Denton,
Your observations on 80 meters and 75 is indicative of a matching
variation across those bands, not at all abnormal for ANY tuner at those
bands under a mismatch condition. Your antenna is not resonant likely
at either 75 or 80m at that elevation.
You did not list another important ingredient to the ANTENNA SYSTEM, the
length of the 600 ohm feeder, and then the length of the coax post the
balun. If either of these set up a quarter wave resonance or odd
multiple of quarter wave at bands where the SWR is higher, you would
have to add a few feet of feeder to give the tuner a better impedance to
match.
The surrounding terrain, and local earth character as to RF conductivity
can also affect a large antenna.
Check out the other factors, and remember everything from the tuner to
the antenna makes up the Antenna System, and must be compatible with the
band in use.
30 meters and 17 meters are not even multiples of the lower bands and
thus are perhaps always the worst to match on a multiband antenna.
-Stuart
K5KVH
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