1. Low Band DX / Contest Receiving Antennas Using End-Fire Arrays of K9AY Loops
Richard C. Jaeger, K4IQJ
Auburn, AL
Huntsville, August 20, 2011

2. OUTLINE Introduction & Overview K9AY Array Simulation Results
Array Implementation
3 Element
2 Element
Results
Discussion / Observations
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3. BACKGROUND Low Band Receiving
Started with K9AY loop pair
Added 4-square of short verticals (100’ side)
Very poor ground conditions
Very rocky with rock shelves and clay
2-3 mS/M ground conductivity
4-Square not level
K9AY loop pair generally better than 4-square
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4. BACKGROUND Wanted to try a 4-square of loops
Could not site the 4-square array well on my lot
Uneven lot + esthetic considerations
Reviewed some existing literature
K9AY paper on loop arrays [1]
ON4UN book [2]
Dallas Lankford Papers [3]
Realized that the side elements of the 4-square essentially operate in parallel
Decided to try a binomial array of loops
Design goal - maximize RDF
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5. BACKGROUND 4-SQUARE / END-FIRE “TRANSFORMATION”
4-Square Array End-Fire Array
Incoming
Signal
1/0
2/q
1/2q
1/q
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6. RDF Receiving Directivity Factor
Noise generally comes in from all directions
RDF compares main lobe gain to average gain over whole antenna
RDFdB = Gfor(dB) - Gavg(dB)
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7. ARRAY COMPARISON K9AY Loop
Forward Gain: dBi
Average Gain: -31.0
RDF: 7.4 dB
Horizontal Beamwidth: 173o
F/B: 9.5 dB
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8. ARRAY COMPARISON Two-Element Endfire Array - 80’ Spacing
Gain: dBi
RDF: 10.5 dB
Horizontal Beamwidth: 96o
F/B: 16.0 dB
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9. ARRAY COMPARISON Three-Element Endfire Array - 80’ Spacing
Gain: dBi
RDF: 12.7 dB
Horizontal Beamwidth: 75o
F/B: 24.0 dB
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10. ARRAY COMPARISON Four-Element Endfire Array - 80’ Spacing
Gain: dBi RDF: 14.4 dB Beamwidth: 54o F/B: 24.4 dB
(1:2.65:2.65:1)
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11. ARRAY COMPARISON Vertical Patterns vs. Number of Elements1 2 3 4
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12. ARRAY COMPARISON Horizontal Patterns vs. Number of Elements1 2 4 3
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13. ARRAY COMPARISON Three-element Array - 160M & 80M
1.825 MHz
3.505 MHz
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14. ARRAY IMPLEMENTATION Placement of the Arrays
Layout of NE/SW (160’) & NW/SE (115’) Arrays
Heavily wooded lot
Front yard is left of house
Small lake off to the right
Downhill slope to right
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15. 3-ELEMENT ARRAY OPTIMIZATION Alternate Current Ratios
Design point
1:1.8:1
3 Current Ratios
1:1.9:1
1:2:1
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16. 3-ELEMENT ARRAY OPTIMIZATION Alternate Current Ratios
Enhanced RDF achieved with other current ratios
Settled upon 1:1.8:1
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17. ARRAY IMPLEMENTATION System Design
Controllers
One Hi-Z
One DX Engineering
Hi-Z Amplifiers
500  antennas connected directly to amplifier inputs
Center amplifier drives a coax pair & two controller inputs
Output Resistance Rout
75 W for ends
≈ 38 W for center - adjusted for 1.8:1 output
Must switch loop termination with controller phasing
Beaded chokes (The Wireman)
50  coax
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18. ARRAY IMPLEMENTATION Miscellaneous
Make Loops as identical as possible
3-ft ground stake under antenna
Four 20’ radials under each loop (45o relative to loop)
Beaded chokes throughout
Approximately 1000  on TB
“Braid breakers” now in
NE/SW array
No apparent difference
No observed interaction with grounded aluminum supports
Simulation shows small effect
Plan to use as short vertical array
Feedline Choke
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19. ARRAY IMPLEMENTATION Phasing Lines
Network or antenna analyzer
Adjust by measuring the resonant frequency of open-circuited coax lines
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20. ARRAY IMPLEMENTATION Loop Termination and Switching
Single Termination with
DPDT Switch
Doubly Terminated with
SPDT Switch
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21. ARRAY IMPLEMENTATION Loop Antennas & Supports
“Hidden” in Front & Side Yards - Black Wire & String
Fiberglass (NE/SW) or Aluminum Poles (NW/SE)
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22. ARRAY IMPLEMENTATION Amplifier/Switching Boxes
Single Loop Corner Loop Pair
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23. ARRAY IMPLEMENTATION Amplifier/Switching Boxes
Weather-Proof Boxes (Lowes)
Hi-Z Amplifier: should be ac coupled
Direction Relay
Termination Resistor
Stainless Steel HW
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24. RESULTS Experimental Setup
Array Solutions VNA 2180 (50 W)
Port A drives 50 W coax with 50-W termination at input of High-Z amplifiers
75 W coax from controller to VNA
75 W - 50 W Pad at input to VNA Port B
Measurements repeatable to within 0.3 dB and less than 0.5o
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25. RESULTS Measurements Note: Same phasing line utilized on 160 & 80 M
Gain in good agreement with SPICE models
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26. RESULTS Final Simulations - 160 M
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27. RESULTS Final Simulations - 80 M
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28. RESULTS Final Simulation Comparisons
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29. RESULTS DX - The Bottom Line
Copied FR/DJ7RJ & 5R8RJ night after night on 160
Not readable on inverted L transmit antenna
Worked S79GM on both 160 M & 80 M.
