I was just testing the grounding of my Diamond X30N and discovered that the 1 foot aluminum mast mount tube isn't conductive at all. Is this supposed like this?
Tube is anodized which protects from weather and has an electrical insulating effect. Screws fastening the antenna to the tube will break thru that layer or should. There is a hole for a grounding lead that will do the same when tightened. Measuring across the surface with your probes it will appear as non-conductive.