low band dxing
DESCRIPTION
Low Band DXing. There’s life below 14 MHz! 40 meter attributes Global coverage “Convenient” hours for West Coast DXing Minimal TVI concerns 40 meter challenges Interference (local & AM broadcast) Low Band DXing takes a good antenna. Low Band DX Antennas. - PowerPoint PPT PresentationTRANSCRIPT
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The Half Square Yagi
K6EI
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The Half Square Yagi
K6EI
Low Band DXing• There’s life below 14 MHz!
• 40 meter attributes– Global coverage
– “Convenient” hours for West Coast DXing
– Minimal TVI concerns
• 40 meter challenges– Interference (local & AM broadcast)
– Low Band DXing takes a good antenna
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Low Band DX Antennas
The Good, The Bad, and the Ugly
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The Half-Square Yagi
A New, High-Performance, Low-Cost Design for Low-Band DXing
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The Half Square Yagi
K6EI
What makes a Good Low Band Antenna?
Common Antenna Myths• Myth #1 Commercially-made antennas are
better than homebrew• Myth #2 Directivity and Gain are
basically the same thing• Myth #3 A monoband yagi on a 60 foot
tower good enough, regardless of the band• Myth #4 Low Band DX antennas gotta be
huge
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The Half Square Yagi
K6EI
Gain
Critical Attributes for an Effective 40 meter DX Antenna
• Efficiency
• Directivity
• Low Angle of Radiation
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The Half Square Yagi
K6EI
Quiz Question #1)
Between what elevation angles do most West Coast 40m openings to Japan occur?
A) 30 to 45 degrees
B) 20 to 30 degrees
C) 3 to 20 degrees
D) 3 to 10 degrees
E) All of the above
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The Half Square Yagi
K6EI
West Coast 40-meter openings to the Far East
(via IONCAP)
If your antenna’s main elevation isn’t between 3 and 20 degrees, you’re toast !
0
2
4
6
8
10
12
14
16
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
Elevation Angle, Degrees
% o
f O
pen
ing
s
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The Half Square Yagi
K6EI
Quiz Question #1) Between what elevation angles do most West Coast 40m openings to Japan occur?
A) 30 to 45 degrees
B) 20 to 30 degrees
C) 3 to 20 degrees
D) 3 to 10 degrees
E) All of the above
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The Half Square Yagi
K6EI
West Coast 40-meter openings to the Europe
02468
101214161820
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
Elevation Angle, Degrees
% o
f O
pen
ing
s
Aiming for Europe? Two to 12 degrees is what you want!
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The Half Square Yagi
K6EI
West Coast 80-meter openings to the Japan
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2
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10
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1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
Elevation Angle, Degrees
% o
f O
pen
ing
s
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The Half Square Yagi
K6EI
Truly High Performance Low HF Antennas Exist . . .
Elevation Angle of main beam: 8 degrees
Elevation Angle of main beam: 8 degrees
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The Half Square Yagi
K6EI
A 350 foot tall Rotable Curtain Array for 7 MHz:
$3,000,000
But . . .They Come At a Price!
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The Half Square Yagi
K6EI
Quiz Question #2)
Which antenna is a better for working 40m DX?
A) Dipole at 45 feet
B) 1/4 Vertical & Ground Plane 10 ft above the ground
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The Half Square Yagi
K6EI
7 MHz Dipole at 45 feetVia NEC-2 (EZNEC)
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The Half Square Yagi
K6EI
7 MHz Vertical & Ground Plane
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The Half Square Yagi
K6EI
Vertical vs Dipole
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The Half Square Yagi
K6EI
Quiz Question #2)
Which is better for working 40m DX?
A) Dipole at 45 feet
B) 1/4 Vertical & Ground Plane 10 ft above the ground
C) A Tie: Neither is very good
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The Half Square Yagi
K6EI
7 MHz 2 element Monoband Yagi at 45 feet
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The Half Square Yagi
K6EI
7 MHz 2 element Monoband Yagi at 45 feet
But you need to be concentrated below 20 degrees (and preferably below 12 degrees) to work Low Band DX!
