OK. I posted on this a few months ago but cant find original post so I'll do again.
I've got a super three rod mounted in a plastic box. Attached in parallel is an L type attenna tuner like an MFJ. I've wrapped a few more turns around the center of the rod and coupled a trimmer (fixed) cap which I took from the super three board across the output. It resonates proper up to about 1 MegHz but above that tunes only on strong local stations. I'm testing on weak daytime stations and it works well on 910kHz with some added inductance from the antenna tuner but at 1240 it's very weak with no added inductance. I have more trimmer caps of different colors that I can cannibalize from the super 3 board but don't know how to adjust them or what values the colors represent. They look very fragile like an adjustment might break them. The one I'm using now is white. Would adding another trimmer cap across the output move the bandwidth up, or would it lower the freq?