[SEDXC] [SECC] Question about 30 meter halfwave vertical for the antennagurus
Joe Subich, W4TV
lists at subich.com
Sat Oct 23 10:05:26 PDT 2010
On 10/23/2010 11:15 AM, Bill Coleman wrote:
> But I agree about the 43 foot thing. It seems to be a cult-like
> condition, like the 88 foot dipole in QRP circles. Of course, LB
> modelled the 88 foot dipole at 100 feet and 70 feet. Most of the
> guys who put these up rarely get them over 35 feet.
The 43 foot vertical is 5/8 wave on 20 meters. Its input impedance
happens to be within range of the automatic antenna tuners in many
of the current crop of rigs.
However there are several problems with the 43' vertical as an "all
band" solution. First, as already mentioned the feed impedance is
so low on 80 and particularly 160 meters that efficiency is very
low and feedline losses are quite high. What most reviewers fail to
note is that the take-off angle is quite high on 17 meters and above.
Band Take-off Angle
17 43 degrees
15 37 degrees
12 32 degrees
10 56 degrees (!)
In almost every case, there is less radiation in the 0 - 30 degree
range useful for DX with the 43' vertical than with a simple quarter
wave vertical. Coupled with previously reported efficiencies in the
5 to 20% range on 80 and 160, the 43' vertical is simply a lot of
hype with very little performance.
... Joe, W4TV
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