Friday, July 29, 2011

The 4 band Broadband Hex beam

The 4 band Broadband Hex beam
20-17-15-10 meters

Wanted: HF beam, must be small, light, inexpensive, easy to build, enter the Broadband Hex beam. I first was introduced to a hex beam back in 2001 at the Huntsville, Alabama Ham fest by a company call Traffie Technology ( It looked pretty impressive but I was moving to Montana so I grabbed a brochure and filed it for future reference.

Living in western Montana is great but usually all the eastern US stations beat me in pileups trying to work Europe on 20 meters and higher bands. I thought it might be time to replace the little 20-6 meter hybrid quad that had served me well for several years with something that had a little more gain and not much more weight and wind load. I started searching the web for potential candidates. I came across the hex beam users group (
). After seeing the prices on the commercially made hex beam I knew I’d never talk the xyl into that so I started searching for alternatives. I saw several web sites that were dedicated to the construction of a home made multiband hex beam. It looked pretty hard to build but I kept at it, studying and learning as much as possible about the hex beam. I then noticed several posts about a Broadband Hex Beam being developed by G3TXQ that had more gain and was much easier to build. Hey, this could be the one.

I would recommend anyone interested in this antenna to go to (
) where you will find a wealth of knowledge by G3TXQ or Steve who is the father of the BBHB (Broadband Hex Beam).

After gaining a stronger understanding of the antenna I went to Leo’s website (
) who has presented an easy to follow step by step instructions on building this antenna and I highly recommend it. I left off the 24 MHz band because of the likelihood of interaction and I’d never had much interest in that band anyway. If you want this band by all means go ahead and add 24 MHz, I just decided not to. So instead of the 5 band described, I was going to build a 4 band version of the G3TXQ BBHB.
Step one: Gathering the parts
To get all the parts and materials as outlined in Leo’s plan proved to be the most challenging of this whole project. Now, its easier with more sources so don’t be scared off.

I got the spreaders off eBay to save a few bucks.

I found the base plate locally but it was a little thicker than called for and that changed a few bolt lengths and made it a bit heavier. I got a local ham friend (W8QMD) who runs a machine shop to score and mark the plate for me. Now you can order the base plate already drilled in different levels of completeness from (

Also you can order the spreaders from (
You can find some of the parts locally such as clamps, bolts, electrical PVC conduit. You may have to order the 16 gauge wire, Dacron and Kevlar rope from other sources such as http://www.thewireman
.com and

The connectors come from Radio Shack; I could never find them from any other source in the jumbo size.

Just follow Leo’s parts list and you won’t go wrong. Expect to fork out 200 to 300 dollars if you have to purchase everything. I scrounged as much as possible so I saved a few bucks along the way, but sometimes cheaper in not necessary better.
Step two: Construction
I followed Leo’s plans to the letter and did not deviate from it until construction was nearing completion and I saw some improvements I could implement. I strongly advise you to do like wise. Leo was a great help when I emailed him with questions and he was quick to respond.

I started by drilling holes in the base plate and mounting the flange to it.

Then I inserted the 1 1/4 inch electrical PVC conduit through the center hole and securing it in place.

I then took the fiberglass spreaders and measured them out to proper length and painted them flat black to reduce UV damage.

I also used schedule 40 1 in diameter PVC sections cut in about 5 inch lengths on the base plate so the spreaders could go inside of them to keep from tightening down directly on the fiberglass. I also painted these black. I attempted to glue the spreaders together with liquid nails but this didn’t work very well. So, I drilled a small hole through the spreaders where they joined together and put a small screw with a flat washer at both ends. This proved to work well and they didn’t move at all.

After putting clamps at the designated places on the spreader I set the spreaders aside.

Next, I measured out the wire to the specified lengths. This proved to be challenging by myself but after triple checking I had the correct measurements for the 4 bands I wanted, both director and reflector per band.

Then I made the end spacers (two for each band) using small dacron rope and the radio shack connectors

I carefuly coiled up each wire and labeled them and set them aside for later use. I then measured and drilled the holes in the center mast.

I followed that by making up the harnesses to go from band to band.

The antennas feeds from the top with 20 meters being first, then 17, 15 and finally 10 meters just 6 inches above the base plate.

I drilled a hole in the base plate to run the feed line through, then ran it up the opposite side of the feed point connections and over the top of the center post and connected to the 20 meter feed point.

To get the screws inside the center mast and protruding through each respective hole took a little time. Leo recommended a metal clothes hanger which I didn’t have. I tried 10 gauge wire looped around the screw once and that worked for the 20 meter holes. The wire was too flexible and bent when I tried to get the other screws through their respective holes. I ended up finding an old fiberglass antenna (probably 11m) and taped the 10 gauge wire to it. In 5 minutes I had it done.

