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Edward M. Nole, W3FQJ.
Additional material and projects provided by Roger, K6LMN
Edward M. Noll, W3FQJ, an accomplished consulting engineer, author of many technical books, lessons, articles and antenna designs has contributed an enormous amount of knowledge, hands on experience and skill to Amateur Radio. Ed built, tested and used every one of the 73 antennas in the book. We hope to help his contributions in the Ham antenna field to live on by presenting in edited form, one of his many projects taken from the book!
THE 3 HALF WAVELENGTH HORIZONTAL VEE BEAM! by
Edward M. Nole W3FQJAntennas 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 half-wavelength 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 wave-lengths long. Instead of the two lobes of a standard dipole, the 3/2 wavelength standard dipole antenna has four major and two minor lobes if erected in standard dipole fashion, i.e., horizontally parallel with the earth. The Vee configuration of the same antenna can be made more directive by forward tilting of the legs toward the desired direction or station. (See Figure 1 below) The legs can be tilted forward, like the point
of an arrow reversed , from about 90 degrees to around 110 degrees. When
they are tilted forward, horizontally, the antenna displays a maximum
directivity along a line that bisects the angle. Minor side and back lobes
remain; therefore the antenna has omni directional capability as well.
(See Figure 2
below)GainThe
standard 3/4 wavelength per side antenna at 100 degrees "tilt" has 2.5 dB
gain according to a chart in the book. 5/4 per side at 86 degrees has
3.3dB gain, 7/4 per side at 76 degrees has 4.0dB gain, 9/4 wavelengths per
side at 67 degrees has 4.75dB gain and 11/4 wavelengths per side at 60
degrees tilt has 5.3dB gain. Editors note :..."It is assumed these figures are
referenced to a standard dipole but not stated in the
article."Antenna resistance rises slowly with leg length and is also influenced by the included angle. These antennas are considered to be " Short
Vee Beams" if at; or under
1 1/4 wavelengths long per side or less than 100 feet per side. Longer vee
beams greater than 1 1/4 wavelengths per side require 2 to 1 or 4 to 1
baluns to insure equal currents in each leg for the desired lobes but can
achieve much higher gains. An example for 10 meters at 28.6 mhz for a 10
dB gain antenna requires a length of over 283 feet per side! At 40 meters
(7.1mhz), you would need only 1143 feet per side!Man, talk about an antenna farm.....if someone was standing at the center support and another was yelling at you from the other end, it would take over a second for you to hear him at the speed of sound....about 1100 feet per second! THE ALL IMPORTANT FEED LINE LENGTH In most cases the horizontal-vee type antennas require some 4
to 6 percent shortening from the standard formulas below. See the examples
further down the page for several bands.Transmission line lengths must be cut to an EVEN multiple of an electrical half wave length using the formula: Length = 492 X vf (velocity factor of line) /
frequency: Example.....492 X .66 / 7.1mhz = 45.73 feet for an electrical half wavelength of .66 velocity feed line like standard RG/58U. So if you plan to operate a dipole on 7.1 mhz, and the approximate distance between the antenna and transmitter is 100 feet, it is wise to use a length of feed line of approximately 2 or 3 wavelengths long such as 91 or 137 feet corresponding to either 2 or 3 half wavelengths of regular RG/58U line. These formulas were taken from a chart in the book for calculating the feed line lengths for .66 velocity factor line. There is some very slight difference between using the formula above (492 X .66 / freq) and the formulas in the chart. The bold type numbers in the formulas are "magic
number constants" arrived at by experimentation.1 half wavelength length = 325 /7.1 = 45.77 ft.2 half wavelengths length = 650 /7.1 = 91.55 ft.3 half wavelengths length = 975 /7.1 = 137.3 ft.Editors
