[Antennas] Re: Ground losses in ohms

[Sam Morgan]

Roy Koeppe wrote:
> 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?"
> 

> 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.
> 
I neglected to add the antenna has a base coil for impedance matching.
-- 
GB & 73's
KA5OAI
Sam Morgan