Cable ? for HF use | Tower Damage Recommendation

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N9NU, Oct 1, 2018.

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  1. N9NU

    N9NU Ham Member QRZ Page

    Hi Guys

    First, an easy one:

    I would like a recommendation on which type/brand of coax to use on all my cable runs (all < 150'). When I put up the tower back in 93 I had someone who liked to climb give me several lengths of (don't throw up :eek:) Radio Shack 50 ohm foam type...along the lines of RG-8...what shielding type and % is I am sure below my standards. I didn't know it was RS coax at that time as I was out of town, otherwise I would have steered clear.

    I am know a lot use Belden 8813, RG-213, TLMR-400/600, etc. and would like to get some ideas from the community. I do have a requirement: NO FLEX cable for the majority of the run up the tower. I will adapt/convert/reduce to a flex cable IF necessary when it's inside. The length to my benches from the closet with outside access is < 5 feet.

    I don't need T-LMR-600 type [unless I can get a 100' run at a great price - used] for anything. I think 400 series would suffice. The longest run from any antenna would be ~ 110'. In total I would need about 300' of cable. I have 75' of 213 I believe on hand for the 5 element V/U yagi. I know Belden is a good name as well as TLMR of course and Cable X-Perts which has everything is North of me and I can pick-up as well.

    Here is a list of the hardware:


    Tower: US Tower HD-55 - 3 section crank up - the two sections are blocked off and clamped as to take off the load on the crack up aircraft cable**


    HF/UHF/VHF Antennas:

    • Cushcraft A3WS WARC band tri-bander 12/17/30 (Lowest on main mast)
    • Homebrew 5 element 6-meter beam (not shown in picture) - Above the A3WS
    • Cushcraft 13B2 13 element VHF yagi - Above the 13B2
    • Cushcraft 5 element UHF/VHF yagi side mounted on tower - abt 30' AGL
    Wireless ISP Antennas:
    • 5.7x GHz Omni vertical - At the very top of the primary mast ~ 70'
    • 5.4x GHz Omni vertical - Mounted on a 2nd mast which is clamped to the west side of the tower leg ~ 65'
    • Hi gain microwave dish (18") for TX/RX of all ISP signals to primary commercial tower 5 miles away
    • 2.4 GHz semi-directional sector antenna - At ~ 45'
    ** I have this setup so the tower climbers can climb as needed to diagnose/maintain/etc their WISP antennas.

    I also need to replace the G-800 rotator cable. I have that on hand. I need to buy a new/used G-800 (or compatible) rotator control box.

    ----------------------------------------------------------------------------------------------------------------

    Okay. Now to a PROBLEM with the tower at the base.

    A handful of years ago someone (I wasn't present) backed into my tower with a truck and sometime thereafter I noticed a few z braces that were detached (broken weld) from one of the 3 legs (x 3 braces). The biggest issue is that one of the three legs COMPLETELY cracked through and was immediately reinforced with a steel fence pole section which is clamped alongside it from the concrete up to ~ 4 feet. The crack is ~ 1 foot above the 'T' plate. Not good.


    Now I have a second leg that is partially cracked (~ 1/4 way around) and will have to reinforce that one as well. The problem is that the base (during winds >35mph) is starting to twist and that is something it is NOT rated for nor engineered for.

    Other than buying a new tower (out of the question), I have at least 3 ideas that I am considering:

    1. Thermite? Possible? I was told galvanized piping cannot be welded back in place (true or false, I am unsure)

    2. Drill holes in the concrete to sink 3 steel fence type posts down 3 feet alongside each of the three tower legs and somehow create a cage around the bottom 5 feet or so and weld/clamp them to the legs and reinforce it by cross bracing it, etc.

    3. Build a form around the lower base up to 4-5' above and sink it in concrete. Then use some angle iron or something to wrap around the block of concrete (lower & upper) to give it extra strength. This of course would not allow for it to be tilted over.


    In addition to any of the three I can use the one leg (3 if needed) to create a side mounted bracket system and drill through the aircraft hanger it's up against into and through the large 8x8 horizontal bracing they used to build the hanger. Then put a steel plate on the inside and run large lag bolts through and secure it at the 14' level (where the horizontal beams are)

    Does anyone have any experience with something like this happening and is one or more methods I listed seem reasonable? I can live without the tilt over aspect, however, that would be the last option.

    If anyone has any other suggestions, I am game. Please feel free to contribute.

    I WILL POST pictures of my tower & base TOMORROW (NOV 1) to help everyone visualize the problem.

    Thank You

    Tim Dickerson
    ARS N9NU
     
  2. WB5THT

    WB5THT Ham Member QRZ Page

    I would get a mobile welding guy to take a look, they aren't structural engineers but the good ones have a lot of practical knowledge. Gavalnized steel can be welded but the fumes are noxious. As far as coax, take your pick.
     
  3. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    Boy, this is a tough one.

    If the tower can fall on anyone else's property, and especially on anyone's house, I would take it down, now, no matter how much that hurts. There is no way your insurance company would pay a claim if something happened to your repaired tower, and you would be leaving yourself open to expensive lawsuits.

    If any kind of permitting process was necessary when the tower was put up, your repaired tower will violate the permit, with all the accompanying civil/criminal liability.

    And god forbid, it's such a horrible thing I hate to mention it, but if somebody was permanently injured/killed by your repaired tower, that would be hard to live with.

    I'm not an engineer, but both my father and brother were/are structural engineers who designed steel structures professionally. I worked with my father quite a bit on various jobs. I know what they would say, especially if that tower can hit a house.

    I would have taken it down as soon as I noticed the cracks.
     
    Last edited: Oct 2, 2018
    WB5THT and WZ7U like this.
  4. WZ7U

    WZ7U Ham Member QRZ Page

    Anything less is irresponsible. Besides, had it been dealt with on the homeowners policy back when it originally occured, this wouldn't be a hazard today.

    Don't be a hammy hambone.
     
    WB5THT likes this.
  5. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Hollow tube tower legs CANNOT be welded! The heat will weaken the steel even more.

    Since the tower can be folded over, it would not be that hard to lay it over and then replace the bottom section.

    Are you sure all the damage was caused by a truck? The vertical crack looks just like when water is trapped, inside the tower leg, and then is frozen.

    Over the years, I have been involved with hundreds of two-way radio, and microwave radio, towers ranging from about 40-feet above ground to well over 500-feet above ground. Frankly, any tower with such a damaged leg would be immediately taken down. No professional tower man would even think of climbing a tower with that kind of damage without a LOT of reinforcement to hold the tower while it was being dismantled.

    The last tower that I had anything to do with, that had that kind of damage, was about 200-feet high. Fortunately, it was adjacent to a parking lot. Since no one would climb the tower, on a Sunday morning, when the parking lot was empty, the guy wire, on the side opposite the parking lot, was cut and the tower fell over into the parking lot. Then, it was hauled off as scrap metal!

    Glen, K9STH
     
  6. WB5THT

    WB5THT Ham Member QRZ Page

    Welding can cause embrittlement and a reduction in yield strength - welding tube or pipe is especially difficult (for me anyway.) A final test for a welding class I took was doing a fillet weld on two coupons (small squares of mild steel), clamping the plates in a very large vise and whacking the exposed plate with a sledgehammer. If your coupons bend without the weld breaking, that was a mark of success (I passed.) Not very scientific but I was fairly amazed at my results with a Lincoln buzz box and a non-auto darkening helmet.

    A field repair of leg tubing would indeed be very problematic.
     

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