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Message Digest
Volume 28 : Issue 127 : "text" Format
Messages in this Issue:
Re: Waveguide (was "size a major consideration...")
Re: Waveguide (was "size a major consideration...")
Re: Waveguide (was "size a major consideration...")
Memory Lane -- a photo collection
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Date: 8 May 2009 09:51:00 -0400
From: kludge@panix.com (Scott Dorsey)
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Waveguide (was "size a major consideration...")
Message-ID: <gu1dc4$1ti$1@panix2.panix.com>
Scott Dorsey <kludge@panix.com> wrote:
>
>Given the cost of Heliax, and the losses of generic coax at 70cm, is
>it possible/advisable to homebrew waveguide? A previous post mentioned
>circular waveguide, and I wonder if I could feed 70cm or 23cm antennas
>with waveguide made from copper pipe.
You could, but copper pipe is very expensive. It's cheaper to move the
transceiver up closer to the antenna in most cases today.
I'm not sure where the price breakeven point between hardline and waveguide
is. You look at all those 2GHz Bell microwave towers with the cornucopia
antennae, and you see waveguides coming down from all of them. These days
that would all be done very differently.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
------------------------------
Date: Fri, 8 May 2009 18:32:21 +0000 (UTC)
From: David Lesher <wb8foz@panix.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Waveguide (was "size a major consideration...")
Message-ID: <gu1trl$qha$1@reader1.panix.com>
kludge@panix.com (Scott Dorsey) writes:
>I'm not sure where the price breakeven point between hardline and waveguide
>is. You look at all those 2GHz Bell microwave towers with the cornucopia
>antennae, and you see waveguides coming down from all of them. These days
>that would all be done very differently.
Those horns often carred six circuits: 4 Ghz horz polarization, 4 Ghz
vertical, 6 Ghz h & v, 11 Ghz h & v. They delivered a jaw busting 48dB of
gain at 11 Ghz, with a beam width of about 0.75 degrees. But then they
had 36 ft^2 of throat, were 14 ft+ tall and weighed several thousand
pounds... despite being aluminum...
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
***** Moderator's Note *****
What puzzles me is how microwave could be retired in favor of fiber,
given the immense investment required to lay it: the cost of labor
alone would dwarf all other considerations. How is fiber so much
"better" than microwave?
Did we just run out of radio channels?
Bill Horne
Temporary Moderator
------------------------------
Date: Sat, 9 May 2009 00:33:29 +0000 (UTC)
From: David Lesher <wb8foz@panix.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Waveguide (was "size a major consideration...")
Message-ID: <gu2j0p$gf3$1@reader1.panix.com>
>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?
Blame Candice Bergen. Her Sprint "pin drop" commercials sold the country
on digital trunkage vs the hissss of analog muxed paths. She forced Ma to
wake up & start catching up. Now, there's zero analog trunkage left.
Digitized trunkage takes far more BW than analog, as
Al Varney used to point out here regularly. Fiber
offers many orders of magnitude more. (Contrast OC-768
to http://en.wikipedia.org/wiki/Optical_Carrier#OC-768_.2F_STM-256x to
the 19,200 VF (300-3000 hz) channels in the newest TD {4 Ghz} microwave.
And microwave is very maintenance intensive; needing regular expert
tweeking, etc. Massive power bills to boot. Fiber is high capital cost
but low O&M. Your big concern is backhoe fade.
--
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 *****
I'm reluctant to challenge someone in an area where my knowlege is
dated, but please bear with me.
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 question
the "pin drop" effect: if it _was_ a factor, it was a marketing one,
because all Ma Bell had to do to compete was turn off the noise
generators.
Maintenance - I'd like to see more info on this, especially
considering that techs don't require licenses anymore.
Power - typical power levels for microwave are measured in milliwatts,
so that's not a factor. Where you refering to the whole system?
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.
Bill Horne
Temporary Moderator
------------------------------
Date: Fri, 8 May 2009 04:06:56 +0000 (UTC)
From: David Lesher <wb8foz@panix.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Memory Lane -- a photo collection
Message-ID: <gu0b50$d2e$1@reader1.panix.com>
Even Ernestine will shed a tear...
http://www.flickr.com/photos/9479603@N02/
--
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
------------------------------
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End of The Telecom digest (4 messages)
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