Thread: Yagi efficiency
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Old December 3rd 06, 06:30 PM posted to rec.radio.amateur.antenna
John Smith John Smith is offline
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First recorded activity by RadioBanter: Nov 2006
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Default Yagi efficiency

Cecil Moore wrote:
John Smith wrote:
Cecil Moore wrote:


Can people who live by the trivial sword, also
trip and fall on that same trivial sword? :-)


Cecil:

Yes they can. And, that would be no trivial trip! It is just, in the
dark, like I am most of the time, I can't seem to avoid them, the trips.

However, what I am saying can be proved, or disproved in the real world.
What I am saying, is construct a SHF antenna and chuck a xmitter and
pa behind it. Encase the antenna in good insulating (polyurethane foam
for instance?) material and have a temperature sensor attached to each
element. Crank up the power and you will see some sort of rise in temp
in the director (indeed, it should be seen in ALL elements), since heat
= loss (actually, since we all accept the law of conservation of energy,
loss is a misnomer, really it is only a change in frequency, from rf to
infrared--beware a trivial trip!) we demonstrate an induced loss in the
system.

Next, remove all elements and materials to a distance from the de where
absolutely no coupling can occur. Tune and match the de to the pa
output, now bring the director into proximity to the de, observe the
power flow to the de as you finally set the director into proper
position to form a good frontal lobe, you MUST now re-tune and adjust
the de, this is because electrical factors (resistance, reactance and
possible other factors we are not even aware of) of the director are now
being "mirrored" into the de (an ohmic loss (heat) should also have
risen in the de due to the mirrored directors imperfections.)

That is all I am saying. Now we would have go get out our equipment
which can measure the weight of fly wings to know the real importance of
all that...

Geesh Cecil, you never ask ANY simple questions!

Warmest regards,
JS