RadioBanter - View Single Post

Ian White GM3SEK · December 4th 06, 03:47 PM posted to rec.radio.amateur.antenna

wrote:

The autotuner should be fairly efficient on 40m and up, though you
might want to add a few feet to the vertical to avoid the high
impedance of a half wavelength on 20m, but I dunno.

Not a problem. When a half-wave vertical is fed against ground, the
impedance is lower than many people imagine, and well within the
efficient matching range of most auto-tuners.

When you're using an auto-tuner, your whole approach to antennas gets
turned around. Just put up whatever you want, or whatever you can, and
in most cases the tuner will take care of it.

At the old QTH, I had a 33ft pole which was guyed at the top, and had an
auto-ATU and plenty of radials at the bottom. That simple pole worked
well on 3.5-18MHz, and would work after a fashion from 1.8 to 30MHz. In
addition, it could be tilted over quickly and various other add-ons
plugged into the top.

The simplest was a 12ft fishing-pole extension, which favored DX on
3.5-14MHz.

Another configuration added a 30ft horizontal extension wire to make an
inverted-L, about a half-wave on 40m and about a quarter-wave on 80m.
That one was excellent for 80m DX, and quite usable on 1.8MHz.

For more serious 1.8MHz work, the free end of the horizontal wire could
be very quickly lowered to ground level, and an extra 100ft of wire
added. This gave a quarter-wave on 1.8MHz, and also an end-fed half-wave
for 3.5MHz. It was good for local working on 3.5MHz because the
high-current portion was horizontal at about 30ft.

I really couldn't tell you what the exact height and wire lengths were -
whatever, the auto-tuner took care of it.

--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek