Thursday, October 12, 2017

Bad Vibrations

When we think about fasteners for antennas perhaps the most common questions are about stainless steel and yield strength. There is more to it than that. This was brought home to me recently when I went up my Trylon 70' tower to remove a wire antenna, to do a general inspection and to plan coax routing improvements for the Hy-Gain TH7 and the Cushcraft A50-6.

That's when I saw the following on the TH7. Can you see what's wrong?

The splice bolt holding the boom sections together has lost its nut and lock washer and had worked itself halfway to freedom. The one on the other side of the boom was not quite as bad since the nut had loosened but not yet fallen off. Left uncorrected the boom would soon be held together only by the tension of the boom truss. I put other projects on hold since this called for an emergency repair.

The bolts were out of reach and the antenna could not be easily rotated due to its weight and the 6 meter yagi stacked above. A closer visual inspection uncovered other problems. The antenna had to be lowered to the ground for a full maintenance overhaul despite having been up for only 4 months.

Obviously I had made mistakes. I was in a rush at the time and took a few shortcuts. Nothing serious, or so I thought. Or at least nothing that couldn't be remedied before winter, which was my plan and why I did this inspection climb.

I had several days leeway since I had to wait for helpers to resume work on the big tower. Once the weather was cooperative I rigged the tower for lowering the antenna with my lawn tractor. It came down surprisingly well considering I did it myself. I was able to handle the tag line while the tractor rolled forward.

Once on the ground I gave the antenna a thorough inspection. The number of problems was depressing. Just because I write a blog about towers and antennas does not mean I do every job perfectly. Far from it. I make mistakes and I take shortcuts like any ham.

First about those boom splice bolts. There was an interior start pattern lock washer on the one bolt that had not yet entirely unscrewed itself. Presumably the other had the same. Lock washers on round surfaces, especially small diameter tubes (2" in this case) don't bite well. I redid the bolts using the pattern for the Cushcraft XM240: lock washer under the bolt head and nyloc nut on the other end.

Before undertaking repairs I went to my favourite fastener store and stocked up on ¼" stainless lock washers and nyloc nuts. I had an interesting conversation with the clerk helping me out. He pointed out the labels they stuck on the stainless steel fastener bins: "beware of galling!" They'd gotten weary of dealing with irate customers who would try to return stainless fasteners that were over-tightened (excessive torque) and not lubricated. Careless handling can ruin a stainless steel fastener in an instant. I lubed the boom splice bolts before firmly applying torque.

Lubrication of fasteners

Lubricating the threads of a bolt (or nut) before use is often good practice. Aside from prevention of galling of stainless steel fasteners there are other benefits. One is that non-stainless, non-galvanized fasteners succumb to rust far slower when coated with grease, and grit has more difficulty being driven into the threads by weather. Later removal of the fastener is easier. Common grade 5 bolts and nuts fall into this category.

The second benefit is setting the correct torque. When nuts are tightened on a bolt some of the applied torque is due to friction in the threads rather than axial force of the thread surfaces. This results in increased risk of insufficient torque leading to future loosening due to vibration or thermal cycling. A thin film of grease reduces this risk by eliminating friction, without increasing risk of the parts "sliding" apart.

There are unique lubes available for every imaginable fastener alloy. Those are the best though not always necessary. A thin coating of a non-optimum lube is better than none at all. Most often I use white lithium grease. Over many years I've had good success with it. It's cheap and widely available.

Lock washers vs. double nutting

Writing about lock washers on round tubing reminded me of a conversation I had with a tower pro. He said that they are increasingly skipping lock washers entirely since they have had too many instances of lock washers failing in service. That is, they break in two. Whether this is due to the rigours of weather and stress cycling or washer quality wasn't made clear to me.

The alternative they and many others often use is to start with a flat washer rather than a lock washer between the work surface and the nut. After applying the required torque they then put on a second nut. The first is held with a wrench as the second nut is tightened. The claim is that the locking action is excellent and due to the nut being thicker than a lock washer there is less chance of fatigue failure or loosening.

