low band dx / contest receiving antennas using end-fire arrays of k9ay loops richard c. jaeger,...
TRANSCRIPT
Low Band DX / Contest Receiving Antennas Using End-Fire Arrays of
K9AY Loops
Richard C. Jaeger, K4IQJ
Auburn, AL
Huntsville, August 20, 2011
8/20/11 © RCJ - 2
OUTLINE
• Introduction & Overview
• K9AY Array Simulation Results
• Array Implementation– 3 Element– 2 Element
• Results
• Discussion / Observations
8/20/11 © RCJ - 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
8/20/11 © RCJ - 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
8/20/11 © RCJ - 5
BACKGROUND4-SQUARE / END-FIRE “TRANSFORMATION”
4-Square Array End-Fire Array
IncomingSignal
1/
2/
1/2
1/ 1/
1/2
1/
8/20/11 © RCJ - 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)
8/20/11 © RCJ - 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
8/20/11 © RCJ - 8
ARRAY COMPARISONTwo-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 - 9
ARRAY COMPARISONThree-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 - 10
ARRAY COMPARISONFour-Element Endfire Array - 80’ SpacingGain: -37.2 dBi RDF: 14.4 dB Beamwidth: 54o F/B: 24.4 dB
(1:2.65:2.65:1)
8/20/11 © RCJ - 11
ARRAY COMPARISONVertical Patterns vs. Number of Elements
1 2
43
8/20/11 © RCJ - 12
ARRAY COMPARISONHorizontal Patterns vs. Number of Elements
1 2
3 4
8/20/11 © RCJ - 13
ARRAY COMPARISONThree-element Array - 160M & 80M
1.825 MHz 3.505 MHz
8/20/11 © RCJ - 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
8/20/11 © RCJ - 15
3-ELEMENT ARRAY OPTIMIZATIONAlternate Current Ratios
1:2:1
1:1.8:1
1:1.9:13 Current
Ratios
Design point
8/20/11 © RCJ - 16
3-ELEMENT ARRAY OPTIMIZATIONAlternate Current Ratios
• Enhanced RDF achieved with other current ratios
• Settled upon 1:1.8:1
8/20/11 © RCJ - 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 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 - 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
8/20/11 © RCJ - 19
ARRAY IMPLEMENTATIONPhasing Lines
• Network or antenna analyzer• Adjust by measuring the resonant frequency of
open-circuited coax lines
8/20/11 © RCJ - 20
ARRAY IMPLEMENTATIONLoop Termination and Switching
Single Termination with DPDT Switch
Doubly Terminated with SPDT Switch
8/20/11 © RCJ - 21
ARRAY IMPLEMENTATIONLoop Antennas & Supports
“Hidden” in Front & Side Yards - Black Wire & String Fiberglass (NE/SW) or Aluminum Poles (NW/SE)
8/20/11 © RCJ - 22
ARRAY IMPLEMENTATIONAmplifier/Switching Boxes
Single Loop Corner Loop Pair
8/20/11 © RCJ - 23
ARRAY IMPLEMENTATIONAmplifier/Switching Boxes
• Weather-Proof Boxes (Lowes)- Hi-Z Amplifier: should be ac coupled - Direction Relay- Termination Resistor- Stainless Steel HW
8/20/11 © RCJ - 24
RESULTSExperimental 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 dB and less
than 0.5o
8/20/11 © RCJ - 25
RESULTSMeasurements
Note: Same phasing line utilized on 160 & 80 M Gain in good agreement with SPICE models
8/20/11 © RCJ - 26
RESULTSFinal Simulations - 160 M
8/20/11 © RCJ - 27
RESULTSFinal Simulations - 80 M
8/20/11 © RCJ - 28
RESULTSFinal Simulation Comparisons
8/20/11 © RCJ - 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
8/20/11 © RCJ - 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
8/20/11 © RCJ - 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
8/20/11 © RCJ - 32
TWO-ELEMENT ARRAYImplementation
• Hi-Z Amplifiers• Hi-Z 2-3 Element Controller• 4 Loops for 4 directions• 13o Phasing Line
TWO-ELEMENT ARRAYPhase Plots for Two Antenna Paths
8/20/11 RCJ - 33
Hi-Z Amplifiers
Hi-Z 2-3 Element Controller
150 ft RG-6 Coax
13o Phasing Line
TWO-ELEMENT ARRAYVNA 2180 Results
8/20/11 © RCJ - 34
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.) 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
Front Element -0.38 dB 0 -0.35 dB 0
Back Element +.38 dB -196.1 +0.35 dB -209.4
TWO-ELEMENT ARRAYFinal Simulation Using Measured Data
8/20/11 © RCJ - 35
Gain: -28.6 dBi RDF: 10.4 dB Horiz. Beamwidth: 98o
8/20/11 © RCJ - 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
8/20/11 © RCJ - 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
8/20/11 © RCJ - 38
REFERENCES1. Gary Breed, K9AY, "Arrays of K9AY Loops: "Medium-sized" low band
RX antenna solutions," Sept. 15, 2007. http://www.aytechnologies.com
2. John Devoldere, ON4UN's Low-Band DXing, Fourth & Fifth Editions, ARRL, Newington, CT: 2005 & 2011.
3. Dallas Lankford, http://groups.yahoo.com/group/thedallasfiles
4. http://www.fcc.gov/mb/audio/m3/index.html
5. Hi-Z Antennas 4-Square, http://www.hizantennas.com
6. DX Engineering 4-Square, http://www.dxengineering.com
7. Max-Gain Systems, http://www.mgs4u.com
8. The Wireman, http://www.thewireman.com
9. 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. ( [email protected] )
