On 9/6/2012 5:36 PM, Joe Subich, W4TV wrote:
flipping phase
Joe,
Please use the right word -- POLARITY when you mean turning the wires
over to invert the signal. Phase is a continuously variable function and
increases directly proportional to frequency. For example, a piece of
transmission line that provides 180 degrees phase shift at one frequency
provides a phase shift of 198 degrees at 1.1X that frequency, but
reversing the POLARITY results turning the signal over at ALL
frequencies. The difference between how these two methods of feeding
antennas can be HUGE in terms of the maintaining performance over a
desired bandwidth.
Engineers working in pro audio had to learn this 30 years ago when
modern instrumentation made the difference glaringly obvious, and
although it's critically important to hams, most don't even have a clue
about the difference.
73, Jim K9YC
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