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Message Digest
Volume 28 : Issue 128 : "text" Format
Messages in this Issue:
CO backup power (was Re: FiOS in MDU Buildings
Re: Waveguide (was "size a major consideration...")
Re: Waveguide (was "size a major consideration...")
Re: Waveguide (was "size a major consideration...")
Re: Waveguide (was "size a major consideration...")
Re: Waveguide (was "size a major consideration...")
Re: Waveguide (was "size a major consideration...")
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Date: Fri, 08 May 2009 21:16:16 -0400 (EDT)
From: "Julian Thomas" <jt@jt-mj.net>
To: redacted@invalid.telecom.csail.mit.edu
Subject: CO backup power (was Re: FiOS in MDU Buildings
Message-ID: <100.7857030060d9044a.006@jt-mj.net>
On Wed, 6 May 2009 10:37:51 EDT Wesrock@aol.com wrote:
>
>
>The traditional Central Office had a diesel generator in addition to
>its batteries, so a few days is not a problem.
IIRC ESS1 (Morris Ill.) had minimal batteries, and a system that was supposed
to start the diesels within 1/3 sec
after a primary power failure.
I have no idea as to how that worked out or was modified.
--
Julian Thomas: jt@jt-mj.net http://jt-mj.net
In the beautiful Genesee Valley of Western New York State!
-- --
A truly wise man never plays leapfrog with a unicorn.
------------------------------
Date: Sat, 9 May 2009 02:54:07 +0000 (UTC)
From: David Lesher <wb8foz@panix.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Waveguide (was "size a major consideration...")
Message-ID: <gu2r8f$5rt$1@reader1.panix.com>
>I'm reluctant to challenge someone in an area where my knowlege is
>dated, but please bear with me.
I'm no expert...
> Noise - L carrier had to have a noise generator (yes, that's right) to
> ADD noise to the calls, because subscribers were so used to the
> "long distance hiss"
L Carrier coax was different, but I'm not aware of the noise
generator. I'd guess its function was to cover crosstalk between channels
during quiet periods of a conversation. I'll ask.
> Maintenance - I'd like to see more info on this, especially considering
> that techs don't require licenses anymore.
People cost money; skilled people cost more; skilled people 24x7.....
You needed a station every 20-30 miles. It took 150 stations to cover
the 4000 miles coast to coast. (The stations zig-zag across the country
so station #4's output towards #5 does not also spill onto #6 on some
days....)
> Power - typical power levels for microwave are measured in milliwatts,
> so that's not a factor. Where you refering to the whole system?
Yep. A station such as Garden City VA had a BIG 3 phase feed, and
standby Diesels to match -- 500 KW and up.
> Capital Cost - I'm sure fiber is expensive to lay, but I suspect the
> rights of way are the big expense, and Microwave doesn't have that
> problem.
Ma was worried about running out of Long Lines throughput by ~1980. She
added 6 Ghz microwave which tripled a station's capacity; that of course
is a drop in the bucket by our standards. 11 Ghz was another add-on, but it
was shorter range....
To do more; She'd have needed a duplicate backbone say 50 miles south (or
north) of the existing... and all that would do was double it.
Engineering & Ops in the Bell System table 9-10:
Capacity in 1980:
Analog Radio (TD,TH uwave) 623E6 circuit-miles 60%
Coax (L carrier) 197E6 19.3%
BTW, about then, Ma went to LARGE expense to add on a Data Under Voice
microwave scheme to offer coast-coast digital capacity.... It provided a
whopping DS-1, yes... 1.544 MB/s of room...
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
------------------------------
Date: Sat, 9 May 2009 03:46:02 +0000 (UTC)
From: wollman@bimajority.org (Garrett Wollman)
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Waveguide (was "size a major consideration...")
