DG7YBN - GTV 2-6m

Performance Data and Geometry

Pattern and VSWR

Download as File

xpol (CW, SSB)

xpol SAT (145.8 MHz)

Stacking

146.5 MHz DATV Version

GTV 2-6m Yagi with bent Driven Element

This Yagi shows quite a low Antenna Temperature and a moderate gain for its length, which altogether leads to a good G/T number. It may serve as a contest stack or post stamp size EME 4-Yagi-Bay. Which may be useful especially under tough receiving conditions. The bent DE (K6STI style) transforms to 50 ohms at feed point for direct feed. Design date of issue: 2018.08.09

16 x GTV 2-6m xpol built by Bernd, DL7APV

The 16 Yagis are built on 20 x 20 mm boom, 4 mm el. through boom held in place by 7arrays rivets.
Key data: 19.9 dBd (understacked at 2.1 x 1.95 m, sun noise 7 dB at an sfi of 70.

See full building and performance info on Bernds homepage

4 x GTV 2-6m Stagger Stack built by Edy, YO2LSP

Edy reports: "We succeed to execute and install stagger 4 x 6 elements, and now we have them almost for 1 year, since we can work in 2 directions in the same time. The antena works great and now with 2 antenna system we have broken new personal records."

GTV 2-6m built by Mark, VK5LO

This Yagi is built on 20 x 20 mm boom using 1/4 inch elements and dipole held by Stauff clamps.

GTV 2-6m built by John, G7JTT

GTV 2-6m built by Mirek, SP5U

GTV 2-6m built by DG7YBN

Span Width of dipole = 985 mm
Gap Reflector - Tips of dipole = 216 mm

This Yagi is built on a boom 15 x 15 mm, elements 8 mm on standard holders + BC acc. DG7YBN.

Performance Data

Specs: with 8 mm elements @ 144.1 MHz


Gain vs. isotr. Rad.  11.9 dBi
Gain vs. Dipole        9.8 dBD
-3 dB E-plane         46.2 deg.
-3 dB H-plane         56.6 deg.
F/B                  -31.0 dB
F/R                  -22.7 dB
Impedance               50 ohms
VSWR Band Width       1.33:1 *
Mechan. Length        2370 mm
Electr. Length        1.14 λ

Stacking Dist. h-pol.
top-to-bottom         2.19 m or 7.2 ft
side-by-side          2.65 m or 8.7 ft

*) as in VE7BQH G/T table = at 145.00 MHz

How many VHF operators have been looking up this design since August 2018?

Geometry

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

This Yagi with 8 mm elements on a 15 x 15 mm boom with standard insulators

Ele. 8.0 mm
DE 10 mm
Boom 15 x 15 mm

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

Includes an SBC of 2.93 mm

This Yagi with 8 mm elements on a 20 x 20 mm boom with standard insulators

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 Konni, Nuxcom, WiMo, 7arrays:

Includes an SBC of 2.93 mm


SegmentationBC = +2.93 mm = (144.7 MHz - 144.2 MHz) * 5.85 mm/MHz
BaseBC (20x20) = +3.90 mm for semi-insulated on boom
Total          = +6.83 mm				
Note: element lengths for Ø 8 mm fit 5/16" too

On Boom 20 x 20 using SP6GWN Insulators which are a bit flatter


SegmentationBC = +2.93 mm = (144.7 MHz - 144.2 MHz) * 5.85 mm/MHz
BaseBC (20x20) = +3.90 mm for semi-insulated on boom
Add for Ins.   = +1.46 mm
Total          = +8.29 mm				
Note: element lengths for Ø 8 mm fit 5/16" too

The Drivers diameter is 10 mm for all examples.
The EZNEC model is done with Auto-Segmentation at 400 MHz

This Yagi with 3/8 inch elements on a 1 x 1 inch boom with hydraulic clamps (like Stauff) or SM7DTT insulators

Ele. 3/8 inch or 9.53 mm
DE 3/8 inch
Boom 1 x 1 inch

"Ready to saw and drill" data for mounting elements on boom with BC according DG7YBN for hydraulic clamps (like Stauff) or SM7DTT insulator:

Includes an SBC of 2.93 mm

Table 2: GTV 2-6m, 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!

Table 3: GTV 2-6m, 4.76 mm elements through boom:

Imperial Boom 1 x 1 inch x 1.6 mm

This table is only valid for:
Boom shape: square
Boom dim: 25.4 x 25.4 mm
Wall thickn.: 1.6 mm
Holes in boom: 7.5 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!

Sketch of Bent Dipole

Pattern and VSWR Plots

Elevation and Azimuth plot at 144.1 MHz

RL and SWR plots - simulated

Downloads

EZNEC file of this Yagi with 8 mm elements

xpol Details

Pattern with both sources = dipoles fed

General Hints for tuning xpol Yagis

(1) Set up the h-plane only
(2) Tune and plot Return Loss

See to make this single plane work fine, only then proceed.

