When I worked as avionics tech, it got to the point where I could generally tell how we’ll an aircraft’s comm radios work simply by eyeballing the antennas. When an owner complained about VHF nav radio problems, I had visions of a nav antenna coated with corrosion, the result of years collecting water in the vertical tail fairing. When the airplane showed up, my suspicions were usually confirmed.
Truth is, antennas are one of the most neglected accessories on the aircraft. They live hard lives sitting out and flying in all kinds of weather. Plus, belly-mounted antennas collect grease, grime and sustain sizable amounts of heat when in close proximity to exhaust stacks.