CQM10DX 2M Band Low Q Yagi Design

CQM10DX seen in AOP

I designed 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 design was a must have!

YO7 and AOP notes


To reduce screen clutter, YO7 does not 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.


AO displays wire losses in dB.

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

Gain, F/B etc seen in AOP

Gain, F/B etc

Azimuth in AOP


Elevation in AOP


SWR 140-150MHz in YO7

CQM10DX SWR 140-150MHz in YO7

H-Plane NEC2 calibration in YO7

NEC2 H-Plane calibration

E-Plane NEC2 calibration in YO7

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


Propagation Indicators


Estimated Kp

Estimated Kp

Solar X-Rays

Solar X-Rays

Mag Field

Magnetic Field

2M E's EU

2M E's EU Europe

4M E's EU

4M E's EU Europe

6M E's EU

6M E's EU Europe

2M E's NA

2M E's NA North America


MUF/E's Today by MMMonVHF