In a message dated 96-10-20 18:56:09 EDT, you write:
>
>Good job Peter! Your method is also probably the only one that
>an average Ham could consider using to make the determination for
>himself under the constraints of his particular installation.
First, I agree in this specific case base impedance is a reasonable indicator
of system loss, but base impedance measurements can be misleading if the
ground system is resonant! It is possible to have a very "poor ground" that
offers a low base impedance, since the loss resistance is modified by
impedance transformation along the conductors in the system.
Let me give a specific example, an inductively loaded ten foot long radial on
160. The terminal resistance of the radial can be very low, yet such a radial
does a totally ineffective job as a counterpoise when compared to a full size
radial even though that full size radial would offer much higher terminal
resistance.
We have to be very careful assuming a base impedance change directly
indicates anything about antenna efficiency. It is most often distribiuted
resistance that is NOT at the base of the antenna causing most system loss.
The only way to positively tell if an improvement was made with any change is
via a field strength measurement.
73, Tom
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