I don't think your antenna setup is 50 ohms on ANY frequency.
I have put up several horizontal loops but used a quarterwave of 75 ohm line to transform Z down to 50 ohms. (this ONLY works on one frequency) where the loop is one wavelength in circumference on a single band ! (they worked fine without any tuner).
You could hook up your analyzer to the radio end of the tuner but that only tells you the tuner is adjusted and nothing about the actual antenna radiator !
I have resisted using balanced line feeders until I built an experimental DZ/XDZ antenna for some bidirectional gain on 30/20M last fall
.I Had to buy the new MFJ balanced line tuner for it. The directional wattmeter in this tuner measures the SWR on the 50 ohm unbalanced side so you never actually know or worry about the SWR on the balanced feeders to the antenna radiator !
73.....JD, FISTS #3853,cc 455,SKCC # 1395,tribune #12,
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