Tuesday, September 27, 2016

Building a 2 Meter Yagi (Version 2)

A while back I built a 2 meter Yagi and had great fun playing around on my local club net with it  attached to a small rotator, but as is the case, I moved on to other things and sold the TV rotator and the Yagi on to a friend.

The original
I noticed in the stats of this blog that one of the most read items is the building of that 2 meter Yagi. It's a very simple design and for its simplicity it works very well especially for my latest project with my newly acquired Trio 700s where I needed a small Yagi antenna. So I read back in the blog and decided to make a mark 2 version.

The first items I required was three aluminium 18mm tubes, two at one metre length and the other at 1500mm and one boom 15mm by 15mm square also at 1 metre in length. I would also require three pieces of wooden curved dowel (12") to support the aluminium tubes when mounted, a small but thick piece of copper wire for the hairgrip 12.5mm in length and 10 plastic tie grips.

The aluminium tubes will be rear element 1020mm, drive element 920mm and front 890mm. The rear and front will remain at their lengths but the drive will need to be cut accurately in half and then two small hole drilled about 2 mm from one end to take a small screw for the coax and hairpin wire.
The hairpin wire should be 5 cm in length bent at right angles 2.2cm width, and bent again at right angles for another 5cm. the width between ground and live should be the 2.2 cm.

A = 5cm B = 2.2cm

The coax should be roughly a metre long, stripped for a PL259 at one end and split for ground and live at the other with two metal eyes soldered on for a screw placement on the drive element. If this antenna was going outside it would then be waterproofed for protection, but in this case it was going in my attic.

You can alter the length of the A  for minor adjustment of SWR.

The elements are fixed by the plastic tie grips going round each of the dowels and the tubes, they are light and hold the tubes in place. The wooden dowels are then screwed in to place in to the boom by a small screw or you could fit a small bolt and nut.

I got a good 1:1 and 1:2 SWR over the upper part of 144MHz  and lower 145 MHz and as soon as I can will be placing it up in my attic to see how it does with a bit of dxing!

Here is the link to the site for further explanation:  Yagi Build

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