[Antennas] RE: wire gauge

2003年7月11日 12:49:56 -0600

On 2003年7月11日 13:54:50 -0400 "Hart Engel" <[email protected]>
writes:
> When building my dipole antenna, what gauge of wire should I be 
> using? And 
> should the wire be a single strand or multiple wire? Also should the 
> wire be 
> coated or bare?
>> Hart

 Hart,
Any wire will work. It's the length that makes the difference. Coated
or bare also makes no difference unless it comes into contact with other
materials that might short it to ground. Use any size (gauge) you want. 
The heaver the wire, the longer it may last. Especially in the parts of
the country where ice loading must be considered. Stranded wire is more
flexible than solid. The size of the wire can make a difference in how
broadband the antenna is, but not measurable unless you are using large
diameter tubing instead of wire or building a "cage dipole" 
 The following was copied from QST: (see the ARRL web site for the
accompanying photos)
The "Cage" is Back! W1AW Installs New/Old Antenna
NEWINGTON, CT May 3, 2001--Good ideas seem to have a way of coming back
into style. Joining the W1AW antenna farm this week is an 80-meter "cage"
dipole. The new antenna is not too different from ones used in the early
years of Amateur Radio--including during the transatlantic tests of the
early 1920s. 
W1AW Station Manager Joe Carcia, NJ1Q, says the new dipole--oriented to
radiate east-west and approximately one-quarter wavelength off the
ground--will complement an existing "coaxial dipole" that's been in use
for several years. Visitors to W1AW now will have the option using either
antenna when operating 75 or 80 meters. US visitors wishing to work a
station "back home" probably will choose the new antenna, Carcia said. 
The current 75/80-meter dipole at W1AW, designed by Frank Witt, AI1H, is
oriented to radiate north-south and also is about one-quarter wavelength
above ground. It requires some re-tuning to be used over the entire band,
however. 
In addition to its more favorable domestic orientation, it's hoped the
new antenna will provide the greater bandwidth W1AW needs to cover the
entire 75 and 80 meter band without encountering severe SWR problems. The
multi-wire "cage" appears as a much larger single conductor and has a
lower Q than typical single-wire antenna. Therefore, it can be shorter
physically--the W1AW cage is about 120 feet long--while still covering a
larger chunk of spectrum. 
In radio's early days, large, multi-wire antennas were standard equipment
at Amateur Radio stations, and the "cage" was a common design. Carcia
says he reviewed back issues of The ARRL Antenna Book and ARRL's Wire
Antenna Classics looking for just the right antenna. The latter featured
a December 1980 QST article, Broad-Band 80-Meter Antenna. Carcia decided
that the classic design could meet his modern requirements. 
The decision to go with the cage design was based on several
considerations. The primary mission of W1AW is to reliably disseminate
information--bulletins and code practice--in several modes. This means
W1AW must be able to span the spectrum at full power from the 80-meter CW
band to the 75-meter phone band. 
W1AW transmits CW on 3.581 MHz, digital on 3.625 MHz and SSB on 3.990
MHz. W1AW's FET power amplifiers do not tolerate high SWR, and a
self-protection circuit automatically reduces power to 500 W if SWR
exceeds 2:1. Additionally, W1AW wanted to make it easier for visiting
operators to use these bands without having to make special provisions to
tune the existing antenna system. A broadband antenna definitely would
offer greater operating convenience. 
There were other considerations too. For safety reasons, W1AW does not
have antennas with active elements near ground level. Vertical antennas
pose an additional safety problem because of guying and a requirement
that the tower be a safe distance from other objects. Another dipole
antenna was the obvious choice. 
My best advise would be for you to spend 25ドル.00 and get yourself some
good reference material.
The following was also copied from the ARRL web site:
You need REAL-WORLD antenna solutions. Use this extensively rewritten
edition to design and build antennas using modern materials (antennas
that work for you and your station!). The latest computer modeling
techniques have improved traditional antenna designs. Find a new
treatment of broadband antennas; gain and size comparisons for multi
element arrays; and updated information on log periodic, quad, long-wire
and traveling-wave antennas. 
CD-ROM INCLUDED with two new Windows programs (Yagi for Windows and
Transmission Line for Windows), detailed propagation forecasts, and more.
There are so many reasons to add THE ARRL ANTENNA BOOK�the ultimate
reference for antennas, transmission lines and propagation�to your
library.
816 pages, softcover. 19th edition, second printing, � 2000-2002, The
American Radio Relay League. 
SPECIAL! ONLY 24ドル.95 (was 30ドル) 
73 de Jerry, K�EJF
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