What to use for a Mast on a Rohn HDBX48 Tower

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W4MRP, Apr 17, 2019.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Nah, it's a local place I've used for years: M&K Metal Co. in Gardena, CA. I just call in an order and go pick it up; although I haven't ordered any in a couple of years...but they always had Chromoly steel 4130 tubing in stock.
    W4MRP likes this.
  2. W4MRP

    W4MRP Ham Member QRZ Page

    Sounds like a smokin deal. Well, I'll look around some more locally too. Thx!

    --- W4MRP
  3. N7WR

    N7WR Subscriber QRZ Page

    Do NOT use aluminum or water pipe for a mast, particularly with a yagi as big/heavy as the one you inherited. A moly steel mast (and yes they are expensive) is the only way to go. Use aluminum or water pipe and stand by for a mast failure which also means loss of the yagi, the rotator, and perhaps much of the tower. Been there, done that
    K8PG, N2EY and W4MRP like this.
  4. K4ZA

    K4ZA Ham Member QRZ Page

    Answers to your questions may be found here: QST, Sept 2014, "Antenna Masts: Safety & Selection" & you might also
    benefit from perusing "Antenna Towers for Radio Amateurs" (ARRL). Yes, the BX-series come with manufacturer's recommendation
    for mast lengths not to exceed 10-ft. Hams have violated that from the beginning & gotten away with it. Does that mean that it's a
    good idea or something one should emulate? Probably not IMHO... Have I done exactly that for clients? Yes, always with the caveat
    that we're violating an important rule: to do what the manufacturer says to do. Period. I have built & installed torque tubes, so that
    the rotator could be located close to ground level. But alignment of the tube (to say nothing of the mechanical aspects of getting the
    long tube inside the tower, securely spliced, etc.) almost make it not worth the time/trouble, etc. YMMV If you take away one thing from this post, remember this: Please, NO WATER PIPE!
    Don K4ZA
    Tower Works
    Charlotte NC
    N2EY and W4MRP like this.
  5. W4MRP

    W4MRP Ham Member QRZ Page

    Thanks Don! A tower pro! These forums are great.

    Will check out the QXT article. I have the ARRL tower book as well as Up The Tower. Read them both. I like Up The Tower more though. They seem to be the only two books on towers for amateur radio.

    Not going to use water pipe or aluminum for this big antenna. I was mostly asking because if the Rohn mast was plain steel, then it seems like water pipe would work. But it's not plain steel and for a good reason. I'm putting a lot of effort into restoring this tower and antenna. Don't want it to be falling down any time soon. And if it does, I want it covered by insurance.

    --- W4MRP
    N2EY likes this.
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Re insurance: My experience with that (a few incidents with clients over many years) is if it's a small claim they accept a couple of photographs and don't even bother sending an adjuster out. But if it's a big claim, yeah, an adjuster visits and wants all manufacturer documents for everything, as well as building permits in those cases where they're required (in my cases, they were always required) and if anything exceeded what was specified it was a big problem.

    Big as in they won't pay the claim.:p

    The Rohn BX series engineering documents do specify 10' as the maximum length for an antenna boom or element and obviously your beam greatly exceeds that. Hams have been exceeding that for decades all over the place. But it could become an issue for a building and safety office inspector or an insurance adjuster.
    W4MRP likes this.
  7. W4MRP

    W4MRP Ham Member QRZ Page

    There are several reasons this 50' tower is 100' from my house. ;)

    I've been talking to my insurance company (State Farm), but I really don't trust that any of the insurance agents know enough about the actual policies of their companies to advise you on stuff like this. Like so many business these days, they are just paper pushers who scarcely understand their own products. They're just human faces to the big machine. State Farm has always done good by me and my extended family, though. State Farm said that the tower and antenna would be covered under my external structures coverage and treated like a barn, shed or other outbuilding. Didn't make a lot of sense to me and I'm not sure if I even believe that they know what they're talking about. I'm a bit overinsured on the home insurance front, but still, I don't want to test it.

    I've been looking into these guys too. https://www.hamradioinsurance.com/

    Anyone had any dealings with them?

    --- W4MRP
  8. W4PG

    W4PG Super Moderator Lifetime Member 279 Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    One other aspect of this tower that used to come up is many folks I knew way back when in the 70s when I had one of those Rohn towers was that several bought 10-foot straight sections and added that to the bottom to boost the height. Apparently Rohn figured out folks were doing this and stopped providing them. At least when I went looking, I could not buy one from them. I'm sure there are some floating around somewhere. Since folks pretty much ignored the 10-foot boom length issue, they had no problem using the 10 foot straight section to add height. I probably wouldn't recommend doing that today. I was a teenager back then working after school and weekends and the tower I got was, as I remember, only $2-300 dollars at the time. I drove 70 miles to a store to pick it up and brought it home in an old Ford truck my Dad had bought for other reasons, added a couple of quarts of oil along the way and checked the gas. Literally.

