8:1 sounds like an open circuit somewhere, even if the screws rot & a section drops inside it would not be that high,
double check the coax plugs are ok, maybe put a dummyload at the antenna end & confirm low vswr,
then its time to take the tornado down and clean & tighten all connections,
sirio base antennas are riddled with issues that only show up over time,
the self tapping screws are stupid, they make a poor connection when new & get worse over time until they rot and sections drop inside,
i slot the tube and use hose clamps, others cross drill & use nuts & bolts,
the plastic joints are useless, throw them in the bin & use electrical tape,
grub screws work lose with vibration,
on sirio 827 besides the dissimilar metals causing open circuit coil connection issues,
pop goes you cb amp
the sintered hubs sirio use on most of their base antennas can go none conductive with weathering so you lose connection between the riveted top hub and the radiator on 827's,
pop goes your cb amp
tornado looks like rain & dirt can wash down between radiator and outer tube if you don't tape over the joint,
that over time would likely cause a problem it too is riveted together,
sorry to sound negative but i call a spade a spade,
i have had more blown amps given due to sirio open circuits than any other fault,
& fixed more sirios than i can remember..