I cannot vouch for whether this is indeed superior. It is a technique I've used in other applications with good effect but never on towers and antennas.


Most hams have experienced or are aware that yagi tubing elements are prone to high frequency oscillation when the wind blows. The sound may be audible and thence comes the name of the phenomenon.

Damping can be used to reduce singing, and eventual element failure from metal fatigue. Old Hy-Gain mono-band yagis are especially notorious in this regard. Rope inserted in the elements is a common method of mechanical damping. Newer Hy-Gain element tips are roped. This may be inadequate.

15 meter reflector (second element from the end of the boom) singing in the wind

I mention this since during my inspection of the TH7 I discovered that the 15 meter (mono-band) reflector was singing, even though the tips are roped. After lowering the antenna I reconfirmed that the ropes were in place. None of the other elements was singing at the time or during a later climb. I find that the trapped elements are more immune from singing, likely due to the tube diameter transitions from small to large to medium around each trap.

I decided to leave the damping alone for now. The singing was intermittent rather than continuous so it may be that the tip ropes alone keep metal fatigue under control. I will check again next year.

More problems

There were additional mechanical problems with the TH7 that I had to address. Several of the boom-to-element clamps were inadequately tightened, and some bolts lacked a lock washer. They had not loosened: I didn't tighten them enough. A few of the elements had rotated on the boom a few degrees. This is not enough to be a problem, but it would surely become one in future.

I carefully tightened all the clamps and realigned the elements. Or perhaps not so careful since I managed to miss one of the driven elements. The driven elements are close to the tower so this oversight was easily remedied.

When the TH7 first went up in June I noticed that the SWR minimums were at higher frequencies than expected (per the assembly instructions) on 15 and 10 meters. I rechecked all measurements. I discovered a few small (< 1") errors and that the first 10 meter director was 3" off its correct position on the boom. By placing the antenna 6" higher on the mast I was better able to route the rotation loops of the this and the 6 meter antenna above it so that they ran orthogonal to the boom and driven element phasing harness rather than parallel.

The SWR problem did not go away. I tested it with an analyzer at the antenna. The ancient RG213 feed line show a small amount of age-related irregularity and could affect the measurement. I now suspect the balun since the pattern of the TH7 seems to be fine; that is, it is a feed point problem. I will test that hypothesis later by attaching the analyzer directly to the feed point.

While the TH7 was off the tower I measured the SWR of the A50-6. It improved a small amount. This is evidence of unwanted mutual impedance that could be affecting 6 meter performance. This is not unexpected for yagis with 20'+ boom separated only 7' on the mast. I plan to push the A50-6 higher up the mast to reduce coupling. But not right now.

The TH7 boom truss mast support that I cobbled together from spare parts was unstable and ready for replacement. I had done this because not all the original parts for the truss came with the antenna (I bought it secondhand). I constructed a better support bracket and installed it when the antenna went back on the tower.

Hopefully no more distractions

Trouble on the Trylon was not accounted for in my fall antenna and tower planning. Luckily the cost in time was not excessive. What it did was pretty well push me off the air for close to two weeks, and missed one contest I had intended to operate: the California QSO Party.

Now it's back to work on the big tower. Progress has gone in bursts depending on availability of friends for ground crew. I am gradually getting closer to having antennas nice and high.

Monday, October 2, 2017

Hanging a Top Loaded 160 Meter Vertical From the Big Tower

There is a lull for the moment in activity on the big tower. Parts are on order, metal fabrication needs to be done and I need to wait for helpers to be available. Although I hate the delay this is an opportunity to get busy on other priorities, which are numerous.

One of these is an antenna for 160 meters. So I sat down to review my options and design something that will get me through the winter season. I decided to shelve my original 160 meter antenna plan as too problematic and time consuming to be undertaken this year, if ever.

