Pat, the Editor

27 Years of the Digest ... founded August 21, 1981

Classified Ads
TD Extra News

Add this Digest to your personal   or  

 
 
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...") 


====== 27 years of TELECOM Digest -- Founded August 21, 1981 ====== Telecom and VOIP (Voice over Internet Protocol) Digest for the Internet. All contents here are copyrighted by Patrick Townson and the individual writers/correspondents. Articles may be used in other journals or newsgroups, provided the writer's name and the Digest are included in the fair use quote. By using -any name or email address- included herein for -any- reason other than responding to an article herein, you agree to pay a hundred dollars to the recipients of the email. =========================== Addresses herein are not to be added to any mailing list, nor to be sold or given away without explicit written consent. Chain letters, viruses, porn, spam, and miscellaneous junk are definitely unwelcome. We must fight spam for the same reason we fight crime: not because we are naive enough to believe that we will ever stamp it out, but because we do not want the kind of world that results when no one stands against crime. Geoffrey Welsh =========================== See the bottom of this issue for subscription and archive details and the name of our lawyer, and other stuff of interest. ---------------------------------------------------------------------- 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 ------------------------------ TELECOM Digest is an electronic journal devoted mostly to telecom- munications topics. It is circulated anywhere there is email, in addition to Usenet, where it appears as the moderated newsgroup 'comp.dcom.telecom'. TELECOM Digest is a not-for-profit, mostly non-commercial educational service offered to the Internet by Patrick Townson. All the contents of the Digest are compilation-copyrighted. You may reprint articles in some other media on an occasional basis, but please attribute my work and that of the original author. The Telecom Digest is currently being moderated by Bill Horne while Pat Townson recovers from a stroke. Contact information: Bill Horne Telecom Digest 43 Deerfield Road Sharon MA 02067-2301 781-784-7287 bill at horne dot net Subscribe: telecom-request@telecom-digest.org?body=subscribe telecom Unsubscribe: telecom-request@telecom-digest.org?body=unsubscribe telecom This Digest is the oldest continuing e-journal about telecomm- unications on the Internet, having been founded in August, 1981 and published continuously since then. Our archives are available for your review/research. We believe we are the oldest e-zine/mailing list on the internet in any category! URL information: http://telecom-digest.org Copyright (C) 2008 TELECOM Digest. All rights reserved. Our attorney is Bill Levant, of Blue Bell, PA. ************************ --------------------------------------------------------------- Finally, the Digest is funded by gifts from generous readers such as yourself who provide funding in amounts deemed appropriate. Your help is important and appreciated. A suggested donation of fifty dollars per year per reader is considered appropriate. See our address above. Please make at least a single donation to cover the cost of processing your name to the mailing list. All opinions expressed herein are deemed to be those of the author. Any organizations listed are for identification purposes only and messages should not be considered any official expression by the organization. End of The Telecom digest (7 messages) ******************************

Return to Archives**Older Issues