A Super-quiet 9 element EME and Weak signal antenna for 144MHz

Model: 9OWL-GT-ZB

Many believe that an antennas G/T performance (Gain over temperature mean opinion scoring) is the most important attribute for weak signal reception within VHF Yagis. While I do not believe this to be true (I believe much lower temperature antennas will yield better receive performance in most real-world environments) I decided to produce a range of VHF Yagis with best-ever G/T performance. Additionally, at time of publishing, there are no other antennas showing as much gain over the same bandwidth of any of my 2013 Yagi per metre of boom.

If you are not sure how good this antenna is, divide the gain by boom length to achieve a gain figure per metre of boom and compare this antenna to others. Note this is wideband and thus stable in wet and icy weather too!

Each of these 2013 OWL Yagi will provide stunning 'best in class' performance, you can be assured of that!


The only place you can buy this antenna is InnovAntennas

I have proven that very low impedance Yagi antennas can be very stable and wide band too. This is a perfect example and can be fed with a normal split dipole (12.5Ω feed point) or with a folded dipole (50Ω direct feed). 


The first 9-144-ZB built and tested by G0KSC at the InnovAntennas Factory

 Performance Plots

Note the very fast drop off to high suppression either side of the antenna from the 45 degree line backwards. This is key in ensuring you receive no unwanted noise (from directions other than which your antenna is facing).


Elevation plot


This super-clean antenna when placed 10m above ground is a serious performer.


A nice flat, SWR curve as I am sure you have come to expect from me!



Gain @144.1MHz: 14.74dBi

F/B @144.1MHz: 25.03dB

SWR/Performance bandwidth: better than 1:2.1 from 143.8-144.8MHz

Stacking Distances (DL6WU): 3.196m Vertically 3.480m Horizontally

4 x Sky Temperature: 239.4 Kelvin

4 x G/T: -3.10dB GT

Stacking Distances (G0KSC): 3.280m vertically 3.480 Horizontally

4 x Sky Temperature: 241.0 Kelvin

4 x G/T: -3.08dB GT

Tant output with DL6WU recommended spacings


Tant output using G0KSC recommended spacings


VE7BQH table comparisons with other antennas of the same size (bay of 4 antennas, DL6WU Stacking distances):

Antenna      Length (wl)     Gain single antenna (dBd)     Temperature (Kelvin)  G/T (dB)    SWR across 1MHz

Flexa 224               2.34                            11.52                  254.6                      -4.44             1.09:1

RA3AQ 9                2.35                            12.38                  234.3                      -3.24             1.10:1

G0KSC 9 (DL6WU)  2.37                            12.50                  239.4                      -3.10             1.20:1

G0KSC 9 (G0KSC)   2.37                            12.50                  241.0                      -3.08             1.20:1

CT1FFU 9                2.38                            12.23                  226.8                      -3.33             1.14:1

ZL1RS 9                 2.38                            12.24                  227.2                      -3.28             2.19:1

Eagle 10                 2.38                            12.28                  243.0                      -3.43             1.33:1

DK7ZB 9                 2.39                            12.41                  250.5                      -3.39             1.23:1                  

Notes: The lower the temperature figure, the better but it is. The G/T figure is the most important attribute in the above specification (more positive the G/T figure, the better the antenna is for receiving weak signals) and as you can see, this antenna is better than anything else listed of the same or similar length. 1MHz bandwidth normalised to best 1MHz bandwidth not 144Mhz to 145Mhz. If the antenna is very narrow band, it is more likely to shift in wet weather conditions.              

So here are the details for this one if you want to go build it yourself.

Boom positions:

Ref: 0

DE: 132.5mm (12.7mm - 1/2'' DE. email for different sizes)

D1: 423mm

D2: 979mm

D3: 1697.5mm

D4: 2503mm

D5: 3328mm

D6: 4192mm

D7: 4938.5mm


Element Lengths - (All elements 1/2'' diameter, 3/8'' folded dipole ends) (12mm element details further down the page)

Ref: 1028mm

DE: 953mm (folded dipole sizing see folded dipole notes below)

D1: 941mm

D2: 910mm

D3: 888mm

D4: 874mm

D5: 864mm

D6: 854mm

D7: 858mm


Element Lengths - (All elements 12mm diameter, 10mm folded dipole ends)

Ref: 1027mm

DE: 956mm (folded dipole sizing see folded dipole notes below)

D1: 943mm

D2: 912mm

D3: 890mm

D4: 876mm

D5: 867mm

D6: 852mm

D7: 852mm


Folded Dipole Notes:


 Folded Dipole Recommended Construction Method


Pitfalls and Cliffs

If you want to use a folded dipole, mail me. I will help you calculate the sizes of this both width and height for your chosen boom diameter

DON'T offset a folded dipole and expect to have the nice clean pattern you have seen above, it will not happen. Any change needs to be modelled and checked. If a folded dipole is offset, the elevation plane pattern will be distorted. However, this distortion can be used to your advantage (noise reduction) especially when stacking. For out side of the square scenarios like this, mail me.

It is perfectly expectable to use the DK7ZB twin 50Ohm coax match on a split dipole version of this antenna. However, ensure you measure the coax you will use to check its exact velocity factor (VF). If this is wrong, the transformer will not work correctly. I have not found any coax that fits the specified (manufacturers) suggested VF and of course this VF will change with frequency! If you do not have an antenna analyser, borrow one!

There is NO CORRECTION added to any element lengths. If you follow my mechanical construction guidelines, nothing will need to be added at all. DO NOT use any insulators where bolts pass through the boom and element without establishing correction factors, your antenna elements will need to be lengthened should you chose to go down this route.

Any questions just ask. Within this next few weeks, I will add this antenna to as new category and will add another version.


Copyright G0KSC 2013 all rights reserved