[AMPS] Voltage at antenna end. de K0FF

[Chuck Counselman]

>Perhaps at the very end the current is zero and the voltage is
>infinite...not probable, but the range of possibility is large.

The voltage isn't infinite, of course.  The "fringing-field" capacitance of
the end of the wire limits it, and the dielectric polarization of the end
insulator reduces it further.  I don't know just what it is.  To estimate
it you'd need E-M field modeling s/w that I don't have, although I may take
a shot at it with NEC-4, which I do have.  The problem with NEC-4 is that
it can't properly model the end-insulator. Perhaps someone on the
<amps@contesting.com> list has s/w that can?

To reduce the voltage and E-field at the end of an antenna it would help to
put a ball, or something approaching a ball -- even a few small loops or a
"snarl" of wire -- on the end.  Whether this would help to prevent
insulator failures, I don't know.  The main reason for electrically-induced
insulator failures is probably moisture inside the insulator.  I suggest
taking a lesson from the electric power utilities, and using a _string_ of
insulators at the end.

-Chuck W1HIS



--
FAQ on WWW:               http://www.contesting.com/FAQ/amps
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com