Ian Jackson wrote:
In message ,
writes
Ian Jackson wrote:
In message ,
writes
Ian Jackson wrote:

snip

Despite the obvious theory, and over 50 years in amateur radio, I still
find it hard to believe that, in real life, an 80m dipole at (say) 20'
ever really outperforms (at any distance) one at (say) 100'. Given the
choice, I know which one I would choose!

Try reading these:

http://www.qsl.net/wb5ude/nvis/
http://en.wikipedia.org/wiki/Near_ve...idence_skywave
http://www.w0ipl.net/ECom/NVIS/nvis.htm
http://kv5r.com/ham-radio/nvis-antennas/
http://www.arrl.org/nvis

Thanks, I'll certainly have a good read of those articles. But
regardless of what they say, in a typical amateur scenario, I still
reckon that at (say) 300 miles, an 80m signal from a dipole at 100' is
likely to be stronger than one from one at 20' (or even at 60').

As 300 miles is at the upper end of NVIS and the lower end for skywave

NVIS IS skywave - only that it's more straight up-and-down than at an
angle. It's only a matter (literally) of degree, and there's no real
point at which NVIS becomes 'normal' skywave.

NVIS is generally defined as aiming the power straight up and the S
in NVIS stands for "Skywave". So if you want to be pendatic, you are
correct.

However, if you look at the links above, the real world DOES make
a distinction between NVIS and skywave.

it would be a crap shoot.

NVIS distance is typically 30-400 miles.

OK, let's make it a bit less - say 50 or 100 miles. I still feel that,
in practice, a dipole at 100' would be unlikely to be less effective
than at 20'.

The experience of all the world's militaries and those others who have
done actual measurements come to a contrary conclusion.


--
Jim Pennino

On Saturday, November 22, 2014 4:01:08 PM UTC-6,
NVIS is generally defined as aiming the power straight up and the S
in NVIS stands for "Skywave". So if you want to be pendatic, you are
correct.

However, if you look at the links above, the real world DOES make
a distinction between NVIS and skywave.

I'll have to read through them, but myself, I consider any signal
which is reflected off the ionosphere back to the target receiver, as
being skywave, no matter if the angle is 90 or 10 degrees.
If it doesn't use the ionosphere, it's not skywave. Sometimes you can
have a mix of path modes. IE: being able to receive both the skywave,
but also the ground or space wave. In most cases like that, the NVIS
path will overwhelm the ground or space wave unless the two stations
are very close together.

On 11/22/2014 5:33 PM, wrote:
On Saturday, November 22, 2014 4:01:08 PM UTC-6,
NVIS is generally defined as aiming the power straight up and the S
in NVIS stands for "Skywave". So if you want to be pendatic, you are
correct.

However, if you look at the links above, the real world DOES make
a distinction between NVIS and skywave.

I'll have to read through them, but myself, I consider any signal
which is reflected off the ionosphere back to the target receiver, as
being skywave, no matter if the angle is 90 or 10 degrees.
If it doesn't use the ionosphere, it's not skywave. Sometimes you can
have a mix of path modes. IE: being able to receive both the skywave,
but also the ground or space wave. In most cases like that, the NVIS
path will overwhelm the ground or space wave unless the two stations
are very close together.


You are correct - NVIS is a form of skywave. And it is considered by
experts in the field to be a form of skywave (hence the "S" in NVIS),
although for much shorter distances than skywaves utilizing a lower
angle of radiation.

--
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Jerry, AI0K

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