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Diplexing routes

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  • Mike Cowen
    How common was it to diplex smaller offices using only one antenna for both T/R channels? How much did that affect bandwidth (vs. dedicated antennas)? Did
    Message 1 of 6 , Apr 22, 2011
      How common was it to diplex smaller offices using only one antenna
      for both T/R channels? How much did that affect bandwidth (vs.
      dedicated antennas)? Did they use cross polarization, freq.
      diversity, or both?

      Thanks,
      Mike


      ---------------------------------------------------------------
      Mike Cowen Practice random acts of kindness
      and selfless acts of beauty.
      mcowen@... -Anonymous
    • Jim
      Most of our offices along the back of the Sierra Nevada mountains were diplexed. Though many had a space-diversity receiver to combat flutter. The spectrum was
      Message 2 of 6 , Apr 24, 2011
        Most of our offices along the back of the Sierra Nevada mountains were diplexed. Though many had a space-diversity receiver to combat flutter.

        The spectrum was channelized, standard pairs were used. "bandwidth" per-se was not a problem, if an office *ever* had upwards of 600 trunks either an additional RF channel pair was deployed, or, as it turned out, the paths were converted to QAM.

        Jim

        --- In coldwarcomms@yahoogroups.com, Mike Cowen <mcowen@...> wrote:
        >
        > How common was it to diplex smaller offices using only one antenna
        > for both T/R channels? How much did that affect bandwidth (vs.
        > dedicated antennas)? Did they use cross polarization, freq.
        > diversity, or both?
        >
        > Thanks,
        > Mike
        >
        >
        > ---------------------------------------------------------------
        > Mike Cowen Practice random acts of kindness
        > and selfless acts of beauty.
        > mcowen@... -Anonymous
        >
      • widebandit
        The use of single antennas was quite common. The band-plans for 6GHz TH/TM and 11 GHz TJ were designed for single-antenna use. The TH band provided 8 RF
        Message 3 of 6 , Apr 24, 2011
          The use of single antennas was quite common. The band-plans for 6GHz TH/TM and 11 GHz TJ were designed for single-antenna use.

          The TH band provided 8 RF channels - four on one polarization, four on the other, with all Tx channels in one-half of the band, and all Rx channels in the other half. This, of course requires 16 frequency assignments - 8 low-band, 8 high-band. Tx and Rx channel assignments would reverse - or frog - from hop to hop.

          For a single-antenna example: Microwave channel 4 could Tx Vert. polarization on the Ch 24 frequency of 6286.2 MHz and Rx Horz. polarization on the Ch 14 frequency of 6034.2 MHz; both on a single antenna. This route may also have a protection-channel operating on channel 8, Tx Vert. on Ch 28 freq. of 6404.8 MHz and Rx Horz. on Ch 18 freq. of 6152.8 MHz. Tx and Rx freqs. would reverse on the next hop. Growth would continue by adding Ch 22/12 and 26/16, after which a second antenna would be installed for odd-channel growth.

          The ability to transmit on one polarization and receive on the other is what makes the band-plan work for single-antenna operation. The 252 MHz frequency shift from transmit to receive plus 25 dB cross-polarization discrimination (XPD) provides enough isolation to preclude self-interference or feed-back in the common antenna waveguide run. If the radios are working on dual-polarized dishes, two separate waveguide runs are needed to the antenna. The polarization combiner is either behind the dish or at the feed-horn.

          The channel 4, 8, 2, 6, growth sequence was dictated at the time TH radio was developed because of frequency assignments already in use by short/medium-haul radio systems. The sequence was intended to minimize interference with existing systems.

          To avoid the embarrassment of bringing a TH high-band transmit route into a high-band receive junction station - a situation that could block all channels and is sometimes called "buck-station" - Long-Lines went over their entire existing microwave network and pre-designated which TH stations would be high-band transmit and which stations-would be low-band transmit. Even with that there are several instances where an 'extra' repeater had to be inserted into a route to make the frequencies of a new route compatible with the assignments of existing junction stations.

          One of the first applications of transistorized TH-3 radio was to provide two duplex channels between New Orleans Broadmoor and Morgan City out on the delta. It was a three-hop route using single horn-reflectors.

          TH-3 was also used as overbuild on an existing TJ (11 GHz) four-hop route from Great Falls, Montana to Shelby Junction. There was a combination of dual horns, single-horns, direct radiating dishes, and periscope antennas - sometimes the engineers get to play.

