Being a vertical aficionado, I lust over manufacturers radial plates popping up. Too rich for my blood, however, at $50 a pop. I read a recent QST Hints and Kinks column where someone decided to use a stainless drain insert and I my mind started racing.
Stainless over Aluminum? Yes. W8JI states what is most important is to minimize resistance in the ground system. Any method taken one needs to guard against the formation of oxides to limit resistance and “diode-effect”. I picked stainless steel, while exhibiting slightly inferior conductivity to aluminum, to limit the amount of maintenance required.
Rather than solder, I intend creating oxygen-free mechanical connections to hold copper-lugged radials to the radial plates. There are conductive greases available specifically formulated for copper-to-stainless connections. I will solder the radial wires to crimped lugs, however, mostly to protect and fill any mechanical voids between wire and crimped connector to protect against weather. I will be using silver solder for this job.
Why not use an even cheaper heavy copper wire buss and silver-solder radials to it? First, I will be adding in stages, and do not want to risk undoing what I have already soldered. A copper buss also becomes very rigid, and I want some flexibility in order to move things around without too much trouble. Also, my wire choice can be anything from surplus computer cabling to flex-weave spool ends. It is easier to use lugs to make attachment to the radial system due to the dissimilar wire types.
Hardware store crawl: Found several stainless steel drain inserts – one heavy gauge and one lighter. Each had holes that fit at 10 – 24 stainless-steel pan-head machine screw, and could accommodate 8 – 15 screws and therefore 8 – 15 radials each, or 20 – 30 each if I doubled them up which is intended. I removed the center posts from each of the drain inserts…not needed.
For hardware I selected packs of 10 – 24 1⁄2 inch machine screws, along with mating lock nuts with nylon inserts. Split-ring and regular #10 stainless washers make up for each screw. Bolt goes through the “under-side” of drain insert (I flipped it upside down so it is domed rather than cupped) with split washer between screw-head and drain insert. The other side I place a SS flat washer and lock nut. I may decide on a split-washer as well on top depending on how well everything holds. Pictures to follow soon. All told this system has cost me about $15 total. Each one of these will be attached to the base of my vertical by a short piece of heavy copper. One system will serve as the attachment point for south-bound radials, the other for north-bound.
I wonder about the durability and finish of the lighter gauge sink insert. Periodic checks this winter will provide the answers. In the meantime, I will have created a radial attachment system much more flexible for my use and at a quarter of the cost.
