A response to a question I asked about using my AT-180 along with my IC-706MKIIG on 17M….
The biggest problem I found with the AT-180 is it has to have a good, very good ground. If it doesn’t you will find that some of the bands can’t be tuned and it will also narrow the usable band width on each band. I’ve experienced this first hand and to solve it just get an eight foot piece of 1/2 copper pipe the ridged type and hammer it into the ground as close as you can to your radios, like right outside a window near the radios. Run a good # 8 wire down to it and get a bronze ground anchor that will go over the 1/2 pipe. Tin the end of wire and clamp it to the pipe. One other thing clean the pipe with some emery cloth or sand paper before you put the clamp on. And you will have to go outside and clean this thing several times a during the year. I had a similar problem with one of my full wave loops. It would tune flat match but when I went to talk during a QSO it would kick out the tuner into by-pass. Turned out I had to make a better grounding system and I had to move the hook up point on the loop. It was too close to a corner and the ground wasn’t very good at all. Also make sure you run your grounds run separately one from each radio, tuner and even antenna switches. I purchased a ground buss bar out of an old electric service panel and bolted it onto a larger piece of 1/4 inch steel plate which I then sent a #8 wire out to my 1/2 inch copper pipe. It made the radio a lot quieter and my swr cam right now to flat. I don’t know for sure this will fix our problem, but a bad ground will drive you crazy and it will make your radio/tuner do stupid things as well.
I hope this will help you, let me know then I might be able to give you a little more of an idea where or what to look for.
Oh ya one other thing hook up a dummy load to the back of the tuner and see if it will tune it. If it will ten it’s ikely your antenna or feed line. If it won’t then you have a problem with the tuner it’s self.