[Premium-Rx] Satellite Stuff

[David I. Emery]

On Sun, Apr 02, 2006 at 05:06:01PM -0700, Geoff Fors wrote: 

> This doesn't relate to cell phones, but satellites are passé for long
> distance telephone networks as well.  AT&T abandoned their use of
> satellites for long-lines at the end of 2004, along with the network of
> earth stations, and now uses undersea fiber optic cables.  Hence all the
> carrier telephone test equipment and 4 GHz waveguide plumbing piling up
> on eBay.

	Almost ALL analog FDM-SSB (carrier) plant used for US long
distance telephone communications was rather rapidly phased out in the
1985-1990 period.   Use of satellites for long lines within the USA was
phased out well before that (early 80s).    The domestic long distance
network has been very very close to 100% digital since the very early
90s - with almost the entire network now fiber based with very little
microwave (digital microwave) left (though it is used to reach a few
remote places still).

	And there has been damn little international FM-FDM traffic in
on satellites in the western hemisphere in at least 15 years and  very
little use of satellite international trunking (because of the long
delays) at all as more and more wide bandwidth undersea digital fiber is
installed.    Most satellite capacity in the western hemisphere is used
for video or internet connectivity or digital telephone and data
connections to remote places like oil platforms or cruise ships (and US
Navy ships) (and now airliners in flight) rather than international
telephone calls between major hubs.  (There is more use of satellites in
the Eastern hemisphere for telephone links, though this two is rapidly
being phased out).

	What HAS been going on in the last couple of years is the sale
and complete stripping of all the old AT&T microwave relay sites 
scattered throughout the US.   Up until around 2000 these remained owned
by AT&T and kept in a mothballed state (abandoned in place) with a few
stray microwave paths still used in some places - more recently almost
the entire network of stations has been sold to companies such as
American Tower who in turn has sold the great  majority of them to
various smaller wireless and mobile radio companies and private
individuals.    Most of the new owners have completely stripped the old
AT&T microwave gear and removed the waveguides and horns and converted
the towers to cell or other two way radio use.    Thus a lot of
waveguide and carrier gear has shown up on Ebay and surplus - though
much more of the waveguide from these abandoned sites has apparently
been stolen by gangs of high tech thieves for its copper content.

	But analog FM-FDM-SSB microwave in general (for private use
rather than telephone trunking) has rapidly declined because among other
things parts for installed gear are no longer available as nobody makes
or supports old analog FDM-SSB any more and existing installations are
becoming unmaintainable.    So test gear for maintaining these
FM-FDM-SSB systems such as selective level meters and microwave link
analyzers has become obsolete and is getting thrown out and rescued and
sold on Ebay.

	And indeed, in certain respects some of these old selective
level meters are premium receivers, though usually not with the same
dynamic range and IP specs of real premium receivers.   They do have the
fully synthesized high frequency accuracy and low phase noise LOs,
however...  but often lack any kind of AGC unless modified.   And are
tunable in .1 hz steps compared to 10 or 100 hz for many premium
receivers.

-- 
   Dave Emery N1PRE,  die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."