DG7YBN / 432 MHz / GTV 70-9w
  Last Update Apr.15th 2017


Performance Data and Geometry
Pattern and VSWR
Download as File
Stagger Stacked 4 Bay

GTV 70-9w Yagi   with bent Driven Element

EME + SSB band to FM up to 436 MHz. With marginal degradation it can be used even in the
satellite band section (max. VSWR 440 MHz ~ 1.5). Its VSWR is flat well below 1.1 from 430 to 436 MHz.

This Yagi has very low back lobes for its length. It may serve as single antenna for portable
use and certainly make a useful 4 x vertical stack. It makes a quiet contest antenna due to its
high F/B. The bent DE (K6STI style) transforms from approx. 17 ohms to 50 ohms at feed point.

4 x vertical 'stagger stack' of GTV 70-9w built by Mathias, DJ5QX:   Click on images to enlarge

Look up the effect of stagger stacking for this bay simulated with CST Software


GTV 70-9w built by Mathias, DJ5QX


and his plots with HP8753C, precalibrated with HPCalkit, thru 10 m of EcoFlex 10, final 200 mm of RG316
dismissed by applying port extension: Return Loss, S11 and Z = R + jX as Smith Chart.
We find 2 chartlines for antenna beaming at different angles for judging the influence of the home 'test range'.

And Sheet Metal Dipole the other way round:

GTV 70-9w built by Kazuo, 7L1TIG, see his website for details and VSWR plot
Photo: with kind permission of Kazuo, 7L1TIG

Current distribution

3D Pattern

Performance Data

Specs: with 4 mm elements @ 432.1 MHz

Gain vs. isotr. Rad.  13.5 dBi
Gain vs. Dipole       11.4 dBD
-3 dB E-plane         40.4 deg.
-3 dB H-plane         45.8 deg.
F/B                  -30.0 dB
F/R                  -25.5 dB
Impedance               50 ohms
Mechan. Length        1438 mm incl. 2 x 30 mm stand off
Electr. Length        1.99 λ

Stacking dist. h-pol.
top-to-bottom         0.89 m or 2.92 ft
side-by-side          1.00 m or 3.29 ft

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Ø8 mm Elements - On Boom - Dimensions (BC acc. DG7YBN)

Actual BC for on a 20 x 20 mm Boom with standard insulators is 7.5 mm, SBC is 1.46 mm,
total length to add is 8.96 mm ~ 9.0 mm

                  Refl   DE(b)   DE(a)   D1     D2     D3     D4     D5     D6     D7
Pos.                 0    82.7   104.5   151    247    428    641    884    1145   1378
NEC 1/2 ele.	 164.5	(161.7)  (33.5)	 154.5  151.0  145.0  141.5  137.0  133.0  126.5
Boom 20x20 mm    338.0  (332.4)  (67.0)  318.0  311.0  299.0  292.0  283.0  275.0  262.0

Bent Dipole: DE(a) is the inner straight length and pos. on boom, DE(b) is position of tips and span width when bent

    <=   NEC Geometry for 4 mm ele. insulated through boom excluding BC

Ø4 mm Elements - Through Boom - Dimensions (BC acc. SM5BSZ's BC.exe)

EZNEC wire table for Ø 4 mm elements

The model uses EZNEC's Auto-Segmentation at 1050 MHz.
The DE's is 10 mm for all examples.
Using a 'Blade Dipole' is recommended with elements through boom

A simple symmetrising section may be made from a 3 x 1/4 Lambda line grounded at the far end with
N-flange-bushing and an aluminium plate and ferrite core added as close as possible to the DE,
see below.

Table 1: GTV 70-9w, 4 mm elements through boom:

"Ready to saw and drill" data for mounting elements through boom with BC according SM5BSZ's BC.exe:
Note: with through Boom BC it is important to stick to the boom end offsets given below!

This table is only valid for:
Boom shape: square
Boom dim: 20 x 20 mm
Wall thickn.: 2.0 mm
Holes in boom: 6.0 mm
Offset rear: 30 mm
Offset front: 30 mm

Note: This does include a "Segmentation Density Correction" (SBC) of 1.46 mm.
Which does not include any correction for the insulators, which is around 0.7 mm depending on
the very insulator properties
and is still to be added to the length of each element as fix offset.
Read abt. the SBC here .

