DG7YBN / 28 MHz / GTV 28-7w
  Last Update Apr. 07th 2023


Performance Data and Geometry
Pattern and VSWR
With Ground Gain

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

GTV 28-7w built by Javier, EA1IF

Holding plate for the K6STI style dipole

2023-02-19, Javier reports: "I finally installed the antenna this afternoon, I have only checked the ROE (VSWR) which is 1.5 at 27000, 1.1 at 27200 and continues flat at 1.1 up to 28500 and rises to 1.5 at 28650, perfect! (...) adjusting the dipole to the measurements with the reflector was a bit complicated, it's not so much with the normal dipole, I did everything on the ground and I didn't have to rectify anything, it was going up and the result of the nip is what I comment."

2023-02-20 "Throughout the morning I dedicated myself to listening and observing the front, back and side, I only have one word, the antenna is like a sharp knife, it significantly discriminates everything that is not in its direction."

Note that this is a lower frequency version 27.5 to 28.5 MHz primarily by design.

Photo Credit: EA1IF, tnx Javier!

Lower frequency 27.5 to 28.6 MHz taper version as PDF  

Currently this Yagi becomes known on the 11 m and 10 m band under a pseudonym or
battle name Mazinger Z:

Mazinger Z or "Majingā Zetto" in romanised letters Hepburn-style Japanese is a robot from the 1972-1973 Japanese 'Super Robot' manga series by Go Nagai.
This robot is constructed of a fictional material 'Super-Alloy' from the element 'Japanium' as a weapon against the 'forces of evil'.

Source basic Image before processing: https://de.wikipedia.org/wiki/Mazinger_Z#/media/Datei:Mazinger_Z_en_Tarragona.jpg
Quotes in above text: https://en.wikipedia.org/wiki/Mazinger_Z

Current distribution


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


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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.


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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