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

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  • 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 1 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.



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      A host is a host from coast to coast.................wb8foz@...
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      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 2 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 3 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.



          Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
        • 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 4 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 5 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 6 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 7 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 8 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 9 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 10 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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