    I did mention a water pipe I used but it could have been something else. I just wanted to clarify like others have said DO NOT use a water pipe on your setup. I didn't make that clear earlier in my post. I currently have a US Tower 89 foot crank-up fold-ever with a DB-36 on top of is, previously had a 4 ele SteppIR and 2 ele Cushcraft 40 meter beam. I had a major reinforced mast I used I got at the time back in 2009 that was 16 feet long (6 feet into the tower or so) that I spent something like $400 dollars for but when I replaced the two antennas with the single DB-36, now have the antenna mounted just above the top of the tower and cut the mast down to size since I didn't need that long a mast anymore.

    I NEEDED a building permit but likely would have gotten one even if I didn't legally require it for insurance reasons. A PE signed off on my install and all proper docs are with the city so folks can see all is legal. I had a crazy lady complain and even tried to start a petition to have my tower taken down but all was legal with the city and that was that. If you ever have the need to file a claim, the insurance company will likely want to know that the tower was installed to local code. Without a permit, you might have a hard time proving that. Likely would never be an issue but something you need to factor into the equation.

    PS: I used to be a volunteer counsel for the ARRL who helped folks with tower building permits, etc. I went back to making an honest living as a doctor so I don't do the law anymore. :p

    W4MRP likes this.
  9. W4MRP

    W4MRP Ham Member QRZ Page

    HA! Added oil and checked the gas.

    $2-300 !!! It's costing me that much just to restore it!

    Funny you mention the 10' extensions. I was seriously considering building a 20' base extension -- but a REALLY butch one since I have welding and metalworking capability. It would put the 40m elements just over 1/2 wavelength. But Isaac Newton kept whispering depressing things in my ears and eventually he talked me out of it. Main reason is that I want to tilt it instead of climb it, but with that base extension I don't think the HDBX would have survived the lift with the lift point at the top of the 20' section. Now, whenever the wind blows, Isaac Newton's voice is whispering in the breeze. There was also the insurance angle to it. Now that reality has set in, the idea looks scarier and scarier the more I think about it. Still want to tilt it though.

    Yup: NO. WATER. PIPE. EVER. Got it. Don's (K4ZA) QST article was very good. Highly recommended. Described the mast as the the core of the antenna/mast/rotor/tower system. I supposed that's a good way to look at it -- the mast is the only piece that attaches directly to all the other components.

    Not sure I want to get the super expensive DX Engineering mast because I don't need 20'. If DXE had a 10' or 15', I might bite. But the US Tower masts are looking good. The US Tower M-15R mast has 0.12" wall (~11 gauge, same as Rohn M200H) but the bottom half has a reinforcing liner in it that brings half of it to 1/4" wall. Mast and liner galvanized as one piece. I have email in to them about what type of steel. Surely it's not just mild steel -- might as well use water pipe. [Errr, that was a hypothetical, people. I wouldn't dream of using water pipe! Honest! No scolding necessary.]

    Since I'm redoing the top plate and the rotor plate on the HDBX, I may move the rotor plate down toward the bottom of the top tower section. Then I could use a slightly longer mast (like the 15' US Tower M-15R) to make up the difference. Not really liking the small distance between the thrust bearing and the top of the rotator. The US Tower M-15R mast's reinforcing section (7.5' of its 15' length) should be long enough to get the 1/4" wall part up through the thrust bearing to where the Mosley beam will attach. Seems like it would work well. Might have to shorten the unreinforced part of the mast a bit. The only other thing I want on that tower is a dual band VHF/UHS vertical right at the top of the mast. Considering the ginormous Diamond X700HNA.

    Don't get me start on permits. I'd rather pay the fines than pay someone to give me permission to build something on my own land with my own hands. Thankfully, I live outside the city limits on 5 acres and therefore don't have as many permit requirements. No other houses within several hundred feet. I could build a trailer park in my front pasture if I wanted to. [Another hypothetical.]

    Wow, a doctor AND a lawyer.

    You know anything about these guys: https://www.hamradioinsurance.com/

    Thanks for the entertaining and informative post!

    --- W4MRP
    Last edited: Apr 18, 2019
  10. W4MRP

    W4MRP Ham Member QRZ Page

    BTW, US Towers got back to me and said their masts are made of "A36 standard steel".

    The ASTM describes A36 as "carbon structural steel". Wikidpedia says "A36 steel is a common structural steel in the United States." and they list all the specs.

    Probably the same stuff the Rohn M200H is made of.

    Seriously leaning toward the US Towers M-15R. Bout $300 at HRO.

    --- W4MRP

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