note: NOTICE that the number 325 is added to the "magic number constant"
calculation for each half wavelength of feed line
added.So for 4 half
wavelengths the formula would be 1300 / 7.1 = 183 ft. and so on for each
half wavelength added..The other section of the same chart was for .81 velocity factor line such as foam RG/58U and used 400
as the magic number in the formula.Example: 2 half wavelength line for 7.1mhz is, 800 / 7.1 = 112.67 ft of feed line.For 3 half wave lengths of line, just add 400 to 800 = 1200 for the "magic constant" for each added half wavelength
added.As with most antenna projects, some trimming may be
needed so cut each leg length a little long and resonate antenna as
required. Leg length examples
for
3/4 wave length per side:20
METERS LEG LENGTH
= 738 / 14.2 = 52 feet less 6 percent
shortening = 49
feet15 METERS LEG LENGTH = 738 / 21.3 = 34 feet 6 inches........less 6 percent = 32 feet 6 inches 5/4 wave length formula is 1230/fmhzJust add the number 492 to the previous "magic number
constant" for the next odd higher wavelength
addition:Example: 3/4 = 738/f 5/4 = 1230/f 7/4 = 1722/f 9/4 = 2214/f and so on. 2 BAND OPERATION
WITH THE SAME
ANTENNA!If you will notice in the 15 meter version above, the final
length comes out to be, 32 feet 6 inches
per side,,,,using the standard formula for a regular dipole....468 /
freqmhz, 468/7.2mhz = 65 feet for total length of a 40 meter dipole......
each side would be 32 feet 6 inches.....40 meter operation
included for free! What a deal! This can be applied to two band operation with other designs as well. MORE GOOD STUFF! The short vee beam described in the book has a reasonable omnidirectional pattern with a maximum directivity in a line that bisects the angle between the legs. Good low-angle radiation is obtained when a horizontal antenna has a one wavelength height above ground. Below .5 wavelengths give marginal performance. For lower heights (.5 wavelengths and less),
some improvement in low angle propagation can be had by tilting the leg
ends below the center feed point. This will help improve DX but at the
expense of the omni pattern not being as good and will increase the
vertical pattern more skyward at a higher angle. Try it on higher frequencies too....EXPERIMENT !MORE BELOW!
Freq = 28.6 Mhz50 feet above ground EZNEC PLOT COURTESY K6LMN, ROGER
Plot
for this design is same as aboveand shows results at Maximum Gain Takeoff Angle. 50 feet above groundApex = 100 degrees Z in = 110 ohms VSWR = 2.2 : 1 Element lengths 25.8 feet Good groundNo element losses #10 wire Freq 28.6
MhzGain 11.06 dBiAngle: 0 deg F/B 2.0dB Bmwidth: 35.3 deg -3: 342.3 17.6 deg Slope 8.98 dBi Angle: 180 deg F/S lobe 2.08dB Max
Gain =
11.06dBi- 2.14 = 8.92d - 5.50 ground enhancement Yields aprox 3.42 dBd in free space! Comments:
Good backyard antenna for 10 Meter
band.Apex angle not critical, 95 to 105 degrees OK. Slightly more gain at 105 degrees with stronger sidelobes and higher feed impedance. More Comments from
Roger, K6LMN:"Now with modern
computers and antenna modeling programs we can go back an analyze these
old antennas and also create new ones. I like the EZNEC program
since I have used W7EL's programs since the early '80s. There are a
few others of course. I would like to try YAGIMAX or whatever
program that optimizes
Yagis."
Roger, K6LMNIf you can locate the book described above, by all
means, get it if you have questions. It is loaded with many Dipole and
Long Wire antennas by Ed Nolls, W3FQJ that you will enjoy adding to your
station for many more years of fun thanks to Ed!The main article and project above is one of many Ed contributed to Ham Radio, WITHOUT THE AID OF A COMPUTER!...... Many thanks to Roger, K6LMN for providing his time, talents and skill with the additional material! More fun to come, stay connected with Ham Radio, get on the air!....N4UJW
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