This Transmatch(MFJ-969) has it's sensing circuitry too close to other circuits.
I would prefer to use a Transmatch that kept the sensing circuits somewhat "isolated" from other circuits.
Try using a Transmatch with no extras inside and an external Wattmeter / V.S.W.R. meter combination.
The following Transmatch(MFJ-901B) has no sensing circuitry. It can't interfere them. It's also well proportioned inside.
Circuits are direct. Less of an opportunity to induce stray R.F. inside. It's a step-inductor, but at least it's an air-
I found a MUCH BETTER Transmatch!
There seem to be 2(two) versions of this transmatch. I think the one with the internal balun is the better one.
P.S.: Sorry about the size of the pictures. They were the only ones I could find that were still relevant! I usually
watch the scale on pictures. I hope this isn't a problem.
P.P.S.: Joe(JOE-KB3ZGV), please take note! This would be a better instrument for you to utilize!