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The Half Square Yagi
K6EI
Quiz Question #3)
How high does a 40m dipole need to be for its main beam to be at 15 degrees?
A) 45 feetB) 60 feetC) 100 feetD) 130 feetE) Higher than 200 feet
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The Half Square Yagi
K6EI
7 MHz Dipole at 130 feet
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The Half Square Yagi
K6EI
Quiz Question #4)
How high does a monoband 40m yagi need to be for its main beam to be at 15 degrees?
A) 45 feetB) 60 feetC) 100 feetD) 130 feetE) Higher than 200 feet
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The Half Square Yagi
K6EI
7 MHz 2 element Monoband Yagi at 130 feet
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The Half Square Yagi
K6EI
7 MHz 2 element Monoband Yagi at 130 feet
Using horizontal polarization for Low Band DXingisn’t ideal for the average ham
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The Half Square Yagi
K6EI
Current Distributions
1/2 DipoleFeed Point
Feed Point
Half Square
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The Half Square Yagi
K6EI
/ 2
The Traditional Half Square
Y
X
Z
Feed point Detail
RF Choke
Main Beams
/ 4
/ 4
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The Half Square Yagi
K6EI
Advantages of the Traditional Half Square
• Low Angle of Radiation
• Inexpensive, Simple Construction
• Moderate Gain
• No Radials, Traps, or Tuning Unit Required
• Most of the energy is radiated from up high, not near the base of the antenna
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The Half Square Yagi
K6EI
Half Square Azimuth Pattern
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The Half Square Yagi
K6EI
Half Square vs Vertical & Ground Plane
Quarter Wave Vertical & Elevated Ground Plane
TraditionalHalf Square
6 dB at 15 degrees
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The Half Square Yagi
K6EI
The Half-Square Yagi
Y
X
Z
Reflector
Driven Element
Feed point Detail
RF Choke
Main Beam
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The Half Square Yagi
K6EI
Elevation Patterns for a 2-element Conventional Yagi & Half-Square Yagi with horizontal wires at the same 45-foot height
Conventional2 el Yagi @ 45 ft
2 el Half Sq Yagi
over 9 dBi @ 15 degree elevation
10 dB better F/B
10 to 15 dB more low angle gain
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The Half Square Yagi
K6EI
2 el Conventional Yagi vs Half Square Yagi
Half SqYagi
Conventional2 el Yagi @ 45 ft
Half SqYagi
at 15 degree elevation angle
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The Half Square Yagi
K6EI
Gain vs Frequency
5
6
7
8
9
10
7 7.05 7.1 7.15 7.2 7.25 7.3
Frequency (MHz)
Gai
n (d
Bi)
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The Half Square Yagi
K6EI
Front-to-Back vs Frequency
0
5
10
15
20
25
30
35
7 7.05 7.1 7.15 7.2 7.25 7.3
Frequency (MHz)
F/B
(dB
)
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The Half Square Yagi
K6EI
SWR versus Frequency
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The Half Square Yagi
K6EI
Dimensions for 7.025 MHz
Reflector
Driven Element
5-10 feet
5-10 feet
491.2 / f (70 feet
nominal)
499.7 / f (71’ 3” nominal)
24
5.6
/
f (3
5’
nom
inal)
24
5.6
/
f (3
5’
nom
inal)
24
9.9
/ f
(3
5’ 8
” nom
inal)
24
9.9
/ f
(3
5’ 8
” nom
inal)
5-10 feet
5-10 feet
• Height• Feeding• Pruning• Nearby structures
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38
The Half Square Yagi
K6EI
How the Half Square Yagi Performs
(The Proof is in the Pudding)
• Installed for 40 meters in my backyard
• Loaded up as predicted
• Actual F/B and F/S patterns consistent with model
• 90 trans-Pacific contacts in the first 30 days
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The Half Square Yagi
K6EI
For more details on the Half Square Yagi . . .
Email me:Jim Peterson, K6EI
Or read my article