On 10/19/2010 6:25 PM, Howard Lester wrote:
> OH -- and the window line is twisted about every three or four feet.
>
> I'm very pleased with this antenna's performance and its simplicity. I
> welcome any further comments.
The individual performance of antennas notwithstanding, we usually end
up putting the antenna up that will suit our needs and location.
For instance, at our club mountaintop station, our dipoles for 40 and
80, and 160 meters when it goes in, are copperweld single band dipoles
with coax to the mid-point of the tower to allow lowering for
maintenance, and hardline the rest of the way to the shack. Two separate
antennas for each band except 30 meters.
Now of course, we have 4 towers to work with also. No reason to not put
up an antenna for each band and feed it with as good of coax as we can
afford.
At home, where I am limited in space and with just how much wire I can
put up,, and still wanting to work all bands, the ladder line fed
doublet is simply a better choice. All the issues of wet performance and
noise and lightning susceptibility are side issues, and probably almost
irrelevant. I've got arresters on both sides of my ladder line. If not
working high power, some gas discharge tubes on each side would be the
hot setup.
Now for the real disadvantage of the doublet fed with ladder line. At
say my setup, roughly 100 feet at a bit over 50 feet, 80 meters will act
about like any antenna at that frequency/height. A fair amount of the
power is going up. but you can still work just fine with it.
40 meters, and it works very well.
Above 40 meters and the antenna pattern gets pretty squirrley, both via
height and length/frequency. In some respects it's almost
omnidirectional, but with some pretty deep nulls here and there. IMO,
those nulls can be worse than the NVIS characteristics on 80 meters.
There are some alternatives, such as Fan antennas and traps, each with
their own issues, and of course the folded terminated dipole, which is
agile but not all that efficient.
And of course the G5RV and the OCF, which in their present form utilize
tricks to have decent SWR.
But looking at all the alternatives, if I was going to use coax, and not
an OCF, I'd be doing a loaded at 80 meters, probably fan for 40 and 20.
I'd likely skip the other bands. I'd use a messenger line because of all
the weight. The ladder line to doublet starts looking pretty good at
this point. Then with an autotuner, I'm doing pretty nicely, and just
put up with the occasional weird null on 20 and above.
- 73 de Mike N3LI
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