Thread: Dish reflector
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Old April 18th 09, 08:51 PM posted to rec.radio.amateur.antenna
Cecil Moore[_2_] Cecil Moore[_2_] is offline
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First recorded activity by RadioBanter: Mar 2007
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Default Dish reflector

Roy Lewallen wrote:
I measured current (of which the definition is well understood except
apparently by Cecil), and took a lot of care to do it right.


Roy, I am not questioning the accuracy of your
measurements - I'm sure they are extremely
accurate.

What I am questioning are your concepts and
conclusions about those measurements.

As illustrated in Kraus' antenna book, the end-
to-end current phase changes by about 3 degrees
for a 1/2WL dipole or a 1/4WL monopole. My question
for you is:

How can a current that changes phase by 3 degrees
in 90 degrees of antenna possibly be used to
determine the delay through the antenna wire?
- or through a loading coil?

Hint: The current in a standing wave antenna is of
the form:

I(x,t) = C1*cos(bx)*cos(wt) + C2*cos(wt+bx)

where C1 C2

i.e. the phase changes primarily with t but primarily
not with x. For any time t, the measured phase up and
down the antenna changes very little.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com