GTV 28-4w

Performance Data and Geometry

Pattern and VSWR

With Ground Gain

Stacking

GTV 28-4w with bent Dipole

27.6 to 28.9 MHz with VSWR < 1:1.2 (Return Loss better -20 dB)

On 28 MHz we should less look for gain but very clean directivity, because if the band is open successful DX more or less comes down to fade out unwanted signals. If we can easily produce a signal that enables us to ping our own echo when twice (!) around the globe with less than 100 watts of output, we may pass on 0.5 dB gain. And when band is closed that little bit would not help at all.

The patterns scattering factor (dt.: Streufaktor) as ratio of all rear and side lobes against the beam lobe is what we should look for in first place.

Note: This is not a beginners Yagi. Like on VHF the bent dipole needs trimming regarding bending angle and final length. Thus you should be able to lower this Yagi for a few times on the mast easily for final trimming.

Design date of issue: 2023.04.21

GTV 28-4w built by Xu Da, BG5TOX.

... in 2023 ARRL 10 m contest

Current distribution

Performance Data (28.4 MHz, 16 mm el.)


Gain vs. isotr. Rad.   9.0 dBi
Gain vs. Dipole        6.9 dBD
-3 dB E-plane         59.4 deg.
-3 dB H-plane         89.0 deg.
F/B                  -23.9 dB
F/R                  -20.9 dB
Impedance               50 ohms
Mechan. Length        5177 mm + 2 x 50 mm offset
Electr. Length        0.49 λ

Stacking Dist. h-pol. (28.4 MHz)
top-to-bottom          7.53 m
side-by-side          10.65 m

Geometry - Elements 16 mm insulated on boom:

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Pattern and VSWR Plots

Elevation and Azimuth plot at 28.5 MHz

SWR and Return Loss plots - simulated with 4nec2

3D pattern

Radiation pattern with Ground Gain (28.5 MHz)

• At 8 m above perfect ground


Gain vs. isotr. Rad.  14.7 dBi  at  18 deg.
Gain vs. Dipole       12.6 dBD
F/B                  -28.7 dB   at 166 deg.

• At 12 m above perfect ground


Gain vs. isotr. Rad.  14.9 dBi  at  12 deg.
Gain vs. Dipole       12.7 dBD
F/B                  -25.2 dB   at 169 deg.

• At 16 m above perfect ground


Gain vs. isotr. Rad.  14.6 dBi  at  9 deg.
Gain vs. Dipole       12.8 dBD
F/B                  -25.1 dB   at 171 deg.

• At 20 m above perfect ground


Main Lobe
Gain vs. isotr. Rad.  15.0 dBi  at   7 deg.
Gain vs. Dipole       12.8 dBD
2nd Lobe
Gain vs. isotr. Rad.  14.4 dBi  at  23 deg.
Gain vs. Dipole       12.2 dBD
F/B                  -25.6dB   at 173 deg.

Stacking: SIMULATION OF 2 x VERT. STACK ABOVE GROUND

1. Yagi 16 m agl, 2. Yagi +8 m = 24 m agl


Gain vs. isotr. Rad.  17.7 dBi at   7 deg.
Gain vs. Dipole       15.5 dBD at   7 deg.
F/B                  -24.9 dB  at 173 deg.

Stacking: SIMULATION OF 2 x HORIZONTAL STACK 16 m ABOVE GROUND

Yagis 12m apart:

73, Hartmut, DG7YBN