On Wed, 12 Oct 2005 04:06:07 GMT, Cecil Moore wrote:

Owen Duffy wrote:
The Bird does not measure or report the conditions on the coax, it
measures and reports the conditions in the immediate region of the
sampling element which is some 40mm inside the Thruline coupler
section.

I don't know what this argument is all about. Consider the
following:

XMTR---75 ohm coax---Bird---75 ohm load

Are you saying the Bird's placement will result in a reflection
coefficient of 0.2? I seriously doubt that is true.

I don't have the equipment at hand to do that experiment, but I have
done another experiment.


XMTR -- 2m of RG58 -- Bird43 -- 1.2m of RG213 Bird43 -- 20m RG6 (75
ohms) -- antenna.

1.2m of 50 ohm coax between the Birds is 4.2% of an electrical
(wavelength.)

I have made measurements with only one 100W slug which is moved from
instrument to instrument.

The tx was adjusted to 100W forward on the first instrument.

Both instruments read 100W forward.

Both instruments read 2W reflected.

When I swap the instruments around, I get the same results. It is only
a simple test, but I am not convinced that measurements from one
position are signficantly different to the other position, despite the
transmission line "environment" being different.

I am not surprised that both instruments read similarly, despite the
fact that one doesn't have any 50 ohm coax on the load side of itself,
whereas the other one does.

Owen
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