To All from
PA0SE
I wrote:
................
> Measuring earth resistance at 50Hz has no meaning for the loss
at 136kHz
> because the earth resistance (impedance is more correct) is
frequency
> dependent.
Upon this Uwe, DJ6WX, remarked:
but you use a noise
source ie. not 136kHz only. does that not matter
?
The noise source indeed produces
noise over a wide band of frequencies. But as a detector a receiver is
used and therefore only a small frequency band around 136kHz is used to
balance the bridge. The width of that band depends on the pass band of
the receiver. Because the bridge can theoretically be
balanced for one frequency component of the noise only it is
necessary to use as small a bandwidth as possible. With a wide pass band
of the receiver a minimum in the noise can still be found but it is not
very pronounced. So the narrower the pass band of the receiver, the
deeper the noise minimum becomes.
73, Dick, PA0SE
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