[TowerTalk] Interesting problem

[Dave Hachadorian]

On Sat, 11 Oct 2003 17:37:14 -0500 "Mark Beckwith" <mark at concertart.com>
writes:
> Hello sages of RF wisdom.  I have one for you.  Not being an RF 
> engineer,
> the solution escapes me:
> 
> I have two identical antennas on one tower at different heights.  
> They each
> have feedlines coming down to the bottom of the tower.
> 
> If I wanted to feed these two antennas in phase, is there a way to 
> figure
> out how long a piece to add to the lower antenna's feedline so it is 
> in
> phase with the higher antenna?  The velocity factors of the 
> feedlines are
> unknown.  The feedlines are not the same material.
> 
> I have a dummy load, one of those Autek RF-1s and an MFJ antenna 
> analyzer
> with two meters (SWR and impedance).
> 
> Have at it.  Thanks in advance.
> 
> Mark, N5OT
> 
> PS If it matters, the antennas are for 10M and one is at 50 feet and 
> one is
> at 100 feet.

There is (or at least, was) a procedure for
phasing dissimilar antennas on the
array solutions web site. It involves
a dual-trace scope, and transmissions
from a nearby ham.

Dave Hachadorian, K6LL
Yuma, AZ