G0KSC SC43008M 8el 430Mhz Yagi Antenna with a 1 Metre Length Boom
This Yagi covers the whole of the band from 430 to 440Mhz within an SWR of 1.1. In fact the SWR is below 1.1 until 439Mhz when it starts to creep above. Furthermore, the SWR is below 1.5 all the way down to 420Mhz so this one is good for the US market too.
Remember, this is a very wide band Yagi although it only has 8 elements it provides good forward gain and excellent front to back. Performance of this antenna is very good with maximised radiation efficiency. Take a look at the images below.
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!
Minor errors in measurement during the construction of this antenna WILL NOT have a big impact on it's performance due to this antennas non critical design.
Dimensions in Metres
Element spacing:
- Ref = 0
- Driven = .103
- D1 = .145
- D2 = .269
- D3 = .334
- D4 = .546
- D5 = .764
- D6= .97
Element sizes per element half:
- Ref = .165
- Driven = .16
- D1 = .145
- D2 = .135
- D3 = .128
- D4 = .136
- D5 = .137
- D6 = .127
Performance figures @ 435Mhz:
- Froward Gain: 12.61dBi free space
- Front to Back: 22.12dB
- Radiation angle at 7 Metres above ground: 2 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 1,1/4 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.
