G0KSC SC14407L 7el 144Mhz Yagi Antenna with a 3.2 Metre Length Boom

This Yagi has been designed to cover 144Mhz to 145Mhz with an SWR figure less than 1.25 and at the same time exhibits a very good Front to Back ratio. It has a boom of 3.2 metres and therefore can be made from a single piece 1inch square tube section. No boom support will be required.

This antenna will not be affected be changes in weather or nearby antennas which can have an effect on lower impedance types. Also, small errors in your calculations or building the antenna WILL NOT greatly effect performance due to it's non-critical design.

The SC14407L Built by G4PDS

'Yes thanks, all is well. Have just completed a 7 element for 2 metres
(3.2 metre boom version) and have been testing it this afternoon.
Appears to be fine. Looked fine on the MFJ269 and when mounted on the
temporary mast in the garden there is nothing visible in the way of
reflected power, so I'm really pleased. '

'Had it on the mast in the garden this afternoon, and among others
worked EB1LA in IN63VN (not sure what propogation mode, but may have
been tropo - 50W, IC-7000). So quite content with that - thanks !'

Ian G4PDS

Hi Justin,

I finished installation of my antennae. It's performing AMAZING, doing
great job. I am supriosed to see that the SWR is flat all way down the
band.

I used commercial anennas before but didn't act like this SWR wise.
Please find the photos of my setup attached to this email. My plan is
writing down all my experience on my BLOG (sorry but Turkish :
http://blog.barisdinc.net but you will find lots of photos of my
construction step there, hopefully tomorrow)

best 73's de TA7W
baris

ZL1RS made 4 of these for portable DXpedition work, the first was to the South Cook Islands. He also installed folded dipoles instead of a split dipole too.

Dimensions in Metres

Element spacing:

• Ref =      0
• Driven = .302
• D1 =      .486
• D2 =     1.02
• D3 =     1.741
• D4 =     2.547
• D5 =     3.208

Element sizes per element half:

• Ref =       .505
• Driven =   .499
• D1 =        .468
• D2 =        .452
• D3 =        .442
• D4 =        .437
• D5=         .435

Performance figures @ 144.300Mhz:

• Froward Gain: 13.19dBi free space
• Front to Back: 34.16dB
• 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 1,1/4 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.