Performance Data and Geometry
Pattern and VSWR
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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.
Gain vs. isotr. Rad. 12.8 dBi Gain vs. Dipole 10.7 dBD -3 dB H-plane 42.4 deg. -3 dB E-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 mGeometry
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
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
EZNEC file of this Yagi
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