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Re: [coldwarcomms] Re: Dual towers, how common?

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  • David Lesher
    Waldorf MD. I seem to recall seeing multiple towers there. -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host
    Message 1 of 14 , Nov 6, 2001
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      Waldorf MD. I seem to recall seeing multiple towers there.


      --
      A host is a host from coast to coast.................wb8foz@...
      & 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
    • David Lesher
      ... I m sure I ve seen steel superstructure added to the top of silos such that they got more err antennas. (Skirting the were they horns? issue.) I am
      Message 2 of 14 , Nov 6, 2001
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        Unnamed Administration sources reported that dsandow@... said:
        >
        >
        > The whole design of the silo never contemplated the horn
        > reflector, with its bottom-feed. So you would have to put up a new
        > steel tower if you needed to upgrade to a horn reflector (for
        > improved performance) or raise the antenna (for obstruction
        > avoidance). But there was not a "transfer" of the horn reflectors.

        I'm sure I've seen steel superstructure added to the top of silos
        such that they got more err antennas. (Skirting the "were they
        horns?" issue.) I am thinking of the one along the Ohio Turnpike
        east of Cleveland. I have the Lat/Long in my GPS still, I think.



        --
        A host is a host from coast to coast.................wb8foz@...
        & 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
      • dsandow@garden.net
        ... There are 4 circumstances where 2 towers are required. 1. The first tower on the site was limited capacity. The very first route (Boston-Washington) used
        Message 3 of 14 , Nov 6, 2001
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          --- In coldwarcomms@y..., "Pj" <packy41@y...> wrote:
          > How common (or uncommon) were the use of dual towers on a site? I
          > personally only know of two towers, one in PA and one at Durham CT.
          > Any other large use of dual towers?

          There are 4 circumstances where 2 towers are required.

          1. The first tower on the site was limited capacity. The very first
          route (Boston-Washington) used concrete towers - for rigidity - to
          prevent the tower from twisting in the wind. These were called
          "silos". The antenna deck was designed for the older "delay lens"
          antennas (a squat pyramid laid on its side), and could not physically
          accommodate the later horn reflectors. Further, there was only one
          antenna deck, so any additional routes through the repeater site
          could not be handled on the existing tower. By the time a second
          route was needed, the technology was steel towers and horn
          reflectors. Example of a silo and a steel tower side-by-side was
          Martinsville, NJ. (The silo was demolished in the '80s).

          2. Excessive weight/twisting. Colesville NJ was a major NYC junction.
          It had 8 routes (16 horns.) Just too much weight for 1 tower. (The
          added horns also added to the wind load, which increased the "sail
          area" of the tower, and increased the problem of the tower twisting
          in the wind.) The second tower was built right beside the first to
          share the load.

          3. The first tower was built high enough to carry antennas for the
          first route through the station. A later route required a higher
          tower. It's easy to hang additional antennas BELOW the top of an
          existing tower, but not easy to hang them ABOVE the top. The
          alternatives were to build a monopole extension (probably not good
          for much more than 20-40 feet due to wind-twist), OR to build a
          second tower higher than the first (again, Colesville, NJ).

          4. The most insidious reason for 2 towers is the alternating
          frequency plan. The available bandwidth was divided into "A" and "B"
          frequencies. A given station would transmit on the "A" frequencies
          and receive the "B" frequencies. This prevented RF crosstalk between
          the transmitters and receivers at the same station. (see more below).

          Now if my station transmits on "A" and receives on "B", then all the
          surrounding stations must be "B" transmitters, and so on forever. If
          you count all the hops on all the routes between - say - NY and
          Chicago, you will find that the hop count for every possible route is
          either an odd or an even number, because NY had to be an "A" station
          for all its routes, and CHI had to be a "whatever" station for all
          its routes. All the adjacent stations on all routes had to conform to
          the alternating pattern - ocean-to-ocean.

          In the case of NYC (call it "A"), all the adjacent repeaters (Jackie
          Jones, Green Pond, Martinsville, Iselin, Highlands) had to be "B"
          sites.

          So what happens if the alternation "slips", and a new route is built
          that would directly connect 2 adjacent "A" stations. It can't be
          done. You either have to build an intermediate station (2 short hops)
          to keep the plan straight, OR you build a second tower somewhere.

          An example of this is Green Pond, NJ. The first route was E-W
          (NY-Colesville-Jennerstown and points west.) Green Pond was the first
          hop out of NYC ("A" freq transmitters), so it used "B" freq
          transmitters. Then, someone decided to build a bypass around NYC. It
          connected Martinsville - Green Pond - Jackie Jones, ALL "B" stations.
          Something had to give. In this case, a new "A" station was built at
          Green Pond. It was really a separate station more than 500 ft from
          the existing. It was named Green Pond #2. Fortunately, the "B"
          transmit antennas at Green Pond #1 were pointing east-west and the
          "B" receive antennas at Green Pond #2 were pointing N-S, and the new
          tower was sited so that the receive antennas did not point at the old
          tower, so they got away with it. (And saved the zoning hassle of
          finding a different mountaintop in suburban NJ.)

