Eric wrote:

I know that a vertically polarized antenna would work groundwave
better, but we need to be able to maintain reasonably reliable
communications pretty much everywhere within about a 200-mile circle.
We can use 160, 80, and 40 meters to do it, and theoretically we can
use any amount of power up to the legal limit but in reality, as a
practical matter we are limited to 100-200 watts.

There are some in our group who really, REALLY think that the vertical
is the way to go, and I need some debating points. So, if I had a
decent ground-mounted vertical, should I expect to get the ground wave
distances that G4FGQ indicates in his calculation program?

You really need both. I'd not put in a vertical unless I had a
horizontal one also. If I had to choose one, it would be the dipole. But
if you can do both, the vertical has it's uses.

Is there any area / radius that would be covered by a ground-mounted
vertical that wouldn't be covered by an NVIS horizontal (assuming that
we're operating below the critical frequency)? I have always assumed
that by the theory behind NVIS, the answer would be no... NVIS should
cover everything out to a radius well beyond groundwave distance.
But, I suppose we could install NVIS antennas AND verticals and switch
between them to see which one works best at any given time.

That is the ticket. I'd done some experiments between the two antennas,
using an attenuator and antenna switch. Aside from generalities, which
have become "truth" under different circumstances, the antenna that
performed best at any given time changed, and not always in the way you
thought. Sometimes in mid-QSO.

Too many people think of take off angle as some sort of blob of RF that
comes out of the antenna at one place, and not much elsewhere. All
antennas radiate at all angles. Some just more at some angles than
others. The point of this is that that vertical better be pretty
efficient, because what use is a lower angle of radiation if it is
putting out less RF than another antenna that even though the other
antenna might have a higher take off angle, but have still more power
output at the lower angle.

While I'm at it, how do I estimate antenna efficiency? What is the
average range of efficiencies normally seen with a quarter-wave
ground-mounted vertical, with an adequate ground radial system, in
average soil?

Best way is to use an antenna design program. This would probably be a
very good idea if you need to convince your cohorts The big thing is,
don't just look at the SWR plots, and don't just look at the antenna
patterns. Looking at the bigger picture, it becomes more than just a
Ford versus Chevy argument.

- 73 de Mike N3LI -