[TowerTalk] No Explanation

[rt_clay at bellsouth.net]

>Tor N4OGW Stated
>"Also note that the phasing for the cardioid array shown in that
>report is incorrect. You can't just add a "delay" line of 1/4 wavelength
>to get 90 degree phasing." and
>
>"Two verticals, 1/4 wave spacing, 90 degrees out of phase."
>
>withour any explanaiton.
>
>Please explain Tor.  It has worked for me.

You can find a detailed discussion in the ARRL Antenna book, or better in ON4UN's book.  The difference in the length of the two feedlines is not 90 deg because of coupling between the verticals. This way of phasing is known as the Christman method.

ON4UN has a plot of the gain and F/B comparing correct phasing with the "add 90" approach. With sloppy phasing, you get most of the gain, but the F/B is much worse than it could be.

Or see the reference listed first at:

http://home.earthlink.net/~jimlux/radio/antenna/phased/arrl.htm

Tor
N4OGW