At 07:51 PM 7/8/2006, Gary Schafer wrote:
>In addition to Jim's comments, remember that the current will divide pretty
>much equally between all radials that are attached to the tower so each will
>only carry a fraction of the total current.
It occurs to me that one should probably also design for the maximum stroke
current, not the average.. e.g. 200 kA instead of 20kA or so. Even so, if
you've got 10 or so wires, they don't need to be very big.
A much more interesting problem is not actually handing the stroke current,
but figuring what's the optimum setup to suppress a coupled transient from
a nearby stroke. Since it's for 160m, I assume you'll have some sort of
big loading coil and/or top hat on the antenna, so it's going to be narrow
band. You might want to look at what the flashover voltage of the loading
coil is, and what happens if that occurs.
I know folks that have had "exciting" experiences with unpowered tesla
coils at a teslathon from coupled energy from the powered coils. A short
160m antenna isn't much different from a tesla coil.
You could probably model the sender as a 100 meter long vertical wire with
a current transient of a few hundred kA/microsecond as a worst case. Pick
some reasonable distance (10m?) from sender (stroke) to victim (your
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