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Re: [TowerTalk] 4 Square phase line length question

 To: "Tom Rauch" , "Dan Levin" , Re: [TowerTalk] 4 Square phase line length question "Jim Lux" Sun, 9 May 2004 06:32:17 -0700
 ```----- Original Message ----- From: "Tom Rauch" To: "Jim Lux" ; "Dan Levin" ; Sent: Saturday, May 08, 2004 7:23 PM Subject: Re: [TowerTalk] 4 Square phase line length question > > Here's the interesting thing..I assume you're using some > scheme where you > > use 1/4 wavelength lines for current forcing, right? so > the element current > > will be what it should be, regardless of the element > impedance. The > > mismatch at the feed eventually winds up back at the > hybrid/phasing network, > > where you can take it out by changing the L or C of the > phasing network (or, > > just ignore it, and take it out at the array feed point). > > Forcing equal currents requires equal input voltages and > correct input voltage phase. 1/4 wl away that becomes equal > currents and with correct current phase. > > The hybrid does NOT provide equal voltages at the output > ports, and it requires matched loads for predicted phase. However, it's presumed that one could adjust fewer components in the hybrid to compensate for the band change than fiddling with each element. If you use an approach like a 90 degree T or pi network for the phase shift, then you've got three components to fool with, so you can transform not only phase but voltage (i.e. impedance). One could either switch between two networks, or use some tapped/adjustable components. For that matter, if the frequency is a big percentage change, then the phasing lines aren't going to be 1/4 wavelength long, regardless of the notional element impedance. > > Fortunately the 4 square is somewhat forgiving of errors. > > 73 Tom > > > _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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