You may wanna do about 5-6 turns on a 3/8” form. Then just use the piece of unshielded coax and start about the 4th turn and solder to. See what you get. May or may not need to move trimmer to other end of coil.
I stripped out some 12 awg Romex and made a 6 turn 3/8 coil. The swr is the same except instead of 1/4 turn from snug, the cap wants to be full snug. Like it needs a little more capacitance. I am going to swap a 468 back in the same spot.You may wanna do about 5-6 turns on a 3/8” form. Then just use the piece of unshielded coax and start about the 4th turn and solder to. See what you get. May or may not need to move trimmer to other end of coil.
The black wire is the bias power and the ceramic cap is part of the bias network. The alligator clip is a quick way to reduce the number of coils for testing purposes. Thanks for all your help. I really do appreciate it. Maybe the goofy bias arrangement is throwing me for a loop.You got something weird going on. It’s not this complicated. I’ve never had a problem like this.
Why is the black wire going out past resistors? What is that ceramic cap right by trimmer? It should tune easily. Why is that alligator clip on there? I’ve helped all I can. Without having it right in front of me. I can’t help you anymore
I am driving it with a Stryker 955 with the dead key set to 4 watts. I have a 29 that I can try too. The output SWR is 1:1 and doesn't even move the needle when modulating. This is into my antenna, I have not tried the dummy load yet. The input SWR used to be better before I changed the pills. I do have a scope but I assumed that it was not oscillating after I was able to get the output SWR down. I will have to check it to be sure.There's something I've been wondering and may have missed. Are you using a dummy load and what radio are you driving it with? Try a Cobra 29/25 to eliminate the possibility of this being an exciter problem. A scope would be nice. If the thing is still oscillating that would explain the difficulty you're having.
Somehow I am making this harder than it needs to be. I appreciate everyone that has offered advise and everyone who is following along. I can hear the skip rolling when I go to test this thing. I just gotta make this work. I was going to make a new coil with about 3 turns, then I thought what the heck. I will try another trimmer on the other end of the coil just to see. So I grabbed the 464 and backed it off half a turn from snug and put it in.I figured you weren't so much struggling with a huge problem, but enjoying working on it and discussing. At least I've enjoyed the great photos and all the input from everyone.
I suppose now you could always try Nomad's trick with the resistor again, with the coil now in place, to confirm you've not added so much to the impedance to be having the opposite problem.
You could also put another 464 at the other end of the coil and try tuning that way.
Anyone in the know...is it possible to "see" the input impedance with an analyzer? Or does it change too much when power is applied to provide anything useful?
EDIT, having gone back and read Nomad’s post he did seem to recommend the coil be placed between the cap and the combiner....and references the difficulty of making the coil “small” enough, which I’m assuming refers to the value and not physical size. If you’re having to add capacitance, maybe the coil is just too much, and/or maybe the cap would be better of moved?