Re: NEC-LIST: induced voltages

If I understand you correctly ...

To my knowledge, "antenna factor" can be viewed as an efficiency of
the antenna - how the antenna transduces the signal from the cable to
an output signal radiated from the antenna. Technically, it involves
the boundry conditions of a signal being transported from a relatively
conductive medium (the innards of the antenna) to a relatively
dielectric medium (space).

As far as optimal load has been concerned for me, everything should be
50 ohms - antenna, cable, device (be it spectrum analyzer or
receiver). I have found people that gave no regard to the cable
between the antenna and SA/receiver. This gave erronous results. At
a former company, I was able to easily check the loss of the cable
with a network analyzer on a regular basis.

Regards, Doug

Graeme Cairns wrote:
>
> Throw me in the dumb corner too, but I'm confused about several points
> that have come up in this discussion and I'd appreciate it if someone
> would clarify them:
>
> 1) What exactly determines the "antenna factor" mentioned by Cliff
> Kraft? I expect it is a combination of losses in the antenna and
> impedance matching between the antenna and the load.
>
> 2) What is the optimal impedance relationship between the load and the
> cable for accurate measurement of ambient fields? - In his original
> question, Grant Bingeman suggested that the load impedance might be
> the complex conjugate of the cable impedance. Max Schmitt's analysis
> also assumed a matched impedance. However, the electric field probes
> mentioned by Matt Taylor have high impedance loads.
>
> It seems to me that with a low impedance (obtained by matching load to
> cable) the load would tend to short the measured field. On the other
> hand a load with a high input impedance will generally give you a
> noisier measurement.
>
> This issue interests me as I'm looking at measuring weak ambient
> electric fields on the seafloor using electric dipole receivers. In
> experiments to date, the fields I've measured have tended to be weaker
> than I'd expected from theory, and the discussion in this group may
> help explain why.
>
> Thanks,
> Graeme Cairns

************************************************************
------------------------------------------------------------
The comments and opinions stated herein are mine alone,
       and do not reflect those of my employer.
------------------------------------------------------------
************************************************************
Received on Mon Jun 29 1998 - 09:14:08 EDT