A horizontally polarized antenna for 160 meters is a poor choice even with a 43 meter tower; that's still only ¼λ, far too low for effective DX communication. So it has to be a vertical. I could shunt feed the big tower, except that for SO2R and multi-op contesting use of the tower in this fashion pretty well precludes use of any of the antennas for other bands mounted on the tower. Besides which, with all the yagis and mast on it the electrical length would be longer and therefore less predictable. Radials have to be rolled up in the spring before the hay grows and the ticks return.

The trees near enough to be useful as vertical supports are under 25 meters height and near to other planned antennas or the power line. In any case I don't have a good way to send a rope and wire that high and through dense foliage. It's a solvable problem but not expedient.

Since my long term plan for 160 meters remains unsettled I am happy to pursue a temporary solution to get me through this coming winter and contest season. Doing nothing isn't an option since I am missing too many QSOs and multipliers with makeshift approaches such as loading my 80 meter inverted vee last contest season. I worked some DX (over 30 countries) with great difficulty, and almost all were contest super-stations.

I settled on a what is a fairly popular antenna: a wire vertical top loaded with a 2-wire capacity hat. It is effective, can hang off the big tower with long rope and is efficient with a modest number of radials. The design is also popular in vertical yagi arrays since multiple elements for multiple directions can be hung around a big tower. The tower serves as the driven element.

Basic design and potential problems

After some geometry and experimentation with EZNEC I settled on a design where the vertical is 21.3 meters tall and each half of the top hat 13 meters long. It resonates at 1.830 MHz, near the centre of the band segment for CW DXing and contesting. The 'T' is at an angle of 45° so that it can be placed 20 meters from the tower and the catenary rope tied off near the top of the tower. Impedance at resonance is 27 Ω.

The choice of distance from the tower allows enough space in the hay field for 30 meter long radials without the need for an extremely long transmission line. The area is to the southwest of the tower, approaching the stone wall surrounding the yard area, and overlapping the south guy anchor. The catenary rope will be tied off to a tree or a stake in the ground, which will be determined during final layout of the antenna.

Transparent 60 m diameter circle roughly marks the extent of the antenna's radial system

The antenna is easy to model, with a few cautions. The tower is grounded for lightning safety with a 10' long ground rod (9' in the ground). This cannot be directly modelled in NEC2 so I used the MININEC ground option in EZNEC. The impedance of the ground connection must be estimated and simulated with a resistance load at the bottom end of the wire representing the tower. The tower itself is simply modelled as a 30 cm diameter wire, which is consistent for a lattice triangular structure with 20" (50 cm) faces.

I tested the model with both grounds before adding the tower to identify any modelling anomalies. MININEC ground is required in the full model since the tower is grounded. The antenna is raised slightly above ground (20 cm) so that it and the radials can be modelled in NEC2. The 27 Ω resonance impedance mentioned earlier is from the real, high-accuracy ground option in EZNEC. Switching to MININEC ground the reported impedance drops 10% and the resonant frequency moves downward an insignificant 2 kHz (-0.1%). The reported gain also shows a small change due to ground loss differences in the two ground models. MININEC reports 1.0 db gain versus 0.4 db for real, high-accuracy medium ground.

Based on this comparison the antenna is remarkably similar with both EZNEC high-accuracy ground and MININEC ground. This provides some assurance that the full model that uses MININEC ground is useful and reasonably trustworthy.

The antenna and capacity hat are 14 AWG TTHN house wire. There are 16 30-meter long radials made of 24 AWG insulated copper wire that are tentatively planned to be the individual strands taken from stripped bulk data cable. With this many radials the system begins to show the characteristics of a non-resonant ground plane, so the chosen length can work well. More radials are of course better though not enough to justify the trouble for a temporary antenna.

The major difficulty using 24 AWG wire for radials is their fragility. I²R losses are negligible at 1,000 watts since the current divides among the radials. It is quite low in each, low enough to substantially minimize loss. It works out to a small fractions of a decibel.

There is no real need for the radials to be 40 meters long since the system is non-resonant, and in any case they are electrically longer due to the adjacency to ground which lowers the velocity factor (VF). A good place to learn more about this at N6LF's site where he has extensively documented his many careful experiments on low band verticals and radial systems.

