Vertical Delta Loop
• What is it?
• Why do I care?
• How can I make one!
July 19, 2014 September 17, 2014
Vertical Delta Loops
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Basic Antenna Types
Dipole
Monopole
Loop
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Basic Antenna Types Con’t.
½ Wave Dipole
Bow Tie
Pattern
¼ Wave Monopole
Round
Pattern
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Basic Antenna Types Con’t.
Loop Antennas (both 40M)
Long Loop about
1 Wavelength Long
Small Loop less than
1/10 Wavelength Long
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Oval
Pattern
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Basic Antenna Types Con’t.
Most articles are about Horizontal Loops
tonight is about Vertical Loops
Vertical Loops
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Horizontal Loops
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WL Loop Fundamentals
• A loop antenna is composed of a loop of wire a wavelength long.
• The loop does not have to be any particular shape.
• RF power can be fed anywhere on the loop.
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~
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Round, Square, Rectangular, Triangular and
Vertical Delta Loop
All are the Same Length
Example of 20M Vertical Delta
•
Can be any shape to fit your landscape
•
Material
o
o
o
64 Feet #20 AWG Bell Wire
4:1 Current BALUN
Fishing Pole (Something for Support)
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Area of Loop = Efficiency
•
•
•
•
The goal is to get the greatest area inside the loop.
A circle is the perfect shape, but difficult to build for HF.
Both Triangles and Rectangles are good performers.
A Vertical Delta Loop uses a single support on an equilateral
triangle.
~
~
50 - 75 %
100 %
79 %
~
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Maximum
Area
is the
Objective
60 %
~
~
40 - 50%
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The Vertical Delta Loop
• A three sided loop is known as a Vertical Delta loop sitting on the ground.
• For best results, the lengths of the 3 sides should be approximately equal
• The resistive impedance is ~130  interface with 4:1 BALUN
• 2:1 VSWR Bandwidth Covers whole band at 40M and up (~ 4 % of Freq)
• The pattern is almost round, +/- 1 dB and the radiation pattern has no
nulls. Max radiation is broadside to loop.
Almost Omni !
They Lied!
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Why do I care?
Why use a Vertical Delta Loop?
Pro’s
•
•
•
•
•
•
•
•
Good on the Air Performance Sitting on Ground
Single Support
Almost Omni-Directional
Wide VSWR range (no tuner)
Cheap (wire + fishing pole + BALUN)
Simple to build
Great for portable or backpacking
Low visibility
Con’s
• Size a problem for 80M and 160M
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Why not use a Dipole?
(G5RV, Windom, Sloper or other dipole variant)
• All these dipole related antennas are good
• Performance suffers when too close to the ground
• Everyone has lied to you about your antenna pattern
(or they didn’t tell the whole truth)
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Why not use a Dipole?
(performance is all about radiation takeoff angle)
• 10˚ is good because you get more distance per hop & less loss
• 50˚ still works, but may cost 3 hops & not always make it
• 90˚ is bad because there can be only ONE hop
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40M Dipole at 140 Ft above ground
x
Feedpoint Impedance = 74 + j08
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40M Dipole at 98 Ft above ground
x
Feedpoint Impedance = 70 + j30
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40M Dipole at 70 Ft above ground
x
Feedpoint Impedance = 71 – j0
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40M Dipole at 42 Ft above ground
x
Feedpoint Impedance = 100 + j32
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40M Dipole at 14 Ft above ground
x
12 dB
Less than at 140 Ft
Feedpoint Impedance = 23 + j39
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Why not use a Dipole?
(Conclusion)
Dipoles are at a disadvantage when
too close to the ground,
but you can get a better result with a Vertical Delta Loop
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Why not use a Vertical?