          Green Pond #2 was absolutely a separate station from Green Pond #1.
          The only thing they share is a driveway. Even the alarms went to two
          different places - because the two towers belonged to 2 separate
          routes. There was no capability to do resoration patching between
          the two buildings. Just 2 separate repeaters on two separate routes
          that happened to share the same tax bill.

          More on crosstalk/leakage. Even though the horn reflectors had a very
          sharp beamwidth, you could still pick up a usable signal about 1/4
          mile off the centerline at 30 miles. IF an "A" transmitter and an "A"
          receiver were pointed in exactly the same direction, you could still
          get crosstalk from nearby reflectors. A building a mile away just
          slightly off the centerline could bounce the signal back. A passing
          truck on a highway in front of the beam could do the same, etc. To
          say nothing of ordinary leakage inside the station, regardless of how
          well shielded the receiver front ends were. The alternating
          frequency plan was one way to handle the crosstalk/leakage problem.
          There was also cross-polarization of the antennas for further
          isolation. But that's a different thread.
        • Terry Feathers
          I will agree that AT&T alternated frequency plans an almost all microwave sites. The exception was a route that had no growth potential or an engineer made a
          Message 4 of 14 , Nov 6, 2001
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            I will agree that AT&T alternated frequency plans an almost all microwave
            sites. The exception was a route that had no growth potential or an
            engineer made a very big mistake. Not alternating the frequency plan caused
            a "BUCK" station and you were limited to only using 1/2 of the possible
            channels or less. It would be time for the engineer to find a new job
            within AT&T.

            Regards
            Terry Feathers
            ComSpec Corporation
            Phone: 336-370-1456
            Fax: 336-370-4116
            email: tfeathers@...

            -----Original Message-----
            From: dsandow@... [mailto:dsandow@...]
            Sent: Tuesday, November 06, 2001 9:06 AM
            To: coldwarcomms@yahoogroups.com
            Subject: [coldwarcomms] Re: Dual towers, how common?


            --- In coldwarcomms@y..., "Pj" <packy41@y...> wrote:
            > How common (or uncommon) were the use of dual towers on a site? I
            > personally only know of two towers, one in PA and one at Durham CT.
            > Any other large use of dual towers?

            There are 4 circumstances where 2 towers are required.

            1. The first tower on the site was limited capacity. The very first
            route (Boston-Washington) used concrete towers - for rigidity - to
            prevent the tower from twisting in the wind. These were called
            "silos". The antenna deck was designed for the older "delay lens"
            antennas (a squat pyramid laid on its side), and could not physically
            accommodate the later horn reflectors. Further, there was only one
            antenna deck, so any additional routes through the repeater site
            could not be handled on the existing tower. By the time a second
            route was needed, the technology was steel towers and horn
            reflectors. Example of a silo and a steel tower side-by-side was
            Martinsville, NJ. (The silo was demolished in the '80s).

            2. Excessive weight/twisting. Colesville NJ was a major NYC junction.
            It had 8 routes (16 horns.) Just too much weight for 1 tower. (The
            added horns also added to the wind load, which increased the "sail
            area" of the tower, and increased the problem of the tower twisting
            in the wind.) The second tower was built right beside the first to
            share the load.

            3. The first tower was built high enough to carry antennas for the
            first route through the station. A later route required a higher
            tower. It's easy to hang additional antennas BELOW the top of an
            existing tower, but not easy to hang them ABOVE the top. The
            alternatives were to build a monopole extension (probably not good
            for much more than 20-40 feet due to wind-twist), OR to build a
            second tower higher than the first (again, Colesville, NJ).

            4. The most insidious reason for 2 towers is the alternating
            frequency plan. The available bandwidth was divided into "A" and "B"
            frequencies. A given station would transmit on the "A" frequencies
            and receive the "B" frequencies. This prevented RF crosstalk between
            the transmitters and receivers at the same station. (see more below).

            Now if my station transmits on "A" and receives on "B", then all the
            surrounding stations must be "B" transmitters, and so on forever. If
            you count all the hops on all the routes between - say - NY and
            Chicago, you will find that the hop count for every possible route is
            either an odd or an even number, because NY had to be an "A" station
            for all its routes, and CHI had to be a "whatever" station for all
            its routes. All the adjacent stations on all routes had to conform to
            the alternating pattern - ocean-to-ocean.

            In the case of NYC (call it "A"), all the adjacent repeaters (Jackie
            Jones, Green Pond, Martinsville, Iselin, Highlands) had to be "B"
            sites.

