Ed,
Could you expand on your comment about connecting the radials to a ground. The ground radials are normally part of the mounting structure and are usually connected to the metal mast. As you indicated the NEC does require that the coax shield be connected to ground before it enters the building. I don't think I saw anything about running the coax underground helping with lightning protection in the Motorola R-56 manual.
BB
Since we're in the scanner forum I'm assuming a VHF/UHF antenna. The theory is the same with a receiver as with a transmitter but in practice an impedance mismatch is not a big deal for a modern receiver, so it's not that important. Grounding the antenna directly at the antenna connection can upset the radiation angle as can mounting it on a metal pole unless the pole is below the bottom of the antenna.
In practice grounding the cable somewhere between the receiver and the antenna should be good enough for safety but strictly this does not ground the actual antenna element, only the radials. For that you need to spend some bucks on a proper lightning bypass which will shunt electrostatic fields to ground from both the radials and the quarter wave vertical. You only want a D.C. ground to prevent buildup of electrostatic fields around the antenna. You don't want radio frequencies to go to ground, you want them to go to the receiver. The Radials, if properly designed, are all the RF ground you need.
But it's not that big a deal with a receiver. When we get to transmitters it becomes more important because an impedance mismatch can cause damage to a radio if it gets too bad. Most modern transmitters will prevent the damage by reducing there output before it can happen.
As for running coax underground for this purpose it's something I read a long time ago and probably I shouldn't have mentioned it.