DG7YBN / 144 MHz / GTV 2-14w
  Last Update Apr. 15th 2017




.......


     

Performance Data and Geometry
Pattern and VSWR
Download as File
Stacking


GTV 2-14w Yagi   with bent Driven Element

From EME + SSB band to 145.5 MHz - Wideband Antenna Version (OWA-style)

This Yagi has an exceptionally low side- and back lobe volume for its length. It may serve as single antenna for Tropo, Meteor Scatter or even EME or make a very quiet contest antenna due to its high F/B and clean overall pattern. The bent DE (K6STI style) transforms from approx. 17 ohms to 50 ohms at feed point. The GTV 2-14 challenges the popular DK7ZB 12 ele. 28 ohms Yagi. Being just 0.15 λ or 312 mm longer it provides significantly better G/T at more bandwidth, s. data taken from VE7BQH G/T table (G/T is better the more positive the number is):

               Length.       Z         Gain      Gain of 4 Bay   Antenna Temp.   G/T of 4 Bay   VSWR Bandwidth
GTV 2-14w      8278 mm    50 ohms    14.1 dBD      20.0 dBD         218 K         -1.25 dB         1.07:1
DK7ZB 12 ele.  7960 mm    28 ohms    14.2 dBD      20.1 dBD         237 K         -1.49 dB         1.46:1          

pic1

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A GTV 2-14w X-pol shortened to 10 elements by Wolf, DF7KB

... and a 26 ele. DL6WU as "counterpoise". Note the Blade Dipole version for both planes made of thick stripes of aluminum. The GTV 2-14 minus 4 ele. keeps a relatively clean pattern, just loses a bit of band width and 1.7 dB of forward gain.

pic1





2 x vertical stack of GTV 2-14w by DL2VL

These Yagis are built with Ø 8 mm ele. + standard insulators, DG7YBN on-boom-BC, mid boom section is 25 x 25 mm, front & rear section 20 x 20 mm.

And DL2VL/p in MMC 2016: Click the image to enlarge

This Yagi stack has been measured thoroughly, find real world Return Loss and pattern plots
that verify its simulated properties down the page

Marconi Memorial Contest, International Results 2017: DL2VL #13. QSO'S 319, points 114,252

    < Official Results MMC 2015 for DL; DL2VL: "All in all I managed an All-Time-Location-Record."





2016-04-12: GTV 2-14w on 25 x 25 mm Boom at Christian, DL8YE

A pretty antenna tree on top of his houses roof: 50 MHz: 6 ele. YU7EF, 2 m: 14 ele. DG7YBN, 70 cm: 23 ele. DK7ZB




GTV 2-14w built by Radioclub Köszeg - HA1KYY
Good neighbourhood - DG7YBN 2 m GTV Long Yagi above a bay of DJ9BV 70 cm Long Yagis



   Read Jozsef, HA1VQ's comments using the GTV 2-14w in contests


The Yagi is built on a 35 mm round boom, 8 mm elements + 13 mm clearence to boom with a BC of 8 mm incl. the SBC.






Performance Data

                      ele. 1/4"     ele. 8 mm
Gain vs. isotr. Rad.  16.2 dBi      16.2 dBi
Gain vs. Dipole       14.1 dBD      14.1 dBD
-3 dB H-plane         29.8 deg.     29.8 deg.
-3 dB E-plane         31.6 deg.     31.6 deg.
F/B                  -33.0 dB      -33.3 dB
F/R                  -28.1 dB      -28.3 dB
Impedance               50 ohms       =
Mechan. Length        8278 mm         =
Electr. Length        3.98 λ

Stacking Dist. h-pol.    DL6WU
top-to-bottom           3.82 m
side-by-side            4.05 m

Stacking Dist. h-pol.   max. G/T
top-to-bottom           4.00 m
side-by-side            4.20 m
       


Geometry

                                                          
        Pos.    Full Length    Full Length    Full Length      incl. BC    1/2 Length     Full Length      incl. BC
                 Free Space     Free Space     Free Space   on 25x25 Boom    in NEC        Free Space    on 25x25 Boom
                 incl. SBC     incl. SBC      incl. SBC
Refl.     0      1023.7         1023.3          1019.1        1026.7          508.5          1017.0         1026.3
DE(b)   232       983.7**        982.7          982.7           989.3       100-490.5        981.0          989.3
DE(a)   286       100.0          100.0          100.0           100.0         0-100           100.0          100.0
D1      421       972.2          971.3          967.2           974.3         479.5           959.0          968.3
D2      707       964.7          963.8          957.9           965.5         475.5´          951.0          960.3
D3     1246       943.1          942.0          936.1           943.7         463.75          927.5          936.8
D4     1886       928.0          926.8          919.5           927.1         455.5           911.0          920.3
D5     2628       916.3          915.0          907.9           915.5         449.2           898.4          907.7
D6     3419       905.1          903.8          895.3           902.9         443.0           886.0          895.3
D7     4239       893.7          892.2          884.1           891.7         437.0           874.0          883.3
D8     5086       885.1          883.8          875.3           882.9         432.5           865.0          874.3
D9     5939       879.3          877.8          869.5           877.1         429.5           859.0          868.3
D10    6771       878.9          877.3          868.5           876.1         429.0           858.0          867.3
D11    7580       871.9          870.3          862.3           869.9         425.5           851.0          860.3
D12    8278       859.9          858.4          850.1           857.7         419.0           838.0          847.3
                ele. 5 mm      ele. 1/4"       ele. 1/4"     ele. 8 mm*     ele. 8 mm*      ele. 8 mm*     ele. 8 mm*

