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.

G0KSC SC2806M 6el 28Mhz Yagi Antenna with a 9.3 Metre Length Boom

This antenna has been designed for someone who loves 28mhz and who has a bit of space too! Working the WHOLE BAND from 28Mhz to 29Mhz, not just the CW or SSB portion. With great gain and front to back ratio to boot. Power limitations are whatever the limit of your coax is so if you have good coax, 3KW+ is not a problem.

Mechanical Construction

This Yagi has been designed to be built on a boom of 3 sections. The centre section should be a 5 metre length of 2 inch aluminum tubing whilst the out 2 sections should be 1, 3/4 inch tubing slotted in to the 2 inch section by around 600mm each end. Boom guying should not be required on this antenna.

If G0KSC insulators are to be used, these should be engineered to be 300mm long rather than 100mm and the width of each also should be doubled.

Small errors in your measurements or calculations when building this antenna WILL NOT greatly affect performance due to it's non-critical design.

Dimensions in Metres

Element spacing:

• Ref =      0
• Driven =  1.244
• D1 =       1.727
• D2 =       3.779
• D3 =       6.683
• D4 =      9.311

Element sizes per element half:

• Ref =       2.654
• Driven =  2.583
• D1 =       2.458
• D2 =       2.408
• D3 =       2.402
• D4 =       2.311

Performance figures @ 28.500Mhz:

• Froward Gain: 11.11dBi free space
• Front to Back: 21.03dB
• Radiation angle at 10 Metres above ground: 15 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 2inch or 3 inch boom as the elements sit high enough above the boom for the boom to have no influence.

If you are only able to obtain 1/2 inch elements in 6 metre lengths and can only obtain 5 metre lengths, join them in the middle at the insulator with a small piece of 3/8 inch tubing (600mm long) bolt the element to the insulator with 2 bolts either side of the boom.

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.