(1/4 WL, 5/8 WL, 3/4 WL Flagpole or other vertical variant)
• All these vertical monopole antennas are good
• Performance suffers in poor sandy soil like The Villages
• Performance suffers without sufficient radials
• Radials require lots of work to install, but you got to have them
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Verticals vs Ground Radials
# of radials are critical to RF Gain
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Verticals vs Ground Radials
7 Ft
Short Antennas
suffer twice as
much from fewer
radials
34 Ft
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Verticals vs Ground Radials
Number of radials
16
24
36
60
90
120
Power loss relative to
“perfect” ground plane
50%
37%
29%
21%
6%
1%
Feedpoint impedance in
ohms
52
46
43
40
37
35
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Why not use a Vertical?
(Conclusion)
What does this
measurement
mean with
respect to
radials?
Lots of work to install all those radials,
but you can get a better result with a Vertical Delta Loop
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How to make a Vertical Delta Loop
Vertical Delta Loop Materials
•
•
•
•
Pole
– Crappie Poles are cheap and telescope for storage
– Crappie Poles 15 to 20 Feet ($10 - $25)
– PVC pipe will work too
– Trees are even better, except for storage
Wire
– Any wire will do, just need a size that doesn’t break
– #20 AWG (bell wire) is plenty strong and cheap
– Stranded is better for handling and strength
– Insulated is readily available
BALUN
– 4:1
– Balanced to Unbalanced
– Current type (Guanella is best)
Miscellaneous
– Wood or plastic stake for fishing pole
– Stake, milk bottle or rock to hold one corner
– Plastic Shower Rings or Nylon Cable Ties for fishing pole apex
Round, Square, Rectangular, Triangular and Delta Loop
Wire Length
Band
160 (1.83 MHz)
80 (3.6 MHz)
75 (3.9 MHz)
40 (7.1 MHz)
30 (10.1 MHz)
20 (14.2 MHz)
17 (18.1 MHz)
15 (21.2 MHz)
12 (24.9 MHz)
10 (28.7 MHz)
Bare Copper
549 ft
279 ft
257 ft
141 ft
99 ft
70 ft
55 ft
47 ft
40 ft
35 ft
Plastic
Insulated #20
Wire = 64 Feet
Shorter if insulated
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What can you do with 2 fishing poles?
Two 20 Foot poles, 20 AWG bell wire and a 4:1 Current BALUN
Plastic Insulated #20
Wire = 40 Feet Wide
Ht
Width
4:1
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Putting up a Vertical Loop
Vertically oriented loops may be erected with one or more supports
Circumference = ~135 feet trim tune to 40M and Harmonics
Feed Point = 130 R + 0 j at 40, 20, 10, 6 M (measured)
Current BALUN 4:1 on ground at Pergola (33 R + 0 j )
Tuner at T/R in Bandstand for 30, 17, 12M
1:1.4 VSWR No tuner required for 40, 20, 10, 6 M
Wire #22 AWG Bell Wire
Not pulled just placed in trees with fishing pole
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Harmonic Operation of Loops
40M, 20M, 15M, 10M bands without needing a tuner
40M through 6M with a tuner
•
•
•
•
A loop antenna is resonant at integral multiples
Harmonics 200 - 300 ohms (50-75 after 4:1 BALUN) lower in real life
Less directivity at harmonics
Higher high angles of radiation on harmonic frequencies.
Gets higher
at harmonics
Gets fuller at harmonics
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Polarization of Loop Antennas
•
•
•
•
•
HF DX signals are constantly changing in polarization
The loop may be vertical or horizontal depending on feed point
Vertical polarization is preferred when antenna is low
DX rule is to feed the loop for low radiation angle
Practical consideration is feed at ground level
Select Feed Point to keep
Main Lobe Angle Low for
better DX
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Feed Point for Loop Antennas
• Best rule is to feed the loop for low radiation angle
• Practical consideration is best at ground level
4NEC2 shows feeding
1/3 up will give the
lowest main lobe
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~
~
~
Area is more
important than
shape or feed point
~
On-Air results show corner feed
on triangles or bottom center of
rectangles work well
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Conclusion
Vertical Delta Loops are good performers, cheap, simple,
portable and one more option to get on the air
ANTENNA
Pros
Cons
Vertical Delta Loop
Portable
Very large on low bands
Dipoles
No Radials
Need altitude for DX
Monopole
Good on low Bands
Many radials required
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