DG7YBN / 144 MHz / GTV 2-12n
  Last Update May 28th 2016




.......

     

Performance Data and Geometry
Pattern and VSWR
X-pol Details
Download as File
Stacking


GTV 2-12n Yagi   with bent Driven Element

EME + SSB narrow band version        

This Yagi has very low back lobes for its length. It may serve as single antenna for Tropo, MS and top performing for EME
or make a quiet contest antenna due to its high F/B. The bent DE (K6STI style) transforms from approx. 28 ohms to 50 ohms at feed point.

A narrow band version of the GTV that needs skills and precision when building it, but will reward with neat properities in return.

Though being a narrow band design it obviously provides a stable SWR so that even the Crossyagi or "xpol" built is managable without much
challenges. One can imagine from the very deep dip in the simulated (-60 dB) and measured Return Loss that this design "rests in its center
frequency position",see the confirming feedback below:

Some feedback:




A 4 bay of GTV 2-12n xpol built by John, ZS6JON    Oct. 09th 2016

This array is build with 4.76 mm elements through 25 x 25 mm booms. Find this geometry down the page


John paints his first impressions as follows:

"Well, all I can say is that they blew me away. Just as you predicted. Everything has changed. My Noise levels are lower. I have less Birdies. Screen is clearer. I used to get bad lines across Map 65 when elevating ... now nothing. Today I switched on again as there is an expedition on. They signals are just amazing. I have never seen anything like it. Even Alex, ZS6EME logged into my PC via Teamviewer and couldn’t believe it. His first comment was ... 'what happened to all your Noise?'.

The signals are amazing Hartmut. A new world for me. Not only on RX but TX as well. When I started calling I got Whatsapp and emails asking 'What the xxxx are you using? Never heard you so strong.'"



ZS6JON used 4 x 20 element DJ9BV xpol Yagis and I3DLI 4 x 9 ele. hor. pol. & 4 x 6 ele. vert. pol. before. I wish to add, that the tribute is not mine solely but also goes to SM5BSZ for his obviously very sound BC.exe



Slideshow: GTV 2-12n xpol by John, ZS6JON
Return Loss, h-pol and v-pol, feed point and more




How many prolific VHF Operators have looked up this website since the ZS6JON array notes have been pubished?

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GTV 2-12n built by Ian, VA3DIF / G7ORZ / YO3DIF

Click on images to enlarge

   



Ian, VA3DIF after having trimmed the GTV 2-12n to work that close to the house and only just high enough to elevate it:

"Finally I did it !!! I have an antenna with spot on SWR at your choice from SSB to FM. Resonance can be moved from 145,5 all the way to 143.55 and back with no problems. There is only ONE deep resonance…so is ideal for EME. Today Monday was a great day on the Moon with Rx reports up to -11db. Something new for me I started to decode QSOs at -30dB and worked my first single Yagi station with also 400W and some ground effect there .

Congratulations for a great design !!! 73 Ian"

He adds: "The whole trick was D1 which acts like tuning knob"


Here is a video of a 150 W EME QSO between VA3DIF and KK6FAH:
it is done by KK6FAH and uploaded on his Dropbox for Download 98 MB, here

VA3DIF used 150 W in shack only, single GTV 2-12n in low position, LNA homebrew PG 103 +,
KK6FAH has a 3 x 13 elem. LFA stacked in a triangle with fully rotatable boom axes he calls
TARP (Triangular Array Rotatable Polarity) which is described in Dubus 4/2016.








2 x GTV 2-12n xpol built by Patrick, F4EGA using 20x20 mm boom and 8 mm elements:

"Hello Hartmut, I love your beautiful website and all the informations about antennas. I was interested about your GTV2-12n ver3. I made one the last week and am very happy with the low level noise so I made one this morning in Xpol configuration and I will make the second one tomorrow and I'll test it on EME."       ... and just a few days later he sent this photo and more ... " .. the ROS is ok" see his VNA plot taken in xpol below. And after some days of operating ... "... I found it very silent, in some directions I have noise with all others antennas and with this antennas the noise is reduced or absent, very interesting for me because I have some houses at proximity."







