A Study of Stacked Arrays of Yagi-Uda Antennas Jay Terleski, WX0B 1.

A Study of Stacked Arraysof

Yagi-Uda Antennas

Jay Terleski, WX0B

1

15m Example 120/90/65

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WX0Bs 10 and15 m stacks

15m Example

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• 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

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Gain

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Single 15m yagi at 125 feet 14.71 dbi gain @ 5

Gain

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125/95 stack with 17.01 dbi gain @ 6 degrees

Gain

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120/90 stack with 17.01 dbi gain @ 6 degrees125/95/65 stack 18.34 dbi gain @ 6 degrees

Gain

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125/95/65/35 stack 18.54 dbi gain @ 7 degrees


• Gain • Control of Take-off angle

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Control of Take-off angle

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35ft lower one in stack 14 dbi @23 degrees


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65/35 lower two in stack 16.3dbi gain @ 12 deg

1295/65 middle two in stack 16.64 dbi @ 8 degrees


13125/95/65 top 3 in stack 18.43 @ 6 degrees


Control of Take-off Angle

1495/65/35 lower 3 in stack 17.54 dbi @ 9 degrees


15125/35 upper lower in stack 15.91dbi @ 27 degrees


1695/35 lobes at 9, 32, 54 degrees are possible


• Gain • Clean up pattern • Control of Take-off angle

•

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BOP

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43 m

32 m

BIP both in Phase

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42m/32m 125/95 17.3 dbi @ 6 degrees BIP

BOP 180 degrees out

2042/32 m 125/95 BOP 180 degrees 15 dbi 39 deg

BIP / BOP

20aComparison both in Phase and Both out of Phase

4 high BOP or FOP

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0 delay

0 delay

180 delay

180 delay

Four in phase FIP

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FIP 18.54 dbi gain @ 7 degrees

FOP

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FOP 17.67 dBi @ 17 degrees, bottom 2 BOP

FIP / FOP

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FOP 17.67 dBi @ 17 degrees

FIP 18.54 dbi gain @ 7 degrees

Some BOP rules

Gain is always less at main lobe

Phase delays that are not 180 do

not work !

OR DO THEY???OR DO THEY???

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Can other angles be used to change angles?

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0 delay

0 delay

-90 delay

-90 delay

FOP lower 2 -90 degrees

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Smeared and loss of gain 15.52 dBi @ 7 degrees Loss of exactly 3db at 7 degrees

Can other angles be used to change angles?

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FIP 18.54 dbi gain @ 7 degrees 15.52 dBi @ 7 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

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Fill in pattern by adding delay

15m 2 stack at 0 degrees 15m 2 stack at -90 degrees

phase relationship delay of bottom beam

17 dBi

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15 dBi

Apparatus

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Narrow beam

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Target area

Wide slurred pattern

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What are the effects of Boom length and spacing

Example:

Short booms vs. spacing

C3 stack or any short Yagi.

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Boom length and spacing

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C3 @ 95 feet 12.01 dBi @ 7 degrees


2914.97 dBi gain @ 8 degrees - bad lobe goin UP!

30 ft space


30Great pattern - gain 15.28 dBi @ 8 degrees

25 ft space


Short booms vs. spacing

C3 stack or any short Yagi.

31Just right 15.46 dBi @ 8 degrees

27 ft space


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How to calculate the best spacing based on boom length?


• 1.0 WL booms = 1 WL spacing

• .75 WL booms = .87 WL spacing



•Short booms are very critical, model it to be certain.

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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?

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Dissimilar antenna stacks

• It can be done with certain precautions

• Example 3 ele with 4 ele 15 m.

• Same match, same balun

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3 foot offset


35Slurred pattern less gain 15.7 dbi @ 6 degrees


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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


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Well defined nulls, more gain, 17.03 dBi @ 6 degrees a gain of 1.33 dBi


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Well defined nulls, more gain, 17.03 dBi @ 6 degrees a gain of 1.33 dBi

Slurred pattern less gain 15.7 dbi @ 6 degrees


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What if Beams, Matching and Baluns are not the same?

3 foot offset

Gamma matched balun X

Hairpin matched & balun Y


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O-Scope, equal feed lines, and a friend are needed.


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• 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

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Y

Horizontal Stacking

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PY5EG 10 Meter H frame Stack

Horizontal Stacking

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PY5EG 10 Meter H frame StackPutting it together

Horizontal Stacking

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17.76 dBi gain 5 degreesRoster tails as expected

84 foot Separation 125 ft tall - TOO WIDE

Horizontal Stacking

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16.5 dBi gain 5 degreesRoster tails as expected

24 foot Separation 125 ft tall

Horizontal Stacking

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16.5 dBi gain 5 degrees14.66 dBi 5 degrees

One 15 m beam Two 15m Beams

Horizontal Stacking & Vertical Stacking

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Horizontal Stacking

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20.16dbi @ 6 degrees Optimized at .75 WL wide 1 WL tall

125/82 ft - 2KW into this array = ERP 200,000 Watts!

Horizontal Stacking

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Is EASY

What if we turn the antennas 45 degrees on two towers

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XY

34 feet

24 feet24 feet

Horizontal Stacking

Horizontal Stacking

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IN Phase BIP = 15.95 dbi at 26 degrees Not what we want

Horizontal Stacking

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Delayed 180 degrees 17.38 dbi @ 5 degrees

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X

Y

34 feet

Spacing is .75 WL between driven elements

Horizontal Stacking

Horizontal Stacking

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BIP 16.1 dBi @ 5 degrees close but.........

Horizontal Stacking

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16.5 dBi @ 5 degrees with a delay of 298 deg. Drive impedance varies as delays are changed

Issues With Stagger Types That Turn

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• 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?

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• 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

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Rotate this beam

90 and 180 degrees


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Same direction - 3 high 6 degrees AZ pattern - 18.46 dBi gain


58Middle rotated 90 degrees - 14.86 a loss of 3.6 dBi this is fine


59Rotate 180 degrees - 15.84 dBi forward loss of 2.62 dBi forward F/B is now only 8.2 dB - This is effective and expected


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• 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 2.2-3 dB from adding second antenna

• Gain of 1.5-2 dB by adding a third antenna

• Gain of .5 - 1 dB by adding a fourth antenna

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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

• 18-20+ 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

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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

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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

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to beam in two or three directions at once.

Example - 40 meter stack

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• How does a 3 ele full size 40 meter beam compare to a stack of shorty 40 meter beams like the CC 420?


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12.56 dBi @ 13 degrees

145’ 3 ele 40m full size

12.54 dBi @ 14 degrees 99.8% efficient


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10.98 dBi @ 13 degrees 72 % efficient

Shorty 40 145’

10.88 dBi @ 13 degrees 72 % efficiency

Shorty 40 145’


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13.08 dBi @ 16 degrees +.54 dB over full size

Shorty 40 Stack, 145/70’


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13.08 dBi @ 16 degrees +.54 dB over full size

12.54 dBi @ 14 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!

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• 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

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W7GG 180 ft rotating tower

3 - KT34XAs 2 - 3 ele full size 40s

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K3MM

3 - KT34XAs

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N0AV W4ZV

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N5CQ A61AJ

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WX0B

Side Mount Clearance

25G 44”

45 G 56.5”

55G 58”

X

2X

Antenna

swing arm

side mount

Tower legs

A Study of Stacked Arraysof

Yagi-Uda Antennas

Jay Terleski, WX0B

75

QUESTIONS

Thank You All - You’re the Best Customers in this World!

A Study of Stacked Arrays of Yagi-Uda Antennas Jay Terleski, WX0B 1.

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