DG7YBN / 432 MHz / GTV 70-13m
  Last Update Mar. 24th 2020




.......



Performance Data and Geometry
Pattern and VSWR
Stacking
Matching


GTV 70-13m Yagi 'Aquarius'

  with bent Driven Element

EME and weak signal operation trimmed but OWA character Yagi ... strictly G/T breeding


This Yagi has very low back lobes for its length. It comes with lower Antenna Temperature then most at given
length but provides full gain. Hence it delivers a respectable G/Ta. 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.
Date of issuing this design : 13th of March 2020

  The GTV 70-13m Aquarius is EME tested

3D Pattern


GTV 70-13m Aquarius built by Thomas, M0ABA

This Yagi is built on 5/8 inch boom using 4 mm el. through boom and 7arrays insulators acc. table below.

And an easy EME QSO in WSJT JT65 with antenna not even positioned to moon carefully.

Gear: This Yagi, 60 W at feed, Yaesu FT 847, Thomas: " ... I have no preamp even! Barefoot"


Name giving and occasion

Apollo 13 was a 1970 manned spaceflight with the objective to land on the moon:
Saturn V rocket SA-508 carried Service Module with Command Modue Odyssee, Lunar Module Aquarius.
Launch was on schedule on April 11, 1970 at 19:13:00 UTC. At flight time 55:54:53 in a distance of 330,000 km
from Earth the exident occured.
The systems of the CM had to be shut down to spare any remaining air and power for reentry.
So the crew had to transfer to the lunar module Aquarius as their life boat.

 

Left: Jack Swigert, Jim Lovell, and Fred Haise one day before launch, 10 April 1970. Research by Ed Hengeveld.
Source: crop of www.hq.nasa.gov/alsj/a13/ap13-S70-34767.jpg

Right: Saturn V Apollo 13 launch, Scan by Kipp Teague, Nasa
Source: www.hq.nasa.gov/alsj/a13/ap13-S70-34853.jpg


 

Audio on  www.DG7YBN.de


Listen to the audio of the radio contact between Apollo 13 and Houston Nasa Ground Control at the
moment the probleme was discovered at 55 h 54 min of flight time in a distance of 330,000 k from earth.

This is an original sound file from the Nasa Project Apollo Archive ( = source)



"... we had a pretty large bang associated with the CAUTION AND WARNING there...."




 

Left: Aquarius, Source: Project_Apollo_Archive AS13-59-8566

Right: AS13-59-8500A (17 April 1970) view of the severely damaged Apollo 13 Service Module (SM)
photographed from the Lunar Module/Command Module

Source: https://spaceflight.nasa.gov/gallery/images/apollo/apollo13/html/as13-59-8500a.html

Joe Kerwin, Capsule Communicator (CAPCOM): "Farewell, Aquarius, and we thank you."
as she was set adrift after keeping the astronauts safe.



Current distribution







Performance Data

Specs: with 4 mm elements @ 432.1 MHz

Gain vs. isotr. Rad.  15.7 dBi
Gain vs. Dipole       13.6 dBD
-3 dB E-plane         31.7 deg.
-3 dB H-plane         34.6 deg.
F/B                  -31.7 dB
F/R                  -28.8 dB
Impedance               50 ohms
Mechan. Length        2568 mm incl. 2 x 40 mm stand off
Electr. Length        3.59 λ

VSWR Bandwidth        1:1.5 (at 435.0 MHz as in VE7BQH Antenna Table)

Stacking dist. h-pol.
top-to-bottom         1.21 m or 3,97 ft
side-by-side          1.07 m or 3.51 ft


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Geometry

        

Table 2: GTV 70-13m, 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!




Metric Boom 20 x 20 x 2 mm

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: 40 mm
Offset front: 40 mm
 



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






Metric Boom 25 x 25 x 2 mm

This table is only valid for:
Boom shape: square
Boom dim: 25 x 25 mm
Wall thickn.: 2.0 mm
Holes in boom: 6.0 mm
Offset rear: 40 mm
Offset front: 40 mm
 



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






Imperial Boom 1"

This table is only valid for:
Boom shape: square
Boom dim: 1 x 1 inch
Wall thickn.: 1.6 mm
Holes in boom: 6.0 mm
Offset rear: 40 mm
Offset front: 40 mm
 


Note: All the above include a "Segmentation Density Correction" (SBC) of 1.14 mm plus an offset of 0.70 mm per element = 1.84 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!

Read abt. the SBC here .







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

Ele. 8.0 mm
DE 10 mm
Boom 20 x 20 mm


"Ready to saw and drill" data for mounting elements on boom with BC according DG7YBN for standard insulators as sold by WiMo, Tino's Funkshop, HF Kits.nl, 7arrays:

Includes an SBC of 1.84 mm




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

Ele. 8.0 mm
DE 10 mm
Boom 25 x 25 mm


"Ready to saw and drill" data for mounting elements on boom with BC according DG7YBN for standard insulators as sold by WiMo, Tino's Funkshop, 7arrays:

Includes an SBC of 1.84 mm






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

Sketch of Bent Dipole



The real blade dipole. The bending angle is much less then for the GTV 70-14 ... 19 models.

• Drawing of the blade dipole as PDF  










Radiation Pattern and VSWR Plots

Elevation and Azimuth plot at 432.1 MHz (4 mm ele.)

 


SWR and Return Loss plots - simulated with 4nec2
(I have settled the best Retrun Loss a bit higher for giving headroom in wet weather)



Return Loss and VSWR plots by M0ABA: -33 dB at 432.2 MHz and a fine coincidence simulation to real Yagi

   










Stacking

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               1.251 m
E-plane               1.167 m


A 4 Yagi bay



Antenna View, EZNEC+ v5


Elev. Plot


Azim. Plot


Gain vs. isotr. Rad.  21.6 dBi
Gain vs. Dipole       19.4 dBD
-3 dB H-plane, appr.  15.6 deg.
-3 dB E-plane, appr.  14.6 deg.
F/B                  -33.7 dB
F/R                  -32.6 dB
T_ant                 59.1 K*
G/T                   3.83 dB*

at Tsky = 27 K, Tearth = 1800 K as in newer VE7BQH Antenna Table


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


Antenna G/T with AGTC lite:

at Tsky = 27 K, Tearth = 1800 K as in newer VE7BQH Antenna Table



A 6 Yagi bay



Antenna View, EZNEC+ v5


Pattern Plot (4nec2) : 23.3 dBi


3D pattern plot with 4nec2












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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