The Ladder Tower": A Simple Antenna Structure

Discussion in 'General Technical Questions and Answers' started by K4EEZ, Feb 1, 2009.

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  1. K4EEZ

    K4EEZ Ham Member QRZ Page

    I just found this post on another website and thought i would pass it along to the Zed's so dont shoot the messenger. ;)

    by Fred Race, W8FR​
    These days many Hams are seeking ways to improve their reception and up their signal strength, while limited, or being modest in their antennas and antenna-related structures. An easy way to get some short-boom UHF/VHF antennas "up" is by constructing and using a Ladder Tower. Figure 1 illustrates an installation, with three antennas at nearly 30 feet.

    [​IMG] [​IMG]
    Figure 1 Ladder Tower
    The Ladder Tower isn't a new idea by any means as it is one of the several Wooden Tower structures of early Ham Radio days, when even rotary-beam antennas were mounted on wooden frameworks using stand-off insulators. When you don't want/need, or just can't invest in a conventional structure (25G, etc.), look to your hardware store for an inexpensive aluminum extension ladder. A convenient length is 12 feet, with extension to 20 feet plus, depending on your load. The ladder used in Figure 1 supports 225 pounds, is lightweight, and of sturdy construction.

    The method of fixing the Ladder Tower to the house is simple and somewhat unique. The overhang attachment uses two mounted, 6-inch, heavy barrel bolts that can be positioned to hold the Ladder Tower in-place, and locked on either side of the ladder. Simple 3/8th-inch holes were drilled in each side of the ladder, and the bolts slid through to hold it in place. Six, 3-inch drywall screws hold each barrel bolt in place. Using U-bolts to attach the Ladder Tower to the base is very simple: two 1-3/4-inch steel post pipes at 16-inches each were set in the ground, while one bag of quikcrete mixed to a slurry was poured and dried for 3 days. Figures 2 and 3 illustrate these attachment points for the Ladder Tower.

    Figure 2 Right-side Barrel Bolt Fixture (in-place)

    Figure 3 Base Pipe Attachment Scheme

    Let's start with the overhang and base preparation. The overhang is prepared with one 36-inch treated 2-by-4 to span 3 roof-rafter ends. Three-inch dry-wall screws are used to attach the 2-by-4 through the flashing, and it provides the mounting surface for the two upper Ladder Tower barrel bolt mechanisms (right and left sides of the ladder to hold it to the house. A hole is dug down to around 12 inches in a rectangular shape extending about 4 inches beyond the ladder width, and a front/back depth of 6-8 inches to accommodate the base attachment scheme.

    Positioning and "plumbing" the ladder is simple, but done in a prescribed manner. First, the ladder is set into the hole (hole dug/centered beneath overhang attachment point) to enable driving the two pipes in on either side of the ladder to a depth of 8 inches, while holding the ladder plumb (a two-man job, of course; three might even be better). Once one is driven in, shift to the other side while maintaining plumb, and drive in the other base pipe. Work stops at this point in construction to allow the concrete to set (3 days).

    After the base concrete sets, re-position the ladder to plumb, and with it setting on the concrete, mark each side for U-bolt holes; one is sufficient. This is accomplished by placing the U-bolt over the pipe, and against the ladder side at a point on the pipe, and draw around the threaded shanks on either side of the pipe. When ready for drilling the holes, use a centerpunch to mark in the center of the drawing circles. All the holes in the ladder, including the rotor base pipe holes, are marked and drilled later.

    Maintaining plumb and held against the overhang, center the barrel bolts on the 2-by-4 mounting surface and mark the point at which they are aligned and the point on the ladder sides the bolt must pass through. This completes the preliminary alignment and enables the drilling. Of course, all the holes are drilled into the stationary 12-foot ladder, not the extension, which slides and rests on the stationary section.
    When finished drilling the marked holes for base and overhang attachment, mark and drill the four holes to accommodate the two U-bolts associated with the rotor pipe. This pipe is 1-3/4 inch gas pipe (extremely robust) and serves as the rotor mount. It must be aligned along one side of the ladder at the top of the extension section.

    You place the ladder on its side (using two saw horses as the table) and center the pipe in the flange wells of the ladder side. Plumb the pipe to the ladder side by aligning through equal distance measurements from one flange or the other, and hold the U-bolts over the pipe, which is also being held in-place, and mark the shank ends as in the Ladder Tower base u-bolt alignment procedure.

    Use a center punch to determine the center of the markings and drill through the side, afix the U-bolts and pipe, and mount the rotor on the pipe (use standard rotor alignment procedures). Figure 4 illustrates the rotor in final placement.

