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## [Towertalk] Re: Phasing Lines For Stacks

 To: [Towertalk] Re: Phasing Lines For Stacks btippett@alum.mit.edu (Bill Tippett) Thu, 22 Aug 2002 13:23:41 -0400
 ```SM2EKM wrote: >eeee hmmm, guys dont kill me now but to be in phase, and I guess that´s what you want, the feedlines has to be EXACTLY the same lenght. Hi Jim! This bothered me a little too but I believe I have the answer. Consider a CW signal split to 2 phase lines, 1 wl to antenna A and 2 wl to antenna B. Under steady-state, both signals are in phase because phase repeats every 360 degrees. However, they are time-shifted by one period (35 nanoseconds at 28.4 MHz). This means antenna A radiates the signal by itself for the first period, and antenna B radiates the signal by itself for the last period. For all periods between, the signal is the combination and the result is "in-phase". Since we are talking about a CW, there is no distortion caused by combining two time-shifted CW signals, and I doubt we would ever notice the first or last 35 nanosecond periods when the signals from the two antennas are separated. For SSB, it is a little more complex since the signal is time-varying with the modulation. However, since the maximum modulation bandwidth for SSB is around 3 kHz (333 microsecond period), any distortion from combining signals shifted by one period (35 nanoseconds) should not be noticeable to humans. EZNEC verifies that there is no difference in far-field patterns between phasing of 0/0/0 and 0/360/720 degrees for the 3 antennas in my stack, but I am sure EZNEC assumes steady-state conditions, and not the case of the first and last signal periods covered above. Hope my simple-minded explanation helps! 73, Bill W4ZV ```
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