DG7YBN / 144 MHz / GTV 2-7n
  Last Update June 29th 2020


.......

     

Performance Data and Geometry
Pattern and VSWR
Download as File
Stacking


GTV 2-7n Yagi   with bent Driven Element

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

This little Yagi has a high F/B. It may serve as a contest stack or small but effective EME 4-Yagi-Bay.
The bent DE (K6STI style) transforms from approx. 17 ohms to 50 ohms at feed point for direct feed.

The concept of the GTV 7 element goes back to the demand for a narrow band, short Yagi, on which
the characteristics of the bent DE and Boom Corrections could be studied. And that, thanks to being
a responsive narrow bander, with explicite reactions of the real world build. Thus this Yagi lends
itself for getting into building Yagis with bent DE, but also for testing BC factors for unknown
element mounting methods or building styles.

With being a design devoted to narrow bandwidth and low rear lobe volume comes a high performance
in terms of gain and antenna temperature - making a Yagi with very good G/T for a length < 1.5 wl.


GTV 2-7n built by 2M0ETJ

This Yagi is built on 20 x 20 mm boom using 7arrays insulators and 8 mm elements.

Glyn reports: "... tried WITHOUT the tuning stubs (so DE was now -10mm shorter that spec )
swr measured 1.01 @ 144.174 mhz so thats close enough for me ..."

2M0ETJ, 45 W into 1 x GTV 2-7n to IK4FMT in FT8 in nill cdx, QRB = 1608 km




GTV 2-7n built by DG7YBN, Boom 20 x 20 mm, standard insulators, 8 mm elements




Performance Data 

Gain vs. isotr. Rad.  12.8 dBi
Gain vs. Dipole       10.7 dBD
-3 dB E-plane         42.4 deg.
-3 dB H-plane         49.8 deg.
F/B                  -27.4 dB
F/R                  -23.2 dB
Impedance               50 ohms
Mechan. Length        2994 mm
Electr. Length        1.44 λ

Stacking Dist. h-pol.
top-to-bottom         2.47 m
side-by-side          2.88 m
Geometry

Nec Geometry with 8 mm Elements


The Segmentation BC is 2.3 mm:
with is derived at by simulating an f_res of 144.20 using auto segmentation at 350 MHz and 144.60 MHz using
auto segmentation at 144.1 MHz and multiplying the resulting delta in freqency by * 5.85 mm/MHz. 

        Pos.    1/2 Length  1/2 Length
                  in NEC      in NEC
				 
Refl.     0       505.0       502.0
DE(b)   194      100-471     100-471
DE(a)   275       0-100       0-100
D1      463       480.5       478.0
D2      867       471.0       468.0
D3     1510       460.0       457.5
D4     2302       446.0       443.0 
D5     2994       428.0       425.5
                ele. 1/4"   ele. 8 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 350 MHz.

"Ready to saw and drill" data for mounting elements on boom with standard insulators on 20 x 20 mm boom including a 30 mm offset from booms end:


Note: The end tips of the pilot antennas bent DE had to be pulled forward by 38 mm
against the NEC model position for best SWR as seen in VNA plot.



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Pattern and VSWR Plots

Current distribution

Elevation and Azimuth plot at 144.1 MHz

 


RL and SWR plot - simulated


RL and SWR plot - measured 



Measured RL and SWR
 MHz        RL        SWR
144.2    -39 dB      1.0:1







Downloads

EZNEC file of this Yagi  








Stacking 



Stacking Dist.    DL6WU Formula
H-plane               2.47 m
E-plane               2.88 m

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

  


Gain vs. isotr. Rad.  18.7 dBi
Gain vs. Dipole       16.6 dBD
-3 dB H-plane         19.0 deg.
-3 dB E-plane         22.2 deg.
F/B                  -30.1 dB
F/R                  -24.2 dB
T_ant                242.7 K*
G/T                  -5.15 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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