Now, about that tower...

The antenna itself is unremarkable. Many hams use this or a similar design on 160 meters. There are enough of them out there to assure that it can work quite well. My model of the antenna confirms that and it appears reliable based my explorations with EZNEC.

Now we come to what is perhaps my greatest concern: the impact of the 150' (really ~143' or 43 meter) tower on antenna performance. Notice in the EZNEC model view above that there is significant current on the tower since, at 43 meters and grounded, it is resonant at or near the 160 meter band. Worse, the distance between the tower and vertical is 20 meter (⅛λ), an ideal separation for a 2-element yagi!

With only a single antenna for 160 meters I am concerned that if the tower acts too much like a parasitic element that the pattern will discriminate against directions that are useful for DX and contest contacts. When loaded with mast and antennas it will be electrically longer and may act as a reflector which will inhibit my ability to work Europe (northeast). That would be bad. Some hams use this effect to create a directional set of verticals surrounding a tall tower. Since I will have only one an omni-directional pattern is preferred.

Of course there would also be gain towards the southwest, covering the bulk of the US. This is not a great trade off since the gain is small. F/B is the greater concern. That's what yagis do.

Exploring the landscape

To investigate the range of possible outcomes I ran the full model while varying the height of the tower. This is not exactly equivalent to a 43 meter tower with a capacity hat (top mounted yagis) however as long as the effective (electrical) length is not too much more than the physical height the modelled results will be more than close enough to gain an understanding of the tower's impact. I need insight more than I need high accuracy.

I varied the height from 35 meters to 55 meters in steps of 2 meters. At each step I used the model to measure the gain, F/B, feed point impedance and resonant frequency (X = 0). The plot is quite interesting. Tower grounding (ground rod) is simulated by a 20 Ω load in series with the ground connection.

The first thing to notice is that at a shorter height the tower acts as a director element. Since the pattern is with respect to the southwest I show that reversal as a negative F/B, while keeping the gain relative to the main lobe. At 41 meters height the tower's action as a reflector is accentuated.

The true maximum F/B is very sensitive to tower height and my chosen steps of 2 meters is too coarse to show how high the F/B can go, which is in fact more than 12 db. On 160 meter a yagi has a very narrow effective bandwidth.

Azimuth plot for an electrical tower height ~43 meters;
almost, but not worst case for high F/B
Radiation resistance of the vertical dips sharply in the tower's "yagi zone", as expected. It gets as low as 12 Ω, or half its value in isolation. The plot does not clearly show the change in resonant frequency due to the scaling. It dips down to 1.810 MHz (-1%) when the tower is an optimum reflector then slowly rises to 1.820  (-0.5%) MHz. Up to 55 meters height it never quite makes it back to 1.830 MHz, its resonant frequency in isolation from the tower.

Of most interest to me is that the gain and F/B only gradually return to normal as the electrical height of the tower increases. With a mast projecting 3.5 meters above the tower and holding two large yagis this is what I can expect to experience. That is, a loss of 2 db towards Europe and a similar gain towards the US midwest. Anecdotal data from hams with a similar antenna is consistent with the model. There is little effect in other directions.

Impedance at the greater (electrical) heights is a respectable 21 Ω, a drop of only 10%. The antenna will need an L-network to lower the SWR from slightly over 2 at resonance. This is easy to build. Most likely I'll reuse the box for the 80 meter feed of my previous tower back in Ottawa. I'll do the design once the antenna is built and I measure the actual R and X values. The antenna's SWR bandwidth is good and will exhibit a good SWR across 1.8 to 1.9 MHz with a simple L-network at the feed point, provided the tower resonance is outside its yagi zone. L-network tuning is expected to change as yagis are added to the tower since that will change the mutual impedance with the vertical.

