Topband: Gamma matched crank up tower

[john]

Good day everyone and seasons greetings,
I have just change from a full size inv vee to a shunt fed tower 24.6m ht, with 4 top loading wires, the antenna dips with a gdo at 1.5 mhz, 110 degs, I have installed a shunt at 16m point with about 1m spacing I found I could only tune with a T match I put together, a series cap or an omega match did not give results, the antenna works great with the T match, I have installed more radials and am up to 60 now with about 25 of them 1/4 wave, the radials are still work in  progress.

Today I tried the series cap again and moved the bottom of the shunt wire closer to the mast about 300mm off the mast and found I could tune with a series C and found a 1.6 - 1 match with about 275 pf.

I have looked at the graph in the ON4UN book and it looks like I am a bit low with my gamma arm it seems it may have to go to the 19m point and then fine tune with gamma spacing.

I did want the antenna to be on 1.5mhz so was please at that but could anyone tell me if I am correct in thinking the gamma arm needs to go up, it would be good just to use a motorised C possible a vacumm one eventually.

regards HNY all
John G4EIM