I then inserted the short 1” PVC sections in the u-clamps and then inserted the spreaders in each one respectively and tightened them but not too tight.

Make sure to install lock washers on the u-clamps.

Next I made up the 130 inch nylon sections of rope including s-hooks on each end. I used bailing twine since I had plenty lying around and it worked great.

Then I started installing the cords with 6 radial cords first as Leo’s plans suggest and then install the perimeter cords. You’ll find it incredibly easier to install the wires in the beam if you have it pulled up to proper shape.

The HexBeam Spreading it's wings in beautiful country!

Next, install your 20 meter driven element and reflector. You should make sure each half of the director extends 128 inches out from the center post to each connector and then tighten down on wire with the set screws. I made a 128 inch measuring stick out of 2 pcs of fiberglass.

After securing the director, install the reflector making sure there is 128 inches between all spreaders and center post to connector or corresponding clamp by using lengths of dacron rope. Also add the 2 shorter lengths of dacron rope on the front side of the director (this is the front of the beam). After achieving 128 in spacing screw all the remaining connector screws down to hold it in position.

Once you achieve that tighten down on all the connectors to hold the exact measurements and shape. Then take off the supporting nylon cords. The 20 meter antenna now holds the shape of the antenna.
I had about 2 ft of center post extruding out the bottom of the base plate. I placed this in a 5 gallon plastic bucket containing several large rocks. This let me have the antenna low enough to the ground so I could work on and install all the elements. Once all were installed, I used a rather large wooden reel used for wire or cable on its side.
This let me do preliminary testing of the antenna.
Step 3: Testing
Finding a suitable mast that the plastic center post would slide into proved to be a challenge. I finally took a piece of the pvc to a fencing company and found one. It was marked 20SS. I attached the 10 ft pipe with the hex beam on top to a fence post.

Antenna mounted on fense post for testing.

The beam performed fairly well even at this height. Resonance points were on the low end of each band. The antenna tested very broadband and had good side and back rejection. I expected the resonant frequencies to rise when put up to at least a 1/4 wavelength and they did for all bands.

Back down to the bucket again so I could strengthen clamps and connections. I wrapped Dacron rope tightly around the connectors that held a lot of tension (20 meters).

I noticed a little splitting in the spreader junctions and I installed hose clamp to help prevent this. I doubled up on the plastic ties on the non tensioned connectors.

I got an 8 in piece of 4 inch PVC drainpipe and made a choke by wrapping 7-8 turns of RG-8X around it and mounted it to the bottom of the base plate.

I checked Dacron cord measurements and had to readjust for stretching.

Everything now looks good so back on the fence post and made a few contacts including some dx.

I decided to let it sit there for about a month to give it a chance for anything to stretch, break or come undone. Patience is a great virtue. Don’t get in a big hurry with this antenna.
Step 4Installation
I got several friends together on a nice day with a winch mounted on a UTV. I put a pulley about 20 ft in a tree and connected the winch cable to a strong rope I had tied around the tower.

I took the guys loose and the bolts out at the bottom and we laid it over within a few minutes. This shouldn’t take long I thought, wrong! The mast would not fit through the tube in the top of the Rohn AG25 so it could mate up with the rotor. The mast was too thick.

I quickly called on W8QMD again and he made an adapter pin that would fit down through the top section tube and would let the antenna mast slide over it. That solved that problem.

I hinged the tower up so the top would be about 10-12 ft off the ground. I then positioned an 8 ft step ladder so I could walk the BBHB up the ladder and mount it to the adapter pin. It went off without a hitch except sore muscles from lifting and straining the antenna above my head. We winched the tower back up and checked the swr, and it was very good.

I connected the coax to the radio and made a few contacts. I had excellent results with the beam headed SSW. It was 3-5 S units better than my loop. I then tried to turn the antenna and it didn’t turn. I took for granted since the rotor turned before I brought the tower down that it would continue to work, not the case. I finally got a new Yaesu G-450 rotor.

I rented a man lift that went to 42 ft and on a warm Nov day I changed out the rotator and it works fine. My first contacts were DU2, BX5, and I was running low power.
SWR was not over 1.2 to 1 over all bands covered except the upper end of 10 and it approached 2 to 1 at 29.6.
As a bonus, it also loaded easily on the 30 meter band and the 6 meter band with my built in tuner on the 746 pro...

Up in the air!

In Conclusion!
This was the most complicated antenna I’d ever built but well worth the effort. If you’re considering one, do the research on the above web sites and forums; gather your parts then go for it. This is going to be a super antenna and I built it myself. Feel free to contact me with any questions but please refer to the web links above first.

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