have more difficulty transmitting through rain than at 38 GHz.

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