          If you're wondering about the odd RF frequency numbers like 6286.2 MHz, Bell Labs decided to get cute when they designed TH radio and built a common frequency generator to supply all frequencies from a single oscillator (plus back-up, of course, a second back-up was deemed not essential). In order to get everything to fit into the 6 GHz band they chose 14.825930 MHz as the fundamental frequency; 6282.2 is the 424th harmonic of the fundamental. This led to a channel spacing of about 29.65 MHz, an Intermediate Frequency (IF) of about 74.13 MHz, and a shift oscillator frequency of about 252.04 MHz. If you want to understand some of the reasoning behind the choice - grab a copy of the November 1961 Bell System Technical Journal and read all about it. BTW - the TH common-carrier supply used the TD-2 '416' triode as a high frequency multiplier.

          The 4 GHz TD-2 band-plan used interleaved transmit and receive channel slots spaced 20 MHz across the band; so single-antenna operation was usually not practical unless one could synthesize a duplex channel using the Tx and Rx frequencies of two widely separated channel assignments. However once that was done, it would be a real pain to expand the route capacity by adding channels - not to mention the interference possibilities to and from parallel or crossing routes.

          Needles to say, when TH radio was overbuilt onto a TD-2 route already using dual-horns, the TH channel assignments took advantage of the available second antenna.

          This post is a bit long but, well... you asked for it - waw -

          >
          > How common was it to diplex smaller offices using only one antenna
          > for both T/R channels? How much did that affect bandwidth (vs.
          > dedicated antennas)? Did they use cross polarization, freq.
          > diversity, or both?
          >
          > Thanks,
          > Mike
        • Mike Cowen
          Perfect, thanks! ... Mike Cowen Practice random acts of kindness and selfless acts of beauty. mcowen@mindspring.com -Anonymous [Non-text
          Message 4 of 6 , Apr 24, 2011
            Perfect, thanks!


            At 02:25 PM 4/24/2011, you wrote:
            >
            >
            >The use of single antennas was quite common. The
            >band-plans for 6GHz TH/TM and 11 GHz TJ were designed for single-antenna use.
            >
            >The TH band provided 8 RF channels - four on one
            >polarization, four on the other, with all Tx
            >channels in one-half of the band, and all Rx
            >channels in the other half. This, of course
            >requires 16 frequency assignments - 8 low-band,
            >8 high-band. Tx and Rx channel assignments would
            >reverse - or frog - from hop to hop.
            >
            >For a single-antenna example: Microwave channel
            >4 could Tx Vert. polarization on the Ch 24
            >frequency of 6286.2 MHz and Rx Horz.
            >polarization on the Ch 14 frequency of 6034.2
            >MHz; both on a single antenna. This route may
            >also have a protection-channel operating on
            >channel 8, Tx Vert. on Ch 28 freq. of 6404.8 MHz
            >and Rx Horz. on Ch 18 freq. of 6152.8 MHz. Tx
            >and Rx freqs. would reverse on the next hop.
            >Growth would continue by adding Ch 22/12 and
            >26/16, after which a second antenna would be installed for odd-channel growth.
            >
            >The ability to transmit on one polarization and
            >receive on the other is what makes the band-plan
            >work for single-antenna operation. The 252 MHz
            >frequency shift from transmit to receive plus 25
            >dB cross-polarization discrimination (XPD)
            >provides enough isolation to preclude
            >self-interference or feed-back in the common
            >antenna waveguide run. If the radios are working
            >on dual-polarized dishes, two separate waveguide
            >runs are needed to the antenna. The polarization
            >combiner is either behind the dish or at the feed-horn.
            >
            >The channel 4, 8, 2, 6, growth sequence was
            >dictated at the time TH radio was developed
            >because of frequency assignments already in use
            >by short/medium-haul radio systems. The sequence
            >was intended to minimize interference with existing systems.
            >
            >To avoid the embarrassment of bringing a TH
            >high-band transmit route into a high-band
            >receive junction station - a situation that
            >could block all channels and is sometimes called
            >"buck-station" - Long-Lines went over their
            >entire existing microwave network and
            >pre-designated which TH stations would be
            >high-band transmit and which stations-would be
            >low-band transmit. Even with that there are
            >several instances where an 'extra' repeater had
            >to be inserted into a route to make the
            >frequencies of a new route compatible with the
            >assignments of existing junction stations.
            >
            >One of the first applications of transistorized
            >TH-3 radio was to provide two duplex channels
            >between New Orleans Broadmoor and Morgan City
            >out on the delta. It was a three-hop route using single horn-reflectors.
            >
            >TH-3 was also used as overbuild on an existing
            >TJ (11 GHz) four-hop route from Great Falls,
            >Montana to Shelby Junction. There was a
            >combination of dual horns, single-horns, direct
            >radiating dishes, and periscope antennas - sometimes the engineers get to play.
            >
            >If you're wondering about the odd RF frequency
            >numbers like 6286.2 MHz, Bell Labs decided to
            >get cute when they designed TH radio and built a
            >common frequency generator to supply all
            >frequencies from a single oscillator (plus
            >back-up, of course, a second back-up was deemed
            >not essential). In order to get everything to
            >fit into the 6 GHz band they chose 14.825930 MHz
            >as the fundamental frequency; 6282.2 is the
            >424th harmonic of the fundamental. This led to a
            >channel spacing of about 29.65 MHz, an
            >Intermediate Frequency (IF) of about 74.13 MHz,
            >and a shift oscillator frequency of about 252.04
            >MHz. If you want to understand some of the
            >reasoning behind the choice - grab a copy of the
            >November 1961 Bell System Technical Journal and
            >read all about it. BTW - the TH common-carrier
            >supply used the TD-2 '416' triode as a high frequency multiplier.
            >
            >The 4 GHz TD-2 band-plan used interleaved
            >transmit and receive channel slots spaced 20 MHz
            >across the band; so single-antenna operation was
            >usually not practical unless one could
            >synthesize a duplex channel using the Tx and Rx
            >frequencies of two widely separated channel
            >assignments. However once that was done, it
            >would be a real pain to expand the route
            >capacity by adding channels - not to mention the
            >interference possibilities to and from parallel or crossing routes.
            >
            >Needles to say, when TH radio was overbuilt onto
            >a TD-2 route already using dual-horns, the TH
            >channel assignments took advantage of the available second antenna.
            >
            >This post is a bit long but, well... you asked for it - waw -
            >
            > >
            > > How common was it to diplex smaller offices using only one antenna
            > > for both T/R channels? How much did that affect bandwidth (vs.
            > > dedicated antennas)? Did they use cross polarization, freq.
            > > diversity, or both?
            > >
            > > Thanks,
            > > Mike
            >
            >

