On 4/1/97 12:17 PM, Carlos Augusto S. Pereira at
csilver@riosoft.softex.br wrote:
>I will raise a a tribander beam for 10-15-20 however for 40/80 I am still
>thinking about. Some US hams have pointed the G5RV as a good solution but
>there is a necessity of a 32ft tower, isn't it?
Rather than a G5RV, I suggest you put up a simple doublet (dipole) fed
with tuned feeders (open wire or twin lead). It will have as good as
performance as the G5RV.
The G5RV isn't magical. It is merely an extended double zepp for 20m fed
with an appropriate matching section. The only band it is resonant on is
20m. It just happens to be easy to tune for other bands. A doublet (of
any length) with tuned feeders (of any length) is a simpler and better
solution.
>My questions are:
>
>1) Will the G5RV cover 40/80 meters with a reasonable performane? Does it
>require a standard Antenna Tunner?
Yes, the G5RV will require an Antenna Tuner, especially with today's
solid state rigs that fold power back at SWR higher than 1.5 or so.
>2) To raise it 10 meters up is a must? It doesn't work lower? There is a
>limitation of 5 meters over the building's roof.
The single most important dimension in a horizontal antenna (ie dipole)
is height above ground. (At least for heights less than a wavelength or
two - that's 80-160m!)
The answer is to put it up as high as you can. It will work lower, just
not quite as well. I'm using a 125 foot doublet that's only 10-15 feet
off the ground right now.
>3) Does it work in an inverted V configuration?
Yes, but a simple doublet works just as well.
>4) Van Gorden manufactures one like that with a transformer. Is it good?
The transformer is ok, if you have to run coax. However, since the
antenna is non-resonant, you'll have higher losses in the coax.
Open wire has less loss, but is troublesome to bring into a building. For
years I've run transmitting twin-lead to the house, then switched to a
balun with a short run of coax to the shack. Use only solid dielectric
coax (RG-8)! Sure, foam dielectric has lower losses, but substantial
voltages can be present in the coax in this "unmatched" configuration.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@radio.org
Quote: "Not in a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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