To: <topband@contesting.com>
> Date: Thu, 02 Apr 1998 22:06:41 -0500 (EST)
Hi Earl,
The EWE is easily and correctly analyzed as two short verticals.
> 33.5 degrees. The 180-S formula says that, for max F/B, that phase
> difference should be 180 - 33.5 = 146.5 degrees (or inverted, -33.5
> degrees?). Nothing seems to correlate, inverted vertical or not.
The elements are 180 out of phase. The phase delay is 41 degrees plus
the 180 degree inversion. The net phase **delay** of the feedpoint
element end is 139 degrees. (Remember the NULL element is the phase
reference, not the feedpoint!) 180-S is 146.5 degrees. The phase
error is 146.5-139= 7.5 degrees.
On 80 meters, the same EWE's spacing would be 67 degrees. The delay
would be about 82 degrees. The phase delay of the feedpoint end
would be 280-82= 98 degrees. The ideal delay would be 180-67=113
degrees. The error from ideal is 15 degrees.
When one element's feed is inverted the correct phase delay in the
delay line for a backfire null is exactly equal to the spacing in
degrees (spacing less than 1/4 wl). This is how I feed my
four-square, my 40 meter beam, my loops and any other directional
driven arrays.
Using this system phasing becomes frequency independent if a delay
line (rather than lumped components) is used. I use the same delay
line on 80 meters as on 160, and that delay line is the correct
length all the way down to "dc".
For example, my loop arrays fire in the same direction at 100 KHz as
they do at 7 MHz, with NO change in delay lines. They have the same
direction response at 100Hz as at 100 KHz. The only thing that
happens is sensitivity goes away.
If the EWE system had a transmission line delay of 41 in the
line (modeled value) and the spacing is 33.5 degrees, the error is
only 7.5 degrees! That's not a large error.
73, Tom W8JI
w8ji.tom@MCIONE.com
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|