I put up an NVIS antenna for 80m a number of years ago. It works great
for local 80m nets.
It is a full wave length loop (more square) mounted about 10' above the
ground.
It is feed with 450 ohm ladderline from a 1:1 current balun at the ATU.
EZNEC shows the radiation is UP.
It also shows gain and not as much UP on 40m and 20m.
I have worked DX on all bands.
73, steve WB3LGC
On 12/18/21 4:09 AM, Ken WA8JXM wrote:
--- "In Hawaii, 40 meters worked great for NVIS probably 11 out of 12
months a year. Someone else who knows can comment, but I got the impression
that 40 meters almost never works for NVIS in the mainland US. If this is
true, an Elecraft NVIS field day might be limited to those who either have
room for an 80 meter dipole, or who can devise some other kind of 80 meter
antenna that can radiate up."
I think it depends on time of day, time of year, and what part of the
sunspot cycle. 40m is pretty much the top limit for NVIS though. But
sometimes 40 works for NVIS. That's one of the reasons for our 60m
allocation, NVIS when 40 is too long and 80m is dead. OTOH I've seen
160 too long for statewide coverage at times.
FWIW, I agree a vertical is not an NVIS antenna. Some people may be
confusing groundwave (usually up to 25 miles) with NVIS. They are totally
different propagation modes.
Ken WA8JXM
On Fri, Dec 17, 2021 at 7:22 PM David Herring <david.n5...@gmail.com> wrote:
It is absolutely true that antennas intended for NVIS use do not have to
be hung low. But they CAN be. And there are instances where doing so can
be desirable.
When I lived in Hawaii, we used NVIS for reliable statewide HF
communications to very good effect. When I hung my dipole up about 30 feet
or so, I would frequently get calls from hams in Japan, Oceana, mainland
US, Canada and elsewhere. Ordinarily that would be nice, but when one is
specifically focused on local comms, that can get to be a problem. When I
hung my NVIS dipole down around 10 feet, I still got excellent statewide
communications but no longer got calls from afar.
So I kept my dipole low for local, and erected a vertical for DX. Both
worked perfectly for their intended use.
In Hawaii, 40 meters worked great for NVIS probably 11 out of 12 months a
year. Someone else who knows can comment, but I got the impression that 40
meters almost never works for NVIS in the mainland US. If this is true, an
Elecraft NVIS field day might be limited to those who either have room for
an 80 meter dipole, or who can devise some other kind of 80 meter antenna
that can radiate up.
73,
Dave - N5DCH
On Dec 17, 2021, at 11:05 AM, Julia Tuttle <ju...@juliatuttle.net>
wrote:
Wait, why would people think verticals are good for NVIS? Isn't a
vertical's radiation pattern pretty much "sideways but not up", and NVIS'
desired radiation pattern "up but not sideways"?
On Fri, Dec 17, 2021, 12:54 Jim Brown <j...@audiosystemsgroup.com
<mailto:j...@audiosystemsgroup.com>> wrote:
On 12/17/2021 6:12 AM, Greg Herman wrote:
What if there was the annual event called the The Elecraft
NVIS field day?
There is a major myth regarding NVIS that antennas must be low. This is
totally false. The facts are that vertical antennas are terrible for
NVIS, and that horizontal antennas work better up to nearly one-half
wavelength above ground. This study ran in National Contest Journal
several years ago.
http://k9yc.com/AntennaPlanning.pdf
73, Jim K9YC
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