            ---------------------------------------------------------------
            Mike Cowen Practice random acts of kindness
            and selfless acts of beauty.
            mcowen@... -Anonymous



            [Non-text portions of this message have been removed]
          • OZOB99
            ... The Project Offices & Monrovia used single(hardened)antenna TD2 operation; also some temporary feeds/TV pickups/disaster restorations used it back in the
            Message 5 of 6 , Apr 25, 2011
              --- In coldwarcomms@yahoogroups.com, Mike Cowen <mcowen@...> wrote:
              >
              > How common was it to diplex smaller offices using only one antenna
              > for both T/R channels? How much did that affect bandwidth (vs.
              > dedicated antennas)? Did they use cross polarization, freq.
              > diversity, or both?


              The Project Offices & Monrovia used single(hardened)antenna TD2 operation; also some temporary feeds/TV pickups/disaster restorations used it back in the 1950's & 60's; mainly with TE radio into TD2 if I remember right.
            • james kester
              I dunno whose answer that was, but it had to come out of Dustie G s office? Great   ________________________________ From: Mike Cowen
              Message 6 of 6 , Apr 26, 2011
                I dunno whose answer that was, but it had to come out of Dustie G's office?
                Great


                 



                ________________________________
                From: Mike Cowen <mcowen@...>
                To: coldwarcomms@yahoogroups.com
                Sent: Mon, April 25, 2011 2:14:18 AM
                Subject: Re: [coldwarcomms] Re: Diplexing routes

                 
                Perfect, thanks!

