Thread: Brainteaser
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Old May 26th 06, 01:09 PM posted to rec.radio.amateur.antenna
Buck
 
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Default Brainteaser

On Fri, 26 May 2006 03:16:38 GMT, Cecil Moore
wrote:



If the source power is 100 watts, the forward power is 200
watts, the reflected power is 100 watts, and the load power
is 100 watts, all the joules per second needed to support
that forward and reflected power was supplied by the source
before steady-state was reached. Anything else would violate
the conservation of energy principle.

This is easily proven using a one second long lossless
transmission line as a conceptual training aid for the
uninitiated.


I gathered that from an earlier post, but I think the confusion comes
in the second second, doesn't it? 100 watts of power is generated
from the generator for two seconds. the first second, 100 watts
travels to the antenna and only 100 watts is in the transmission line.
Then for the second second, 100 forward watts is moving towards the
antenna and 50 reflected watts are returning to the transmitter for a
total of 150 watts in the transmission line? Of course, since the
transmitter isn't matched to the antenna, the reflected power is
reflected again for 25 watts being reflected back to the antenna
bringing the power from 100 forward watts to 125 watts (the reason
power meters go up in wattage when SWR rises) thus the antenna
reflects 62.5 watts which adds to the 125 for a total of 187.5 watts
in the transmission line. Sooner or later one will have a meltdown
that will make Chernoble look like a firecracker compared to a
fireworks display. lol


--
73 for now
Buck
N4PGW