    Figure 4 Final Stand Pipe and Rotor Configuration

    The Ladder Tower is now ready for final installation against the overhang. It is an option to install the antenna(s) and mast into the rotor prior to attaching the Ladder Tower to the overhang. The most important part of the procedure follows:
    1. Place the Ladder Tower (in the nearly down position) between the base stand pipes and against the overhang.
    2. Align at the base, and between barrel bolts.
    3. Install U-bolts at base; close barrel bolts; tighten all fixtures.
    4. Follow rotor alignment procedures (set to North; install antenna(s); mast)
    5. Tie-wrap cabling to ladder extention as desired; raise extention.

    The installation illustrated in Figure 1 depicts three antennas:
    1. A 3-element six-meter lightweight yagi.
    2. An 11-element 432 MHz short boom Yagi.
    3. A 10-element 144 MHZ short boom yagi.
    Other antennas might include:
    1. A Dou-band UHF/VHF Yagi in place of the two discrete 144/432 MHz Yagi's, or mount it vertically below the other antennas, or by itself for FM use.
    2. A vertical base antenna for 146/440 MHz atop the mast.
    3. An offset mast attached to the other ladder side top to accommodate a non-rotatable short ground plane, or a Wi-Fi Yagi antenna.
    In any use, this Ladder Tower should prove to be an inexpensive way to improve your lot in VHF/UHF operating without creating what some may consider an "eyesore" of "too busy an installation" for the neighborhood. No guys, no incredible height-getter; just a modest, practical effort to expand operation. Isn't that what we all want; to operate?

    :eek: and dont forget to GROUND the tower to Ground :eek:

    I hope you will benefit from this presentation.
  2. VE6WTF

    VE6WTF Ham Member QRZ Page

    that ladder coulda gone up another 6-7 feet!!!!
  3. N7WR

    N7WR Subscriber QRZ Page

    He must live in a very low wind area---if not that thing is going to come crashing down at some point.
  4. NA0AA

    NA0AA Ham Member QRZ Page

    I liked this the first time I saw it. It seems to address pretty much every possible objection to a temporary erection problem. AND you can work it from more or less ground-level which is always a bonus.
  5. NA0AA

    NA0AA Ham Member QRZ Page

    I thought about that, but if you lowered the extension, it's probably barely loading the house at all - and you of course could guy it.
  6. K2COM

    K2COM Ham Member QRZ Page

    After looking at it and reading n7wr's post I agree to a certain point. I would however make some adjustment to where it is attached to the home as we get winds that gust up to about 30-40 mph at times, not steady or always, but they do happen. The slide bolts are nice because of their price but they are not really grabbing all that much of the ladder. He should have put some sort of solid bracing around the top instead of the slide bolts. Then again this is my thinking and am still new so I could be completely wrong.
  7. N4HLF

    N4HLF QRZ Member

    Look at the length of the mast to the small rotor. That rotor looks like it was designed for a TV antenna or small beam.
    One gust of wind and that rotor is history.
    The mast is too long to support all those antennas.

    Reminds me of my neighbor across the street who put up a 10X20 ft canopy to cover his car.
    He had the 6 support legs just sitting on the ground instead of cementing them in.

    We were making bets on how long it would stay that way. 3 days later we got a thunderstorm
    and the wind blew it on its side and turned it into a pretzel.

    Next morning it was on the curb waiting for the garbage man.

    Howie N4HLF
    Last edited: Feb 1, 2009
  8. W8ZNX

    W8ZNX Subscriber QRZ Page

    what is old is new again

    remember about 30 years ago Paul Lee N6PL
    was using a 40 ft ladder as tower / vertical

    did not house bracket it

    was set up stand alone
    guyed 4 ways at 3 hights

    called it his mark 4 vertical

    can see photos in some old CQ mag
    and his vertical antenna handbook

    he did not have a few vhf uhf yagis on it
    he put a big hy gain triband hf yagi on top

    Last edited: Feb 1, 2009
  9. W6CD

    W6CD Ham Member QRZ Page

    Drive on ladder tower

    Here are pictures of a drive on ladder tower - as used at the 2008 CA QSO party
  10. KF6A

    KF6A Ham Member QRZ Page

    At one time I used a radio shack tv antenna rotator and radio shack masts to support my homebrew 3ele 10m yagi. Surprisingly it survived more than one wind storm and one in particular that had my R-7 bent over so far I thought it was going to snap. That wind storm blew down trees and fences around the neighborhood and did bend my radio shack mast but surprisingly enough the rotor still worked fine. :) I replaced the bent mast and all was well.

    Would I do it again? If that is all I had to work with I would.
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