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 Discussion / Observations 8/20/11 © RCJ - 2

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 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 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 8/20/11 © RCJ - 4

BACKGROUND 4-SQUARE / END-FIRE “TRANSFORMATION” 4-Square Array End-Fire Array Incoming Signal 1/0 2/q 1/2q 1/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 RDFdB = Gfor(dB) - Gavg(dB) 8/20/11 © RCJ - 6

ARRAY COMPARISON K9AY Loop Forward Gain: -23.6 dBi Average Gain: -31.0 RDF: 7.4 dB Horizontal Beamwidth: 173o F/B: 9.5 dB 8/20/11 © RCJ - 7

ARRAY COMPARISON Two-Element Endfire Array - 80’ Spacing Gain: -25.6 dBi RDF: 10.5 dB Horizontal Beamwidth: 96o F/B: 16.0 dB 8/20/11 © RCJ - 8

ARRAY COMPARISON Three-Element Endfire Array - 80’ Spacing Gain: -29.2 dBi RDF: 12.7 dB Horizontal Beamwidth: 75o F/B: 24.0 dB 8/20/11 © RCJ - 9

ARRAY COMPARISON Four-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) 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 2 4 3 8/20/11 © RCJ - 12

ARRAY COMPARISON Three-element Array - 160M & 80M 1.825 MHz 3.505 MHz 8/20/11 © 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 3 Current Ratios 1:1.9:1 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 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 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 (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 8/20/11 © 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 Doubly Terminated with SPDT Switch 8/20/11 © 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 Corner Loop Pair 8/20/11 © RCJ - 22

ARRAY IMPLEMENTATION Amplifier/Switching Boxes Weather-Proof Boxes (Lowes) Hi-Z Amplifier: should be ac coupled Direction Relay Termination Resistor Stainless Steel HW 8/20/11 © RCJ - 23

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 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/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 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 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 8/20/11 © RCJ - 30

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 8/20/11 © RCJ - 31

TWO-ELEMENT ARRAY Implementation Hi-Z Amplifiers Hi-Z 2-3 Element Controller 4 Loops for 4 directions 13o 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 13o 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 (dB) Phase (Deg.) Front Element -18.54 -167.10 -18.61 +37.43 Back Element -17.79 -3.24 -17.92 -171.95 Normalized Values -0.38 dB -0.35 dB +.38 dB -196.1 +0.35 dB -209.4 8/20/11 © RCJ - 34

TWO-ELEMENT ARRAY Final Simulation Using Measured Data Gain: -28.6 dBi RDF: 10.4 dB Horiz. Beamwidth: 98o 8/20/11 © 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+ 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 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 45o directions RDF drops to 10 dB 8/20/11 © RCJ - 37

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 ) 8/20/11 © RCJ - 38

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