DG7YBN / 432 MHz / GTV 70-7w
  Last Update Apr. 2nd 2021




.......



Performance Data and Geometry
Pattern and VSWR
xpol Yagi
Download as File
Stacking
Matching


GTV 70-7w Yagi   with bent Driven Element

Wideband version ... 430 to 438 (440) MHz

This Yagi has very low back lobes for its length and bandwidth.
Simulated Return Loss (S11) is better -30 dB from 430 to 438 MHz. It may serve as single antenna for portable
use and is easy to repoduce. It certainly makes 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. Design date: May 2019.

This designs origin is the YBN 3+7 SAT handheld combination Yagi.
With M0ABA having built it the first thing he did was a moon bounce test,
which went well with only 60 W at the feedpoint.

See building details and screenshots of the EME QSO on the SAT Yagis website


GTV70-7w portable version built by Thomas, M0ABA

This Yagi is built on a boom 5/8 inch with elements 4.0 mm held in place with insulators by 7arrays


GTV70-7w built by Thomas, M0ABA


GTV70-7w built by Wolf, DF7KB

This Yagi is built on a boom 25 x 25 x 2 mm with elements 4.0 mm held in place with insulators by 7arrays


Current distribution


3D Pattern (432.1 MHz)




Performance Data

Specs: with 6.35 mm elements @ 432.1 MHz

Gain vs. isotr. Rad.  12.3 dBi
Gain vs. Dipole       10.1 dBD
-3 dB E-plane         44.3 deg.
-3 dB H-plane         52.2 deg.
F/B                  -26.5 dB
F/R                  -21.5 dB
Impedance               50 ohms
Mechan. Length         960 mm incl. 2 x 30 mm stand off
Electr. Length        1.30 λ

Stacking dist. h-pol.
top-to-bottom         0.79 m or 2.59 ft
side-by-side          0.92 m or 3.02 ft


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Geometry




        

Table 1: 70 cm section, 6.35 mm elements through a 5/8 inch boom,
formast mount with 280 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: 5/8 x 5/8 inch
Wall thickn.: 1/6 inch = 1.6 mm
Holes in boom: 8.0 mm
Offset rear: 280 mm
Offset front: 30 mm
 


Note: This does include an SBC of 1.74 mm plus a correction for the insulators (v-factor!) of 0.7 mm = 2.44 mm

Note: with through Boom BC it is important to stick to the boom end offsets given below!





Table 1: 70 cm section, 4.00 mm elements through a 20 x 20 mm boom,
formast mount with 280 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: 280 mm
Offset front: 40 mm
 


Note: This does include an SBC of 1.74 mm plus a correction for the insulators (v-factor!) of 0.7 mm = 2.44 mm

Note: with through Boom BC it is important to stick to the boom end offsets given below!





Table 1: 70 cm section, 4.00 mm elements through a 5/8 inch boom,
formast mount with 280 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: 5/8 x 5/8 inch
Wall thickn.: 1/6 inch = 1.6 mm
Holes in boom: 6.0 mm
Offset rear: 280 mm
Offset front: 40 mm
 


Note: This does include an SBC of 1.74 mm plus a correction for the insulators (v-factor!) of 0.7 mm = 2.44 mm

Note: with through Boom BC it is important to stick to the boom end offsets given below!








For making of a 'Blade Dipole' which I recommend for elements through boom builds

Sketch of Bent Dipole










Radiation Pattern and VSWR Plots

Elevation and Azimuth plot at 432.1 MHz (6.35 mm ele.)

 


SWR and Return Loss plots - simulated with 4nec2



M0ABA plotted Return Loss 70 cm: -44 dB at 435.5 MHz

... and Return Loss of the portabel Version (tnx Thomas)



Elevation Pattern 430 - 438 MHz

 


 











xpol Details


Offset between h and v-plane is 270 mm



xpol Table 1: 70 cm section, 4.00 mm elements through a 15 x 15 mm boom,
formast mount with 340 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: 15 x 15 mm
Wall thickn.: 2.0mm
Holes in boom: 6.0 mm
Offset h-plane rear: 340 mm
Offset h-plane front: 310 mm
Offset v-plane rear: 610 mm
Offset v-plane front: 40 mm
 


Note: This does include an SBC of 1.281.74 mm plus a correction for the insulators (v-factor!) of 0.7 mm
for compensation of the insulators (7arrays.com ) as shown above in combination with SM5BSZ'S BC.exe values.

Note: with through Boom BC it is important to stick to the boom end offsets given below!










Downloads

none so far









Stacking


Stacking Dist.    DL6WU Formula
H-plane               0.79 m
E-plane               0.96 m


A 4 Yagi bay




Elev. and Az. Plot @ 432.3 MHz

   



Data for elements 6.35 mm @ 432.3 MHz

Gain vs. isotr. Rad.  18.25 dBi
Gain vs. Dipole       16.10 dBD
-3 dB H-plane, appr.  19.8 deg.
-3 dB E-plane, appr.  23.2 deg.
F/B                  -29.4 dB
F/R                  -23.9 dB
T_ant                140.1 K*
G/T                  -3.21 dB*
Theoretical numbers, no phasing line losses
nor imperfections caused by mast included
*) T_sky = 27 K, T_earth = 1800 K as in newer VE7BQH G/T table

3D pattern plot with 4nec2's 3D viewer







4 x vertical Stack at 770 mm each

Elev. Pattern @ 432.3 MHz






8 x vertical Stack at 770 mm each

Elev. Pattern @ 432.3 MHz










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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