On to construction

This antenna project will go ahead later this month. It'll be done after the prop pitch rotator shelf and mast are raised to avoid the catenary interfering with the lift. I am also waiting to see whether my neighbour will bother to take a second hay crop off the field. There may not be enough there for him to take the trouble, so I am likely free to proceed when ready.

I am looking forward to operating 160 meters this winter. Never before have I had a good antenna for that band so it'll be a new experience. Most of my 160 meter operation in the past has been contests from other stations. I expect to have some fun bumping up my DX totals and contest scores.

Once the tower project is complete you can expect a return to more articles like this one, about antennas and operating. Building support structures is important but is not my primary interest.

Sunday, September 24, 2017

Raising the LR20 150' Tower (Part 2)

150' at last
When I left off in Part 1 the tower was 70' high and had the first two sets of guys attached. From here on upward required a change of strategy. The equipment I used to get this far was no longer suitable. I needed power and I needed additional help on the ground.

There are also considerations for working at height that are usually not required for smaller towers. The increase in difficulty and tooling does not increase linearly with height. That is, twice the height is far more than twice the challenge.

In this article I'll focus on the differences in technique to get from 70' to 150'. And get there I did, as you'll see.

Lifting power

Not having a suitable off-road vehicle or truck handy, unwilling to ask a friend to risk their vehicle, and unimpressed with the cost of renting or buying suitable power equipment I decided I would drive my low ground clearance car into the hay field to power further lifts.

With this much power and momentum the lift must be done carefully. A snag can result in damage to the tower, guys or gin pole. Slow lift speed is mandatory, as is a person on the tag line and everyone being very observant. The car was operated in reverse for maximum visibility and communication.

Testing vehicle rigging with my car
One important addition was a pulley as close to the ground as I could get it. The purposes of the pulley are to ensure the forces on the gin pole are entirely vertical and to allow rope attachment to the tow hooks, without risk to the vehicle body. The pulley was attached to a short length of EHS tightly wound on the concrete tower base and scrap lumber in between to avoid abrasion.

Cars are not tractors. I used fabric tow straps to be especially kind to the vehicle body and shackles for fast, reliable connection and disconnection.

I tested the system with my own car and successfully raised one section on my own. Notice that the car faces the tower and lifts in reverse gear. The driver has a full view of the area and crew communications is easier.
In addition to the tow hooks at either side my car also has a centre hook which was more convenient. On other vehicles we used the driver side tow hook since it puts the rope directly in front of the driver. There is no reason to centre the force on a vehicle for a lift of 120 lb since it has ample power and traction wherever you attach.

I had a few concerns with a vehicle lift. First was the hay field itself. I carefully chose a path that was free of surprises so that the driver can focus on the forward view. Second was what would happen when snags occurred during the lift. Again this wasn't a problem. There was excellent "feel" through the throttle when snags occurred. Nothing was forced and nothing was damaged. You simply drive forward and the crew assesses the situation and takes action. Third was my car's manual transmission. An automatic is far better at this task since the smooth torque adjustment avoids jerky motion and there is no risk of clutch overheating.

One friend suggested turning the vehicle off when not actively working despite losing the comfort of the air conditioning since catalytic converters get very hot and could start a grass fire.

In addition to tower sections we used power to lift the upper guys. They are heavy. For lighter items it was easier to used the same rigging and muscle, not a vehicle, to do the lifting. You simply pull the rope while walking away from the tower base.

Rope vs. steel

Lifting 150' requires more than 300' of rope or cable. The tag line must be as long as 200'. I had to make a decision whether to use steel aircraft cable or rope for the lifting. The tag line is easier, ending up as two 100' ropes joined with simple knot. Rope and steel each have their advantages and disadvantages. I'll mention a few of these here.

Wrap rope multiple times for easy knot removal
To meet my minimum working load of 200 lb (90 kg) I could use a variety of ½" diameter synthetic fabric ropes (1,200 lb breaking strength) or ⅛" aircraft cable (2,000 lb breaking strength). I already have that amount of new unused aircraft cable. The longest rope I had was 200' of ½" nylon. Aside from working load there is value in going to wider diameter (and expense) to avoid tangling and to lower breakage risk due to abrasion.

