Presentation on theme: "A Study of Stacked Arrays of Yagi-Uda Antennas Jay Terleski, WX0B 1."— Presentation transcript:
A Study of Stacked Arrays of Yagi-Uda Antennas Jay Terleski, WX0B 1
15m Example 120/90/65 2 WX0Bs 10 and 15 m stacks
15m Example 3 A good model which applies to 20 and 10 meters will be a 4 element 23 foot design. Most antenna manufactures offer a similar antenna to this design. 40 meters we will will use 2 and 3 element beams common to Hams.
Why do we stack yagis Gain Clean up pattern Control of Take-off angle Beam in multiple directions Suppress rain, snow, wind static 4
Gain 5 Single 15m yagi at 125 feet dbi 5
Gain 6 125/95 stack with dbi 6 degrees
Gain 7 120/90 stack with dbi 6 degrees125/95/65 stack dbi 6 degrees
Gain 8 125/95/65/35 stack dbi 7 degrees
Why do we stack yagis Gain Control of Take-off angle 9
10 35ft lower one in stack 14 degrees
Control of Take-off angle 11 65/35 lower two in stack 16.3dbi 12 deg
12 95/65 middle two in stack degrees Control of Take-off angle
13 125/95/65 top 3 in stack 6 degrees Control of Take-off angle
Control of Take-off Angle 14 95/65/35 lower 3 in stack degrees
Control of Take-off Angle /35 upper lower in stack 27 degrees
Control of Take-off Angle 16 95/35 lobes at 9, 32, 54 degrees are possible
Why do we stack yagis Gain Clean up pattern Control of Take-off angle 17
BOP m 32 m
BIP both in Phase 19 42m/32m 125/ degrees BIP
BOP 180 degrees out 20 42/32 m 125/95 BOP 180 degrees 15 dbi 39 deg
BIP / BOP 20a Comparison both in Phase and Both out of Phase
4 high BOP or FOP 21 0 delay 180 delay
Four in phase FIP 22 FIP dbi 7 degrees
FOP 23 FOP degrees, bottom 2 BOP
FIP / FOP 23 FOP degrees FIP dbi 7 degrees
Some BOP rules Gain is always less at main lobe Phase delays that are not 180 do not work ! OR DO THEY??? 25
Can other angles be used to change angles? 23 0 delay -90 delay
FOP lower degrees 24 Smeared and loss of gain degrees Loss of exactly 3db at 7 degrees
Can other angles be used to change angles? 23 FIP dbi 7 degrees degrees -3db at lower lobe lost but at 25 degrees the gain is +20db more !
Some BOP rules Gain is always less at main lobe But the gain may be better at all the nulls. Lets test this on two beams 25
Fill in pattern by adding delay 15m 2 stack at 0 degrees15m 2 stack at -90 degrees phase relationshipdelay of bottom beam 17 dBi dBi
Narrow beam 25 Target area
Wide slurred pattern 25
What are the effects of Boom length and spacing Example: Short booms vs. spacing C3 stack or any short Yagi. 27
Boom length and spacing feet degrees
Boom length and spacing dBi 8 degrees - bad lobe goin UP! 30 ft space
Boom length and spacing 30 Great pattern - gain degrees 25 ft space
Boom length and spacing Short booms vs. spacing C3 stack or any short Yagi. 31 Just right degrees 27 ft space
Boom length and spacing 32 How to calculate the best spacing based on boom length?
Boom length and spacing 1.0 WL booms = 1 WL spacing.75 WL booms =.87 WL spacing.5 WL booms =.707 WL spacing.25 WL booms =.5 WL spacing Short booms are very critical, model it to be certain. 33 S (WL) = ( Boom Length in WL)
What about stacking Dissimilar antennas? Matching technique - are they the same? Driven element offsets must be know. Baluns are they the same? 34
Dissimilar antenna stacks It can be done with certain precautions Example 3 ele with 4 ele 15 m. Same match, same balun 34 3 foot offset
Dissimilar antenna stacks 35 Slurred pattern less gain degrees
Dissimilar antenna stacks 36 3 feet / 44.4 ft (WL) X 360 degrees = 24.3 degrees of delay is required to put these antennas in phase. 3 feet X.66 (VF of RG213) = 1.98 feet of coax would need to be added to the leading driven element. Lets correct the model by adding in the delay line and see the resulting pattern
Dissimilar antenna stacks 37 Well defined nulls, more gain, degrees a gain of 1.33 dBi
Dissimilar antenna stacks 37 Well defined nulls, more gain, degrees a gain of 1.33 dBi Slurred pattern less gain degrees
Dissimilar antenna stacks 37 What if Beams, Matching and Baluns are not the same? 3 foot offset Gamma matched balun X Hairpin matched & balun Y
Dissimilar antenna stacks 37 O-Scope, equal feed lines, and a friend are needed.
Dissimilar antenna stacks 37 Measure the angle of delay needed to align pattern Build a coax delay line and add to the leading antenna’s feed line.
