On 29/06/15 16:48, 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.

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

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.)

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?


I'm not going to disagree with Dave Platt's post re how the matching on
a 43' vertical works.

As for a simpler way, I'd recommend a remote auto-matcher like an SGC at
the antenna base. It will minimise coax losses and should give you a
good match, at least for most bands. I've used a similar set up (with
radials) and achieved a good match even on 80m.

If your radio has a built in tuner, then it can be used to 'tweak' the
match in the event the radio isn't 'seeing' 1.5:1. Turn it off
initially. Let the SGC find a match. If it isn't ideal, use the local
ATU for a final tweak. I never found this was required but YMMV.

Remember, you really want a low SWR for two reasons, one because modern
radios demand it but also to reduce coax (or feeder) loss. With an
matcher at the antenna feed point, coax losses are minimised. An ATU at
the TX end does nothing to reduce coax losses in real terms.