G0KSC SC0609L 9el 50Mhz Yagi Antenna with a 12 Metre Length Boom

This a long boom 9el Yagi for 50Mhz. It has a boom which is made from a 2 joined pieces 1.25 inch square tube section of 5 metres in length with one addition 5 metre 1.25 inch box section secured beneath the first to in the centre and therefore, bracing the first 2 elements. To extend the boom the 12 metres (additional 2 metres), it is recomended to install a 1 inch box section of 2 metres at the end of the antenna and still mount the antenna at the centre point of the 2 5 metre 1.25 inch box sections. The reason for this is there is additiona weight at the back of the boom due to the concentration of elements. the additional length at the front, acts as a counter balance.

No boom support should be required.

Dimensions in Metres

Element spacing:

Ref = 0
Driven = .678
D1 = .886
D2 = 2.02
D3 = 3.724
D4 = 5.738
D5 = 7.839
D6 = 10.312
D7 = 12.001

Element sizes per element half:

Ref = 1.497
Driven = 1.475
D1 = 1.391
D2 = 1.366
D3 = 1.34
D4 = 1.328
D5 = 1.307
D6 = 1.304
D7 = 1.305

Performance figures @ 50.250Mhz:

Froward Gain: 13.92dBi free space
Front to Back: 33.91dB
Radiation angle at 10 Metres above ground: 10 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 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.