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Low Band DX / Contest Receiving Antennas Using End-Fire Arrays of K9AY Loops Richard C. Jaeger, K4IQJ Auburn, AL Hunts

Low Band DX / Contest Receiving Antennas Using End-Fire Arrays of K9AY Loops Richard C. Jaeger, K4IQJ Auburn, AL Huntsville, August 20, 2011 K4IQJ@mindspring.com. OUTLINE. Introduction & Overview K9AY Array Simulation Results Array Implementation 3 Element 2 Element Results

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Low Band DX / Contest Receiving Antennas Using End-Fire Arrays of K9AY Loops Richard C. Jaeger, K4IQJ Auburn, AL Hunts

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

  2. OUTLINE • Introduction & Overview • K9AY Array Simulation Results • Array Implementation • 3 Element • 2 Element • Results • Discussion / Observations © RCJ - 2

  3. BACKGROUNDLow 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 © RCJ - 3

  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 1-2-1 binomial array of loops • Design goal - maximize RDF © RCJ - 4

  5. 4-Square Array End-Fire Array 1/0 Incoming Signal 1/0 2/q 1/q 1/q 1/2q 1/2q BACKGROUND4-SQUARE / END-FIRE “TRANSFORMATION” © RCJ - 5

  6. RDFReceiving 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) © RCJ - 6

  7. ARRAY COMPARISONK9AY Loop Forward Gain: -23.6 dBi Average Gain: -31.0 RDF: 7.4 dB Horizontal Beamwidth: 173o F/B: 9.5 dB © RCJ - 7

  8. ARRAY COMPARISONTwo-Element Endfire Array - 80’ Spacing Gain: -25.6 dBi RDF: 10.5 dB Horizontal Beamwidth: 96o F/B: 16.0 dB © RCJ - 8

  9. ARRAY COMPARISONThree-Element Endfire Array - 80’ Spacing Gain: -29.2 dBi RDF: 12.7 dB Horizontal Beamwidth: 75o F/B: 24.0 dB © RCJ - 9

  10. ARRAY COMPARISONFour-Element Endfire Array - 80’ Spacing Gain: -37.2 dBi RDF: 14.4 dB Beamwidth: 54o F/B: 24.4 dB (1:2.65:2.65:1) © RCJ - 10

  11. ARRAY COMPARISONVertical Patterns vs. Number of Elements 1 2 3 4 © RCJ - 11

  12. ARRAY COMPARISONHorizontal Patterns vs. Number of Elements 1 2 4 3 © RCJ - 12

  13. ARRAY COMPARISONThree-element Array - 160M & 80M 1.825 MHz 3.505 MHz © RCJ - 13

  14. ARRAY IMPLEMENTATIONPlacement 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 © RCJ - 14

  15. 3-ELEMENT ARRAY OPTIMIZATIONAlternate Current Ratios Design point 1:1.8:1 3 Current Ratios 1:1.9:1 1:2:1 © RCJ - 15

  16. 3-ELEMENT ARRAY OPTIMIZATIONAlternate Current Ratios • Enhanced RDF achieved with other current ratios • Settled upon 1:1.8:1 © RCJ - 16

  17. ARRAY IMPLEMENTATIONSystem 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 © RCJ - 17

  18. ARRAY IMPLEMENTATIONMiscellaneous • 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 © RCJ - 18

  19. ARRAY IMPLEMENTATIONPhasing Lines • Network or antenna analyzer • Adjust by measuring the resonant frequency of open-circuited coax lines © RCJ - 19

  20. ARRAY IMPLEMENTATIONLoop Termination and Switching Single Termination with DPDT Switch Doubly Terminated with SPDT Switch © RCJ - 20

  21. ARRAY IMPLEMENTATIONLoop Antennas & Supports “Hidden” in Front & Side Yards - Black Wire & String Fiberglass (NE/SW) or Aluminum Poles (NW/SE) © RCJ - 21

  22. ARRAY IMPLEMENTATIONAmplifier/Switching Boxes Single Loop Corner Loop Pair © RCJ - 22

  23. ARRAY IMPLEMENTATIONAmplifier/Switching Boxes • Weather-Proof Boxes (Lowes) • Hi-Z Amplifier: should be ac coupled • Direction Relay • Termination Resistor • Stainless Steel HW © RCJ - 23

  24. RESULTSExperimental 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 © RCJ - 24

  25. RESULTSMeasurements Note: Same phasing line utilized on 160 & 80 M Gain in good agreement with SPICE models © RCJ - 25

  26. RESULTSFinal Simulations - 160 M © RCJ - 26

  27. RESULTSFinal Simulations - 80 M © RCJ - 27

  28. RESULTSFinal Simulation Comparisons © RCJ - 28

  29. RESULTSDX - 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 © RCJ - 29

  30. RESULTSContesting - 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 © RCJ - 30

  31. TWO-ELEMENT ARRAYDesign & 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 © RCJ - 31

  32. TWO-ELEMENT ARRAYImplementation • Hi-Z Amplifiers • Hi-Z 2-3 Element Controller • 4 Loops for 4 directions • 13o Phasing Line © RCJ - 32

  33. TWO-ELEMENT ARRAYPhase Plots for Two Antenna Paths Hi-Z Amplifiers Hi-Z 2-3 Element Controller 150 ft RG-6 Coax 13o Phasing Line RCJ - 33

  34. TWO-ELEMENT ARRAYVNA 2180 Results © RCJ - 34

  35. TWO-ELEMENT ARRAYFinal Simulation Using Measured Data Gain: -28.6 dBi RDF: 10.4 dB Horiz. Beamwidth: 98o © RCJ - 35

  36. DISCUSSION / OBSERVATIONSLoops 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 © RCJ - 36

  37. DISCUSSION / OBSERVATIONSOther 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 © RCJ - 37

  38. REFERENCES • Gary Breed, K9AY, "Arrays of K9AY Loops: "Medium-sized" low band RX antenna solutions," Sept. 15, 2007. http://www.aytechnologies.com • John Devoldere, ON4UN's Low-Band DXing, Fourth & Fifth Editions, ARRL, Newington, CT: 2005 & 2011. • Dallas Lankford, http://groups.yahoo.com/group/thedallasfiles • http://www.fcc.gov/mb/audio/m3/index.html • Hi-Z Antennas 4-Square, http://www.hizantennas.com • DX Engineering 4-Square, http://www.dxengineering.com • Max-Gain Systems, http://www.mgs4u.com • The Wireman, http://www.thewireman.com • 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. ( k4iqj@mindspring.com ) © RCJ - 38

  39. THANK YOU FOR YOUR ATTENTION • QUESTIONS? K4IQJ@mindspring.com © RCJ - 39

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