G0KSC SC144010L 10el 144Mhz Yagi Antenna with a 5.4 Metre Length Boom
This is a good wide band Yagi optimised for 144 to 145Mz. It has a mid-sized length boom of 5.4 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 3 metres (1.5 metres either side of the boom centre.
Remember, this is a very wide band Yagi although it only has 10 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. Within these is the front panel of 4nec2 reporting for each 100 watts presented at the feed point, exactly 100 watts will be radiated. You can not get better than that!
Front to Back ratio has been tuned to allow you to still hear signals from behind although well down on the forward signal. This will ensure any rearward DX will be heard too!
Dimensions in Metres
Element spacing:
- Ref = 0
- Driven = .27
- D1 = .374
- D2 = .795
- D3 = 1.466
- D4 = 2.25
- D5 = 3.093
- D6 = 3.918
- D7 = 4.746
- D8 = 5.4
Element sizes per element half:
- Ref = .508
- Driven = .5
- D1 = .473
- D2 = .46
- D3 = .446
- D4 = .439
- D5 = .433
- D6 = .434
- D7 = .436
- D8 = .438
Performance figures @ 144.300Mhz:
- Froward Gain: 15.03dBi free space
- Front to Back: 23.13dB
- 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.
