More Excavation For Feedline Conduits

We are planning a pretty extensive feedline and control system for our new tower. The plan current includes:

  • Two 7/8′ hard lines to feed the SteppIR DB36 array
  • One 1/2″ hardline to feed the 80m Delta Loop and 160 Invert-L antennas on the tower
  • Two 1 5/8″ hard lines to feed future UHF antennas
  • At total of 6 control cables for the two SteppIR Beams, two rotators for the Beams, Stack Match System and Remote Antenna Switch
  • Capacity for 6 additional control cables for future use

We also need a 120 VAC outdoor outlet at the base of the tower to provide power for the ring rotator.

The accommodate all of this, we are placing several plastic conduit pipes in a trench from our shack entry point to the tower. The conduits include:

  • One 4″ run for the three new hardline feeders
  • One 6″ run for the future UHF hard lines
  • Two 2″ runs for control cables
  • One 3″ run extending beyond the tower to the back of our lot for possible future use on antenna(s) in this location
  • One 1 1/2″ conduit for the 120 VAC cable to the tower

As you can imagine, this requires quite a trench! This part of the construction is compounded by the existence of a sprinkler system and train pipes for the rain spouting as well as the radial field all of which are already in place in the area where the conduits must run. This is yet another job for Brian Veillette (Nashyei@aol.com), our excavation contractor on the project. As you can see from the pictures below, Brain has done a very careful job of creating the trench to minimize the damage to our lawn.

Conduit Trench Run

Conduit Trench

The conduits are laid in a bed of sand and then covered completely with another layer of sand to ensure that the pipes are not damage by freezing and thawing of the ground. We also constructed two moisture drains under the conduits at the ends and place small holes in the pipes at the bottom to allow the water that will ultimately accumulate in the pipes to drain into the ground. Also note the drainage pipes installed on the rain spoutings to carry rainwater from the room away form the conduit area and the shack in the basement. These are important steps to ensure that the feedline in the conduits stay dry and perform well for an extended period of time. It’s also important to create a gradual up slope at the ends of the conduits which will contain hardline feeders as these cable are stiff and cannot be bent sharply as the come out of the ground. This is accomplished by using a pair of 22.5 degree elbows on each end of the conduits to bring them out of the ground.

Conduits at Shack entry

Conduits at Shack

As you can see, we still have some work to do to complete the conduit work. We expect to finish this part of the project early next week. Once this is done and the remaining parts arrive for the tower, we will be ready to put it up!

– Fred (AB1OC)

One thought on “More Excavation For Feedline Conduits

  1. HI Fred,

    Where the conduit terminates above the ground the cable should have a good neck or “head” [think updside down J) so the end is not a rain collector.

    All the coax should terminate in a grounded box at the base of the tower
    with lightining arresters then continue to the antennas. This give the possible
    lightining strick a best path to ground away from the house. The second path
    to ground is in the conduit being under ground then any grounds at the house entry.

    There should also be a ground wire in the conduits to BOND the house end ground to the tower grounds (NEC/local code compliance).

    All ground rods should be thermally welded and burried.

    Allison/kb1gmx

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