Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 11/08/85; site unccvax.unccvax.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!gamma!epsilon!zeta!sabre!petrus!bellcore!decvax!mcnc!unccvax!dsi
From: dsi@unccvax.UUCP (Dataspan Inc)
Newsgroups: net.space,net.aviation
Subject: Re: "Shadowing" geosync satellites
Message-ID: <397@unccvax.unccvax.UUCP>
Date: Wed, 18-Dec-85 07:49:38 EST
Article-I.D.: unccvax.397
Posted: Wed Dec 18 07:49:38 1985
Date-Received: Fri, 20-Dec-85 03:30:33 EST
References: <441@brl-tgr.ARPA> <605@riccb.UUCP>, <1770@utcsri.UUCP> <6226@utzoo.UUCP> <1360@poseidon.UUCP>
Organization: UNC-Charlotte
Lines: 34
Xref: watmath net.space:4986 net.aviation:2279

> >> Now for the key question: do you call your lawyer when a 747 flies
> >> overhead?  Do you KNOW?

     Is it necessary?  Back in the dark ages (when satellite antennas cost
$2000 and there was no such thing as a 120 degree LNA) we were installing a
satellite system on Interstate-85 in Charlotte, NC.  This earth station turns
out to be right at the end of R/W 5-23 at Douglas Field. I don't know what
the horizontal distance is exactly to the end of 23 but the aircraft on
approach are sufficiently low enough to see small mechanical parts. They
are the usual short-haul stuff (727/737/DC-9/BAC 1-11) flying over (directly)
and cause no problems for TASO Grade 1 downlinking of television.

     However, you can see the effects of the radar altimeter for about 5 sec
after flyby...at the output of the LNA.  It was not visible at the first IF
and has caused our client no problems.

     In the transmit case, I don't know if the high EIRP (typically 5000 w)
would cause the aircraft any problems, or for that matter, the occupants
inside.  However, I believe (and am going to check the dreaded cookie company
rules and regulations) that you would have no standing if you were stupid
enough to put your earth station at the end of a runway, or, for that matter,
between the outer marker and the runway and 10000 feet on either side.
Outside the controlled area (I'm not a pilot, and know very little from doing
numerous broadcast applications) the "footprint" of a 747 wouldn't affect
anything...

     If you can afford an uplink, you can afford a consulting engineer whose
job is to plan for contingencies like this.  The Commission common carrier
bureau is a whole 'nother world from Mass Media, and they can be picky to
the point of trivia.  Has a 747-flyby actually screwed up someone's uplink?

David Anthony
Chief Development Engineer
DataSpan, Inc.