The National Electrical Code specifies wire size for antennas (I realize the US
NEC does not
apply to ON land), though the concern in the NEC is mostly mechanical - i.e. it
will stay up,
not fall and give someone an RF burn or electrical shock.
The NEC recognizes 3 categories:
Receive only antenna up to 35 feet: #18 hard drawn copper or copper clad steel.
Antenna with under 150 feet long span: #14 "
Antenna over 150 feet: #12 "
While I have put antennas that don't meet these guidelines, they also tended to
break within
a few years.
>From the point of view of losses, even #24 would only take 5 or 10% off
efficiency for an 80m dipole. Legal limit power in a 50 ohm antenna would be
under 6 amps
which would require #18 to #20 in an extension cord, but a wire in free air has
less heat
problems than bundled or in conduit so somewhat smaller wire would still stay
cool enough.
Darrel AK6I
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|