Vee Beams for HF/VHF

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From: William K Hibbert (wb2vuo@juno.com)
Date: Sat Sep 06 1997 - 09:36:07 EDT


                          Vee Beams

The Vee Beam is one of the earliest, and simplest directional
arrays in radio. Basically, a Vee Beam is a pair of long
wires (1-wave or greater), aligned in such a way that the
major lobes (points of greatest radiation) combine additively
producing a sharper beam pattern, and greater gain.

The gain of a Vee Beam, according to the ARRL Handbook, 1947
edition, "increases with the length of the wires, but is not
exactly twice the gain for a single long wire..." As an
example, the Handbook states that the gain of a Vee Beam, 8-
waves per leg would be around 12 dB whereas doubling the gain
of a single 8-wave longwire would result in approximately 9
dB. This "extra" gain is due to mutual coupling between the
wires.

The directional pattern for a Vee Beam is bidirectional (no
Front-Back ratio), with the strongest lobe along the bisector
of the included angle. As the leg length increases, the
included angle (V in the drawing) decreases. The antenna is
fed with open-wire, ladder line, twin lead or other balanced
lines, and the longer arrays show very good multi-band
characteristics.

Let's say that you wanted to cover the 20 thru 10 Meter
bands, including the 17 and 12 Meter bands. Due to the
broadbanded characteristics, you could design a Vee Beam for
the center of this range, (15 Meters), and tune it to all the
bands. Your wave angle would be higher on the lower bands,
and the beamwidth a bit narrow on the upper bands, but you
would get reasonable gain and directivity thru the entire
range.

A good example, listed in the ARRL Antenna Book for decades,
would be a 3-wave Vee Beam for 15 Meters. The leg length
would be 135 feet for 21.2 MHz. This is 2 waves on 20 Meters
and 4 waves on 10 Meters (2.5 waves on 17 M and 3.5 waves on
12 M). The gain would be approximately 6 dB on 15 Meters,
5 dB on 20 Meters and 6.5 dB on 10 Meters. A fair gain
comparison is a 2-element yagi. So, the gain of the Vee Beam
would be in line with a 2-element tri-bander, but on 5 bands,
and at a much reduced cost. The included angle for the 3-
wave Vee Beam is 60-degrees, so 3 supports would be required,
falling on the corners of an equilateral triangle with sides
of 140 feet. This is about the space needed for a 1-wave
loop for 160 Meters.

Here's a "drawing" of the Vee Beam:

                     b
                    /
                  /
                /
              /
            /
          /
        /
      /
    /
a./ \ Feed at points ac. L = ab
c. V ab = cd; V = Included angle
  \ /
    \
      \
        \
          \
            \
              \
                \
                  \
                    \d

The included angle "V" decreases as the leg length "L"
increases. Here's a chart with Included angle, base on
wavelengths, and (very) approximate gains:

Waves "V" Gain (App'x)

1 110-degrees 3.5 dB
2 71-degrees 5.0 dB
3 60-degrees 6.0 dB
4 52-degrees 7.0 dB
5 45-degrees 8.0 dB
6 40-degrees 9.5 dB
7 37-degrees 10.5 dB
8 35-degrees 12.0 dB

This is not to say that you can't go past 8-waves for a leg
length, but that's as long as most hams can handle in the HF
spectrum, or even the low VHF spectrum. 8-waves on 6 Meters
is about 160 feet, and is almost 65 feet even on 2 Meters.

With our 3-wave, 15 Meter design, one can make it into a
steered all-bander by putting up a total of 4 wires, spaced
60 degrees and selecting the desired two for the band of
interest. It would look something like this:

           d e
             \ /
               \ /
                 \ /
                   \ /
         -----------O----------
         a b c

With line ac running from West to East, you can steer it on
20 - 10 by selecting ab and bd, bd and be or be and bc,
giving you 3 different bi-directional patterns, 60 degrees
apart. On 40 and 30 Meters, you can select ab and be or bd
and bc for two bi-directional patterns 120 degrees apart, and
on 160 and 80 Meters you can select ab and bc for a "dipole".
By feeding with a 4-wire balanced line, you can select the
appropriate wires in the shack, or with a relay box at the
base of the pole ("O"), they can be switched remotely. This
array would require 5 poles and would take up 3/4-acre, quite
a bit of real estate! Not for the City Lot, unless you have
VERY understanding neighbors!

An old idea, but my 10 -Meter Vee Beam plays really well.
Give is a try if you have the room...

72/73, Keith, WB2VUO, QRP-L #582, scQRP 40, AR QRP #68, 100% QRP
Tech Specialist (ARRL/WNY), ARRL Life Member,
Trustee, NQ2RP/B 10 Mtr QRP Beacon (125 mW @ 28.287 MHz)
"In the Depths of the Great Bergen (NY) Swamp...FN13ac"
Packet - wb2vuo@w2im.#wny.ny.usa.noam *** Email - wb2vuo@juno.com
SnailMail - CBA *** Phone - 716.494.1239

"My Night Light runs more power than my Rig!!!"


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