I have tried mount ham sticks on SUV and a convertible use trunk lid mount, especially on 40m on the convertible I notice the SWR changes from opening the door and close the door. Now I am quite interested to find out how much radials a car would present to the antenna. Are there any ways to measure or give a somewhat quantified indication of how much radials an HF vertical is lacking? Something that indicates the "unblancy"? Maybe on a network analyzer?