Two very low Q 2M (144MHz) yagis by G4CQM


CQM10DX at G4CQM's QTH in rural Devon (IO70ST)

CQM10DX seen at G4CQM's QTH in rural Devon (IO70ST)

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CQM10DX seen in AOP

CQM10DX seen in AOP

I designed and built CQM10DX in 2016 for my own personal use at my hill top (450 feet ASL) QTH in rural Devon. It uses 5/8 Inch OD tube for the driven element and 1/2 Inch OD tubing parasitic elements. We often suffer from high humidity and very damp/wet conditions so a low Q yagi design was a must have. Five years later on in 2021 she's still going strong, no problem!


 

Gain, F/B
Gain, F/B etc
Azimuth
Azimuth
Elevation
Elevation
SWR 140-150MHz (Uncalibrated against NEC-2)
CQM10DX SWR 140-150MHz in YO7
H-Plane NEC-2 calibration
NEC2 H-Plane calibration
E-Plane NEC-2 calibration
NEC2 E-Plane calibration
Element positions and half-lengths
Element positions and half-lengths
Element diameters
Element diameters
Average Q-factor = 13
Average Q-factor

 


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CQM6DX at G0RQL's QTH in rural Devon (IO70UV)

CQM6DX seen at G0RQL's QTH in rural Devon (IO70UV)

| MENU | Home | CQM6DX | CQM10DX | Balun | Construction | PARTS | YO7 and AOP notes | Top ^ |


CQM6DX seen in AOP

CQM6DX seen in AOP

I designed and built CQM6DX during 2017 for a near neighbour to the North of Holsworthy Devon. Don G0RQL had problems with his previous antenna and needed help. CQM6DX also uses 5/8 Inch OD tube for the driven element and 1/2 Inch OD tubing parasitic elements. Don also suffers from high humidity and very damp/wet conditions so a low Q yagi design was needed, he reported that even in the very worst winter weather this yagi was stable!


 

Gain, F/B
Gain, F/B etc
Azimuth
Azimuth
Elevation
Elevation
SWR 140-150MHz (Uncalibrated against NEC-2)
CQM6DX SWR 140-150MHz in YO7
H-Plane NEC-2 calibration
NEC2 H-Plane calibration
E-Plane NEC-2 calibration
NEC2 E-Plane calibration
Element positions and half-lengths
Element positions and half-lengths
Element diameters
Element diameters
Average Q-factor = 11
Average Q-factor

 


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Construction

Please carefully read the following notes... If you haven't built your own yagi before, construction guidance offered here will hopefully stop you making mistakes that will prevent your build from working as it should! These designs don't require any adjustment!

 


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PARTS

8 Nut Clamp and Yagi Element Clip from BadlandDE G6HKS Yagi Kits & Parts
8 Nut ClampYagi Element ClipDE Moulding

 


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YO7 and AOP notes

YO7

To reduce screen clutter, YO7 doesn't label the figures displayed within the Yagi patterns. They are as follows (shown in yellow font)...


1. Frequency
2. Forward Gain
3. Front-to-Rear Ratio
4. Input Impedance
5. Standing-Wave Ratio
6. Elevation Angle or Gain FOM

YO displays elevation angle for Yagis over ground and gain figure-of-merit for single-Yagi, free-space models.

YO defaults to a generalized definition of front-to-back ratio.

The notation 12.7-j15.4 means a resistance of 12.7 ohms in series with a reactance of -15.4 ohms.

Z stands for impedance.

The lambda symbol (λ) means wavelengths.

YO uses a generalized notion of standard front-to-back power ratio to characterize pattern quality. Conventional F/B is the ratio of forward power (at 0 degrees) to that radiated in the opposite direction (at 180 degrees).

YO's generalized F/B is the ratio of forward power to that radiated within a specified region to the rear of the antenna. This is called front-to-rear ratio (F/R).

Yagi designs maximizing conventional F/B often have large backlobes at angles other than 180 degrees. Much better patterns result when you optimize a Yagi for F/R.

The F/R region begins at 180 degrees and extends forward to a specified angle (90 degrees by default).

Finally... Element lengths shown in the tables are half lengths.

AOP

AO displays wire losses in dB.

AO also displays antenna efficiency in percent. This figure includes the effects of both wire and load losses.

 


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