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[FORMER_K9ZE_RAH]

I have six sections of Rohn 25 and would like to use them to build a full-size 80m vertical.  Would like to see if anyone might have suggestions on how the base could/should be insulated from ground.  

[K1RX]

I use Rohn 25 for a 80 M 4 Square system.  The insulators I made up were a double wall PVC about 8 inches in
length, then drilled out to match the holes (only used the larger of the two size holes to actually secure the tower to the PVC.  I think you need a bolt that is 2 1/2 to 3 inches in length.  I left a gap of about 1 inch between the top of the bottom section and bottom of the first section above the insulator. (inside the insulator of course)

These verticals are actually elevated on 20 ft. of Rohn 25 and I use 40 ft.of tower above the insulators.  I resonate the element by extending aluminum tubing out the top of the tower, starting with 1-1/2 inch diameter tapering to 1/2 inch at the top.  I think the overall vertical length is around 70 ft. and with the elevated base this makes it 90 ft. high.  One needs to have a longer element when you drop in diameter from say, 12 inches (tower width) and the aluminum tubing to make it resonate properly.  

With your straight 60 ft. of tower, you should probably not have to add any more to make it resonate.  If ground mounted, the base insulator approach I use will probably be okay as well.  A friend of mine put up a 4 Square with 60 ft. of Rohn 25 elevated on a 10 ft. section and added a cage of wire to make the element even larger to make it more broadband.  I get good bandwidth out of mine as is with the taper and all, his works well too.  I think he effectively made his vertical 3 ft. in diameter with the added wires.

73,

Mark, K1RX
mpride@us.ibm.com