DG7YBN / 144 MHz / YBN 2-8m
  Last Update Nov. 12th 2016




.......

     

Performance Data and Geometry
Sketch of Boom
Pattern and VSWR
Download as File
Stacking


YBN 2-8m 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.
The 8 elem. YBN 2-8m version is the prolonged 5 ele. YBN 2-5m. It uses same Driver Cell elements and dipole.
Thus one can swap between various setups like 5 over 5 to 4 x 8 elem. or to 4 x 5 ele. vertically very easily.
Just as time, place and WX conditions demand. Read the full text in Dubus magazine issue 4/2012.

The YBN 2-10w is the final stage of expansion from YBN 2-5m > YBN 2-8m > YBN 2-10w with same Driver Cell

F4EZJ/p, Stef used 2 single and a 2 x vertical stack of YBN 2-8m's and along 4 x vertical 5 ele. LFA
in Championat de France THF 2016 contest: and finished "with 355 QSOs ... antennas doing excellent!!!"

Contest Station 7S7V from Malmö using 3 x vert. YBN 2-8m with WiMo Folded Dipole
in MMC 2016: Click on Images to enlarge

    




References please?

The 5-8 as 8 ele. seems to have become quite popular to reference other Yagis or serve as base for own design modifications.
We see DK7ZB modifying it to 28 ohms (8-El.-2m-OWM-Yagi) by just changing elements in driver cell and G4CQM compare it to his CQM8C4 design.
Just keep in mind that I wanted the 5-8 to be a very uncritical conventional design and ever planed it to be part of the expandable 5-8 concept.
Which means that the 5 ele. can be expanded to this 8 ele. without modifications to the driver cell and re-using as many elements as possible
Hence it is limited to the needs of that concept, yet capable to be a serious player in the G/T table. The fact that other designers love to
refer to it shows its abilities.




Does this design perform?

YBN 2-8m, FT-736R, 15 m RG213, 680 m ASL in SSB
Saturday afternoon in IARU VHF 2013, in nill cndx

IK1WVQ     769 km        Troposcatter, across the
IK3UNA/P1  725 km        Alps with 25 W only
G8T        626 km ...    Avg. QRB 490 km, 15 QSOs
 



Performance Data

                      Elem. 4 mm     Elem. 5 mm     Elem. 8 mm
Gain vs. isotr. Rad. 13.0/13.1 dBi    13.1 dBi       13.1 dBi
Gain vs. Dipole      10.8/10.9 dBD    10.9 dBD       10.9 dBD
-3 dB H-plane          42.0 deg.      41.8 deg.      41.8 deg.
-3 dB E-plane          48.0 deg.      47.8 deg.      47.2 deg.
F/B                   -28.5 dB       -29.4 dB       -29.0 dB
F/R                   -19.9 dB       -19.7 dB       -19.8 dB
Impedance            50/200 ohms         =              =
Mechan. Length         3485 mm           =              =
Electr. Length         1.68 λ            =              =

Stacking Dist. h-pol.
top-to-bottom          2.59 m
side-by-side           2.94 m

Geometry


               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      471.0      949.2      944.2       945.4      9xx.x
D3     1440      460.5      927.2      923.2       924.4      9xx.x
D4     2130      450.0      907.2      902.2       903.4      8xx.x
D5     2850      448.5      905.2      899.2       900.4      8xx.x
D6     3485      433.5      875.2      869.2       870.4      8xx.x
                ele.5 mm   ele. 4 mm  ele. 5  mm  ele. 5 mm  ele. 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 =>  480.5, 20x20 => 963.2, 25x25 => 964.4 mm, 1"x1"=> 96x.x
ele. 5 mm, Pos. 402 mm NEC =>  481.0, 20x20 => 964.2, 25x25 => 965.4 mm, 1"x1"=> 96x.x

				
                    ON BOOM ELEMENTS (standard ins.)        SM7DTT ins.
        Pos.   1/2 Length  BC 20x20   BC 25x25   BC 1"x1"    BC 20x20 
                 in NEC     = 3.9      = 7.6      = 7.9        = 3.0

Refl.     0      514.5     1032.9      1036.6     1034.9      1032.0
DE      283      496.0      995.9       999.6      999.9      990 Folded
D1      403      475.0      953.9       957.6      954.3       967.0
D2      822      466.0      935.9       939.6      935.9       945.0
D3     1440      454.5      912.9       916.6      912.9       924.0
D4     2130      443.0      889.9       893.6      889.9       903.0
D5     2850      439.0      881.9       885.6      881.9       900.0
D6     3485      423.8      851.5       855.2      851.5       870.0
                ele. 8 mm  ele. 8 mm  ele. 8 mm  ele. 3/8"  ele. 5 mm

Element lengths corrected 2013-03-26
Note: element lengths for Ø 8 mm fit 5/16" too

Use WiMo made Folded Dipole (spare from YU7EF line EF0208c)
or selfmade one with modified D1 as follows:
NEC => 477.0, 20x20 => 957.9, 25x25 => 961.6 mm, 1"x1"=> 961.9
Folded DE tip-to-tip = 990, inner height = 54, diam. = 10

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
The Driver Dipoles diameter is 10 mm for all examples.
Use EZNEC's Auto-Segmentation at 144.1 MHz for RL and SWR plots
Use EZNEC's Auto-Segmentation at 350 MHz and correct elem. lengths
by -2.4 mm to produce radiation plots

Sketch of Folded Dipole



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

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






Sketch of Boom



F4EZJ, Stef, building a 4 Yagi Bay of YBN 2-8

→ Place mouse over images to enlarge

 

 
Four YBN 2-5 basic Yagis lined up ... Four extended YBN 2-5 => YBN 2-8


Stef builds on 20 x 20 mm boom using 8 mm elements mounted semi-insulated
on boom with standard insulators and M3 screws



 

 
2 x YBN 2-8 and YBN 2-10 and YBN 2-10 with strut

External link to Stef's 'Onedrive' online album with many detailed photos

which includes an ingenious way of producing a split dipoles center part.
Well done and thank you Stef!







Pattern and VSWR Plots



Current distribution

Elevation and Azimuth plot at 144.1 MHz

 


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


miniVNA: 144.30 MHz, Z = 50.2 Ohm, SWR = 1.07, RL = -29 dB


Note: this plot is taken on a build without any post tuning on DE or D1.
Just the "On-Boom-BC" added. Use additional Segmentation BC when starting
with the NEC models geometrie or simply take the geometry numbers given above.








Downloads

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


Stacking Dist.    DL6WU Formula
H-plane               2.59 m
E-plane               2.94 m

Data of 8 over 8 Yagi stack using DL6WU stacking distances


Gain vs. isotr. Rad.  16.0 dBi
Gain vs. Dipole       13.9 dBD
F/B                  -33.1 dB
F/R                  -24.8 dB
T_ant                237,7 K*
G/T                  -7,75 dB*
Theoretical numbers, no phasing line losses
nor imperfections caused by H-frame included

Data of 4 Yagi bay using DL6WU stacking distances


Elevation plot


Gain vs. isotr. Rad.  19.0 dBi
Gain vs. Dipole       16.9 dBD
F/B                  -34.6 dB
F/R                  -19.7 dB
T_ant                238.8 K*
G/T                  -4.79 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





73, Hartmut, DG7YBN


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