ARS NB9M Gallery Images

Gallery: Rohn HBX-48 Tower Project

The HBX-48 Tower Project begins with the purchase of a used, solid but somewhat rusty HBX-48 tower from Roger, WB9BXT in February 2019 for a very reasonable $275.  Roger had purchased it a while back from a ham in northern Kentucky, but ultimately decided to stay with his pushup pole arrangement.  He stored the tower safely in his barn until a new home was found. 

The Rohn HBX-48 is a heavy-duty, self-supporting tower with a design going back to the Spaulding days.

After hauling it to Indiana in my trailer, I took it to Maye's Powdercoating & Sandblasting in Whiteland, Indiana.  Larry sandblasted it and powdercoated it a comely ANSI Gray, heat-taping the join portions off to maintain conductivity through the sections.  The results were amazing: the tower sections looked better than new.

The goal was to mount a pre-MFJ Cushcraft A4S (purchased well-preserved and documented from John, W9EHU) and a new Antron Max 2000 for 10 & 11 meters.  I settled on using a Yaesu G-1000DXA rotor (new from R&L) and RG-213 cabling everywhere (also from R&L - my favorite place to buy coax).  I first had purchased a used G-1000DXA off of EBay, which was a waste of time.  It would not rotate fully, the fuse was missing in the controller and the mast mount was cracked.

New tower section hardware was ordered from DX Engineering, and the new base and yoke hardware ordered from Thomas Shelby & Company.  If you have questions abou the BX tower series, ask for Mike.  He's super knowledgable and helpful.  Thomas Shelby & Company bought out this line of towers from Rohn many years ago, and still manufacture it.  The base bolts are 30" long and 1" wide!  At the base of the bolts (in the concrete) are 3.5" reinforcing steel plates.   Mike told me that the tower was likely manufactured prior to 1976, because the base yoke bolt diameter is different than the current specification.  How appropriate to be vintage.

For a mast, I used a length 2" OD, 10' automotive exhaust, with another 1 7/8" length pounded inside it.  You can purchase them from your local NAPA store. The whole mast was then cold-galvanized using a Rustoleum product found on Amazon. The resultant mast is heavy and durable.  Another length of short, 1" mast was wedged and wire-welded on the free end to accomodate the Antron, which needs to be well above the yagi.  The mast standoff ordered from radioparts.com (ordered well in advance) did not arrive until the day after the tower went up.

In late August, the base was dug, the rebar wired up and placed, the bolts set in a template, and 18000 lbs of cement was poured.  A big thanks to my favorite general contractor and good friend, Tom Pfaehler.  Without his many years of experience this part would have been much harder.

I used 2" heat-shrinkable tubing (purchased at Dayton 2019) over the ends of the A4S traps to prolong their lives.   The tower section joins were ground down and coated with a non-corrosive, conductive metal conditioner to help ensure a good ground is established from the top section all the way down to the base. 

As the tower was being assembled, we progressively man-handled it to keep it above the ground.  Near the 3/4 point, it was resting on a sturdy picnic table, which kept the pull angle for the eventual truck reasonable. I used clear silicone over the tower joins to prevent water intrusion, and thick, UV-resistent plastic ties to secure the coax and rotor cable runs down the tower leg.  The 24' Antron was sprayed with a U/V-resistent clear spray.

The tower went up 9/28/2019 with the help of Rick, K9VM.  We both took two days off the day job to work through all the stuff that had to be done.  The boom truck fell through, and we used a local tow truck resource, Ronny Brock, to pull it up slowly with the wench.  Straight and slow is the key!  Rick put up with me being "on the edge" when the old 1970's-vintage tow truck pulled up.

The Cushcraft tribander is not nearly as stout as the old Wilson System One, but the SWR and overall performance seems OK.  The Antron Max 2000 was gratifying; it is very broad, and loads up with a tuner on the 15M and 6M bands just fine.

Some tips:

• Plan.  It takes a lot of time, room and money to do this. 
• Stick to the engineering specs for the tower.
• Beware: we found the base studs supplied by Thomas Shelby & Company were dipped in galvanizing material, and the nuts would not thread down.  Wire brushing, oil and lots of leverage did no good.  The only solution was to heat the bolts with a torch.
• HIre a good contractor to dig and pour the base. Once the base is poured, there is no going back.
• Make sure you order all you need several weeks before you need them.  There WILL be unexpected delays.
• Use the best materials you can find for what you can afford. 
• Use coax sealer and silicone everywhere you think there may be water intrusion.
• Keep the base yokes fairly loose, and have a sledge handy.  The base holes will not line up when the yokes are tightened down first!
• The best way by far to drive down a ground rods is to use a cheap hammer drill and a ground rod driver adaptor.

Total cost for me was around $4200.  Outside unpredictable forces of nature, this tower will be standing for another forty years.  Thanks to all involved in making all this happen.

-Brad, NB9M