G0KSC SC43012M 12el 430Mhz Yagi Antenna with a 1.62 Metre Length Boom

This Yagi has been focused for maximum performance between 430Mhz and 436Mhz and therefore gives excellent performance on the CW and SSB portions with a nice clean pattern. As with most of my antennas, and SWR of less than 1.1 throughout with very low noise and maximum radiating efficiency.

Remember, this is a very wide band Yagi although it only has 12 elements it provides good forward gain and excellent front to back. Performance of this antenna is very good with maximised radiation efficiency for direct 50Ohm feed. For each 100 Watts input, at least 99Watts are radiated so this is idea for QRP (where very Watt counts) or QRO as the power limit for this antenna is your coax rating! 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 = .121
• D1 =      .178
• D2 =      .302
• D3 =      .414
• D4 =      .583
• D5 =      .737
• D6=       .869
• D7=       .996
• D8=      1.174
• D9=      1.418
• D10=     1.62

Element sizes per element half:

• Ref =       .168
• Driven =   .162
• D1 =        .147
• D2 =        .14
• D3 =        .133
• D4 =        .137
• D5 =        .127
• D6 =        .13
• D7=         .118
• D8=         .132
• D9=         .136
• D10=       .132

Performance figures @ 432Mhz:

• Froward Gain: 14.41dBi free space 
• Front to Back: 22.72dB
• 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.