DG7YBN / 144 MHz / GTV 2-9n
  Last Update May 01th 2017




.......




Performance Data and Geometry
Pattern and VSWR
Download as File
X-pol Details
Stacking


GTV 2-9n Yagi   with bent Driven Element

EME + SSB narrow bandwidth version ... strictly G/T breeding

This medium length Yagi is balanced between gain and Antenna Temperature. In comparison to most of the entries with exceptional G/T around 2.09 wl in the 144 MHz VE7BQH G/T table its T_ant is approximately 5 ... 10 K lower. Thus it may be very useful in difficult RXing scenarios like contests or EME from within a city with a small size 4-Yagi-Bay only. The bent DE (K6STI style) transforms from low impedance to 50 ohms at feed point for direct feed.

GTV 2-9n QRO version built by DG7YBN @ 7arrays.com

A GTV 2-9n built on 25x25 mm boom with 12 mm Dipole, Symmetrising Line from Cellflex LCF12-50J and DIN 7/16 bushing.
See details of > 1hp plus Symmetrising Line and Return Loss plot below


GTV 2-9n X-pol QRO version built by DG7YBN @ 7arrays.com. For details on feeds, see here



Current Profile




Performance Data

Gain vs. isotr. Rad.  14.0 dBi
Gain vs. Dipole       11.9 dBD
-3 dB E-plane         37.8 deg.
-3 dB H-plane         42.2 deg.
F/B                  -26.1 dB
F/R                  -25.4 dB
Impedance               50 ohms
VSWR Band Width     1.57:1 *
Mechan. Length        4320 mm
Electr. Length        2.08 λ

Stacking Dist. h-pol.
top-to-bottom         2.89 m
side-by-side          3.21 m

*) as in VE7BQH G/T table = at 145.00 MHz



Geometry


                             
        Pos.    Full Length         incl. BC
                Free Space       on 20x20 Boom
				 
Refl.     0.0     1020.0            1026.2
DE(b)   218.0    100-508          100-511.1
DE(a)   285.0     0-100             0-100
D1      418.0     955.0             961.2
D2      680.0     948.0             954.2
D3     1197.5     922.0             928.2
D4     1910.0     906.0             912.2 
D5     2697.5     886.0             892.2
D7     3520.0     870.0             876.2
D8     4320.0     852.0             858.2
 
                ele. 8 mm        ele. 8 mm
				
SegmentationBC = +2.3 mm = (144.6 MHz - 144.2 MHz) * 5.85 mm/MHz
BaseBC (20x20) = +3.9 mm for semi-insulated on boom
Total          = +6.2 mm				
Note: element lengths for Ø 8 mm fit 5/16" too

The Drivers diameter is 10 mm for all examples.
Use EZNEC's Auto-Segmentation at 380 MHz.


Sketch of Bent Dipole



This design has been viewed how often after the first built has been published in Apr. 2017?

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Pattern and VSWR Plots

Current distribution Elevation and Azimuth plot at 144.1 MHz

 


RL and SWR plot - simulated




• 130 - 150 MHz real world plot of GTV 2-9n QRO version (mind that the 1/4 wl line is frequency selective, hence the 138 MHz bit is less deep)


• Plotted Return Loss of GTV 2-9n X-pol QRO Version, V-Plane mounted horizontally (due to metal pole)





QRO Quarterwave Line with Cellflex 1/2 inch coax and 7/16 connector: View on Dipole Side - to be sealed with Spinner Plast 2000


Connector Side: View into the DIN 7/16 bushing






GTV 2-9n X-pol QRO Version Driver Cell


Note the double reflector in one plane only. The reason for this is nothing but handling the Cellflex LCF12-50J
quarterwave lines of both planes to the rear end of the Yagi without interfering with the other plans reflector.

Details on this QRO Quarterwave Line, see here








Downloads

EZNEC file of this Yagi with 8 mm elem.  

EZNEC file of this Yagi as xpol with 8 mm elem. on 25 x 25 mm Boom  









X-pol Details


• Plane Offset is 220 mm.
• Reflectors are same length for all: 1029.9 mm incl. SBC and BC for on 25 x 25 mm Boom
• Distance Mid-DE to Double Refl. (h-plane) is 285 mm
• Offset Refl. (h-plane) to Mid-Boom is +/- 100 mm
• Distance Mid-DE to Single Refl. (v-plane) is 310 mm











Stacking



Stacking Dist.    DL6WU Formula
H-plane               2.890 m
E-plane               3.211 m

X-pol Stacking Dist.
3050 mm each plane


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

 

TANT screenshot


Gain vs. isotr. Rad.  19.9 dBi
Gain vs. Dipole       17.8 dBD
-3 dB H-plane         17.2 deg.
-3 dB E-plane         19.2 deg.
F/B                  -30.7 dB
F/R                  -27.1 dB
T_los                  4.6 K
T_ant                235.9 K*
G/T                  -3.83 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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