ok thanks all that sent answers. Let me go over this again.   Originally it came with rg58  single length piece of coax 80 1/4 in total length with 78 in of shield total. each end of the coax is attached to the driven elements.... one on each side... and  the shields go to the boom. A beta match tube with shorting bars also attaches to the driven element on each side. according to the manual to use with high power just subsitute rg213 same dimension as the 58 and it should be ready. I used a piece of RG8 with solid dielectric cut the same. I have a hard time believing that this could shift the resonant frequency by 1.5 mhz.  the manual doesn't say anything about it being 4:1 balun it's just a matching line, i would guess. Also I have interaction with the 7 el 10 ft above it; when the two are aligned in the same direction, the swr on the 7 el also jumps to 2:1... go figure! Cort