Message-ID: <gu2u9q$1a43$1@grapevine.csail.mit.edu>
In an addendum to article <gu2j0p$gf3$1@reader1.panix.com>, Our
Esteemed Temporary Moderator wrote:
>Capital Cost - I'm sure fiber is expensive to lay, but I suspect the
>rights of way are the big expense, and Microwave doesn't have that
>problem.
Fiber rights of way are fairly cheap and usually run parallel to
existing infrastructure such as highways or rail lines.[1] In the
overbuild years of the late 1990s, they got even cheaper, and demand
is only now starting to reach capacity in some parts of the country.
The usable bandwidth of a single single-mode fiber is in the hundreds
of gigabits per second, the equivalent of several million traditional
56kbit/s voice circuits (or far more even than that when using a
low-bandwidth vocoder). And a typical fiber path will have thousands
of fibers (because it was cheaper to pull them 192 at a time).
At one time I knew how much a pair of fibers from Boston to New York
cost to lease for 20 years. Perhaps someone who's more up on that
side of the market can give us an idea what the current prices look
like.
-GAWollman
[1] In Massachusetts, one of the biggest dark fiber corridors follows
the Massachusetts Turnpike. It was built by the Turnpike Authority to
replace its own microwave network, and then surplus capacity was
leased to private users.
--
Garrett A. Wollman | The real tragedy of human existence is not that we are
wollman@csail.mit.edu| nasty by nature, but that a cruel structural asymmetry
Opinions not those | grants to rare events of meanness such power to shape
of MIT or CSAIL. | our history. - S.J. Gould, Ten Thousand Acts of Kindness
------------------------------
Date: Fri, 08 May 2009 21:50:38 -0700
From: AES <siegman@stanford.edu>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Waveguide (was "size a major consideration...")
Message-ID: <siegman-273526.21500808052009@news.stanford.edu>
Bill,
Re fiber v. waveguide:
The optical frequencies carried in telecom fibers are
typically in the range from 2 X 10^14 to 3 X 10^14 Hz
-- that's 200,000 GHz to 300,000 GHz -- and a single
fiber can easily transmit that entire band.
But let's say we use only a 10% bandwidth about a center
or "carrier" frequency of say 200,000 Ghz. That's a useful
bandwidth of 20,000 Ghz -- and there are so-called "erbium
doped fiber amplifiers" (EDFAs) that are simple, robust, very
long-lived, and just plain practical, that really can amplify
that *entire* bandwidth, with zilch cross-talk and more
than flat enough gain.
So, you can (in principle, anyway) put up to 10,000 separate
subchannels, each a Ghz wide, with a GHz wide unused guard
band between them, down this fiber; amplify the whole group
ever 10 km or 30 km or so; and really quite simple optical
technology exists to generate, insert, add, drop, pick off, and detect
any channel most any time you want it.
[This is just a hypothetical example, to make the point.
Real systems may use different choices of channel widths
and spacings, and most likely many fewer channels. But,
"many fewer" than 10,000 channels can still be a lot
of channels!]
The carrier frequency in each separate channel is in
essence a very slightly different color of light, generated
by a cheap diode laser. Each of these carriers is digitally
modulated at (in our example) a 1 GB data rate. They
don't interfere; they have very low loss; they have
excellent signal-to-noise ratio; they don't crosstalk; they
can all be reamplified in parallel in these EDFAs -- they're
just insanely good!
------------------------------
Date: Sat, 9 May 2009 01:47:59 -0400
From: T <kd1s.nospam@cox.nospam.net>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Waveguide (was "size a major consideration...")
Message-ID: <MPG.246ee31a951368b8989a0c@reader.motzarella.org>
In article <gu1trl$qha$1@reader1.panix.com>, wb8foz@panix.com says...
>
> kludge@panix.com (Scott Dorsey) writes:
>
>
> >I'm not sure where the price breakeven point between hardline and waveguide
> >is. You look at all those 2GHz Bell microwave towers with the cornucopia
> >antennae, and you see waveguides coming down from all of them. These days
> >that would all be done very differently.
