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To: ftth who wrote (4649)	7/14/1999 11:48:00 PM
From: Frank A. Coluccio	Read Replies (1) \| Respond to of 12823

Dave, that one gets book marked, thanks. If you go over to the GBLX thread you'll see that I covered many of the issues cited in your post, but I wasn't aware of fade margin variances noted therein. While most manufacturers of infra red systems will dutifully place eye warning labels on their goods and make mention of the class of Laser, etc. in their documentation, I've yet to see anyone selling these devices go the extra mile and warn against viewing a transmitter site from a distance through optics (binoculars, telescopes, etc.). The latter have the effect of concentrating even the slightest beams directly onto the eye, which can be extremely detrimental to one's sight. I once stood on the roof of a Lockheed building in their campus outside of San Jose with the owner of a small IR firm called Isher (the company went out of business in '89 when the principal owner passed away). In any event, he was responding to a complaint of foliage which had seasonally emerged, and he went to take a first-hand look before recommending a change of positioning. As we stood atop the roof, I took his binoculars and attempted to view the remote unit which was indeed peeping in and out from behind a tree, but I unwittingly failed to install the necessary filter on the binoculars. The party I was with (the owner of the IR company) smacked it out of my hands, startling me, to say the least. But after he explained why he did it, I felt better for it, and somewhat relieved that I wasn't on top of this building roof with a mad man, and thanked him for it in the end. *CAUTION: DO NOT VIEW INFRARED DEVICES AT ANY DISTANCE THROUGH ANY FORM OF OPTICAL AID SUCH AS BINOCULARS OR TELESCOPES WITHOUT AFFIXING THE APPROPRIATE LENS FILTERS, FIRST!* Regards, Frank Coluccio

To: ftth who wrote (4649)	7/17/1999 11:32:00 PM
From: wonk	Read Replies (2) \| Respond to of 12823

Dave, Frank, all: Regarding the following: ...A fade margin of 15 dB or more is sufficient for reliable transmission at one-half-mile range in heavy rainfall up to 3 inches per hour, in wet snowfall up to 2 inches per hour, and in dry snowfall up to 1 inch per hour. It is also sufficient to penetrate fog at a distance of approximately 110 percent of the actual visibility.... Not knowing laser transmission, I have been looking - and have been unsuccessful - for any authoritative source (IEEE etc) which quantifies attenuation due to precipitation, at various levels of point rain rate, and other atmospherics effects in dB per kilometer. Anyone have a reference source or link? Thanks ww