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Old January 20th 15, 03:54 AM posted to rec.radio.amateur.antenna
[email protected] nm5k@wt.net is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 757
Default Antenna recommendation needed

On Monday, January 19, 2015 at 12:31:04 AM UTC-6,
For 40m NVIS within 500 miles or so, the low dipole will likely smoke
most verticals.


Of course it will as all the energy will go straight up while the
vertical main lobe is at about 30 degrees.

The important factor is the height in wavelengths, not feet. As the
height drops below a half wavelength the main lobe goes vertical
on a dipole (or any horizontal antenna) rapidly.


Sure, but there is still enough at the low angles to make some DX
contacts. And he'll have a decent signal to the stations not so far
away on 40m.




I guess he'll have to decide what he wants to lean to. Whatever he decides
is unlikely to excel at both, and will be a compromise.


If local communications is your goal, then an NVIS antenns is what you
want. However as the frequency increases above about 8 MHz the
probablity for success decreases and drops to near zero at 30 MHz. For
20 meters it is a crap shoot with less than good sunspot activity.


The performance at low angles won't be quite as grim as you might expect.
IE: I had no trouble working 15m DX with a -10 ft high dipole. 20 ft up is
nearly a 1/2 on 15m. And a 20m dipole at 20 ft will be quite decent for
average use being over a 1/4 wave up. Will be good stateside, and usable
for DX. I like converted CB ground planes for 10m. Good space wave for
local, and good for DX. Not much close in sky wave stuff to work on that
band.


I don't really see how a dipole requiring three supports, two at best,
can be considered simpler than a vertical with one support.


A vertical generally needs radials unless it's a "1/2 wave" type
design. And even good verticals can be quite lackluster for close
in work compared to a low dipole on 40m. Good at night to DX though.
But like I say, he's gotta decide what he wants to concentrate on,
and go from there.

If he has trees to tie dipole legs to, he really only needs one
support for the apex. And one can also string them between trees
to where no man made supports are needed at all.
But I don't know what trees he has available.

I usually have one mast for the apex, and tie off to trees or whatever.
At the dirt patch, I use a oak tree as the apex support, and tie
off to other trees. I shoot a weighted line up into the apex tree,
and run it over a tall branch. Then I pull the dipole and coax back
up into the tree with the wire I shot over the tall branch.
When I go home, I let the wire loose, and back down it all falls.
I used to leave it there all the time, but the critters were eating
my coax into shreds, so I had to quit that. :/

And the tuner/ladder line fed dipoles is another option if one wants
all bands with one antenna.