A review on circumstances when making this design

The GTV 2-12n current profile can not deny a close relation to the YU7EF way to design here. But instead of replicating the YU7EF designs
this model is an independant forward development due to quite different radiation pattern, element lengths on booms mid section,
positions and produced G/T numbers. Please note that unlike pubished by DK7ZB I do not "use the YU7EF Director-chain", just some of my designs
are influenced by his way to design. Or do my patterns look like EFxxxx designs at all? There is a line between replicating and following
shared prime design goals. For more on the history of bent DE Long Yagi designs see here .

Discussion: Much of the up and down of gain and thus G/T in the clipping of the G/T Table below is due to bandwidth. Surely I gained G/T on cost
of some bandwidth here. But look up the GTV2-12m mk2's numbers. That design is more OWA style and thus of higher bandwidth with still about
same G/T as the DK7ZB-modified-Driver EF0212B if we extrapolate on electrical length and to be expected gain. Looking at the 12 ele. G0KSC LFA
in the context of G/T and bandwidth it is an excellent antenna.

When DK7ZB first introduced the replicated EF0212B of YU7EF with exchanged Driver in Sept. 2013 he indicated it a design study but
labeled it as DK7ZB-12-50-V "Ultra-Low Noise optimized 50-Ohm-12-El.-V-Yagi" which strongly deduced an own design.
See to how DK7ZB marvels at YU7EF's works today. Lets not forget that it was quite the opposite way for years.

Though being a bit shorter the GTV 2-12n tops the G/T of the DK7ZB Design Study with ease.
Please remember that Low Antenna Temperature is essential but that it is the G/T number that counts if we design for Low Noise objectives

Here is a clipping of the official 144 MHz G/T Table.
The DK7ZB 12 (red row) in fact is an YU7EF EF0212B with bent Driver as I produced it from the K6STI version.






Performance Data

Gain vs. isotr. Rad.  15.68 dBi
Gain vs. Dipole       13.53 dBD
-3 dB H-plane         31.6  deg.
-3 dB E-plane         34.0  deg.
F/B                  -39.4  dB
F/R                  -25.7  dB
Impedance               50  ohms
Mechan. Length        6874  mm
Electr. Length        3.30  λ

VSWR at 144.500       1.49 [/]

Stacking Dist. h-pol.    DL6WU     max. G/T
top-to-bottom           3.56 m      3.74 m
side-by-side            3.82 m      4.20 m


Geometry



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

		Refl	 DE(b)	 DE(a)	D1	D2	D3	D4	D5	D6	D7	D8	D9	D10
Pos. 		0	 184	 243	428	780	1323	1968	2719	3542	4394	5284	6139	6874
Boom 20x20 mm	1014.2	(958.2)	(100)	954.2	947.2	924.2	908.2	897.2	886.2	875.2	870.2	863.2	840.2	
Boom 25x2 5mm	1017.9	(961.9)	(100)	957.9	950.9	927.9	911.9	900.9	889.9	878.9	873.9	866.9	843.9

Ø8 mm Elements - On Boom with Stauff Clamps - provisional Dimensions: only SBC + 0.5 resp. 0.7 mm added here

		Refl	 DE(b)	 DE(a)	D1	D2	D3	D4	D5	D6	D7	D8	D9	D10
Pos. 		0	 184	 243	428	780	1323	1968	2719	3542	4394	5284	6139	6874
Boom 25x25 mm	1010.8	(954.8)	(100)	950.8	943.8	920.8	904.8	893.8	882.8	871.8	866.8	859.8	836.8	
Boom 1x1 inch	1011.0	(955.0)	(100)	951.0	944.0	921.0	905.0	894.0	883.0	872.0	867.0	860.0	837.0

