Topband
[Top] [All Lists]

## Re: Topband: My Turn For a Brain Pick - Sanity Check

 To: "topband" Re: Topband: My Turn For a Brain Pick - Sanity Check "Tom W8JI" Tom W8JI Thu, 13 Jun 2013 13:07:50 -0400 mailto:topband@contesting.com>
 ```Right. There's some discussion of this in the ON4UN book, where I found the Christman matching. As published there, it's 84 degrees of 50 ohm line in each element, plus 71 degrees of 50 ohm line in the element facing the desired forward direction,change directions by switching the 71 degree section. -------------------- So the forward element is actually feed at 155 degrees? `````` ```Phase shift is NOT the length of a transmission line unless the line has 1:1 SWR, is lossless, and/or is a multiple of 90 degrees. ``` ```In a phased array, with equal 90 degree lines feeding each element, the lines cancel out. Phase shift modification between elements caused by the feedlines to the elements is zero. ``` ```In the Christman system, or any system where lines are not 90 degrees or multiples of 90 and are also mismatched, the two 84-degree lines do not quite cancel each other out. They reduce the effect of each other, but not to zero like a 90 line or a matched line. They do add some phase shift, but certainly nowhere near 84 degrees. ``` ```Also the 71 degree line, since it is not 90 and not matched, does not shift phase 71 degrees. ``` ```Adding the line lengths together without considering impedance and transmission line effects doesn't work. It is really a more complex answer that requires looking at the system. Voltage and current are not even in phase, so we also have to know if the element is driven by voltage, current, or someplace between. ``` 73 Tom All good topband ops know how to put up a beverage at night. _________________ Topband Reflector ```
 Current Thread Re: Topband: My Turn For a Brain Pick - Sanity Check, (continued) Re: Topband: My Turn For a Brain Pick - Sanity Check, Jim GM Re: Topband: My Turn For a Brain Pick - Sanity Check, Jim GM Re: Topband: My Turn For a Brain Pick - Sanity Check, Tom W8JI <=