            So what happens if the alternation "slips", and a new route is built
            that would directly connect 2 adjacent "A" stations. It can't be
            done. You either have to build an intermediate station (2 short hops)
            to keep the plan straight, OR you build a second tower somewhere.

            An example of this is Green Pond, NJ. The first route was E-W
            (NY-Colesville-Jennerstown and points west.) Green Pond was the first
            hop out of NYC ("A" freq transmitters), so it used "B" freq
            transmitters. Then, someone decided to build a bypass around NYC. It
            connected Martinsville - Green Pond - Jackie Jones, ALL "B" stations.
            Something had to give. In this case, a new "A" station was built at
            Green Pond. It was really a separate station more than 500 ft from
            the existing. It was named Green Pond #2. Fortunately, the "B"
            transmit antennas at Green Pond #1 were pointing east-west and the
            "B" receive antennas at Green Pond #2 were pointing N-S, and the new
            tower was sited so that the receive antennas did not point at the old
            tower, so they got away with it. (And saved the zoning hassle of
            finding a different mountaintop in suburban NJ.)

            Green Pond #2 was absolutely a separate station from Green Pond #1.
            The only thing they share is a driveway. Even the alarms went to two
            different places - because the two towers belonged to 2 separate
            routes. There was no capability to do resoration patching between
            the two buildings. Just 2 separate repeaters on two separate routes
            that happened to share the same tax bill.

            More on crosstalk/leakage. Even though the horn reflectors had a very
            sharp beamwidth, you could still pick up a usable signal about 1/4
            mile off the centerline at 30 miles. IF an "A" transmitter and an "A"
            receiver were pointed in exactly the same direction, you could still
            get crosstalk from nearby reflectors. A building a mile away just
            slightly off the centerline could bounce the signal back. A passing
            truck on a highway in front of the beam could do the same, etc. To
            say nothing of ordinary leakage inside the station, regardless of how
            well shielded the receiver front ends were. The alternating
            frequency plan was one way to handle the crosstalk/leakage problem.
            There was also cross-polarization of the antennas for further
            isolation. But that's a different thread.



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          • albertjlafrance@cs.com
            Yes, and one of them is a style I don t see often: the legs are vertical, rather than inclined (possibly flared outward slightly at the bottom). I believe
            Message 5 of 14 , Nov 6, 2001
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              Yes, and one of them is a style I don't see often: the legs are vertical,
              rather than inclined (possibly flared outward slightly at the bottom). I
              believe this is an older design.

              Another two-tower site in the DC area is the big radio junction called Omps -
              it's named for a town in WV but actually located just south of the VA/WV line.

              Albert

              In a message dated 11/6/2001 8:53:17 AM Eastern Standard Time, wb8foz@...
              writes:

              > Waldorf MD. I seem to recall seeing multiple towers there.
              >
            • dsandow@garden.net
              ... a ... ice ... Paul Thanks for reminding me that the silos had their radio rooms in the top of the tower. That would be another reason for the solid
              Message 6 of 14 , Nov 6, 2001
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                > Catawba, OH (West of Columbus) - This is a strange beast as this is
                a
                > concrete silo with a guyed lattice tower standing next to it. An
                ice
                > bridge was placed from the TOP of the silo to the lattice tower to
                > bring the waveguides from the lattice tower to the silo. (Obviously
                > this was because the radio equipement was at the top of the silo...)
                > The site was a repeater site (only two paths) and there are no
                > antennas left on the silo... So I think they transferred the horns
                > from the silo to the tower for some strange reason.

                Paul

                Thanks for reminding me that the silos had their radio rooms in the
                top of the tower. That would be another reason for the solid
                construction - to provide a benign environment for the equipment, and
                to allow an enclosed weather-proof (and OSHA-proof) stairway for the
                craftsmen to get to it.

                As I mentioned in my earlier post, the silos were built for the delay
                lens antenna. Think of a squat pyramid laid on its side, with the feed
                point only a few feet from the equipment bays. (Actually, I think the
                radio room was one level below the antenna deck because the antenna
                deck was open to the weather.)

                For more on delay lens antennas, see
                http://www.tpub.com/neets/book11/46b.htm

                The whole design of the silo never contemplated the horn
                reflector, with its bottom-feed. So you would have to put up a new
                steel tower if you needed to upgrade to a horn reflector (for
                improved performance) or raise the antenna (for obstruction
                avoidance). But there was not a "transfer" of the horn reflectors.

                The waveguide bridge - it blows my mind. I suppose it would be cheaper
                than building a new ground-level radio building to go with the new
                tower, but that never stopped ATT. Is it still there?
              • allanbourdius@hotmail.com
                Not always! The Troy Hill silo (AT #88265) north of Pittsburgh has a pair of KS horns on it. You can see them clearly in AT s photos of the site. Allan
                Message 7 of 14 , Nov 6, 2001
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                  Not always! The Troy Hill silo (AT #88265) north of Pittsburgh has a
                  pair of KS horns on it. You can see them clearly in AT's photos of
                  the site.

