DIY Build NextG Yagi

Materials and making a start:

First the Boom I wanted light, rigid and preferably non-metal and found a thick-walled black plastic pipe (called a 'riser'), in the hardware story gardening section. Both ends are threaded as they're used for attaching taps. This riser is 900mm and the final antenna will be around 700mm - cost is about $6.
From the plumbing section I got a straight PVC joiner which fit over the riser - costs about $2.
Get 2 stainless 3mm bolts, long enough to go through your 10mm alum tubing, (excess length won't matter). 2 washers to suit, and 2 small lugs to solder to the coax tails.
Elements are 10mm aluminium tube - you need just under 1200mm of aluminium tubing.
Cut all 8 elements at the lengths shown - mark the D.E. and put it aside till later.

The Specifications & dimensions

Reminder: You can download a PDF document for this project
To clarify some points:

• Measurements are Centre to Centre
• Measuring left side of one element to left side of the next will maintain the C to C relationship
• Measurements begin from the Reflector (the Back element) and each hole placement measurement is taken from that point
• Note the "Element Spacings from Reflector" measurements in the specs image above
• 10mm Aluminium Tubing was used
• 12mm can be used with the same measurements without altering antenna characteristics

Construction Process

Step By Step Build

Drill all 8 holes in the black plastic boom at the correct distances, and fit SEVEN elements - Don't fit the D.E. Yet!
The last hole (Director #6) should be out near the end of the boom, leaving excess at the back, behind the Reflector.
This excess provides a mounting point for a brace onto a mast.
End of the boom was stuffed with lightweight styrene and a blob of silicone, as a seal against rain and bugs.
Do Not fit the Driven Element at this stage.
The elements should be a tight, secure fit or glue in place if necessary.

Later you will cut the boom & place the White PVC joiner into the boom.
The Driven Element was cut at 154mm long, then cut in half.
There is short pencil inside the aluminium 'halves' to keep them about 1mm apart.
Pre-drill 2 small (3mm) holes through the Driven Element quite close to the ends - coax will attach here.

3 holes are drilled in the PVC.
1 hole thru centre, 10mm or diameter of D.E. material being used.
1 hole off-centre, the diameter of Coax. It's a tight space so drilling the coax hole off-centre will aid attaching coax.
Pull coax through so tails [ends], can be prepared.

Make tails by removing 25mm of outer black plastic. Extract the outer mesh braid and twist into a single thick tail.
Remove some inner plastic dielectric, expose the centre wires. Twist into single thin tail.
Keep tails short as possible - tin & solder a ring terminal onto each tail end.
Images shows insulation tape covering to ensure 2 terminals can be screwed into the D.E. without touching.
1 tail must be longer than the other due to the angle of coax.

Bolt the ring terminals onto the D.E. (this is why pre-drilling holes earlier).
A long skinny screwdriver will be needed to fit 3mm stainless bolts & washers. To prevent the coax kinking, slowly withdraw the coax back out of the PVC joiner, while screwing the bolts down onto to the D.E.
Test the coax continuity to ensure no short circuit from all the pulling & twisting.

The 3mm stainless bolts could have been shorter but so long as the boom will fit around them, it's OK.

Almost finished

Cut the Boom

Cut through the boom and pre-fit the ends of the black riser into the PVC joiner.
Before gluing in place double check the dimensions! Ensure the D.E. is at the correct spacing now that it is contained in the PVC.
If measurements aren't correct shave small amounts off the ends of the black riser, try the fit again, repeat until you have the correct dimensions.
The dimensions are critical, so take the time to test at this point.
The distance between Reflector & D.E., when it's assembled, must be 74mm.

The 'roll' in the image is an 'ugly balun' - 6 turns of coax taped together.
The BALUN avoids interference from short lengths of exposed/unshielded coax at the Driven Element.
I use flexible RG58 CellFoam low loss coax which suits my balun.
Buy what you can afford but understand that you get what you pay for.

When the rear section of the boom, which has the reflector, is glued into place the antenna is complete.
As mentioned above, be prepared to shave away small amounts of the boom so the ends fit inside the PVC and maintain those correct dimensions. An additional small piece will be 'nibbled' out until the coax can pass out of the PVC and exit the boom.
Repeating once more...Check specifications throughout the build to ensure your distances are accurate.