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#1
January 25th 08, 07:22 PM
posted to rec.radio.amateur.antenna
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Derivation of Reflection Coefficient vs SWR
On Fri, 25 Jan 2008 16:15:33 GMT
Cecil Moore wrote: Roger Sparks wrote: As I finished writing the post, I wanted to call attention to the assumption that the reflected power is true power and adds to the amount of energy "stored" on the transmission line. But "stored" is a word that implies static conditions, and static conditions are not found on a transmission line. So I substituted "present" for "stored. The amount of energy existing in a transmission line is exactly the amount required to support the measured forward power and reflected power. If the steady-state forward power is 200 watts, the reflected power is 100 watts, and the lossless transmission line is one microsecond long, it contains 300 microjoules of energy. I don't think that is a sheer coincidence. :-) -- 73, Cecil http://www.w5dxp.com Yep, and if we quickly replaced the source with a termination having the impedance of the transmission line, 100 watts of power would continue to be delivered to the load for one microsecond, delivering 100 microjoules of energy. 100 watts of power would be delivered to the reflected wave termination for two microseconds, delivering 200 microjoules of energy. The transmission line was a dynamic power storage device for two microseconds after the power source was disconnected. 73, Roger, W7WKB |
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#2
January 25th 08, 09:18 PM
posted to rec.radio.amateur.antenna
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Derivation of Reflection Coefficient vs SWR
Roger Sparks wrote:
If the steady-state forward power is 200 watts, the reflected power is 100 watts, and the lossless transmission line is one microsecond long, it contains 300 microjoules of energy. I don't think that is a sheer coincidence. :-) Yep, and if we quickly replaced the source with a termination having the impedance of the transmission line, 100 watts of power would continue to be delivered to the load for one microsecond, delivering 100 microjoules of energy. 100 watts of power would be delivered to the reflected wave termination for two microseconds, delivering 200 microjoules of energy. Can we consider the old wives' tale of no energy in reflected waves to be laid to rest? -- 73, Cecil http://www.w5dxp.com |
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