I have a 50 foot aluminum mast on my property, guyed at 32 feet and mounted on a 6" x 6" pressure treated pine post. I put a 15 foot stinger of aluminum tubing at the top to give it a height of 65 feet and hung an arm on it at 50 feet that extends out 3 feet. This holds the vertical part of my 160 m. inverted L, which is positioned over a ground system of 101 radials. It's resonant frequency (where X is minimal) is around 1840. The resistive component at that point is around 11 ohms. This is with the mast grounded. I can also put the mast on a feedline using the wood post as a base insulator and use it as a 1/4 w. vertical on 75 meters. You can co-locate two verticals with a shared ground system and it works okay. I've always grounded the 75 m. vertical when using the inverted L on 160 because that results in the low feedpoint impedance at the inverted L I'd expect to see on 160. It's been a long time and I don't clearly remember what happens when I float the 75 m. vertical above ground except that the 160 m. impedance changes (goes up I think). I should experiment with someone within groundwave distance and see if grounding/floating the support mast changes the efficiency of the inverted L.
73 Rob K5UJ _________________ Topband Reflector Archives - http://www.contesting.com/_topband