QHA

I used 3/8 pipe for the elements. I used hard copper for more strength. I started with straight pipe, I had to go to a Air conditioning supply to find it. Hardware stores only carried 3/8ths in coils I wanted to start off with a straight chunk of pipe. What a mess that would have been trying to work with the coil up pipe. In addition, I had to buy a tape measure that had a metric rule. Don’t try to guess these measurements. They must be dead nut on.

I used a pipe cutter not a hack saw to cut my pipe. Very neat cuts.

Cut pipe to these lengths

2 - 190mm lengths - bottom horizontal tubes

2 - 903mm lengths - short helix elements

2 - 1002mm lengths - long helix elements

4 - 90mm lengths - top horizontal elements

I used my knees to bend the pipes. I bent them in pairs so I could have the same shape for each pair.

I used electrical PVC pipe. It has a flared on one end for the top. I found a piece of water PVC pipe that fit snug over the flared end of the electrical PVC pipe. I drilled the top 4 holes in the water PVC and slid this short pipe over the electrical PVC pipe. The copper tubing rest inside on the electrical PVC pipe. I cut the top off a PVC cap and slid this over the short water PVC pipe; this provides extra support at the bottom for the top copper pipes. I cut 4 each 3/8 notches in a cap and slid on top to seal and support the top 4 copper pipes. The balun is a 4-turn coax. I drilled holes to fish the coax out and back in the electrical PVC pipe. This makes for a much neater finish. Around each 3/8 copper pipe I used rubber cones that are used for the water line under the toilet tank.

(Use Flux!)

Connection at the top of the antenna.

This was the hardest part of the project, Frankly this was a bitch!

My first attempt went up in flames as I sweated the elbow joint inside the water PVC pipe. The PVC pipe caught fire and burned up.

After a good night rest I came up with a better plan:

I junked what I burned up the previous night and started over.

What I ended up doing was mashing the tip of the copper pipe flat with a hammer. I flipped one of the two over so they mated nicely. I lap jointed these flat spots inside the top opening of the antenna. Before I attached these inside the pipe, I ground away the one side of the flat spot so I could push the pipe into the 3/8 hole and so the opposite corners of pipes would not touch each other i.e. dead short L. I then sweated the pipes in place and then I soldered the coax to the pipes. I used a wet rag to keep the rest of the pipe cool and to prevent the PVC from flaming.

I drilled my bottom holes 50mm higher so the vertical elements would bow out more. This will help the apex reception.

Here a web site to check out!

Results:

This antenna works great! VSWR 1:1.2 at 137.5. As a bonus, it is 1:1.5 at 146.5. I pick up signals at 2 degrees above the horizon with some noise. I don’t have any nulls like I did with the dipole and verticals. This antenna works great, if you build it correctly. I don’t see anyway to adjust it after it’s built. Better get it right the first time or junk it and start over.

Here is a zip file with more info

To scale this antenna for 144.5 use the following:

Diameter both loops 188mm

Long loop height 950mm, helix length 961mm

Short loop height 850mm, helix length 863mm