> some suggest that the heliax have a ground kit installed at ground level,
> where the cable leaves the tower base, where there are three ground rods,
> and 100 buried radials. This would result in the outer conductor being
> grounded at 60 feet and 400 feet from the antenna.
I can't imagine why someone running 400 feet of Heliax, and especially with
a tall tower, would not ground feedlines to a radial system at the tower.
Lightning concerns alone dictate proper grounding.
Second, I don't know what type of isolation device you have.
Effectiveness of any isolation depends heavily on how common mode impedances
are distributed in the system. Not grounding a shield sets you up for all
sorts of problems, and can greatly increase the amount of common mode
impedance you need. Any isolation device or system is dependent on the
change in common mode impedance it makes. This is why we should plan the
system to have low common mode impedance at the point where the series
isolation is added.
A properly placed ground and a few beads can mean a whole lot more than no
ground and a few hundred beads.
> additional shielding , but would strapping to ground at the base have
> any advantages?
Lightning alone dictates bonding the cable to the tower, so any RF technical
issues are a moot point. (no, the tower will not shield the cable)
73 Tom
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Topband reflector - topband@contesting.com
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