Table 2: GTV 70-9w, 4 mm elements through boom,
formast mount with 380 mm offset on rear boom end:

"Ready to saw and drill" data for mounting elements through boom with BC according SM5BSZ's BC.exe:

This table is only valid for:
Boom shape: square
Boom dim: 20 x 20 mm
Wall thickn.: 2.0 mm
Holes in boom: 6.0 mm
Offset rear: 380 mm
Offset front: 30 mm

Note: This does include an SBC of 1.46 mm plus a correction for the insulators (v-factor!) of 0.7 mm

The CVS file for the Yagi Element Configuration Tool for own variations:

You can find the CSV file containing the set of data for this design in the download section.
Import that into my Yagi Element Configuration Tool and do your own adaption.

Building hints:

For building hints see the GTV 70-19
For fastening elements through boom
For making of a 'Blade Dipole' which I recommend for elements through boom builds

Radiation Pattern and VSWR Plots

Elevation and Azimuth plot at 432.1 MHz


SWR and Return Loss plots - simulated with 4nec2

Gain, F/B and F/R 431 to 434 MHz

Radiation Pattern 430 to 440 MHz, Elevation Pattern




EZNEC file of this Yagi with Ø 4 mm ele.  

EZNEC file of this Yagi with Ø 8 mm ele.  

CSV file for the Yagi Element Configuration Tool with 4 mm elements


As on 432 MHz the Y-factor = T_earth / T_sky is so high, I see little chances to
improve an array's RX performance by using "Over Stacking" distances. However, depending on
the level of local QRM it might be worthwhile to try a decreased distance, especially in the H-plane.

Stacking Dist.    DL6WU Formula
H-plane               1.00 m
E-plane               0.89 m

A vertical 4 Yagi stack

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

Gain vs. isotr. Rad.  19.36 dBi
Gain vs. Dipole       17.21 dBD
-3 dB H-plane, appr.  40.8 deg.
-3 dB E-plane, appr.  10.0 deg.
F/B                  -29.4 dB
F/R                  -28.8 dB
T_ant                 30.3 K*
G/T                   4.54 dB*
Theoretical numbers - these do not include phasing line losses
nor imperfections caused by H-frames or mast poles etc.
*) T_sky = 20 K, T_earth = 350 K as in VE7BQH G/T table

Screenshot of TANT for this 4 Yagi stack

A vertical 6 Yagi stack

21.1 dBi at a HPBW of 40 degr. on less than 4.5 m of height on pole

Stagger Stacked 4 x GTV 70-9w

Stacking distance is acc. DL6WU = 890 mm + 70 mm = 960 mm each

Gain vs. isotr. Rad.  19.51 dBi
Gain vs. Dipole       17.36 dBD
F/B                  -47.4 dB
F/R                  -32.1 dB

Inner Yagis are displaced in forward direction by 169 mm and fed at -90 degr

Free Space Elevation Pattern

Simulated at 3.0 m over perfect ground - 4nec2's 3D viewer - structure and pattern

Simulated at 3.0 m over perfect ground - Azimuth Pattern

View the effect of Stagger Stacking on a 4 x vert. bay of 4 GTV 70-9w simulated with CST EM Software (tnx Mathias, DJ5QX!)

• Conventional Stack at DL6WU distances.
These are non-normalised cartesian plots: At 20 dB of forward gain a -10 dB (mark 1, 2) on rear lobe means -30 dB of F/B.

• Stagger stacked as described above

Read more about Stagger stacking here
and here

Symmetrising 50 to 50 ohms feedline to 432 MHz Bent DE

The principle is similar to the 1/4 Lambda coax. Adding 2 x 1/4 Lambda or a half wave line does not change anything but allows
to form a gentle bow below the boom or until behind the Reflector. Follow practical construction hints on "Building a Yagi" page.


  Attenzione!     Take care when lengthening the coax, measure the actual electrical length instead of considering v-factors specified in a catalogue only.
                                      A good choice may be the diam. 5 mm PTFE coax RG-142 B/U: real resonate length (432.2 MHz as 3/4 Lambda) shield-shield is around 348 mm

  Find more information on Phasing & Matching Lines page

73, Hartmut, DG7YBN

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