Will a mobile antenna --either mag mount or NMO mount-- couple to surrounding objects such as tall trees, taller trucks, buses, or even people walking by?
If that is the case, would you get slightly better transmission signal if you parked in a crowded parking lot? As you get a better ground plane?
I have an SG7500 NMO mount on the roof of my car, a little bit to the left side. Radio is a TMV71A. Last night, after I stepped out while talking on the repeater, the NET controller then told me that my signal just degraded a lot. The signal returned to normal after I got back in. It was not noisy outside, and so I believe it is a bonding issue.