> A NVIS antenna is a stupid idea. I agree with his Elmer,
NVIS means "Not
> Very Intelligent Selection." Do you notice that that is
all we hear about
> today-how everyone is using a NVIS antenna. Doesn't
anyone want to work DX
> anymore?
The letter writer had the NVIS antenna in the correct
application. He wanted to use high angle skywave.
He just was clueless about groundwave distance of
horizontally polarized HF antennas (which is nearly zero
groundwave distance) and antenna performance changes as
antenna height is reduced.
At 1/8th to 1/4 wl high NVIS signal is maximized. Anyone who
spent any time at all with antennas would know even with a
perfect reflector efficiency drops rapidly when the antenna
is spaced less than 1/10th wl from a reflector, and if the
reflector (earth) was lossy things would go in the toilet
fast as height was reduced.
Now we have people interested in emergency communications
and using "cutting edge" digital emergency communications
systems who don't understand how an antenna works, and who
think people who do understand antennas (an "older Elmer")
are stupid.
In our local community the last Sheriff spent many thousands
of dollars of state or federal grant money building an
emergency communications trailer that just doesn't work,
even though the dozen radios look impressive. In another
county near us the EC was talking about building a trailer
using all EH antennas (another antenna hoax like the CFA).
Now I see 18 inch high 80 meter antennas are also desirable.
I wonder how many other emergency communications systems
won't work when needed?
I'm just waiting for the salt water ground jugs and pie pan
lightning dissipaters to appear as the last few functioning
radio-technical brain cells wink out.
73 Tom
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|