On May 9, 11:07 am, AF6AY wrote:
"Mike Andrews" wrote on Tue, 8 May 2007 11:11:15
EDT:





On Tue, 8 May 2007 03:15:51 EDT, BNB Sound wrote

The first chapter of the "Collins Sideband Book" by Pappenfus,
Bruene, and Schoenike shows an AT&T SSB map with direct
and switched links to worldwide locations, circa 1960. I count
about 122 stations on that map worldwide. Considering that each
commercial SSB circuit of the time could carry two voice and
eight TTY channels simultaneously, that's fairly large. On the
other hand the service was 24/7 and rather routine, not much
emotion-raising (except to the users of such services).

does much if any of this survive to your knowledge?

On May 9, 9:02 am, an old freind wrote:
On May 9, 11:07 am, AF6AY wrote:
"Mike Andrews" wrote on Tue, 8 May 2007 11:11:15
EDT:

On Tue, 8 May 2007 03:15:51 EDT, BNB Sound wrote
The first chapter of the "Collins Sideband Book" by Pappenfus,
Bruene, and Schoenike shows an AT&T SSB map with direct
and switched links to worldwide locations, circa 1960. I count
about 122 stations on that map worldwide. Considering that each
commercial SSB circuit of the time could carry two voice and
eight TTY channels simultaneously, that's fairly large. On the
other hand the service was 24/7 and rather routine, not much
emotion-raising (except to the users of such services).

does much if any of this survive to your knowledge?

Not a great deal of it is publicized so it is hard to say. Most of
the government and military HF stations have changed from
massive terminals to much smaller ones for specific agencies.
Those can be seen in websites carrying SHARES information.
The government conversion to ALE techniques has changed
the nature of stations' operations and reduced the need for
large stations with fixed wire antennas.

The commercial communications world has gone over to
(largely) fiber-optic, extremely broadband carriers for
thousands of voice circuits, hundreds of data circuits, and
dozens of video-audio circuits on one routing...plus the
communications satellite transponder relay services. Note:
at present - and for several years - all the available slots in
the geosynchronous orbit have been filled by commsats.
Note: Much of the underwater cable service has been or
will be soon replaced by "pumped" (self-amplifying) fiber-
optic cable.

Communications such as ARINC stations for relaying HF
from air carriers on long routes still exist in the same number.
So do the private-boat, commercial boat HF relay services.
The availability of HF communications for small stations in
commercial work has caused a shift from reliance on the
bigger mass-communications carriers to individual company
stations.

Yes, one can still hear "other" radio signals outside of the
ham bands. There still exist the strange hum-roar of 12 KHz
commercial SSB here and there on HF but those are far less
numerous than they were three to four decades ago. There's
lots more 'new' sounds of all the various TORs that "others"
use on HF and, once in a while, a rare CW signal. :-)

Thousands of old HF stations for non-ham use have been
closed down worldwide and equipment dismantled or just
junked. Some of the USA transcontinental microwave (FM)
long-distance relay system are still in use and up (visible
to anyone driving cross-country) but fiber-optics and very
high-speed digital time-multiplexed carrier services carry
much of the long-distance telephone signals if not relayed
via commsats. Such is longer-lived and more reliable.

It's difficult for many to reconcile the changes that have
happened in communications in just a half century but
that's how it went down. On a more consumer-oriented
basis, the broadcasting industry is generally wondering
what will become of all those old analog TV transmitters
after the transition to HDTV in the USA. There's no easy
answer for that, either.

73, Len AF6AY

On Wed, 9 May 2007 15:23:30 EDT, AF6AY wrote:

On a more consumer-oriented
basis, the broadcasting industry is generally wondering
what will become of all those old analog TV transmitters
after the transition to HDTV in the USA. There's no easy
answer for that, either.

Do not confuse digital television (DTV) with high definition TV (HDTV)
which is a subset of DTV. All TV stations will be required to use DTV
but the use of HDTV is optional.

As far as the transmitters go, in general they are being junked
because most of them are near the end of their useful lives and are
held together by duct tape and baling wire in anticipation of the
transition.

73 de K2ASP - Phil Kane
Life Member - Society of Broadcast Engineers

Phil Kane wrote on Sun, 27 May 2007
23:00:15 EDT:
On Wed, 9 May 2007 15:23:30 EDT, AF6AY wrote:

On a more consumer-oriented
basis, the broadcasting industry is generally wondering
what will become of all those old analog TV transmitters
after the transition to HDTV in the USA. There's no easy
answer for that, either.