• Insulated through Boom builds: => Use Full Length incl. SegmentationBC in Free Space Use DL6WU/G3SEK BC number for insulated through boom (add +3.4 mm to free length for 25x25 mm boom) or apply SM5BSZ's BC.exe (see my BC page ) for best fitting numbers for your boom and insulators.

• On Boom builds: => Use "incl BC on 25x25 mm boom" numbers and standard insulators plus M3 screw

SegmentationBC = +1.7 mm = (144.4 MHz - 144.1 MHz) * 5.85 mm/MHz
BaseBC (25x25) = +7.6 mm for semi-insulated on boom
Total          = +9.3 mm
(*) Note: element lengths for Ø 8 mm fit 5/16" too (**) Dipole diam. 0.375 in

The Drivers diameter is 10 mm for all examples. Use EZNEC's Auto-Segmentation at 350 MHz.


This Yagi with 8 mm Elements on 25 x 25 mm Boom, incl. DG7YBN BC and SBC = 1,7 mm

BC_on_25x25


Sketch of Driver Cell



Note: DL2VL reports best match with the tips of the dipole bent backwards form the center line
by ~ 64 .. 69 mm = towards 217... 222 mm in the sketch above at a length of 979 mm*

*) with using carefully tuned 391 mm Ecoflex 10 + M3 soldering eyelets on as Quarterwave-to-gnd symmetrising line

Note: HA1VQ had to bring the ends of the bent Dipole quite a bit more straight again.
A good start would be to pick 255 mm as (b) for the tips instead of the 232 mm as per NEC geometry.

Sticking to the building scheme with semi-insulated on-boom elements and screw M3 and proposed BC + SBC
DL2VL reports a best RL at a distance of 69 mm from tips of DE to prolonged line of straight mid section.

  • Bent DE Online Calculator as web app








Pattern and VSWR Plots

Elevation and Azimuth plot at 144.1 MHz

 


Real world azimuth plot of the 2 x vertical stack of GTV 2-14w
.. done by DL2VL with PolarPlot V3.2.7 Software. Tnx Jörg!
The PolarPlot V3.2.7 Software by Bob, G4HFQ is free for non commercial use. Link to G4HFQ's website


Mind that this is not a free space plot but a 2 x vertically stacked array at 18 m AGL.

Same conditions reconstructed in EZNEC V5+ (Perfect Ground)

Distance to TX ∼ 1000 m, avg. height 18 m AGL, pole diameters through Yagis 71 resp. 55 mm


Note:
(1) the slight unsymmetry in the pattern plot is to a certain extend due to reflections on the test range,
as other here plotted Yagis show same regular distortion.
(2) Nulls go no deaper than -40 dB because PolarPlot v3.2.7 is not able to record below -40 dB.

VSWR and Return Loss plots - simulated with 4nec2

and plotted real Yagi by Jörg, DL2VL with Rigol Analyser - On-Boom BC and QW-Line to gnd in place.
Note: due to the narrow band character of the Quarter Wave line made from H2010 trimmed to 144.2 MHz
(Q-factor) used for symmetrising, the Dip at 145 MHz is less intense then simulated.



Gain, F/B and F/R over Freq. - simulated with 4nec2










Downloads

EZNEC file of this Yagi with 3/16 inch elements  

EZNEC file of this Yagi with 5 mm elements  

EZNEC file of this Yagi with 8 mm elements  

EZNEC file of this Yagi as over stacked 4 bay (max. G/T)  









Stacking



Stacking Dist. h-pol.    DL6WU     max. G/T
top-to-bottom           3.82 m      4.00 m
side-by-side            4.05 m      4.20 m

Elevation plot and data of 4 Yagi bay using DL6WU stacking distances


Gain vs. isotr. Rad.  22.15 dBi
Gain vs. Dipole       20.00 dBD
-3 dB H-plane         13.4 deg.
-3 dB E-plane         14.4 deg.
F/B                  -37.5 dB
F/R                  -29.1 dB
T_ant                218.8 K*
G/T                  -1.25 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 and Azimuth plot and data of 4 Yagi bay using distances for max. G/T

 


Gain vs. isotr. Rad.  22.23 dBi
Gain vs. Dipole       20.08 dBD
-3 dB H-plane         13.0 deg.
-3 dB E-plane         13.8 deg.
F/B                  -36.1 dB
F/R                  -28.3 dB
T_ant                220.4 K*
G/T                  -1.20 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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