GTV 70-13m Yagi 'Aquarius'

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...."

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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

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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

How many OMs have been looking up this design?



Geometry

        

GTV 70-13m, 4 mm elements through square boom:

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"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!

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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!

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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!

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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 .

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GTV 70-13m, 4 mm elements through round boom:

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"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!

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Metric Boom 20 x 1.5 mm

This table is only valid for: Boom shape: rounde Boom dim: 20 mm Wall thickn.: 1.5 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!

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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

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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

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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 (tnx Thomas, M0ABA for measuring this!)

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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 Return 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

   

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GTV70-13m prototype built by Thomas, DL1VPL

and simulated plot for same span:

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GTV 70-13m Aquarius with Folded Dipole

The straight split bent dipole can be replaced with a bent folded dipole like in any non-bent Yagi design.
In doing so the transformation ratio of 1:4 remains. The bent folded dipole versions impedance is 200 ohms.

The folded dipole itself is of Ø 6 mm; I recommend an 'elements through boom' built.
So that the folded dipole is centered in the element plane for best symmetry in the elevation pattern.

Geometry of the Folded Dipole

In the model we use the center of the tube, regardless of its actual diameter.
With this height is 44 mm, span width is 314 mm. Adding the real diameter of 6 mm we end up with

inner height = 38 mm, outer span width = 320 mm, see sketch

Note     Folded Dipole mounting in plastic brackets compensation

Whatever plastic block is used to suspend or mount the dipoles wires will need to be compensated
by adding ~ 0.1 mm per millimeter of wire running in plastic. If you attach a 20 mm plastic block on top
of the boom to lead the dipoles upper wire a length of 2.0 mm / 2 = 1.0 mm needs to be added to the dipoles
span width. Assumed it runs free of contact to plastic on the down side.
We use factor 1/2 in a folded dipole then since it is a full wave loop.

Same applies to any BC if the wires run very close (~ < 3 mm) to the boom.


Folded dipoles for the GTV70-11w built by Rob, PD7RKZ

Dipoles bent to above dimensions, using a plastic dipole boxes sold by www.nuxcom.de
and 'smeared (all) well with Plast2000 in the boxes'.

Photo: with kind permission of Rob, PD7RKZ

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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

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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

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Antenna View, EZNEC+ v5

Pattern Plot (4nec2) : 23.3 dBi

3D pattern plot with 4nec2

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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