Ø6 mm Elements insulated through Boom - Dimensions (BC acc. SM5BSZ)

		Refl	 DE(b)	 DE(a)	D1	D2	D3	D4	D5	D6	D7	D8	D9	D10
Pos. 		0	 184	 243	428	780	1323	1968	2719	3542	4394	5284	6139	6874
Boom 30x30 mm	1019.1	(961.9)	(100)	964.4	958.0	936.4	919.3	910.2	899.2	888.1	884.1	877.0	852.8	

Ø4.76 mm Elements insulated through Boom - Dimensions (BC acc. SM5BSZ)

Boom 25x25 mm or 1 x 1 in, see xpol details further down the page, chose one plane only,
BUT leave the boom at length or ask for a recalcuclaton!


This Yagi with 3/16 inch elements (EZNEC Auto Segmentation @ 380 MHz)


Note:   to minimise pattern distortion resulting from DE offset when using the 30 mm boom with ele. though boom the DE
should be insulated passed through boom in ele. plane here and be feed from either side of boom.

The SBC = (144.60 MHz - 144.20 MHz) x 5.85 mm/MHz = 2.3 mm is included
in all of the above numbers so that these all are ready to build measures.

Note:   element lengths for Ř 8 mm fit 5/16" too


  • For details on the On-Boom BC see here
  • For details on DE and BC on it see here   
  • Bent DE Online Calculator as web app     


Bent Dipole










Pattern and VSWR Plots

Elevation and Azimuth plot at 144.1 MHz

 


SWR and Return Loss plots - simulated with 4nec2



Return Loss plot in xpol configuration taken by F4EGA with a miniVNA, tnx Patrick!
Built on 20 x 20 mm boom with 8 mm elements on boom and insulators from Nuxcom. With my BC and SBC applied as given in table above.









X-pol Details

Below: Current distribution feeding h-pol only. The pattern is unspoiled by the x-configuration in simulation) though some
degradation will occure on real builds due to introducing feeding coaxes, dipole boxes, boom and mast clamps etc. as on every x-pol Yagi.


xpol builders table 1: GTV 2-12n, 3/16 inch 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: 25 x 25 mm
Wall thickn.: 2.0 mm
Holes in boom: 7.5 mm
Offset rear: 40 mm resp. 132 mm
Offset front: 132 mm resp. 40 mm

Note: This includes a "Segmentation Density Correction" (SBC) of 2.3 mm

Read abt. the SBC here .

Elements in h-plane

Elements in v-plane


Offset in x (boom positions) of h-pol to v-pol plane is 92.5 mm









Downloads

EZNEC file of this Yagi with 8 mm elements         and with 6 mm elem.  








Stacking

3Dim. plot of a 4 Yagi bay using DL6WU stacking distances



Stacking Dist.    DL6WU Formula    max. G/T
H-plane               3.56 m        3.74 m
E-plane               3.82 m        4.20 m

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


Gain vs. isotr. Rad.  21.60 dBi
Gain vs. Dipole       19.45 dBD

F/B                  -35.5 dB
F/R                  -29.0 dB
T_ant                220.4 K*
G/T                  -1.83 dB*

Theoretical numbers, no phasing line losses
nor imperfections caused by H-frame included
*) T_sky = 200 K, T_earth = 1000 K as in VE7BQH G/T table



Data of 4 Yagi bay using distances for max. G/T



Gain vs. isotr. Rad.  21.71 dBi
Gain vs. Dipole       19.56 dBD

F/B                  -36.0 dB
F/R                  -26.4 dB
T_ant                223.5 K*
G/T                  -1.78 dB*
Theoretical numbers, no phasing line losses
nor imperfections caused by H-frame included
*) T_sky = 200 K, T_earth = 1000 K as in VE7BQH G/T table





73, Hartmut, DG7YBN

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