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 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
3. Blackburns formerly Baco Metal Centres
5. Durbin Metal Industries Ltd
6. Forward Metals Ltd
7. L.A. METALS LTD
8. PR METALS
9. Smiths Metal Centres
|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!
|Badland Element Clip|
|Badland Element Clip|
|PowAbeam DE moulding here||Badland element clips here|
|CQM6DX in AGTC LITE||4 x CQM6DX in AGTC LITE|
|CQM7DX in AGTC LITE||4 x CQM7DX in AGTC LITE|
|CQM9DX in AGTC LITE||4 x CQM9DX in AGTC LITE|
|CQM10DX in AGTC LITE||4 x CQM10DX in AGTC LITE|