G0KSC SC144011L 11el 144Mhz Yagi Antenna with a 6.8 Metre Length Boom

This is a good wide band Yagi optimised for 144 to 144.600Mz. It has a mid-sized length boom of 6.8 metres and therefore can be made from a single piece 1.25 inch square tube section. Boom Support will be required with by guy wire or an additional 1.25 inch boom length bolted to the bottom of the main boom and covering 4 metres (2 metres either side of the boom centre.

Remember, this is a very wide band Yagi although it only has 11 elements it provides good forward gain. Performance of this antenna is very good with maximised radiation efficiency and very low loss. Take a look at the images below.

Dimensions in Metres

Element spacing:

Ref = 0
Driven = .374
D1 = .535
D2 = 1.010
D3 = 1.707
D4 = 2.503
D5 = 3.361
D6 = 4.235
D7 = 5.124
D8 = 6.050
D9 = 6.795

Element sizes per element half:

Ref = .508
Driven = .506
D1 = .478
D2 = .4635
D3 = .452
D4 = .4445
D5 = .437
D6 = .433
D7 = .4265
D8 = .4235
D9 = .4355

Performance figures @ 144.300Mhz:

Froward Gain: 15.78dBi free space
Front to Back: 24.01dB
Radiation angle at 10 Metres above ground: 3 degrees

Element diameter:

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 1.25 inch boom as the elements sit high enough above the boom for the boom to have no influence.

NOTE:

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.