[TowerTalk] Coax Lengths for Stacked Yagis

Jim Brown jim at audiosystemsgroup.com
Mon May 7 02:12:38 EDT 2018


Another point -- a length of line that is a quarter-wave at 14175 is NOT 
a quarter-wave at 14000 and 14350.

To answer both points, it seems best  to build as complete as practical 
NEC model of the antennas, including their physical relationships in the 
stack, and all phasing and matching cables, then studying patterns and 
gains over the needed bandwidth. There's a good discussion of this, with 
examples, in the ON4UN book, credited to Al Christman, K3LC.  I used his 
design method (and built the NEC model) for a 2-el 40M array that we 
used for a couple of CA QSO Party expeditions.

The antenna seemed to work well, but required a lot of work to string 
out the 32 radials we used for each element, which is why we stopped 
using it.

73, Jim K9YC

On 5/3/2018 9:06 PM, Wes Stewart wrote:
> Another point or two and then I'll shut up.
> 1)  The expected phase shift in a line is only achieved when the line 
> is matched.

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