Also could not copy on inverted L
PJ4 - First TB qso required loop array
Missed 9Q5ØQN - couldn’t hear me
Consolation – Easily heard and worked on 80 M for new one
Past season successes
TJ9PF, 4L/UUØJM, XU7ACY, 9L5MS, 5M2TT, BU2AQ
234 Countries, 38 Zones
160M propagation testing with VK3ZL
13 times through June-July-August QRN in 2010
33 times so far June-July-August 2011
Routinely use on 160 M / 80 M to “save ears”
Use on any frequency where there is an advantage
E.g. 40M, 30M and up - there are lobes pointed somewhere
Have used on 17M and 12M
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30. RESULTS Contesting - The Bottom Line
Low Band DX Contests
Can now hear well on 160/80 M
Operation far less difficult / tiring on the low bands
2 EL K9AY Loop Array with Half Size Loops
Worked fine on 80M
Marginal output on 160M
Recent NAQP CW
Much grumbling after the contest regarding qrn problems on 80/160
I really had little trouble hearing on 80 or 160
Biggest problem was selecting the correct direction
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31. TWO-ELEMENT ARRAY Design & Implementation
Simple Implementation
Two-element Arrays Give Very a Useful Improvement (3 dB)
RDF: 7.5 dB  10.5 dB
Narrow Spacing Possible if Space is Limited (30+ feet)
Half Size Loops
Work well on 80/40/30
Marginal so far on 160M
Elements Were Originally Added One at a Time
Significant Improvement Noted at Each Step
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32. TWO-ELEMENT ARRAY Implementation
Hi-Z Amplifiers
Hi-Z 2-3 Element Controller
4 Loops for 4 directions
13o Phasing Line
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33. TWO-ELEMENT ARRAY Phase Plots for Two Antenna Paths
Hi-Z Amplifiers
Hi-Z 2-3 Element
Controller
150 ft RG-6 Coax
13o Phasing Line
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34. TWO-ELEMENT ARRAY VNA 2180 Results
Hi-Z Antennas: Amplifier + Two-Element Array Controller
150 ft RG Degree Phasing Line
Path
1.825 MHz
3.505 MHz
Gain (dB)
Phase (Deg.)
Front Element
-18.54
-18.61
+37.43
Back Element
-17.79
-3.24
-17.92
Normalized Values
-0.38 dB
-0.35 dB
+.38 dB
-196.1
+0.35 dB
-209.4
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35. TWO-ELEMENT ARRAY Final Simulation Using Measured Data
Gain: dBi RDF: 10.4 dB Horiz. Beamwidth: 98o
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36. DISCUSSION / OBSERVATIONS Loops and Short Verticals
A short vertical array parallels NE/SW array
Separated by approximately 20’
Loops almost always better at my location
Vertical array better only one time in two months of comparisons
Simulation indicates small advantage for the loops
Array factor should be the same
Inherent F/B of loop provides some advantage (1+ dB)
Output of wider spaced array is clearly higher
Vertical supports on NW/SE array can operate as short (26’) vertical array elements
Plan to be able to switch back and forth - not implemented yet
My skill level is much higher now than when I did first 4-square installation - phasing not optimal
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37. DISCUSSION / OBSERVATIONS Other Ideas
Latest version
Doubly terminated loops
Switch single amplifier input; Should ac couple loops to amplifiers
An alternative for three-element array ratios
Use identical amplifiers & attenuate the front and rear amplifiers by a factor of 0.54.
Only requires one coax from the center amplifier
Noise figure is degraded by attenuation factor
Degradation was noticeable when I tried it
Side rejection is very high.
One array may be useful as “noise” antenna for the other.
Combine the two array outputs, to fill 45o directions
RDF drops to 10 dB
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38. REFERENCES
Gary Breed, K9AY, "Arrays of K9AY Loops: "Medium-sized" low band RX antenna solutions," Sept. 15,
John Devoldere, ON4UN's Low-Band DXing, Fourth & Fifth Editions, ARRL, Newington, CT: 2005 & 2011.
Dallas Lankford,
Hi-Z Antennas 4-Square,
DX Engineering 4-Square,
Max-Gain Systems,
The Wireman,
Richard C. Jaeger, K4IQJ “Multi-Element End-fire Arrays of K9AY Loops,” expanded version of 2011 Dayton presentation, May 15, 2011, available from the author. ( )
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39. THANK YOU FOR YOUR ATTENTION QUESTIONS?
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