Monday, June 16, 2014

Rebuilding: First Steps Upward

Since describing the tear down of my antennas and towers I have made progress towards the next phase of my suburban mini-antenna farm. But first a word about just how "deep" I went with my tear down.

The bases for both the guyed Golden Nugget tower (supported the multi-band dipole and 40 meters delta loop) and the house-bracketed mast (supported the multi-band inverted vee) were constructed from preserved wood. There are two layers of 4x4's nailed together, with just a bit of the top layer -- the platform -- projecting above grade. My reasons for using floating bases of this type were discussed in an article last year, so I don't need to go into details here.

Although the lumber is rated for ground contact there are many grades of pressure-treated wood preservation. Not all do well when you ground-contact rated lumber is buried. I have some experience with this since I have a 22 year old retaining wall built from 6x6x16' burial-rated lumber which I repaired earlier this spring. It's amazing how well it can endure, typically surviving better when fully buried than when exposed to sun and air.

With this in mind I dug up both preserved wood bases for inspection. My intention was to replace them if necessary or, if in good shape, to modify them to accommodate the new towers.

You can see the imprint of the Golden Nugget tower base in the exhumed platform. Although quite dirty the base is in excellent condition after being planted in the ground for one year. The other base (not pictured) was also in excellent condition.

Both bases are reusable and expandable with additional logs on the top layer. I doubled the number of logs in the top layer of the larger Golden Nugget and put it back in the ground in the same location. This will serve as the base for the guyed DMX-52. The position is important since I will make use of the same opportunistic guying for this tower as the last one.

To erect the Golden Nugget tower I attached it to the house using the same brackets I installed for the pipe mast. This too required adding logs to the base previously used to support the house-bracketed pipe mast. What took some time was manouevering the tower so that the improvised bracket arms could be properly attached and to place the tower close to the eaves (for roof access). The position of the arms has little room for adjustment since they are bonded to the house. This is not something I wanted to redo.

As the picture shows I was able to accomplish the job. It's not particularly pretty at present although I plan to clean it up somewhat. U-bolts attach two of the tower legs to the arms labelled A and B. These are the original ones used to support the pipe and mast for the inverted vee. The arms are commonly-available galvanized, large gauge angle steel that comes pre-drilled.

That third section of angle steel (C) might look redundant but it plays an important role. Without it there is insufficient resistance to lateral motion (parallel to the house wall). That is, the arms bend. While not initially dangerous there is a risk that over time fatigue weaken arms A and B or their attachments into the wood frame of the house. Wade's purpose-built bracket is a single V-shaped steel arm that achieves both objectives. The 3 improvised arms in combination achieve the same result. When installed the tower became rigid.

I will modify the bracket later to improve its appearance and to tie the third tower leg to the bracket. As currently built the rigidly is solely due to the strength of the bolts (and lock washers) tying C to A and B.

Although this tower in its present state is able to support an antenna I am not going to put one up just yet. That would only distract me from the important task of completing both towers.

The enlarged base for the DMX tower, with tower attached, is shown in the picture below. You can get an idea of how the tower will be secured to the base from looking at it.

The heavy-duty corner braces support the full weight of the tower, and those braces are bolted into the platform. The bolts hold the tower's position but do not actually hold the tower up. That is done with guy wires. There will be two set of guys wires.

However this is far from the full story. If you think about it you should be able to come up with several shortcomings with what I seem to be doing here. I deal with these in a future article.

Rope is used for the present in preparation for raising of the third section. The bottom two sections (16' and 100 lb) were walked up to a vertical orientation atop the base. This was easy to do myself since, although I can only reach up to ~7' (less than half way up) a tapered tower is bottom heavy.

Once the third section is lifted into place the first set of guys wires will be installed at the 23' level, which is just below the top of the section. I'll have more to say about guying in a later article. I am using a conventional guy station at the top of the fifth section and an improvised guy station at the top of the third section.

Further progress in the raising of towers and antennas will have to wait. For the next two weeks I have other responsibilities to attend to. I expect to get back to the towers and the blog at the end of June.

Friday, June 13, 2014

Renewing Old Hardware

In many cases it is more economical (time and money) to buy new hardware to replace rusted and damaged hardware rather than to repair the old hardware. Since most of us purchase used towers, antennas and related paraphernalia that must endure the elements we often face this question.