(4) Add v-plane
(5) Replot h-plane
(6) If h-plane is still fine
(7) Mount the Yagi turned by 90 degr. so that freshly added v-plane is in h
(8) Tune and plot v-plane (in h now)

By measuring and trimming the v-plane in position horizontal we eliminate
possible unknown influences v to h mount for the while being. We would not
like to handle two unkowns at a time.

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: 750 / 860 mm
Offset front: 150 / 40 mm

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

Table 3: GTV 2-6m xpol, 4.76 mm elements through boom:

Imperial Boom 1 x 1 x 1/16 inch

This table is only valid for:
Boom shape: square
Boom dim: 1 x 1 inch
Wall thickn.: 1.6 mm
Holes in boom: 7.5 mm
Offset rear: 750 / 860 mm
Offset front: 150 / 40 mm

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

Table 4: GTV 2-6m xpol, 3/8 inch or 9.53 mm elements on boom with hydraulic clamps (like Stauff) or SM7DTT insulators :

Imperial Boom 1 x 1 inch

Ele. 3/8 inch or 9.53 mm
DE 3/8 inch
Boom dim: 1 x 1 inch Offset rear: 750 / 860 mm
Offset front: 150 / 40 mm

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

Table 5: GTV 2-6m xpol, 145.5 MHz version, 8 mm elements on boom w. standard holders:

Metric Boom 20 x 20 mm

This table is only valid for:
Boom shape: square
Boom dim: 20 x 20 mm

xpol SAT Details

Adaption of the GTV 2-6m to 145.8 MHz and element planes 1/4 wl apart for easy feed for Circular Polarisation.
Distance = 514 mm = 1/4 wl at 145.80 MHz
With that distance between the dipoles feeding both planes can be realised with equal length of 50 ohm coax and a 2-way power splitter

Pattern with both sources = dipoles fed

Table 6: GTV 2-6m xpol SAT, 145.8 MHz version, 3/8 inch elements on boom w. hyraulic clamps as holders:

Metric Boom 20 x 20 mm

This table is only valid for:
Boom shape: square
Boom dim: 1 x 1 inch

Notes:
• Shape and length of Dipole h-plane to v-plane differs slightly.
• Distance Refl. to Dipole h-plane to v-plane differs slightly.
• This geometry might also work with 10 mm elements and dipole.
You probably end up at approx. 145.7 MHz or shorten each ele. by roughly 0.6 mm per 100 kHz.

Stacking


Stacking Dist.    DL6WU Formula
E-plane               2.65 m or 8.7 ft
H-plane               2.19 m or 7.2 ft

Plot and data of 2 vertically stacked GTV 2-6m using DL6WU stacking distances

Antenna View & Elevation Pattern

Plot and data of 4 vertically stacked GTV 2-6m using DL6WU stacking distances

Antenna View, Elevation & Azimuth Pattern

Plot and data of 4 bay of GTV 2-6m using DL6WU stacking distances

Elevation & Azimuth Pattern

AGTC_lite screenshot (Traditional Temps: Tsky = 200 K, Tearth = 1000 K)

AGTC_lite screenshot (Redefined Temps: Tsky = 287 K, Tearth = 5126 K acc. ITU)


Gain vs. isotr. Rad.  17.9 dBi
Gain vs. Dipole       15.7 dBD
-3 dB H-plane         25.2 deg.
-3 dB E-plane         20.6 deg.
F/B                  -33.0 dB
F/R                  -23.4 dB
T_los                  3.5 K
T_ant                498.6 K*  (236.1 K)
G/T                  -9.10 dB* (-5.85 K)

Theoretical numbers, no phasing line losses
nor imperfections caused by H-frame included
*) T_sky = 287 K, T_earth = 5126 K as in VE7BQH G/T table

2x 3x vert GTV 2-6m at 2.0 m vert, 2.4 m hor. stacking distances

16 x GTV 2-6m xpol ... 23.4 dBi: click to enlarge

146.5 MHz DATV Version of the GTV 2-6m

This is a scaled to 146.5 MHz version of the GTV 2-6m.

Element lengths and positions are adapted to 146.5 MHz.

Hence the Pattern is same as for the 144 MHz Version

This Yagi with 8 mm elements on a 20 x 20 mm boom with standard insulators

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 Konni, Nuxcom, WiMo, 7arrays:

Includes an SBC of 3.04 mm

This Yagi with 8 mm elements through a 25 x 25 x 1.5 mm boom

Ele. 8.0 mm
DE 10.0 mm
Boom 25 x 25 x 1.5 mm

"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: 25 x 25 mm
Wall thickn.: 1.5 mm
Holes in boom: 10.0 mm
Offset rear: 40 mm
Offset front: 40 mm

Includes an SBC of 3.04 mm

Stacking Info 146.5 MHz DATV Version

Stacking Dist. h-pol.
top-to-bottom 2.16 m or 7.1 ft
side-by-side 2.61 m or 8.55 ft

73, Hartmut, DG7YBN