History Baseplate Centerpost Spreaders Wires & cords
Building SWR & tuning Do's & Don'ts Installation Reference

 

History

Lately I moved to another QTH. Because I can't install a big tower right now, I picked up a used 9m tower. An iron tube
will give me another 3m. My goal was to install an antenna with a small footprint, with some gain and directivity. If possible 5
bands and the antenna should be able to handle QRO (800w).
Because it's temporary I wouldn't spend to much money, so the hexbeam seems to be the ideal solution.
I did some research on the internet and found several websites that helped with designnotes, hardware tips, ....
The word got spread in the clubstation and there was a very positive drive to help and to review the ideas.
Serveral chatsessions with co-builder, ON3TD en Patrick, ON4CLQ (hardware expert) resulted in a "let's go" early
November. The goal is to build it First Time Right. It should be broadband and able to survive 90km/h wind.

 

Baseplate

I had lot's of ideas, but there's a point where you have to start building. One day I received a mail from Patrick, ON4CLQ, he
build the baseplate, wow what a surprise. The baseplate is aluminium, the flence is Inox. Strong, light and well built. Thanks
again Pat. Don't forget to drill a hole in the baseplate for the coaxcable.

Baseplate (under)

Baseplate (support centerpost)

 

 

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Centerpost

For building the centerpost you need a PVC tube of 120 cm and 4cm in diameter. drill 10 holes to install the srews which have to
support the dipoles. The angle should be around 60degr. but is not critical.
Here comes some math in placee. If your PVC tube is 40mm diameter, the perimeter is 40mm x π (3,1415) = 125,66mm
60degr means 1/6th of a circle. So pulle a straight line on your PVC tube. The other 2 lines (+30 & -30) should be at
125,66/12 = 10,5mm. I used M4 20mm inox screws. Here you find the distances from the screws to the baseplate.
Here begins the serious part. Before you start (trying) to insert the screws make sure there are no woman, children or guns around.
I made a usefull tool from an iron coathanger which helped me a lot and saved me from some extra grey hairs.
After stumbeling for another 10 minutes I putted a mark on the coathanger to have an idea of the distance. When this trick was
applied, all screws where fixed within 5 minutes.
When the screws are in place you can start to built the coax feeder. Foresee at least 2 hours to accomplisch this job. You need
1,2m 50ohm coax, 16 cable shoes, a good cutter, and a solderstation.
Because I want to run QRO I used RG213. If you plan to stick with 100W, RG58 will do just fine.

 

Holes are drilled, the "easy" 10m screws ones are fixed

Tool to fix the screws

Finished...yes....

Foresee about 2 to 2.5 cm for easy installation

Coax connections in detail

Centerpost finished

Adding PVC for a perfect fit

Top of centerpost, used to attach support wires

 

 

 

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Spreaders

Spreaders can be made of several materials, some use fiber glass tubes, others use bamboo but most popular here in europe
are the crappy fishpoles. They're quite cheap, I paid 5 each. I consider looking for a 5m pole, so you gonna have to remove
the topend and eventually remove a part at the base. When you slide out the elements make sure they fit pretty tight.
To keep the fiber elements fixed I added silicone base glue (TEC7) on all joints.
As said before, these are crappy fishpoles and they might be the weakest link of the antenna. Try to find some alu-tubing to
re-inforce the base of the fishpole. Forsee about 30cm. I as lucky to find a perfect fit....an old destroyed A3WS did the job.
Then cut the fishpoles on the right length. I'm building the broadband version, the min. length is 353cm, I took 355cm.

6 identical fishpoles

Remove unneeded parts

Add silicones to all joints

reinforce the crappy fishpole with alu-tube (30cm)

Make sure they all have the same size

I used this tool to cut the fishpoles.

 

Support for the S-hooks.

I                                                                                               

 

 

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Wires & cords

A couple of months ago I found some nice lengths 1,5mm2 and 2.5mm2 for a good deal. I Decided to use the 1.5mm2 to reduce
weight and windload. Make sure you have the right lengths. Measure twice, cut once. I advice to cut the reflectors first. If you
make a mistake you can reuse/recuperate the lengths to cut the drivers.
All reflectors where pre-assembled with cable shoes and tip-spaces.
Not affecting the performance, but needed to complete the project are the support cords. You need at least six (from top spreader
to centerpost) but I made 12 pieces. The 6 additional perimeter support cords have to be looped over the ends of the spreaders.
The length of each cord is 328cm, S-hooks included. It's very important to use UV resistent cord with a low stretch factor.
Some builders use the 20m dipoles & reflector as perimeter support, but I didn't want to stretch the VOB cable.
For the tip spaces I used the same wire as the support cord. The length of the 5 tipspaces is available in the table at the bottom
of this page. Make sure you add at least 10cm, it allows you to run the wire twice through the electrical connector for more
security.

 

Dipoles & reflectors

Connections tip space & reflector

The length of all wires & tip spaces. Remember, the driver consists of 2 sections (dipoles) and the reflector consists of one section.
All sizes are in centimeters. 2,54cm = 1 inch.

Band Freq  Length 1/2 driver length reflector tip space distance screws above base plate
20 14.150 553,7 1046 61 15
17 18.100 430,5 815,3 47 25,5
15 21.250 367 697 40,5 35,5
12 24.950 309,1 589,3 34,3 51
10 28.400 271,3 519,2 30,5 106,5

 

 

Go to page 2 for building instructions...

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