When it comes to hardware that is non-standard it can be quite expensive to replace since the only source is the original manufacturer. Such is the case with many towers, which I why I cautioned about this point in my recent article on buying used towers.

If you prefer to renew old hardware rather than spend money on new, expensive replacements, read on. In many cases it is possible to do so with a modest investment of time. What follows is how, earlier this week, I renewed the tower bolts on my used DMX-52 tower.

You'll need a few tools:
  • Tap and die set. No do-it-yourself'er should be without one of these. You say you have no need of one? You're wrong. Although their primary intended purpose is cutting threads in metal stock -- taps for interior threads and dies for exterior threads -- they work wonders on old, damaged threads.
  • Wrenches. To hold the nuts and bolts being cleaned.
  • Machine oil. Used to reduce friction and heating on the cutting surfaces of the taps and dies, and to recoat them afterwards to inhibit rust. Even when just used to clean rust the hardware and tools can get surprisingly warm. The temperature of the working surfaces is much higher, which can damage the tool and hardware if cutting is done dry.
  • Grease. To protect the hardware after renewal.

I bought my tap and die set many years ago (upper right in the picture). It has a wide range of matching taps and dies up to ½" SAE and equivalent SI. It's important to correctly identify the thread pitch before applying the tool to the hardware. In the case of the DMX bolts there are two thread diameters: ½" and ⅜". The thread pitch is NC (National Coarse) so if you use the NF (National Fine) tools the hardware will be ruined.

Apply a bit of oil to the cutting surfaces of the tap or die and carefully thread into the nut (or onto the bolt). If binding occurs you probably haven't properly aligned the tool and hardware. Back off and try again. Once you have positive traction with the tool use a wrench on the hardware and use moderate force to cut through resistance offered by rust or bent threads. On the bolt be sure to advance the die right up to the head.

If you've done it right you'll find that the nut or bolt can be unthreaded from the tool with just your fingers. The cleaned nut and bolt will thread together without appreciable resistance. The elapse time to clean each nut or bolt can be as little as 1 minute, but don't rush matters if you are inexperienced with these tools.

In the picture you can see the rust and debris cut from the just-renewed hardware. The pile grew larger by the time the full bag of hardware was processed. Loose debris left on the tools and hardware after cutting should be brushed off.

Once cleaned and checked the bolt threads (and, optionally, all surfaces) should be coated with a durable, outdoor-rated grease. I use white lithium grease. It's inexpensive, easy to apply and clean up, has a wide temperature range and is good at repelling water. My 500 gram tub of grease is practically a lifetime supply. I also use it in rotators, where it has proved durable and compatible with -25° C temperatures.

Grease on the threads will not result in the hardware loosening over time if the hardware is properly installed on the tower. That requires applying sufficient torque to enable the lock washer to do its job of preventing hardware rotation during the lifetime of the tower.


It is not my intention to provide a tutorial on the care and use of taps and dies in this article. You should learn how to use these peculiar tools from someone knowledgable or (if you're careful) books or internet resources. The cutting surfaces are fragile, very sharp and can be damaged (or injure you or damage hardware) if not correctly applied.

The tower bolts I am renewing are Grade 5 strength. Although the taps and dies are harder yet you should be aware of the potential for damage if the tools are of unknown quality or the hardware is of unknown strength.

There is less risk in this specific case since we are cutting rust and debris, not the high-strength base steel. Oxidized steel (rust) is relatively soft. It also has greater volume than virgin steel, which is why rust seizes threaded hardware. But this is also why it can be removed by the method I've described.

Saturday, June 7, 2014

Reset...and a QRP DXCC Milestone

It's time for a reset, and some reflection. As the picture below shows, all of my antennas and supports are down. The time investment was 6 hours spread over the past week, which is a lot less time than I spent putting them up!

All of this antenna and support removal is in preparation for the raising of my recently acquired 14 meters tall new (used) tower. But it's more than just that. I decided that the mast that supports the multi-band inverted vee would also come down since, although it works much better after making improvements, it is inadequate for the longer term.

Of course this means I am QRT for a little while. Since it's summer I am perfectly fine with this. If I survived being QRT for 20 years I can manage a few more weeks.


