Sep 6, 2019

You're Grounded

Since my "ham budget" is, well... there is no ham budget. So spending big bucks on thick copper busbar, copper mats, copper this, and copper that can get pretty pricey, not to mention a non-negotiable with the wife. This is true especially if it's all prefabricated PnP stuff.

Being like most of you other hams, I like to design and build my stuff myself. In furtherance of this manly, hamly expression of creativity, I designed and built two ground and lightning suppressor boxes, and two interior ground busbars. One set for myself and one set for my friend Stu, KD9MNK. Here is what I came up with.

Busbar in the box with two ATT3G50U's installed

The busbar is constructed with a 1.5 x 1.5 x 0.125" aluminum angle and #10 x 3/4 stainless machine bolts. I drilled 1/4" holes spaced 1.75" apart, allowing for three Alpha-Delta ATT3G50U surge and lightning suppressors to be mounted on the bar, and a heavy ground wire block (top right) for the ground wire. While assembling the busbar, I applied Noalox to all metal surfaces to insure electrical connectivity and prevent corrosion. The exterior bar is housed in a 8 x 8 x 4" PVC junction box with a waterproof cover. The interior and exterior busbars are identical in construction, except for the length - the interior busbar is four inches longer.

The box I made for Stu is fed from the bottom with a 2" PVC conduit running from his home to the back yard where the box is mounted at the base of his antenna. A second 2" opening on the box floor provides the coax exit. this is plugged with a 1/4" thick rubber disk with holes for the coax to pass through. A third exit in the box - also plugged with a rubber disk - is for the cable grounding the busbar and the ATT3G50U's. Water tight. Bug tight. Nice.

The KD9MNK busbar box for the base of the tower

The interior busbar is mounted in the house, just inside the coax conduit feed point. Another set of Alpha-Delta ATT3G50U's reside here, as well as the grounding point for the radios. I designed a 1.25" conduit that passes from the basement, into the wall cavity of the room above, where the KD9MNK station is located. The 20" long conduit terminates into the bottom of a sealed plastic duplex electrical box. A standard blank wall plate holds two SO-239 connections and a grounding stud. Nice and neat. A ground line runs from the wall plate stud to the busbar and out an exit point from the coax conduit, just outside the house. Grounding rods take it from there.

Yup, this should work fine.

The K9KMS busbar box ready for installation at the base of the tower

The KD9MNK interior connectors and grounding stud

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