Low Band DX Contest Receiving Antennas Using EndFire
Low Band DX / Contest Receiving Antennas Using End-Fire Arrays of K 9 AY Loops Richard C. Jaeger, K 4 IQJ Auburn, AL Huntsville, August 20, 2011 K 4 IQJ@mindspring. com
OUTLINE • Introduction & Overview • K 9 AY Array Simulation Results • Array Implementation – 3 Element – 2 Element • Results • Discussion / Observations 8/20/11 © RCJ - 2
BACKGROUND Low Band Receiving • Started with K 9 AY loop pair • Added 4 -square of short verticals (100’ side) • Very poor ground conditions – Very rocky with rock shelves and clay – 2 -3 m. S/M ground conductivity – 4 -Square not level • K 9 AY loop pair generally better than 4 -square 8/20/11 © RCJ - 3
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 – K 9 AY paper on loop arrays [1] – ON 4 UN 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 8/20/11 © RCJ - 4
BACKGROUND 4 -SQUARE / END-FIRE “TRANSFORMATION” 4 -Square Array End-Fire Array 1/0 Incoming Signal 1/0 1/q 2/q 1/2 q 8/20/11 © RCJ - 5
RDF Receiving Directivity Factor • Noise generally comes in from all directions • RDF compares main lobe gain to average gain over whole antenna • RDFd. B = Gfor(d. B) - Gavg(d. B) 8/20/11 © RCJ - 6
ARRAY COMPARISON K 9 AY Loop Forward Gain: -23. 6 d. Bi Average Gain: -31. 0 RDF: 7. 4 d. B Horizontal Beamwidth: 173 o 8/20/11 F/B: 9. 5 d. B © RCJ - 7
ARRAY COMPARISON Two-Element Endfire Array - 80’ Spacing Gain: -25. 6 d. Bi RDF: 10. 5 d. B Horizontal Beamwidth: 96 o F/B: 16. 0 d. B 8/20/11 © RCJ - 8
ARRAY COMPARISON Three-Element Endfire Array - 80’ Spacing Gain: -29. 2 d. Bi RDF: 12. 7 d. B Horizontal Beamwidth: 75 o F/B: 24. 0 d. B 8/20/11 © RCJ - 9
ARRAY COMPARISON Four-Element Endfire Array - 80’ Spacing Gain: -37. 2 d. Bi RDF: 14. 4 d. B Beamwidth: 54 o F/B: 24. 4 d. B (1: 2. 65: 1) 8/20/11 © RCJ - 10
ARRAY COMPARISON Vertical Patterns vs. Number of Elements 1 2 3 4 8/20/11 © RCJ - 11
ARRAY COMPARISON Horizontal Patterns vs. Number of Elements 1 3 8/20/11 2 4 © RCJ - 12
ARRAY COMPARISON Three-element Array - 160 M & 80 M 1. 825 MHz 8/20/11 3. 505 MHz © RCJ - 13
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 8/20/11 © RCJ - 14
3 -ELEMENT ARRAY OPTIMIZATION Alternate Current Ratios Design point 1: 1. 8: 1 1: 1. 9: 1 3 Current Ratios 1: 2: 1 8/20/11 © RCJ - 15
3 -ELEMENT ARRAY OPTIMIZATION Alternate Current Ratios • Enhanced RDF achieved with other current ratios • Settled upon 1: 1. 8: 1 8/20/11 © RCJ - 16
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 for ends • ≈ 38 for center - adjusted for 1. 8: 1 output • Must switch loop termination with controller phasing • Beaded chokes (The Wireman) – 50 coax 8/20/11 © RCJ - 17
ARRAY IMPLEMENTATION Miscellaneous • Make Loops as identical as possible • 3 -ft ground stake under antenna • Four 20’ radials under each loop (45 o 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 8/20/11 Feedline Choke © RCJ - 18
ARRAY IMPLEMENTATION Phasing Lines • Network or antenna analyzer • Adjust by measuring the resonant frequency of open-circuited coax lines 8/20/11 © RCJ - 19
ARRAY IMPLEMENTATION Loop Termination and Switching Single Termination with DPDT Switch 8/20/11 Doubly Terminated with SPDT Switch © RCJ - 20
ARRAY IMPLEMENTATION Loop Antennas & Supports “Hidden” in Front & Side Yards - Black Wire & String Fiberglass (NE/SW) or Aluminum Poles (NW/SE) 8/20/11 © RCJ - 21
ARRAY IMPLEMENTATION Amplifier/Switching Boxes Single Loop 8/20/11 Corner Loop Pair © RCJ - 22
ARRAY IMPLEMENTATION Amplifier/Switching Boxes 8/20/11 • Weather-Proof Boxes (Lowes) - Hi-Z Amplifier: should be ac coupled - Direction Relay - Termination Resistor - Stainless Steel HW © RCJ - 23
