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Back in the '70s SWBell installed mobile phones on oil well drilling rigs with a sleeved vertical antenna. To the best of my memory, it had a 3 or 4 ft stainless steel 1" diameter mast that terminated in a collar at the top. The collar had an 18" long and quarter inch diameter rod attached to coax center conductor. The coax braid attached to a 1-1/2" or 2" stainless steel sleeve extending down. My understanding was the outside diameter of mast to inside diameter of sleeve served to match impedance and a decoupling balun.
I am looking for suggestions on duplicating the sleeve using coax braid. The assembled antenna will strap to top rod of a 20 ft length of fiberglass banner flag mast where lower three sections are tubes and top section a thin rod - so my antenna needs to be lightweight.
Thinking of taking length of coax and cut through insulation and braid 26" from end and pull off the braid, then cut center conductor to 22.5" for 144 MHz. Slide a 1" diameter clear tubing over the top of the length of coax and slide the 26" braid over that. 26" was estimated length as the brad length will shorten as you expand it over the clear tubing.
Ideas and suggestions welcome.
I am looking for suggestions on duplicating the sleeve using coax braid. The assembled antenna will strap to top rod of a 20 ft length of fiberglass banner flag mast where lower three sections are tubes and top section a thin rod - so my antenna needs to be lightweight.
Thinking of taking length of coax and cut through insulation and braid 26" from end and pull off the braid, then cut center conductor to 22.5" for 144 MHz. Slide a 1" diameter clear tubing over the top of the length of coax and slide the 26" braid over that. 26" was estimated length as the brad length will shorten as you expand it over the clear tubing.
Ideas and suggestions welcome.