Topband: Shunt feed procedure?

[kr9u at arrl.net]

Kenny,

I am shunt feeding a 120 ft. tower on 160 with 8 ft. mast out the top with a 432, 20 el antenna at 128 ft.   At 115 ft. is a 2 el 40.   You can see it on my QRZ page.
Measurements show it at 122 degs.   I am using a single wire attached at 70 ft.  The spacing from the tower is about 2 ft. and does change the SWR.   

Jim - KR9U



-Subject: Topband: Shunt feed procedure?

Hi All,  we’re planning on gamma  loading a 130’ tower with a stack of StepIR  antennas using a cage for the shunt wire. We have modeled the tower. Question: is the model sufficient to determine the gamma wire height?  Or is the procedure to use a single wire to per the model height first to find the 50 ohm point and then build the cage to fit the length?

Also, any tips on shorting the elements on the StepIR dream beam so they won’t arc?  Any anecdotal info on StepIR antennas on the shunted tower?

Regards , Kenny K2KW