[TowerTalk] antenna impedence and ground impedence??

[Dan Sawyer]

Tom,

I am trying to increase the efficiency of a center loaded vertical by 
creating a good ground system.

Based on models the antenna 'should' have a have a total impedance of 
less then 10 Ohms. Yet it reads close to 50 Ohms. I assume the 40 plus 
Ohms is related to ground resistance. Is this a reasonable starting 
assumption??

Dan

Tom Rauch wrote:

>>Measuring ground resistance is easy. You just have to make a lot of
>>measurements.
>>This is how we find mineral veins which we can map based on the
>>measurements.
>>Any introductory text on geophysical prospecting using potential methods
>>will
>>teach you all you need to know. The math isn't bad.
>>    
>>
>
>It definitely isn't easy.
>
>It is all but impossible for a ham to measure the radiation resistance,
>ground loss resistance, and antenna loss resistances. Even broadcast
>stations are forced to back the data out of many dozens or hundreds of FS
>measurements in a proof of performance. Even with a full proof and careful
>work you are lucky to be within 3dB.
>
>I don't know what you are measuring, but accurately estimating the portion
>of resistances normalized to one point in the system from antenna loss
>resistances, radiation, and ground losses so you can estimate efficiency is
>all but impossible outside of a complex test environment. This is what he
>wanted to do, not to know the DC or low frequency AC soil resistance between
>two or three probes.
>
>With enough measurements we can learn the average low frequency
>characteristics of soil, but that data doesn't mean anything in this
>application. Neither does a meter at the antenna feedpoint.
>
>73 Tom
>
>  
>