DG7YBN / 144 MHz / YBN 2-5m
  Last Update Sept. 12th 2016



Performance Data and Geometry
Pattern and VSWR
Download as File
Contest 4 Yagi Stack

YBN 2-5m Yagi   with Conventional Driver (Split or Folded Dipole)

This little Yagi has a high F/B, which makes it quite useful as a contest stack,
because the clean rear pattern is kept with stacked arrays.

The YBN 2-5m is the very pilot model which was used to derive
all the "On-Boom-BC-Factors" from (s. Dubus 2/2010). It has been
measured about 50 times using various boom dimensions and
element lengths. Finally for the 5-8 Yagi concept article (Dubus
4/2012) with folded dipole too.

If you stick to the dimensions I give below
and use the right i.e. measured symmetrising coax length
you virtually can not fail with your build.

On right : Stagger stacked 2 x 5 ele. (s. Dubus 1/2014)


Sketch of boom with option to expand to 8 elem. / The additional 200+ mm on the rear enable mounting it formast as on
photo on left side. Note differing position of D1 when using thin through boom elements or folded dipole as given below.

Performance Data

                     Elem. 4 mm     Elem. 5 mm     Elem. 8 mm
Gain vs. isotr. Rad.  10.2 dBi       10.2 dBi       10.2 dBi
Gain vs. Dipole        8.0 dBD        8.0 dBD        8.0 dBD
-3 dB H-plane         73.0 deg.      72.8 deg.      73.2 deg.
-3 dB E-plane         54.8 deg.      54.6 deg.      54.8 deg.
F/B                  -24.9 dB       -25.2 dB       -24.8 dB
F/R                  -23.4 dB       -23.4 dB       -23.0 dB
Impedance           50/200 ohms         =              =
Mechan. Length        1485 mm           =              =
Electr. Length        0.74 λ            =              =

Stacking Dist. h-pol.
top-to-bottom         1.57 m
side-by-side          2.03 m


EZNEC wires for 8 mm elements

INSULATED THROUGH BOOM THIN ELEMENTS (BC acc. 6WU) Pos. 1/2 Length BC 20 mm BC 20 mm BC 25 mm BC 1" in NEC = 2.2 = 2.2 = 3.4 = 3.5 Refl. 0 514.5 1033.2 1031.2 1032.4 10xx.x DE 283 496.0 994.2 994.2 995.4 9xx.x D1 403 480.0 966.2 962.2 963.4 9xx.x D2 822 467.5 942.2 937.2 938.4 9xx.x D3 1485 433.5 875.2 869.2 870.4 8xx.x ele.Ø 5 mm 4 mm 5 mm 5 mm 1/4" Use WiMo made spare Folded Dipole for their YU7EF line EF0208c or selfmade one with modified D1 as follows: Note: for elements 4 mm D1 is of differing length for 5 and 8 ele. Yagi when using a folded DE ele. 4 mm, Pos. 403 mm, NEC => 483.0, 20x20 => 968.2, 25x25 => 969.4 mm ele. 5 mm, Pos. 402 mm, NEC => 481.0, 20x20 => 964.2, 25x25 => 965.4 mm, 1"x1"=> 96x.x

ON BOOM ELEMENTS Pos. 1/2 Length BC 15x15 BC 20x20 BC 25x25 BC 1x1" in NEC = 2.7 = 3.9 = 7.6 = 7.9 Refl. 0 514.5 1031.7 1032.9 1036.6 1034.9 DE 283 496.0 994.7 995.9 999.6 999.9 D1 403 475.0 952.7 953.9 957.6 954.3 D2 822 461.0 924.7 925.9 929.6 925.9 D3 1485 423.8 850.3 851.5 855.2 851.5 ele.Ø 8 mm 8 mm 8 mm 8 mm 3/8"
Note: element lengths for Ø 8 mm fit 5/16" too
The Driver Dipoles diameter is 10 mm for all examples.
Use EZNEC's Auto-Segmentation at 144.3 MHz.

Use WiMo made Folded Dipole (spare from YU7EF line EF0208c)
or selfmade one with modified D1 as follows:
NEC => 477, Boom 20x20 => 957.9, Boom 25x25 => 961.6 mm, Boom 1"x1"=> 961.9

Folded Dipole

Folded DE tip-to-tip = 990, inner height = 54, diam. = 10 for all builds

Sketch of Folded Dipole

Overview on the stages of the YBN 5- 5 / 8 / 10 ele. project

Here is a very helpful overview on the stages of the YBN 5- 5 / 8 / 10 ele. project provided by Stef, F4EZJ (tnx!).
It shows what elements are shared and different at what positions on the boom for the various combinations

Note: Element lengths given fit elements mounted on a 20 x 20 mm boom with 'standard insulators and M3 screw

Pattern and VSWR Plots

Current distribution

Elevation and Azimuth plot at 144.3 MHz


RL and SWR plot - Version with Folded Dipole from WiMo EF0208c

miniVNA: 144.40 MHz, Z = 49.6 Ohm, SWR = 1.03, RL = -36 dB

Note: this plot is taken on a build without any post tuning on DE or D1.
Just the "On-Boom-BC" added.


