sorry to say this but there isnt a 50 ohm version of rg 6 only 75 ohm
for cb we use rg 58 or rg 58u or rg 213 low loss coax both are 50 ohm
i sort of did my apprentaship for aerial starting in 1981 with a cb shop in nottingham called good buddies
and still fitting them now 27 years later not so many cb aerials now though as its past its sell by date here in nottingham
if some one has sold you rg6 as 50 ohm coax take it back and ask for your money back