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

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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

Huntsville, August 20, 2011

K4IQJ@mindspring.com

outline
OUTLINE
  • Introduction & Overview
  • K9AY Array Simulation Results
  • Array Implementation
    • 3 Element
    • 2 Element
  • Results
  • Discussion / Observations

© RCJ - 2

background low band receiving
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

background
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

rdf receiving directivity factor
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

array comparison k9ay loop
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

array comparison two element endfire array 80 spacing
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

array comparison three element endfire array 80 spacing
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

array comparison four element endfire array 80 spacing
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

array implementation placement of the arrays
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

3 element array optimization alternate current ratios
3-ELEMENT ARRAY OPTIMIZATIONAlternate Current Ratios

Design point

1:1.8:1

3 Current Ratios

1:1.9:1

1:2:1

© RCJ - 15

3 element array optimization alternate current ratios1
3-ELEMENT ARRAY OPTIMIZATIONAlternate Current Ratios
  • Enhanced RDF achieved with other current ratios
  • Settled upon 1:1.8:1

© RCJ - 16

array implementation system design
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

array implementation miscellaneous
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

array implementation phasing lines
ARRAY IMPLEMENTATIONPhasing Lines
  • Network or antenna analyzer
  • Adjust by measuring the resonant frequency of open-circuited coax lines

© RCJ - 19

array implementation loop termination and switching
ARRAY IMPLEMENTATIONLoop Termination and Switching

Single Termination with

DPDT Switch

Doubly Terminated with

SPDT Switch

© RCJ - 20

array implementation loop antennas supports
ARRAY IMPLEMENTATIONLoop Antennas & Supports

“Hidden” in Front & Side Yards - Black Wire & String

Fiberglass (NE/SW) or Aluminum Poles (NW/SE)

© RCJ - 21

array implementation amplifier switching boxes
ARRAY IMPLEMENTATIONAmplifier/Switching Boxes

Single Loop Corner Loop Pair

© RCJ - 22

array implementation amplifier switching boxes1
ARRAY IMPLEMENTATIONAmplifier/Switching Boxes
  • Weather-Proof Boxes (Lowes)
    • Hi-Z Amplifier: should be ac coupled
    • Direction Relay
    • Termination Resistor
    • Stainless Steel HW

© RCJ - 23

results experimental setup
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

results measurements
RESULTSMeasurements

Note: Same phasing line utilized on 160 & 80 M

Gain in good agreement with SPICE models

© RCJ - 25

results dx the bottom line
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

results contesting the bottom line
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

two element array design implementation
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

two element array implementation
TWO-ELEMENT ARRAYImplementation
  • Hi-Z Amplifiers
  • Hi-Z 2-3 Element Controller
  • 4 Loops for 4 directions
  • 13o Phasing Line

© RCJ - 32

two element array phase plots for two antenna paths
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

two element array final simulation using measured data
TWO-ELEMENT ARRAYFinal Simulation Using Measured Data

Gain: -28.6 dBi RDF: 10.4 dB Horiz. Beamwidth: 98o

© RCJ - 35

discussion observations loops and short verticals
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

discussion observations other ideas
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

references
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

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THANK YOU FOR YOUR ATTENTION
  • QUESTIONS?

K4IQJ@mindspring.com

© RCJ - 39

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