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CENTERFED MONOBAND INVERTED LONG WIRE VEE Edited from a project by Edward
M. Noll, W3FQJ in the book "73 Dipole and Long Wire Antennas"
published by Editors and Engineers, Ltd, Copyright
1969
Edward Noll had many great antenna projects in his
book. Lots of them were based on the 3/4 wave length per side
dipole. Presented here is one of them!
Antennas can be resonated to a specific frequency by
making their overall electrical length a whole multiple of a
half wavelength. There is a rise in gain with each halfwavelength
addition. In the case of a horizontal antenna, the antenna becomes
more directive with antenna length. The addition of leg lengths
in odd multiples of a half wavelength ensures a low impedance
center feed point because each leg of such an antenna is an odd
number of quarter waveslengths long.
This project will
enable you to build a monoband long wire inverted vee with 3/4
wave length sides that will have a bit of gain, (amount not stated
in the book), for high band operation and long distance compared to
a standard 1/2 wave dipole because of its lower vertical angles of
radiation, and added leg length. The longer the leg lengths in odd
multiples, the more the gain. It amounts to a very low cost and
effective antenna. It is also less directional than the
horizontal dipole or straight long wire antenna. On a horizontal
3/2 wavelength dipole, the antenna presents four major lobes
and 2 minor lobes. The four major lobes are at: 45, 135, 225,
315, degrees The two minor lobes are at: 90 and 270
degrees with respect to the horizontal antenna as viewed from
above as in line below:
VIEW
FROM ABOVE
90
180 Degrees ______________________ 0
Degrees
270
A
practical 20 meter basic design, assuming a 25 to 45 foot mast is
used can be determined by the formulas below: (As always, it is
wise to cut lengths long and trim as needed for best
resonance)
Leg length = 738
divided by frequency in mhz Leg length
each half = 738/14.2 = 52 feet
Line length =
650
divided by frequency in mhz Line length = 650/14.2 = 45 feet 9
inches.
The "magic" numbers
(738 and
650) in the formulas above appear to be arrived at
by trial and error by Ed Noll and were presented in a chart in the
book. To arrive at the "magic" numbers (constants) for each
formula for different leg lengths and feeder lengths as determined
by your particular lot size, just do the following:
For
longer leg lengths add 492 to each odd multiple of a 1/4 wave
length: Example: 3/4 length =
738/freq 5/4 length =
1230/freq 7/4 length =
1722/freq and
so on
For longer feed line lengths, (REMEMBER THAT FEED
LINE LENGTH MUST BE AN INTEGRAL MULTIPLE OF A HALF WAVE LENGTH
TAKING THE VELOCITY FACTOR OF THE LINE INTO
CONSIDERATION!) Example: 1/2 2/2 3/2 4/2
etc VF .66 LINE VF .81 LINE 1/2
325/F 400/F 2/2
650/F
800/F 3/2
975/F
1200/F
Notice that that for .66vf line,
325 is added each time and for .81 line,
400 is added each time for the constants.
(There were no other constants for other velocity factors in the
articles in the book, however, you can still use the formula....Line
length in feet (1/2 wave) = 492 X VF / freqmhz for determining
the electrical half wavelength of a
line) *********** Higher gain figures
can be accomplished by bending the legs forward toward the receiving
station. See the 3 Halfwave Vee
Beam based on these
same principles by Ed Nolls, W3FQJ.
Editor's
note: If you can find a copy of Ed's "73 Dipole
and LongWire Antennas", by all means, get it. Ed also wrote many
other books related to radio. Many are out of print but still
can be found. You will have many hours of fun building and
experimenting with Ed's designs which are a culmination of his many
years of very talented dedication to Amateur
Radio......N4UJW
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RADIO!