My ultimate choice was perhaps an odd one: ½" polypropylene twist rope. A 335' (105 m) roll was so inexpensive as to be disposable. It is also very light and easy to handle. The weight is a factor when one man is lifting the gin pole up a section with perhaps 250' hanging off the top pulley. Its bright yellow colour and thickness make it very visible. This is very helpful to spot problems before beginning a lift operation.

Steel cable and rope are weakened by knots and sharp bends. I used shackles to connect the tow strap to the car and to the rope for rapid connects and disconnects and to avoid rope damage from the sharp edges of the steel hoops on the tow strap. The rope is wrapped several times through the shackle before tying the knot so that the residual tension on the knot is small. Undoing the knot is easy in comparison to one traversal through the shackle where the full tension of the load can make the knot exceedingly tight and difficult to undo. If aircraft cable is used a thimble and at least two clips are required.

If you try this yourself with polypropylene twist rope there are a couple of things to beware of. First is that the new rope kinks easily, even when properly unrolled from the reel. Removing the kinks is aggravating. Once the rope has been under load the kinks tend not to return, so it is a short term difficulty. The second problem is that for long lifts the twist transmits a torque to the load. The person on the tag line will find it difficult to keep the load from doing a partial spin. With a light load where the rope has more freedom of movement the tag line keeps the load from spinning and tangling with the rope.

Braided rope is better though more expensive. But I wanted a cheap way to test a vehicle powered lift that may not have worked at all. Now that the rope has been "de-kinked" I can use it for tramming antennas and other tower tasks.

80' interlude

There was a delay after my test lift while I recruited and scheduled ground crew. The tower stood at 80' for more than a week. Meanwhile I was busy ordering more guying hardware. I had made a calculation order and found that I did not have enough pre-forms. Somehow I forgot to account for the guy section between the bottom strain insulator and the turnbuckle.

After looking over another ham's big towers and recalling an article I'd read somewhere I realized it would be a good idea to add another non-resonant segment to the upper two sets of guys. Otherwise the bottom segment could resonate on one of the low bands. Being so far out from the tower and more vertical than horizontal it would have no impact on tower mounted yagis, which is why I did not at first consider it.

The lower segments can interact with low band vertical antennas within ½λ and even 1λ. On 80 and 160 meters that would be a distance of between 40 meters and 160 meters. I decided to add a 43' section on those 6 guys to ensure no low band resonances with my planned locations for low band antennas.

Safety considerations

I will admit that I often free climb towers. That is where you climb a tower without a fall arrest system, relying solely on your hands and feet to climb and a positioning belt and lanyard to buckle in when working.

This is terribly unwise although most of us can get away with it when towers are of modest height. I know many hams who will never climb without a fall arrest system. It's slower but safer. Climbing (and descending) 150' takes a long time and can tire you if you are not fit and fresh. Mistakes happen when you're tired.

This tower was a call to upgrade my safety equipment. First I did research online and in stores and talked to professionals who told me and even showed me what they use and the advantages and disadvantages of various systems. Provided the equipment was certified for tower use it mainly came down to comfort, fit, money and convenience.

My fall arrest harness is typical, middle-of-the-line equipment. I purchased it from an Ottawa store that caters to trades and utilities, and stocks a wide range of products. The salesman was able to discuss their features and then let me try them each on. Since I climb in every season he recommended the grommet straps so that I can adjust the harness each time to accommodate one or many layers of clothing.

After several weeks use I can say that I quite like it. The double lanyards are large enough to grasp almost all tower steel yet are easy to manipulate. The positioning belt goes over the harness. I learned the importance of placing tool pouches and other appurtenances out of the way of the long lanyards.

There is more to safety than a fall arrest harness. Communication is slower and more garbled between rigger and ground crew. I make a point of rehearsing procedures with my crew and ensuring that they know how to use the tools and equipment involved. A fellow ham loaned me a set of portable radios for communication, which we didn't use. Hand signals were faster and easier. Just be sure everyone knows what each signal means!

