On 9/13/2011 8:06 AM, Antonio Vernucci wrote:
HV loss is hard to estimate. You could make your shunt wire a shunt
tube or rod and basically eliminate corona (A rule of thumb is that
10-15 kV/cm radius will have virtually no corona.. so for your 6kV, a
1cm diameter tube is in the right ballpark) Skin depth at 3.5 MHz in
Aluminum is .043mm, and the usual rule of thumb is to make the tubing
wall thickness 3-5 skin depths. 0.12-0.20 mm seems about right. Copper
could be thinner wall (skin depth is less)

I presume that the corona effect should be visible at dark. So far I
have seen none, but we had not a single day of rain since I mounted this
antenna (incredible summer season...). So, I must verify when rain will
come, in a few days from now they say. Or do you think that corona may
not be visible?


Nope.. you can't usually see the corona discharge. The professionals
use a special camera with a narrow band solar blind filter.




I am using a 4-mm diameter wire so, if I will really have corona
problems, I could insert the (vertical) wire into a 1-cm aluminum tube
connected at the very bottom of the wire (i.e. at the antenna feed
point). Probably a 2-meter long tube could be sufficient (RF voltage
gradually diminishes getting away from the antenna feed point).


Sure..