RESULTS Experimental Setup • Array Solutions VNA 2180 (50 ) • Port A drives 50 coax with 50 - termination at input of High-Z amplifiers • 75 coax from controller to VNA • 75 - 50 Pad at input to VNA Port B • Measurements repeatable to within 0. 3 d. B and less than 0. 5 o 8/20/11 © RCJ - 24
RESULTS Measurements Note: Same phasing line utilized on 160 & 80 M Gain in good agreement with SPICE models 8/20/11 © RCJ - 25
RESULTS Final Simulations - 160 M 8/20/11 © RCJ - 26
RESULTS Final Simulations - 80 M 8/20/11 © RCJ - 27
RESULTS Final Simulation Comparisons 8/20/11 © RCJ - 28
RESULTS DX - The Bottom Line • Copied FR/DJ 7 RJ & 5 R 8 RJ night after night on 160 – Not readable on inverted L transmit antenna • Worked S 79 GM on both 160 M & 80 M. – Also could not copy on inverted L • • PJ 4 - First TB qso required loop array Missed 9 Q 5ØQN - couldn’t hear me – Consolation – Easily heard and worked on 80 M for new one • Past season successes – TJ 9 PF, 4 L/UUØJM, XU 7 ACY, 9 L 5 MS, 5 M 2 TT, BU 2 AQ – 234 Countries, 38 Zones • 160 M propagation testing with VK 3 ZL – 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. 40 M, 30 M and up - there are lobes pointed somewhere – Have used on 17 M and 12 M 8/20/11 © RCJ - 29
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 K 9 AY Loop Array with Half Size Loops • Worked fine on 80 M • Marginal output on 160 M • 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 8/20/11 © RCJ - 30
TWO-ELEMENT ARRAY Design & Implementation • Simple Implementation • Two-element Arrays Give Very a Useful Improvement (3 d. B) • RDF: 7. 5 d. B 10. 5 d. B • Narrow Spacing Possible if Space is Limited (30+ feet) • Half Size Loops – Work well on 80/40/30 – Marginal so far on 160 M • Elements Were Originally Added One at a Time • Significant Improvement Noted at Each Step 8/20/11 © RCJ - 31
TWO-ELEMENT ARRAY Implementation • • Hi-Z Amplifiers Hi-Z 2 -3 Element Controller 4 Loops for 4 directions 13 o Phasing Line 8/20/11 © RCJ - 32
TWO-ELEMENT ARRAY Phase Plots for Two Antenna Paths Hi-Z Amplifiers Hi-Z 2 -3 Element Controller 150 ft RG-6 Coax 13 o Phasing Line 8/20/11 RCJ - 33
TWO-ELEMENT ARRAY VNA 2180 Results Hi-Z Antennas: Amplifier + Two-Element Array Controller 150 ft RG-6 + 13 Degree Phasing Line Path 1. 825 MHz 3. 505 MHz Gain (d. B) Phase (Deg. ) Front Element -18. 54 -167. 10 -18. 61 +37. 43 Back Element -17. 79 -3. 24 -17. 92 -171. 95 Normalized Values Front Element -0. 38 d. B 0 -0. 35 d. B 0 Back Element +. 38 d. B -196. 1 +0. 35 d. B -209. 4 8/20/11 © RCJ - 34
TWO-ELEMENT ARRAY Final Simulation Using Measured Data Gain: -28. 6 d. Bi RDF: 10. 4 d. B 8/20/11 Horiz. Beamwidth: 98 o © RCJ - 35
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+ d. B) • 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 8/20/11 © RCJ - 36
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 45 o directions – RDF drops to 10 d. B 8/20/11 © RCJ - 37
REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. Gary Breed, K 9 AY, "Arrays of K 9 AY Loops: "Medium-sized" low band RX antenna solutions, " Sept. 15, 2007. http: //www. aytechnologies. com John Devoldere, ON 4 UN'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/m 3/index. html Hi-Z Antennas 4 -Square, http: //www. hizantennas. com DX Engineering 4 -Square, http: //www. dxengineering. com Max-Gain Systems, http: //www. mgs 4 u. com The Wireman, http: //www. thewireman. com Richard C. Jaeger, K 4 IQJ “Multi-Element End-fire Arrays of K 9 AY Loops, ” expanded version of 2011 Dayton presentation, May 15, 2011, available from the author. ( k 4 iqj@mindspring. com ) 8/20/11 © RCJ - 38
• THANK YOU FOR YOUR ATTENTION • QUESTIONS? K 4 IQJ@mindspring. com 8/20/11 © RCJ - 39
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