                At 02:25 PM 4/24/2011, you wrote:
                >
                >
                >The use of single antennas was quite common. The
                >band-plans for 6GHz TH/TM and 11 GHz TJ were designed for single-antenna use.
                >
                >The TH band provided 8 RF channels - four on one
                >polarization, four on the other, with all Tx
                >channels in one-half of the band, and all Rx
                >channels in the other half. This, of course
                >requires 16 frequency assignments - 8 low-band,
                >8 high-band. Tx and Rx channel assignments would
                >reverse - or frog - from hop to hop.
                >
                >For a single-antenna example: Microwave channel
                >4 could Tx Vert. polarization on the Ch 24
                >frequency of 6286.2 MHz and Rx Horz.
                >polarization on the Ch 14 frequency of 6034.2
                >MHz; both on a single antenna. This route may
                >also have a protection-channel operating on
                >channel 8, Tx Vert. on Ch 28 freq. of 6404.8 MHz
                >and Rx Horz. on Ch 18 freq. of 6152.8 MHz. Tx
                >and Rx freqs. would reverse on the next hop.
                >Growth would continue by adding Ch 22/12 and
                >26/16, after which a second antenna would be installed for odd-channel growth.
                >
                >The ability to transmit on one polarization and
                >receive on the other is what makes the band-plan
                >work for single-antenna operation. The 252 MHz
                >frequency shift from transmit to receive plus 25
                >dB cross-polarization discrimination (XPD)
                >provides enough isolation to preclude
                >self-interference or feed-back in the common
                >antenna waveguide run. If the radios are working
                >on dual-polarized dishes, two separate waveguide
                >runs are needed to the antenna. The polarization
                >combiner is either behind the dish or at the feed-horn.
                >
                >The channel 4, 8, 2, 6, growth sequence was
                >dictated at the time TH radio was developed
                >because of frequency assignments already in use
                >by short/medium-haul radio systems. The sequence
                >was intended to minimize interference with existing systems.
                >
                >To avoid the embarrassment of bringing a TH
                >high-band transmit route into a high-band
                >receive junction station - a situation that
                >could block all channels and is sometimes called
                >"buck-station" - Long-Lines went over their
                >entire existing microwave network and
                >pre-designated which TH stations would be
                >high-band transmit and which stations-would be
                >low-band transmit. Even with that there are
                >several instances where an 'extra' repeater had
                >to be inserted into a route to make the
                >frequencies of a new route compatible with the
                >assignments of existing junction stations.
                >
                >One of the first applications of transistorized
                >TH-3 radio was to provide two duplex channels
                >between New Orleans Broadmoor and Morgan City
                >out on the delta. It was a three-hop route using single horn-reflectors.
                >
                >TH-3 was also used as overbuild on an existing
                >TJ (11 GHz) four-hop route from Great Falls,
                >Montana to Shelby Junction. There was a
                >combination of dual horns, single-horns, direct
                >radiating dishes, and periscope antennas - sometimes the engineers get to play.
                >
                >If you're wondering about the odd RF frequency
                >numbers like 6286.2 MHz, Bell Labs decided to
                >get cute when they designed TH radio and built a
                >common frequency generator to supply all
                >frequencies from a single oscillator (plus
                >back-up, of course, a second back-up was deemed
                >not essential). In order to get everything to
                >fit into the 6 GHz band they chose 14.825930 MHz
                >as the fundamental frequency; 6282.2 is the
                >424th harmonic of the fundamental. This led to a
                >channel spacing of about 29.65 MHz, an
                >Intermediate Frequency (IF) of about 74.13 MHz,
                >and a shift oscillator frequency of about 252.04
                >MHz. If you want to understand some of the
                >reasoning behind the choice - grab a copy of the
                >November 1961 Bell System Technical Journal and
                >read all about it. BTW - the TH common-carrier
                >supply used the TD-2 '416' triode as a high frequency multiplier.
                >
                >The 4 GHz TD-2 band-plan used interleaved
                >transmit and receive channel slots spaced 20 MHz
                >across the band; so single-antenna operation was
                >usually not practical unless one could
                >synthesize a duplex channel using the Tx and Rx
                >frequencies of two widely separated channel
                >assignments. However once that was done, it
                >would be a real pain to expand the route
                >capacity by adding channels - not to mention the
                >interference possibilities to and from parallel or crossing routes.
                >
                >Needles to say, when TH radio was overbuilt onto
                >a TD-2 route already using dual-horns, the TH
                >channel assignments took advantage of the available second antenna.
                >
                >This post is a bit long but, well... you asked for it - waw -
                >
                > >
                > > How common was it to diplex smaller offices using only one antenna
                > > for both T/R channels? How much did that affect bandwidth (vs.
                > > dedicated antennas)? Did they use cross polarization, freq.
                > > diversity, or both?
                > >
                > > Thanks,
                > > Mike
                >
                >

                ----------------------------------------------------------
                Mike Cowen Practice random acts of kindness
                and selfless acts of beauty.
                mcowen@... -Anonymous

                [Non-text portions of this message have been removed]




                [Non-text portions of this message have been removed]
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