EZNEC file of this Yagi with Straight Split DE  

Read more about building this Yagi in my Article "5-8 ... an extendable 144 MHz Yagi" in Dubus 4/12


Stacking Dist.    DL6WU Formula    min. Side Lobes    max. F/B
H-plane               1.57 m           1.41 m          1.90 m
E-plane               2.03 m           1.83 m          2.01 m

Data of 5 over 5 ele. Yagi stack using DL6WU stacking distances -10%

Gain vs. isotr. Rad.  12.7 dBi
Gain vs. Dipole       10.6 dBD
F/B                  -18.5 dB

T_ant                236,0 K*
G/T                 -11,01 dB*
Theoretical numbers, no phasing line losses
nor imperfections caused by H-frame included

Data of 4 bay 5 ele. Yagi stack using DL6WU stacking distances -10%

Elevation plot

Stacking Dist.         DL6WU -10%       DL6WU
Gain vs. isotr. Rad.   15.8 dBi        16.1 dBi
Gain vs. Dipole        13.7 dBD        14.0 dBD
F/B                   -21.3 dB        -24.3 dB
F/R                   -26.2 dB        -24.3 dB
T_ant                   231 K*          237 K*
G/T                   -7.85 dB*       -7.64 dB*
Theoretical numbers, no phasing line losses
nor imperfections caused by H-frame included
(*) T_sky = 200 K, T_earth = 1000 K as in VE7BQH G/T table

Elevation plot and data of 4 Yagi vertcal bay using distances for max. F/B
Simulated over perfect ground

                    Free Space Data      Over perfect gnd
Gain vs. isotr. Rad.   16.25 dBi            20.9 dBi
Gain vs. Dipole        14.10 dBD            18.8 dBD
F/B                    -27.5 dB            -26.1 dB

Theoretical numbers, no phasing line losses
nor imperfections caused by H-frame included

Stagger Stacked Contest Array

These Yagis are stacked at 1.90 m and upper & lower Yagi in put 502 mm backwards.
The actual shift for this design stack of 502 mm is a little less than the principle 1/4 λ on 144.3 MHz.
Same as the proposed stacking distance of 1.90 m differs from the 1.57 m per DL6WU formular.

Why is that so?

The principle 1/4 λ is a number based on the theoretical concept of canceling backwards
source by a total of 180° of phase shift. But the individual directive Yagi-Uda antenna holds
phase shifts between parasitic elements and exciter (dipole) in itself. Thus best results for
increased F/B and F/R vary slightly. Same to the difference in vertical stacking distance to DL6WU.
A stacked arrays pattern is an intereference pattern of 2 or more sources i.e. Yagis. A stacking
scheme and goals apart from the standard longs for other optimum stacking distances.

Read abt. the principle here: Article 'Stagger Stacking' by Bill Thompson as PDF

Photo: 4 x YBN 2-5m stacked at 1.90 m vertical and 502 mm inner shift

Free Space Elevation Plot of Stagger Stacked 4 x vert. YBN 2-5m

Free Space Azimuth Plot of Stagger Stacked 4 x vert. YBN 2-5m

How to feed?
This idea goes back to Robi, S53WW's
"High Performance Antenna Stack for 2m Contest&Tropo Work", here .

Read S53WW's web article or my article published in Dubus 1/2014 & Dubus Technik XIII for
full details of theory about stagger stacking and feeding with 1/4 λ phase lag into
the front Yagis. Note - line lenghts given hold no errors here, but a creative and proven
use of the periodicity of the sinus wave

Image Source Dubus 1/2014: DG7YBN, Stacking beyond DL6WU - Part 2

These are 50 ohms coaxes, all of them, transformation and phasing is done
by the lenghts only, there is NO power splitter needed.


The inner Yagis are displaced by 1/4 λ. To compensate this the feeding coaxes for the
inner Yagis must be are arranged for a phase lag of -90° compared to the outer Yagis. We will
name that phase correcting length 'L-plus'.

But:  Feeding with a phase lag of -270° makes +90° as 360° - 270° = + 90° (periodicity of the sinus wave)
Prolonging the lines for the outer Yagis by 270° has same effect as feeding the inner Yagis with -90°.
So that instead of increasing the lengths of coax towards the inner Yagi by 90° of phase angle or 1/4 λ and
have those extra lengths hanging about on the pole with this little trick we can fit the -270° into the
lengths to the outer Yagis.

Phasing Coax Lengths

L_plus: We name that extra 270° length as L_plus in the sketch above. With a v-factor of 0.662 for PE coax it
is 1.031 m. The reason for this is to derive shortest possible feed lines up the pole instead of winding up phasing
lines for the inner Yagis as we see so often on vertical stacks.

L_1: L1 lengths are basically ANY length; but stay clear from any multiple of 1/4 λ x velocity factor.

L_2: L2 lengths are basically ANY odd multiples of 1/4 λ x velocity factor. Here they are 5 x 1/4 λ x V-factor.
At the sum point between 2 Yagis of 50 ohms impedance we find 25 ohms. Any odd multiple of 1/4 λ x velocity factor
brings that back to 50 ohms in the centre feed point. No splitter needed.

Total Lengths

Total lengths must include the lenghts inside likewise the N-T-joiners or whatever self made T-junctions.

Velocity Factor

Lengths L_plus, L1 and L2 given are for PE coax only!
For foam and air coax the effective velocity factor of these at 144 MHz must be applied.

See here Symmetrising / Transformation Lines
and here Phasing & Matching Lines

Using 3 N-T-Pieces a flexible, easy to produce phasing line assembly is done at low costs.

73, Hartmut, DG7YBN

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