2M 144MHz custom-designed Low Q Yagis


CQM10DX built by G4CQM at QTH

15-11-2017...

All weather performance, four unique 2M Band 144MHz Low Q Yagis designed and built by G4CQM, featuring fat chunky elements! CQM6DX is now use by Don G0RQL and CQM10DX by Derek G4CQM...

Driven element diameter 5/8 Inch (15.875mm) and parasitic elements 1/2 Inch (12.7mm) diameter. Each design has a relatively shallow Q-factor gradient like that of a highly stable DL6WU long yagi! Meanwhile radiation efficiency >99% ensures best overall performance!

Build dimensions and stacking distances can be found in the .nec files. Consider that when building a four yagi group the length and position of the driven elements will be somewhat different due to mutual coupling!

Using 4nec2 segmentation has been set at 25 segments per λ/2 for tuning purposes. Note that dimensions quoted are for free-space...

However, in the real world using Badland element clips for mounting the parasitics (reflector to final director) add +6mm to each element length. Driven element assumes PowAbeam DE moulding, no addition to length required in this case!

Boom size: All featured designs require 1 Inch (25.4mm) square section aluminium...


Aluminium...

Aluminium for these projects can be obtained from the following suppliers. In the UK we are still using imperial sizes. When ordering aluminium for the elements specify 6063-T832 or equivalent, best for conductivity! For long booms over 4M in length use heavy wall gauge. Links open in a new window:

1. ABS Metals

2. http://www.aluminiumwarehouse.co.uk/

3. Blackburns formerly Baco Metal Centres

4. http://www.clickmetal.co.uk/

5. Durbin Metal Industries Ltd

6. Forward Metals Ltd

7. L.A. METALS LTD

8. PR METALS

9. Smiths Metal Centres


Balun...

λ/4 Half-Loop Trick
 Back in 1976 I attended an international electronics exhibition in Paris and had a meeting with the famous Mark Tonna F9FT. Mark showed me a very simple trick avoiding the need for a balun or ferrite on your 144MHz yagi feeder!

On the 2M band simply measure λ/4 (no Vf correction) from the DE, mark this point with red tape. Push feeder toward DE creating a half-loop and tape red marker point to boom. Continue securing feeder along side of boom as normal.

Seen opposite λ/4 Half-Loop Trick used on CQM10DX!

NB The λ/4 half-loop trick will only work on a metal boom!
 λ/4 Half-Loop Trick used on CQM10DX! 
 

Construction...


Parts...

PowAbeam Antennas
DE moulding
Badland Element Clip
Top View
Badland Element Clip
Side View
PowAbeam Antennas DE mouldingBadland Element Clip Top ViewBadland Element Clip Side View
PowAbeam DE moulding here                        Badland element clips here

CQM6DX 1.16λ...

CQM6DX in 4nec2

CQM6DX built by G4CQM at G0RQL QTH

CQM6DX

CQM6DX Q-factor

SWRHorizontal Plane
CQM6DX SWRCQM6DX Horizontal Plane

 

CQM6DX in AGTC LITE4 x CQM6DX in AGTC LITE
CQM6DX in AGTC LITE4 x CQM6DX in AGTC LITE

 

CQM6DX.nec
4CQM6DX.nec
CQM6DXGNU.xls

CQM7DX 1.23λ...

CQM7DX in 4nec2

CQM7DX

CQM7DX Q-factor

SWRHorizontal Plane
CQM7DX SWRCQM7DX Horizontal Plane

 

CQM7DX in AGTC LITE4 x CQM7DX in AGTC LITE
CQM7DX in AGTC LITE4 x CQM7DX in AGTC LITE

 

CQM7DX.nec
4CQM7DX.nec
CQM7DXGNU.xls

CQM9DX 1.80λ...

CQM9DX in 4nec2

CQM9DX

CQM9DX Q-factor

SWRHorizontal Plane
CQM9DX SWRCQM9DX Horizontal Plane

 

CQM9DX in AGTC LITE4 x CQM9DX in AGTC LITE
CQM9DX in AGTC LITE4 x CQM9DX in AGTC LITE

 

CQM9DX.nec
4CQM9DX.nec
CQM9DXGNU.xls

CQM10DX 2.36λ...

CQM10DX in 4nec2

CQM10DX under construction!CQM10DX ready to lift!

CQM10DX

CQM10DX Q-factor

SWRHorizontal Plane
CQM10DX SWRCQM10DX Horizontal Plane

 

CQM10DX in AGTC LITE4 x CQM10DX in AGTC LITE
CQM10DX in AGTC LITE4 x CQM10DX in AGTC LITE

 

CQM10DX.nec
4CQM10DX.nec
CQM10DXGNU.xls



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