[Antennas] Re: Ground losses in ohms

[Roy Koeppe]

About,

"...So my question to the group is, what would they use for the ohms of
resistance
of a 12' tall center loaded vertical on 40m, when the ground consists of
sixteen
13' long wires in a circle on that tar and gravel roof?"


GB & 73's
KA5OAI
Sam Morgan


Hi Sam,

The equivalent resistance for a radial system as you described above is
approximately 15 ohms. The feedpoint Z at the bottom of the 12' tall 40M
vertical is on the order of 10 ohms. So, adding 10 ohms to the 15 ohms,
your antenna system input Z will be about 25 ohms with a 2 to 1 SWR
using 50 ohm coax and no matching device at the antenna. Overall system
efficiency is around 40% after you do match things up with an antenna
'tuner' or another matching method.

73,   Roy   K6XK/0    Iowa