G0KSC SC14407S 7el 144Mhz Yagi Antenna with a 2.14 Metre Length Boom
This Yagi has been designed to cover 144Mhz to 145Mhz with an SWR figure less than 1.2 and at the same time exhibits a very good Front to Back ratio. It has a short length boom of 2.14 metres and therefore can be made from a single piece 1inch square tube section. No boom support will be required.
Remember, this is a short, very wide band Yagi so there is a little less gain than you could achieve from a beam with seven elements. However, this antenna will not be affected be changes in weather or nearby antennas which can have an effect on lower impedance types.
Dimensions in Metres
- Ref = 0
- Driven = .239
- D1 = .318
- D2 = .621
- D3 = 1.021
- D4 = 1.562
- D5 = 2.14
Element sizes per element half:
- Ref = .517
- Driven = .497
- D1 = .466
- D2 = .457
- D3 = .454
- D4 = .451
- D5= .436
Performance figures @ 144.300Mhz:
- Froward Gain: 11.73dBi free space
- Front to Back: 34.32dB
- Radiation angle at 10 Metres above ground: 3 degrees
Each element is made out of single piece 1/2 inch (12.7mm) aluminum tubing Each element half length needs to be doubled in order to gain your total element size. No difference is length needs to be calculated for the 1inch or 1,1/4 inch boom as the elements sit high enough above the boom for the boom to have no influence.
You can build this antenna with 13mm diameter tubing using the same parameters above. Slightly higher front to back ratio and forward gain will be seen along with a narrower SWR curve.
For construction information see 'G0KSC insulators' and the UKSMG article from the main menu on the home page.