[TenTec] Ten Tec 238A settings?

[Denton]

I have a horizital loop up about 30' that has about 240' of wire in roughly 
a trapazoid shape....have found that by using a certain length of 600 ohm 
feeders with a 4 to 1 balun, I have swr below 3.5 to 1 or below on all bands 
from 80 thru 10 meters, as measured at the balun's input...with the 
exception of 17 and 60 meters. I am also using about 20 ft of good quality 
coax to the shack with a TT 238A tuner to take care of the minor swr on the 
system.
I notice that on 75 and 80 meters there is a large variation in tuner 
settings from one end of the band to the other....is this typical of TT 
tuners and L networks in general?
It appears to be a decent antenna system....if I can hear them, can work 
them.
I have also verified the antenna's effiectiveness by also using it with a 
link coupled transmatch...by extending the 600 ohm feeders and running a 
short stubb of 400 ohm line to the shack.
TT's L network gives me a much broader matching range, otherwise would just 
use the balanced transmatch.