It is generally accepted that a Line Isolator is necessary in most Ham Radio stations. Peter G3OJV, describes a simple method of both in stalling and testing one. It can also help to reduce noise.
For tesring we recommend the RigExoert Zoom AA-230
https://www.hamradiostore.co.uk/product/rigexpert-aa-230-zoom-0-01-230mhz-analyser/
Your Ham Radio Store
https://www.hamradiostore.co.uk