>
> Those horns often carred six circuits: 4 Ghz horz polarization, 4 Ghz
> vertical, 6 Ghz h & v, 11 Ghz h & v. They delivered a jaw busting 48dB of
> gain at 11 Ghz, with a beam width of about 0.75 degrees. But then they
> had 36 ft^2 of throat, were 14 ft+ tall and weighed several thousand
> pounds... despite being aluminum...
>
> ***** Moderator's Note *****
>
> What puzzles me is how microwave could be retired in favor of fiber,
> given the immense investment required to lay it: the cost of labor
> alone would dwarf all other considerations. How is fiber so much
> "better" than microwave?
>
> Did we just run out of radio channels?
>
> Bill Horne
> Temporary Moderator
Wow, they were huge. I remember watching them remove what I think were
TD-2 horns from the Bell building here in Providence back in the late
80's. When they got down on the ground I couldn't believe how big they
were.
But 48db of gain is impressive.
------------------------------
Date: Sat, 9 May 2009 01:46:16 -0400
From: T <kd1s.nospam@cox.nospam.net>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Waveguide (was "size a major consideration...")
Message-ID: <MPG.246ee2b6f4bf61f2989a0b@reader.motzarella.org>
In article <gu1dc4$1ti$1@panix2.panix.com>, kludge@panix.com says...
>
> Scott Dorsey <kludge@panix.com> wrote:
> >
> >Given the cost of Heliax, and the losses of generic coax at 70cm, is
> >it possible/advisable to homebrew waveguide? A previous post mentioned
> >circular waveguide, and I wonder if I could feed 70cm or 23cm antennas
> >with waveguide made from copper pipe.
>
> You could, but copper pipe is very expensive. It's cheaper to move the
> transceiver up closer to the antenna in most cases today.
>
> I'm not sure where the price breakeven point between hardline and waveguide
> is. You look at all those 2GHz Bell microwave towers with the cornucopia
> antennae, and you see waveguides coming down from all of them. These days
> that would all be done very differently.
> --scott
Back a couple years ago I worked for the Sec. State's office. We had
three locations in the city of Providence.
The Admin Director asked how we could cut costs on the VAN circuits we
employed.
I mentioned that the clock tower at the facility we were in had line of
sight to the State House and the State House had line of sight to our
other location in downtown Providence. Proposed an 802.11 based system.
The State House was the sticky wicket. I explained we'd have to run
fiber from the 2nd floor to the top of the dome along with power so that
the transcievers could be near the dish, actually Yagi's would have
worked too but a little harder to conceal.
Did out the costing and then submitted it. It never came to fruition.
***** Moderator's Note *****
That's surprising: these days, every government-owned structure that
offers more than ten feet of HAAT (Height Above Average Terrain) is
festooned with antennas from every cellular provider, every paging,
and every trunked repeater service - sometimes even, believe it or
not, antennas for government use!
Bill Horne
Temporary Moderator
------------------------------
Date: Sat, 9 May 2009 15:03:02 +0000 (UTC)
From: David Lesher <wb8foz@panix.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Waveguide (was "size a major consideration...")
Message-ID: <gu45v6$64c$1@reader1.panix.com>
>Noise - L carrier had to have a noise generator (yes, that's right) to
>_ADD_ noise to the calls, because subscribers were so used to the
>"long distance hiss" that they would hang up during lulls in a
>conversation, assuming that the call had been disconnected.
I asked a retired L carrier tech. No noise generator, but N carrier
[short-range urban; over 2 pairs of cable, not coax] did have a noise
generator, and covering crosstalk was the reason.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
***** Moderator's Note *****
He's wrong and I'm right! L carrier _had_ a noise generator! I used to
joke about the one at Bowdoin Square in Boston, which did not AFAIK
have any N carrier.
Bill Horne
Temporary Moderator
------------------------------
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