                  Allan

                  --- In coldwarcomms@y..., dsandow@g... wrote:
                  > The whole design of the silo never contemplated the horn
                  > reflector, with its bottom-feed. So you would have to put up a new
                  > steel tower if you needed to upgrade to a horn reflector (for
                  > improved performance) or raise the antenna (for obstruction
                  > avoidance). But there was not a "transfer" of the horn reflectors.
                • Paul J Zawada
                  ... That s not necessarily so... I ve seen many concrete silos that had short lattice structures added to the top to acommodate horns. Springfield, OH, off of
                  Message 8 of 14 , Nov 6, 2001
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                    > The whole design of the silo never contemplated the horn
                    > reflector, with its bottom-feed. So you would have to put up a new
                    > steel tower if you needed to upgrade to a horn reflector (for
                    > improved performance) or raise the antenna (for obstruction
                    > avoidance). But there was not a "transfer" of the horn reflectors.

                    That's not necessarily so... I've seen many concrete silos that had
                    short lattice structures added to the top to acommodate horns.
                    Springfield, OH, off of I-70, immediately comes to mind as well as
                    numerous towers along the Ohio Turnpike and Indiana Toll Road. (As
                    someone else has already pointed out.) There must be some reason they
                    didn't take the same approach at Catawba. You are right though...
                    The Catawba Silo may have never seen horns since there is no remaining
                    lattice structure on the silo... The guyed tower may have been there
                    the day the horns arrived. Maybe it was an experiment to determine
                    which way of conversion was better...

                    > The waveguide bridge - it blows my mind. I suppose it would be
                    > cheaper than building a new ground-level radio building to go with
                    > the new tower, but that never stopped ATT. Is it still there?

                    I have been by there in over a year, but I believe it's still there...
                    I've been meaning to run over there to take some pictures; maybe I
                    can do that in a couple of weeks...

                    --zawada
                  • albertjlafrance@cs.com
                    Another example of a combined silo and lattice-tower station is Waggoners Gap, PA: http://radio.ee.psu.edu/td-th/Waggoners_Gap/Waggoner s_Gap.html Albert In a
                    Message 9 of 14 , Nov 6, 2001
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                      Another example of a combined silo and lattice-tower station is Waggoners
                      Gap, PA:

                      http://radio.ee.psu.edu/td-th/Waggoners_Gap/Waggoner's_Gap.html

                      Albert

                      In a message dated 11/6/2001 8:44:41 AM Eastern Standard Time,
                      paul_zawada@... writes:

                      <SNIP>
                      > Catawba, OH (West of Columbus) - This is a strange beast as this is a
                      > concrete silo with a guyed lattice tower standing next to it. An ice
                      > bridge was placed from the TOP of the silo to the lattice tower to
                      > bring the waveguides from the lattice tower to the silo. (Obviously
                      > this was because the radio equipement was at the top of the silo...)
                      <SNIP>
                    • Chris Ness
                      ... Villa Rica, GA . Although one of them has been stripped of horns this Summer. It appears to the major connecting point for the west side of GA as well as a
                      Message 10 of 14 , Nov 9, 2001
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                        On November 6, 2001 01:19 am, Pj wrote:
                        > How common (or uncommon) were the use of dual towers on a site? I
                        > personally only know of two towers, one in PA and one at Durham CT.
                        > Any other large use of dual towers?
                        >
                        Villa Rica, GA . Although one of them has been stripped of horns this Summer.
                        It appears to the major connecting point for the west side of GA as well as a
                        CO.
                        --
                        Chris Ness
                        mailto:mness215@... All jobs are equally easy to
                        http://vivid.nbank.net/~gloster the person not doing the work.
                        Holt's Law
                      • albertjlafrance@cs.com
                        Terry, Thanks - I d seen the term buck station somewhere, but didn t understand what it meant until now. Albert In a message dated 11/6/2001 9:28:53 AM
                        Message 11 of 14 , Nov 20, 2001
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                          Terry,

                          Thanks - I'd seen the term "buck station" somewhere, but didn't understand
                          what it meant until now.

                          Albert

                          In a message dated 11/6/2001 9:28:53 AM Eastern Standard Time,
                          tfeathers@... writes:

                          > I will agree that AT&T alternated frequency plans an almost all microwave
                          > sites. The exception was a route that had no growth potential or an
                          > engineer made a very big mistake. Not alternating the frequency plan
                          caused
                          > a "BUCK" station and you were limited to only using 1/2 of the possible
                          > channels or less. It would be time for the engineer to find a new job
                          > within AT&T.
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