On Fri, 10 Sep 2004 14:25:15 GMT, "Jimmie"
wrote:


"Richard Clark" wrote in message
.. .
On Thu, 09 Sep 2004 19:42:41 GMT, "Jimmie"
wrote:

This equates to about 40 ohms
impedance seen at the antenna base. This also agrees with my antenna
analyzer. Antenna is a full length 1/4 wl antenna on 20m. I was figuring
37
or soo for this.


12 12f t wires, Center ground stake 10 ft long, far end of each wire has a
stake about 3 ft long. These are used more to just hold the wires in place.

Hi Jimmie,

My last post responding to this included a mistaken analysis. I had
picked up the sample vertical and did not notice it was using MININEC
ground, which is unsuitable for this question.

On using the particulars you supply above, the results are very much
different.

With the default ground (0.005/13):
Impedance = 57.96 + J 0.1116 ohms

With extremely poor ground (0.001/3):
Impedance = 65.24 - J 0.1441 ohms
SWR (50 ohm system) = 1.305

With poor ground (0.002/13):
Impedance = 55.64 + J 0.1153 ohms
SWR (50 ohm system) = 1.113

With "Pastoral" ground (0.01/14)
Impedance = 56.62 + J 0.1475 ohms
SWR (50 ohm system) = 1.132

With very good ground (0.0303/20)
Impedance = 54.38 + J 0.3596 ohms
SWR (50 ohm system) = 1.088

For each change of ground I drove out reactance by trimming the
radiatior to