From: Steve Schear <schear@lvcm.com>
Date: Wed, 16 Sep 1998 10:01:20 +0800
To: brianbr@together.net>
Subject: Re: radio net
In-Reply-To: <199809152029.QAA03672@mx02.together.net>
Message-ID: <v04003a00b2251e9d1bc0@[192.168.229.5]>
MIME-Version: 1.0
Content-Type: text/plain



At 11:41 PM -0400 9/15/98, Dave Emery wrote:
>> On 9/6/98 6:20 PM, Steve Schear (schear@lvcm.com)  passed this wisdom:
>
>	I suspect that the cost of equipment and licensing and regulatory
>compliance of various sorts might make it unpleasant for loosely knit
>groups of private citizens - uplinks require competant installation
>and maintainence to keep them from causing interference to other users
>and various other problems such as RF radiation hazards under control.

Because commercial satellite gear is almost always asembled from several
vendors to form a station, and because it can be assembled in many ways and
is invariably done so by professionals, there are no U.S. satellite
equipment regulations for such gear.

>
>	On the other hand, satellites are crawling with little signals
>transmitting streams of data or voice or music to groups of receivers
>scattered over wide geographic areas, so the econmics aren't prohibitive
>for people who have some real need...
>

Surplus gear is pleantiful for those who know where to look. The hardest
part is building the SS mod/demod and that's pretty straight forward for
any competent RF engineer.

If low bandwidth links can suffice, the very large spread codes (such as
those used by GPS) can be used to place the covert channel well below the
noise floor.  GPS uses a whopping 63dB of code gain.  This in turn means a
small earth station with low power (cheap) transmitter can suffice.  I
would be surprised if you could use a backyard or even DirectTV antenna.

--Steve

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