[TowerTalk] Shunt Feeding Towers for 160 & SWR bandwidth?

[Herb Rosenberg]

I have a 72 foot crank up tower, with 18 feet of additional mast above it,
and 4 large HF antennas on top of the tower, that make up the top loading
for a shunt fed tower that I am setting up. 
 
I am connecting the shunt feed to an extended arm at the top of the second
section at around 38 feet above ground, and positioned about 20 inches
from the side of the tower, and running down to the ground.  I am able to
use an omega/gamma match to tune this to a 1.1 swr as measured at the
feedpoint comimg intot he matching network. I currently have 2 elevated
radials, and plan to add 2 more. 
 
I am interested in finding out how the SWR bandwidth is affected on a
shunt fed tower for 160, using this omega match and 4 elevated radials. 
Besides using the omega match to "tune" for minimum swr, can adjustments
be made to increase the bandwidth?  If so, how?  Does the distance that
the shunt is located off of the side of the tower have any effect? 
 
I am beginning to experiment with one for 160, and it seems like my swr 
bandwidth is only about 20khz.  I have heard that others using a similiar 
setup have bandwidths of 60 - 80khz or more, without retuning the 
variable capacitors.   Is this possible, and if so, how?  
 
Any comments would be appreciated. 
 
Thanks.
 
Herb - KG6OK
 
herbr@netcom.com
 
 


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