Regarding grounding, this has been troubling me so I have to ask.
Isn't the antenna electrically isolated from the mast? In my way of thinking, if not isolated, any received signal would be 'grounded' out and not reach the receiver (assume antenna at top of mast, i.e., highest point).
In the case of coax, it is recommended that the shield be grounded at the point of entry. But, what about the center conductor? Doesn't the center conductor 'conduct' the lightning strike inside?
Depends on the type of antenna, but in this case, a discone is not "DC grounded". So, yes, the radiating element is isolated from ground at the antenna. Using a polyphaser or similar product is a good idea. It grounds the outer shield of the coax, but it doesn't technically ground the center conductor. There is a device inside that will ground the center conductor when it sees the sudden voltage surge.
None the less, the lightning will try to find a path to ground, and it will easily "hop" the insulator in the antenna, coax, etc. Think about it: the lightning strike has traveled thousands of feet through the air, an 1/8th of an inch of plastic isn't going to stop it. Grounding the mast is a really good idea, and actually required by the National Electric Code.
So, at least one 8 foot copper clad ground rod pounded into the earth close to the base of the mast. That should have a heavy gauge copper wire (#6 or larger) connected to the mast. The polyphaser needs a ground to, and that should be connected to the same ground rod with heavy gauge cable. NEC also has some wording about bonding the antenna ground rod and the electric system ground rod together.
Direct lightning strikes are not your only concern. Even nearby ones can induce high voltages onto the antenna and coax. Disconnecting your radio from the coax is also a really good idea during a lightning storm.
Of course lots of hobbyists never go this far and still walk the earth. It's a risk not to properly ground your antenna/mast system, but it's a risk that some people choose to take.