Do not confuse digital television (DTV) with high definition TV (HDTV)
which is a subset of DTV. All TV stations will be required to use DTV
but the use of HDTV is optional.

I made an "aside" for comparison and haven't confused anything.
Firstly, DTV isn't about using HF spectrum...I am very aware of that.
The transmitters for television represent a sizeable capital
investment by broadcasters. I am aware of the complaints of the
broadcast industry (pro and con) during the entire time of the "Grand
Alliance" testing that led to the eventual DTV broadcasting format
that went into broadcasting regulations. It's been years since I
"rode gain" at a control console or "took" a particular camera or tape
unit, but I do
know something of the MPEG video transport format even though it
generally gives me considerable confusion every time I've studied
it. :-)

The MPEG video transport format can accommodate four different pixel
arrangements and DTV receivers are supposed to be built to decode all
of them automatically. That video format includes the old-style
analog format (converted from analog to digital) on up to the High-
Definition TV which is considered by most consumers as "wide screen
TV." The DTV transmitters themselves handle the entirety of the video
format sent up from the studios,including the quadraphonic sound, text
for hearing impaired, and whatever else the studio central control
sticks in there.

In the old TV transmitter arrangements of any appreciable power, they
were almost always TWO, one for video (AM sorta SSB called "vestigal
sideband"), one for audio (FM) with a Diplexer (passive filter) to
connect
both to the same wideband antenna. The DTV transmitter is a single
one since ALL of the modulation information is conveyed by it, no
"extra" one for sound, seldom any need for an external filter, let
alone
a diplexer. The internal design of the DTV transmitter HAS to be
different than either the AM video or FM aural transmitters by nature
of the modulation mode. But, that DTV transmitter can handle ANY of
the video transport formats automatically. Whether the TV station
central engineering sends old NTSC video converted to "low grade"
digital format or has gone all-out to run everything in "high
definition"
doesn't bother the DTV transmitter. The end result for conversion to
DTV was a replacement of the transmitters (old) by one new one.
Draconian for the broadcasters but visual and audible pleasure for
millions of consumers receiving the DTV.

As far as the transmitters go, in general they are being junked
because most of them are near the end of their useful lives and are
held together by duct tape and baling wire in anticipation of the
transition.

I disagree with that "junk" figurative phrasing. Here in Los Angeles,
there is one central TV (and most FM) broadcast transmitter site,
Mount Wilson. It's been a few years since I was up there but all the
stations (7 on VHF, 4 on UHF) had good, long-lasting transmitters.
At the time KTLA (ch. 5) was beginning to convert to DTV; they were
a pioneer broadcaster in L.A. and this year is their 60th anniversary
here. Both studio and transmitter sites have excellent equipment and
their DTV signal is absolutely HDTV. Their morning show content
is, in my view, JUNK, but that is CONTENT, having nothing to do with
equipment or signal quality...a personal critique.

What used to be a TV "leader" in quality of equipment, NBC (ch. 4)
under the 'general's" eye of RCA, hasn't fully converted to HDTV in
their studios. NBC evening news is HDTV but local news is still
narrow TV. NBC is owned by General Electric and "RCA" exists solely
as a brand name now. I think...haven't kept up on the mergers and
acquisitions of large corporations lately. :-)

TV is above 30 MHz, definitely not in the HF spectrum. However the
type and kind of modulation carried by any transmitter will determine
whether or not it will be "junked" for a new replacement, NOT it's
supposed "held together by tape and bailing wire." If hams could run
4 KW PEP SSB on HF (not in the USA) then the ages-old Western
Electric LD-T2 SSB transmitter would be a great surplus bargain for
them...Class A stages up to the PA which is AB_2, push-button QSY
to any one of 10 pre-tuned frequencies. Problem is, the SSB format is
12 KHz wide and has internal frequency multiplexing for four 3 KHz
audio inputs combined for the output SSB modulation. A no-no for
amateur radio use, even if well-designed after WW2 by WE. Too much
modification required to fit the "tranditional" and technical specs
even
if a superb design for its intended use. That was the general point
I
was making, not something about the video format of DTV.

73 de K2ASP - Phil Kane
Life Member - Society of Broadcast Engineers

73, Len AF6AY
Life Member - Institute of Electrical and Electronic Engineers


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