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Tuesday 14 August 2012

VK5DJ 14 Element 2m yagi /P version

To keep the weight down to absolute minimum... made up a /P Yagi for 2m... 14 element as will be attempting JT65 EME from 6W or C5 with FT897 and 50W will also be using a 20dB RX preamp from G4DDK.

Start with 2.5mm twin and earth you need about 1m for every element and reflector... so in my case 15 meters. I then cut into 14 x 1m lengths and one a bit longer about 1.1m

Strip out the three conductors.

Save the earth one, but not using it this time.

Take one of the wires and put a bend on one end.

Put the other into a drill (don't strip the insulation off)

Gripping the bent end, holding the wire straight (don't pull it!) trun in the drill, the wire will toughen up and straighten. I turned the drill until the bit in the chuck broke off.

The wire looks like this...

Pull off the insulation, you an sort of see the wire has turned and gone from soft to hard drawn.

Then attach a 6mm ring crimp to one end.

 Tidy up the end.

The other end, slip a crimp on the wire and against a rule measure the length the element needs to me (to outside of the ring clamp)

 Once right length bend
 Solder it in place
 You do not have to bend and can solder straight too. Not I use a G clamp to hold the wire against the rule (cheap £1 thing from Maplins)

I'll add more details as photos available but the driven is a folded dipole. I made three different ones, one is from flat 300ohm, one from 300ohm ladder, one from metal ruler (the one I was measuring with!)

I'll add the VSWR plot later.

The rings are so that you can suspend the elements in a line beneath a pole. The directional part is pretty crude, you 'point' the yagi. In my case in 6W and C5 this will be where the moon rise is expected.

I made a 4:1 balun from 75 ohm CT100 white cable.

Anyway all up weight is about 2kg.

The beams estimated 3dB beam width is 31 degrees.

I'll modify and onsite play if I need to change anything. Photos will be added too, with the moon in shot!

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