Before I discuss my rebuilding plans I want to mention that I did succeed at reaching a milestone, a stretch objective I set for my small QRP station. I have now worked over 200 DXCC countries over the past 18 months.

I was stuck at 198 for a while when in the space of 48 hours I worked 3 more: A3, JY, 9G. Although I have worked some SSB -- mostly during the WPX contest this spring -- all 201 countries are on CW, using no more than 10 watts (5 watts in contests). It goes to show what can be done with a small station. Of course it wasn't easy, but what's the fun in making it easy?

Even so it is time to look onward and upward. I am not philosophically bound to QRP and small antennas.

Tower and antenna plans

By this fall I expect to have a more competitive station for DX and contest operating. I will begin with supports and antennas, and then, but I have yet to decide when, increase power to 100 watts. I purchased a 35 A power supply this spring as preparation. I have pretty much put the refurbishment of my venerable FT-102 off into the unknown future, if ever, and will look at purchase of something more modern. Newer rigs are just too attractive to overlook with regard to features and performance. The FT-102 has a truly great receiver but its time has come and gone.

The plans for my new suburban antenna farm are evolving. I will be assessing options even as I proceed to raise the new support structures.

DMX-52 tower:
  • The first task is to erect the DMX-52 tower. It will be guyed in the same fashion as the Golden Nugget tower it replaces in the same location (Site C). I am well along in preparatory work, of which I'll say more when I am further along. You can see a bit of this in the picture at the start of this article.
  • My objective is to place a 3-element tri-band trap yagi on top of the DMX-52. I am waiting for the right used antenna to come along. I am endeavouring to keep the tri-bander wind load below 4.5 ft², which is why my TH6 will remain in storage. I'll probably turn it with my ancient Ham-II rotator. The rotator has been well-serviced (by me) in the past and has upgrades, including a steel ring gear. The only other rotator I own is a underpowered for what I am planning.
  • I would like to stack a small 6 meters yagi on the tower. If I do this it'll be a cut-down 3-element version of the Cushcraft A50-6 I have in storage. (The 1λ boom of that antenna served as the upper half of the house-bracketed 14.5 meters tall mast for the inverted vee.) Since the DMX tower is 14.1 meters tall and I have to keep everything below 15 meters to remain exempt from municipal involvement stacking will be a challenge. Modelling will help.
  • For the interim I will likely reinstall the 40 meters delta loop on the tower. It will need to be lowered about 2 meters from its previous apex of 14.9 meters and "squashed" a bit to keep the bottom from becoming a safety hazard. I could reshape it as a narrow diamond loop, but only if the interaction with the tri-band yagi is small. I will use EZNEC to determine the potential extent of interactions. I would like to have a 2-element loop array but only if I can manage the interactions with other antennas and the tower. This will be challenging.
  • Further crowding the tower will be an antenna for 80 meters. My current plan is an inductively-loaded half sloper. Loading is needed due to the low height of the tower. This antenna can be an efficient and effective DX antenna since it is vertically-polarized and the current maximum is at the top of the antenna, not the bottom as in most 80 meter monopoles. This is antenna that will require modelling, including the capacity-hat effect of the yagi(s).
  • I am playing around with the idea of resonating a modified yagi boom on either 30 or 40 meters. Other hams have accomplished this with some success. The elements become loading elements of the lower-band dipole, and the yagi performance is not affected because the antennas are orthogonal. I can only work on this after the yagi is bought and installed.
Golden Nugget tower:
  • The 30' Golden Nugget tower will be house-bracketed in the same place as the steel & aluminum mast I just took down. In addition to being stronger and more reliable it will allow me to work on antennas and access the upper roof of my 2-floor house without ladders and pulleys. An added benefit is less wear on the roof shingles.
  • The multi-band inverted vee that was supported by the house-braketed mast will not continue in the same form. One alternative is to replace the 15 meters element with one for 40 meters. This would allow continued resonance on 15 and give me a better antenna for short-paths on 40. The latter will help me in contests I need to work the US, especially the QSO-rich northeast and mid-west. 
All this said my first priority is to get the towers in the air. Once I've done that I'll check their performance in wind and violent weather before putting up any antennas. However I may put up a dipole just so I can do some operating during the early summer.

I'll next post another article on this blog when I've made progress in executing my plan, or if I learn something interesting from the modelling of antenna interactions.