On 6/29/2015 10:48 AM, Wayne wrote:
As a lead in, I use a 16 ft vertical on 20-10 meters, mounted on a flat
metal roof. The antenna is fed with about 25 feet of RG-8, and there is
a tuner at the transmit end.

You use a 16ft vertical as a lead-in? For what and how is that done?

What are the dimensions of the metal roof?

While I'm pretty happy with the antenna, I'd like to simplify the matching.

To what matching do you refer? You don't want to use the tuner, or is
there some other stuff you have not mentioned?

Thus, the question: what is the purpose of a 1:4 unun on a 43 foot
vertical? ( I assume the "4" side is on the antenna side.)

You wrote that you were interested in a 16ft vertical. Now it is a 43ft
vertical?

I'd expect a better coax to antenna match when the antenna feedpoint is
a high Z (example, at 30 meters), but I'd also expect a worse coax to
antenna match when the feedpoint is a low Z (example, at 10 meters).

Is that the way it works, or is there other magic involved?

All this depends on your answers to the above questions.