Towertalk
[Top] [All Lists]

## Re: [TowerTalk] 4 Square phase line length question

 To: "Dan Levin" , Re: [TowerTalk] 4 Square phase line length question "Jim Lux" Sat, 8 May 2004 18:47:00 -0700
 ```----- Original Message ----- From: "Dan Levin" To: Sent: Saturday, May 08, 2004 3:13 PM Subject: [TowerTalk] 4 Square phase line length question > We are building a 4 square, and using Force 12 relay boxes to tune the > elements for phone and CW. These boxes put a coil in series with the feed > point of the antenna to electrically lengthen it for CW, and then short out > the coil using a relay for phone. > > > > Question: Do we need to take into account the length of the wire in the coil > (on CW) when we calculate the length of the RG-11 phasing lines from the > hybrid coupler to each element? To put it differently, are the coils part > of the antenna, in which case we make the phasing lines the right length and > ignore the coils, or are the coils part of the feed line, in which case they > effect the length for phasing purposes? > > The series coil is there to cancel the capacitive reactance of the too short antenna. (and, because the element's not "that much" shorter, the resistive part, (mostly radiation and ground resistance) is about the same, so if you take out the extra C, the match is fairly good). However, in a 4 square (or any driven phased array), the feed point impedances aren't even remotely close to what a single element would be, so the value of switching in a coil is dubious. 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). > > Thanks! > > > > ***dan, K6IF > > > > _______________________________________________ > > 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 _______________________________________________ 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 ```
 Current Thread [TowerTalk] 4 Square phase line length question, Dan Levin Re: [TowerTalk] 4 Square phase line length question, Tom Rauch Re: [TowerTalk] 4 Square phase line length question, Jim Lux <= Re: [TowerTalk] 4 Square phase line length question, Tom Rauch