Korbin Dallas wrote:
What are you disagreeing with? How much DX do you work with
your NVIS antenna? Do you really think the majority of hams
are only interested in local communications on HF?

Yes the majority of hams are indeed interested in Local HF communications
on 80 & 40. Something that will reliably commutate out to 300-400
miles.

They can get that from a 40 ft. high G5RV. No 7' high
NVIS dipole is needed. AND you can work DX on 20m-10m
with that 40 ft. high G5RV. I repeat, the majority of
hams are NOT interested *only* in local communications
on HF. A 7' high dipole is a poor performer on 20m-10m.
--
73, Cecil http://www.qsl.net/w5dxp

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They can get that from a 40 ft. high G5RV. No 7' high
NVIS dipole is needed. AND you can work DX on 20m-10m
with that 40 ft. high G5RV. I repeat, the majority of
hams are NOT interested *only* in local communications
on HF. A 7' high dipole is a poor performer on 20m-10m.


Cecil, since I started this thread with a comment on yours, in retrospect
I will admit what you say above is true! My comment applied to a small
particular group of operators on the lower bands (or is that higher bands?)



Ed K7AAT

Ed wrote:
My comment applied to a small
particular group of operators on the lower bands (or is that higher bands?)

The top band is considered to be 160m so I assume "band" is
associated with wavelength, e.g. "160m band". So it appears
that higher bands = lower frequencies, but I could be wrong.
The IEEE Dictionary is no help. It thinks a "band" is a
track on a rotating memory device. :-)
--
73, Cecil http://www.qsl.net/w5dxp

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What are you disagreeing with? How much DX do you work with
your NVIS antenna? Do you really think the majority of hams
are only interested in local communications on HF?

Some are...Most work only the low bands...I know many
hams who couldn't care less about dx. They only talk to
other regional "good ole boys"....
But saying that, comparing a G5RV at 50 ft, against a
dipole at 7 ft, is fairly silly. The NVIS qualities are more
due to height above ground per wavelength, than the
length of the antenna.
Overall, I think the idea of running low dipoles, or using
ground screens, and pseudo "reflectors" etc, are
generally a waste of time.. If I were working NVIS on 75m,
I'd prefer a dipole at 50ft over one at 7 ft. It will have lower
ground losses, and I'd be willing to bet the NVIS performance
would be just as good as the low antenna. But, the medium
range performance would be a good bit better. Also, you
can work dx also...I've worked dx on 75m, using a dipole
at 35 ft...It's no big deal really...Just finding the DX to talk to
is more difficult. Also...NVIS antennas are not low noise,
unless they are defective in some way...They may reduce
the reception of far off lightning, if that static arrives at
low angles.. A low dipole has great reception of noise...
Straight up....A low to medium height dipole already has
enough gain straight up. I don't really want to enhance it
further...I also want to have decent performance on longer
paths...Listen to all the BIG strappers on 75m...I bet very few
are running real low dipoles with screens...Most will be running
higher dipoles hung from towers, trees, etc...
MK

What are you disagreeing with? How much DX do you work with
your NVIS antenna? Do you really think the majority of hams
are only interested in local communications on HF?

As you may have missed previously, my comments were directed from the
standpoint of a 75M/40M operator. Personally, I don't consider a NVIS
antenna a valid antenna above those bands. So, for the two bands I have in
mind, Yes, I believe the majority of operators there are interested in
local/intra-state communications.


Ed

On Sat, 11 Jun 2005 06:39:12 GMT, William Taylor
wrote:

http://www.hamuniverse.com/supernvis.html

The claim is that a dipole 7 feet off the ground has
a 10db gain over a G5RV at 50 feet.

Is that possible, or hype?


I'll take a stab at it. First of all, its objective is to create
nulls at low-take-off angles so shortwave broadcast stations will not
have so much noise. The antenna is a 300 ohm folded dipole that is
fed with 50 ohms but then the antenna has a reflector on the ground.
It is effectively a 2-element yagi pointed strait up (give or take a
few degrees at the user's choosing.)

I don't think a two element beam has a 10 db gain, but I don't know
the gain of a G5RV on the same frequency. Presumably, the signal
strength of local signals will improve and DX or broadcast stations
will drop.

This is known as a Near Vertical Incidence (I forget the 's') antenna.
Great for operating local districts on 160-30 meters. If the dipole
is raised high enough, it will be just a dipole, but then it will be
mis-matched to the feedline and have considerable loss.

This is my theory, correct me if I am wrong

--
73 for now
Buck
N4PGW