Horizontal Stacking 38 Y
Horizontal Stacking 39 PY5EG 10 Meter H frame Stack
Horizontal Stacking 40 PY5EG 10 Meter H frame Stack Putting it together
Horizontal Stacking dBi gain 5 degreesRoster tails as expected 84 foot Separation 125 ft tall - TOO WIDE
Horizontal Stacking dBi gain 5 degreesRoster tails as expected 24 foot Separation 125 ft tall
Horizontal Stacking dBi gain 5 degrees14.66 dBi 5 degrees One 15 m beamTwo 15m Beams
Horizontal Stacking & Vertical Stacking 44
Horizontal Stacking 45 6 degrees Optimized at.75 WL wide 1 WL tall 125/82 ft - 2KW into this array = ERP 200,000 Watts!
Horizontal Stacking 46 Is EASY What if we turn the antennas 45 degrees on two towers
47 X Y 34 feet 24 feet Horizontal Stacking
48 IN Phase BIP = dbi at 26 degrees Not what we want
50 X Y 34 feet Spacing is.75 WL between driven elements Horizontal Stacking
51 BIP degrees close but
Horizontal Stacking degrees with a delay of 298 deg. Drive impedance varies as delays are changed
Issues With Stagger Types That Turn 53 Close coupling is a problem Drive impedance vary widely as the array turns Matching will be a problem - very difficult to adjust This type of array is probably not suitable unless everything remains fixed as in an H-Frame or parallel tower single direction arrays More work needs to be done on LAPA type arrays for amateur work
What Happens When I Beam in Multiple Directions? 54 Will rotating a Yagi 180 degrees in a stack cancel the forward pattern intended? Or will it allow the forward pattern to survive? Will rotating a Yagi in a stack achieve the intended pattern? That is, to beam in two directions at once? Or will it mess up the pattern?
Multi-direction Beaming 55 Rotate this beam 90 and 180 degrees
Multi-direction Beaming 56 Same direction - 3 high 6 degrees AZ pattern dBi gain
Multi-direction Beaming 58 Middle rotated 90 degrees a loss of 3.6 dBi this is fine
Multi-direction Beaming 59 Rotate 180 degrees dBi forward loss of 2.62 dBi forward F/B is now only 8.2 dB - This is effective and expected
Multi-direction Beaming 60 Will rotating a Yagi in a stack achieve the intended pattern? That is, to beam in two directions at once? Yes, all beams in a properly spaced stack may be rotated individually without regard to cancellation. Will rotating a Yagi 180 degrees achieve the intended pattern? Yes, all three are fine to rotate.
Summary - GAIN VERTICAL STACKS must be properly spaced Gain of dB from adding second antenna Gain of dB by adding a third antenna Gain of dB by adding a fourth antenna 61
Summary -Take off Angle Switching allows control of take off angle including BOP Angle of lobes can be bad due to poor spacing of yagis Stack lobe will always slightly higher than top yagi alone dB of difference can be seen from peak to null - This is more important than the raw gain of the array! Intentionally adding phase delay to one antenna can widen the main lobes to create a larger target and minimize nulls 62
Summary BIP/BOP BOP useful for gaining high angle lobe from a 2 high stack at the sacrifice of only 3db of max stack gain This could be a secret weapon in SS and NAQP contests A high stack can be made to act like its close to the ground 63
Summary - Pattern Stacks can clean up high angle unwanted lobes Separation space and boom length are closely related Always model the intended stack for lobe anomalies due to spacing Rotating an antenna 90 degrees or 180 degrees is an effective way Intentionally slurring a pattern can increase the target area 64 to beam in two or three directions at once.
Example - 40 meter stack 65 How does a 3 ele full size 40 meter beam compare to a stack of shorty 40 meter beams like the CC 420?
Example - 40 meter stack degrees 145’ 3 ele 40m full size degrees 99.8% efficient
Example - 40 meter stack degrees 72 % efficient Shorty ’ degrees 72 % efficiency Shorty ’
Example - 40 meter stack degrees +.54 dB over full size Shorty 40 Stack, 145/70’
Example - 40 meter stack degrees +.54 dB over full size degrees
Summary - 40 meter stack Shorty 40 stacks are VERY effective in gain and pattern Shorty 40 stacks equals or betters a single 3 element full A full size 40 stack RULES but a shorty 40 stack is not bad! 69 Shorty 40 stacks have better pattern than a 3 ele FS beam More flexibility, beam in two directions, more angles Much easier to maintain size 40m beam
Other Benefits of Stacking Snow, Rain, wind, ionization static can be eliminated or reduced by taking the top antenna out of a stack Corona discharge points are on the top beam 70
W7GG 180 ft rotating tower 3 - KT34XAs ele full size 40s 71
K3MM 3 - KT34XAs 72
Side Mount Clearance 25G44” 45 G 56.5” 55G58” X 2X Antenna swing arm side mount Tower legs
A Study of Stacked Arrays of Yagi-Uda Antennas Jay Terleski, WX0B 75 QUESTIONS
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