Let's look at what we know of the situation:
...I have a 120 ft end fed longwire. I checked the SWR with a Rigexpert AA-54 and the highest was 80M at approx 6.5:1.
A 120' end-fed wire
will have a high impedance on 80m - perhaps
2000 ohms or so. It then becomes critical exactly how the wire fed and
the grounding system incorporated. If there is some sort of matching network
(or a quarter wavelength of ladder line to make a Zepp feed) then the SWR
might be usable.
If the coax is connected directly to the wire, then the SWR will be very
high, and we have to suspect that the SWR is beyond what the analyzer can
measure, or that there is an inadequate ground system that is contributing
to the radiation and thereby changing the SWR.
Now it might be that, due to the high SWR, there are high coax losses
that are causing the SWR to be lower at the shack end of the coax. But to
make sense of the situation we really need to know:
1) how the antenna is connected to the coax (if it is)
2) What is connected to the coax shield at the feedpoint
3) the length and type of the coax
4) Where you measured the SWR using the analyzer
With the antenna as described, I'd guess the SWR should be > 20 : 1,
depending on the coax losses. With the SWR significantly lower than that
I'd guess there are other factors at work here other than simply the matching
range of the tuner.