You could be running way too much power if

I once had to set up a coax link using RG-92, but the customer had pulled something huge like RG-15.
Wrong size AND impedance.
Made up matching transformers and adapters, still not good enough.
Following ancient and mysterious training from radio school, I eliminated the xformers and tuned the mismatch by pruning the length to meet the installation then solder finished the terminations. I did not need to use a stub.