DG7YBN / 28 MHz / GTV 28-7w
  Last Update Oct. 28th 2020




.......




Performance Data and Geometry
Pattern and VSWR
With Ground Gain
Stacking


GTV 28-7w   with bent Dipole

Digi Modes + SSB band 28.0 to 28.9 MHz


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: 2020.10.28


Current distribution

GTV28_7w_EZ_3D_pattern.gif




Performance Data (28.5 MHz, 16 mm el.)

Gain vs. isotr. Rad.  12.3 dBi
Gain vs. Dipole       10.1 dBD
-3 dB E-plane         44.4 deg.
-3 dB H-plane         52.6 deg.
F/B                  -28.0 dB
F/R                  -20.9 dB
Impedance               50 ohms
Mechan. Length       13629 mm
Electr. Length        1.29 λ

Stacking Dist. h-pol. (28.5 MHz)
top-to-bottom          11.9 m   or   38.9 ft
side-by-side           13.9 m   or   45.7 ft

Geometry

On Request ...


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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 12 m above perfect ground


Gain vs. isotr. Rad.  17.8 dBi  at  12 deg.
Gain vs. Dipole       15.7 dBD
F/B                  -29.1 dB   at 169 deg.




• At 16 m above perfect ground


Gain vs. isotr. Rad.  18.0 dBi  at  9 deg.
Gain vs. Dipole       15.9 dBD
F/B                  -29.7 dB   at 172 deg.




• At 20 m above perfect ground


Gain vs. isotr. Rad.  18.0 dBi  at   7 deg.
Gain vs. Dipole       15.9 dBD
F/B                  -27.8dB   at 173 deg.



• At 24 m above perfect ground


Gain vs. isotr. Rad.  18.1 dBi  at   6 deg.
Gain vs. Dipole       16.0 dBD
F/B                  -27.9 dB   at 174 deg.








Stacking: SIMULATION OF 2 x VERT. STACK ABOVE GROUND

1. Yagi 12 m agl, 2. Yagi +11.9 m = 23.9 m agl



Elevation plot and data of 7 over 7 array at 11.9 m stacking distance:
Lower Yagi 12 m, upper Yagi 23.9 m above perfect gnd


Gain vs. isotr. Rad.  20.0 dBi at   7 deg.
Gain vs. Dipole       17.9 dBD at   7 deg.
F/B                  -29.5 dB  at 173 deg.










73, Hartmut, DG7YBN



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