From: Floyd Davidson <floyd@ptialaska.net>
Newsgroups: comp.dcom.telecom.tech
Subject: Re: Transmission of network TV video in the "good ole days"
Date: 02 Feb 2001 05:19:41 -0900

"Ed Ellers" <ed_ellers@msn.com> wrote:
>Reed Rinn <reedNO@SPAMrinn.com> wrote:
>
>"When N.E.T. began color programming, they installed a
>satellite receiver at our studios.  (We actually beat the local
>commercial stations in obtaining a satellite feed.)"
>
>There was actually a full decade between the two.  NET first
>fed a color program to public TV stations in 1967, with a heavy
>color programming schedule begun by PBS in 1969; PBS started
>installing its satellite system in 1977.  (A number of PBS
>member stations were able to pick up some revenue in the early
>1980s by taping satellite-fed programming and commercials for
>commercial stations that didn't yet have dishes of their own.)

PBS in the late '60s benefited from a huge funding project that put
it right out there on the edge of technology with color facilities.
I don't recall much of the detail, but it had many many wonderful
benefits.  I think Sesame Street was one of those.  Only the top
market commercial network studios had similar capability.

>"I remember going up on the roof to watch the dish; it was
>pointed at a "geostationary" bird that wobbled a few degrees in
>it's orbit. The dish was actually servoed to follow the
>satellite as it wobbled, and its gears and motors were
>constantly grinding as it tracked the bird."
>
>This was necessary because the PBS stations' dishes were so
>large and consequently tightly focused.  Home satellite viewers
>didn't have any trouble receiving the same satellite
>(originally Westar I) with fixed or polar-mount antennas.

And also that was the result of being there early, while the
technology was still bleeding.

Today any given satellite has better power equipment on board,
and hence can have a stronger signal to begin with.  But the
most significant difference has been the steady improvement in
what are called "Low Noise Amplifiers" or LNAs.  That is the first
amplifier into which the signal from the receive antenna is fed.
In the late 1960s such an amplifier was just barely (at a cost
of thousands of dollars) able to function without
generating more noise than the signal from even a large, high
gain, antenna.  Hence almost all satellite receive antennas in
the 1960's and early 1970's had to be so large (to provide more
gain for a bigger signal) that auto-tracking was required.

The reason for larger antennas is the way that increasing the
size of a parabolic antenna increases the signal.  Bigger
antennas concentrate the focus into a narrower beam to get more
gain.  If the whole antenna is pointed into 1 degree of space,
then the satellite has to stay within 1 degree of where the
antenna is pointed, or the signal is reduced.  "Geostationary"
satellites wobble around in a "box", and at 1 degree of beam
width the antenna has to have auto-tracking to maintain a signal.
If the antenna looks at twice as much area, it picks up half as
much signal from any single point source.  So a wider beam width
to cover the entire box where the satellite might be also means
less signal.

By the middle 1970's it was possible to have a bit more power in
the satellite's transmitter.  And LNAs had improved (remember
that solid state devices like transistors had just come into
their own in the 1960s, and microwave devices operating at 4000
GHz were not well enough developed until the early 1970's),
allowing by that time a 6 degree beam width antenna to be used.
That meant 10 or 12 foot antennas would work here in Alaska, and
probably smaller ones at lower latitudes.  And those antennas
have such a broad beam width that they can be peaked on the
satellite no matter where it is in its "box".  By comparison, a
30 foot dish must be aimed while the satellite is in roughly the
"center of the box", and a 60 or 90 foot dish must have
auto-tracking.

Today a Low Noise Amplifier that is *vastly* better than the
ones used even in the mid-1970s when all of this became truly
economically feasible, is relatively cheap.

Another interesting story resulting directly from the advances
in satellite technology made in the late 60's and early 70's was
a proposal that a couple of engineering professors at the
University of Alaska Fairbanks made to the State of Alaska.
They suggested that the state could fund small earth stations in
every village in Alaska, using a 6 meter dish.  The commercial
long distance company that had been formed in 1971 and given a
monopoly, RCA Alaska Communications, screamed and fought it
tooth and nail.  Then Governor of Alaska Jay Hammond had a
Communications Director who had once worked for RCA and had a
personal relationship with management (not necessarily a polite
relationship) forced the project down their throats and got the
project enacted into law by the Legislature.

So, against their best efforts RCA installed what became one
of the showcases to the world of satellite technology for
TV and telecommunications.  For the next several years various
companies and nations trekked to Alaska to see how it worked.
So RCA sold it!  Pacific Telecom Inc kept it  with almost
no improvements until the 1990's!  At that point AT&T bought
it and has revamped most of it with digital systems.

--
Floyd L. Davidson         <http://www.ptialaska.net/~floyd>
Ukpeagvik (Barrow, Alaska)                 floyd@barrow.com