Hard hats are mandatory for ground crew and most often on the tower when there's steel overhead. I dropped enough parts and tools to make everyone a believer! Heavy duty work boots and protective clothing were strongly recommended for everyone on site. That amateur radio is a hobby is no excuse for a casual approach to safety.

Having a crew is mandatory

I can raise towers on my own when I have to. Doing so isn't advisable due to the lack of backup, the need to make minor adjustments by climbing up and down the tower multiple times and too much reliance on tools and machines. Most of the Trylon was raised on my own and smaller towers I have often done alone.

I had occasional help getting to the halfway point with this tower, and that is as far as I could go without a ground crew. My experience is that when the height is over 20 meters a crew is mandatory. Doing without is a serious safety risk. Experience and expertise are not enough. Don't work alone!

Important tasks that the ground crew perform include:
  • Driving the vehicle doing the lifting.
  • Using the tag line to guide the load around obstacles.
  • Rigging sections and other items for lifting, then retrieving the haul rope.
  • Pulling guys for connection to the anchors.
  • Several pairs of eyes looking out for problems and to alert others.
When it went really well I could climb the tower once to attach multiple sections and guys, leaving all the work on the ground to others. I am fortunate to have friends who can come out to help. It isn't easy for them since my location is far away from everyone.

Most of my crew are retirees since they have the time and enjoy lending a hand. All have been hams, from contesters to casual operators. To acknowledge them I'll list them here, in chronological order:
  • Brian VE3CRG
  • Geoff VE3KID
  • Craig VE3OP/VE3KKU
  • John VE3NJ
  • Don VE3DQN
  • Mike VE3ZY/VE3FFK
Others near and far provided advice and recommendations along the way based on their experience building and maintaining large antenna farms. Most notable has been John VE3EJ. No ham is an island.

Commercial alternative

When for a time I was having difficulty recruiting a crew and my new lifting system was untested I contemplated having the rest of the job done commercially. Indeed friends encouraged me to do so. Quotes were solicited.

There are several types of commercial entities you can turn to for help. The differences are significant and interesting. They are, in descending order of expense:
  • Professional firm that serves the public wireless industry and private wireless systems. They provide the crew and equipment while you watch and write the cheques.
  • Individual rigger on his own time or as a business. In the former case the work is done on weekends. You provide the ground crew or they hire and you pay.
  • Ham supplier who sends someone out who may be no more experienced than you. But at least the assistance provided is helpful. Make sure they're insured against hazards.
The first option is the best and safest, and is the most expensive. There are numerous certifications and safety practices they must comply with. This means a bigger crew and carefully executed process that adds man-hours to the project. The last option is, in my opinion, the riskiest. However all can result in a successful project.

A big challenge with the commercial option is that all material must be prepared in advance. Guys must be fully assembled, all parts must be on hand, machined steel components must be ready to go, and their equipment must have safe access to the site. This is difficult for the typical ham to manage, and I am no different. Miss something and you pay while the crew sits around or leaves and come back another day.

If you have the money and you want a painless path to a big antenna farm by all means call the professionals. For myself I prefer to do and learn by doing. That's part of the fun of amateur radio. Dangerous, too, but then so is the inside of a kilowatt amplifier. Do what works best for you.

I dropped the tag line to take this picture of how the lift is done. Craig VE3OP worked HF during idle periods.

Lifting technique -- getting to 110' feet

Me at 90' (Credit: VE3OP)
During the time that hurricanes Harvey and Irma were devastating the southern US the weather here was unbelievably pleasant. After a record breaking wet spring and summer the skies in September cleared and for nearly three weeks not a drop of rain fell. The only downside was the masses of biting insects that often made working in the hay field torture, especially in the hours after sunrise and before sunset and any time in the shade. Everyone dosed themselves with insect repellent.

Aside from being terrorized by black flies and worse this was perfect tower raising weather. I rushed to capitalize on it. I called in favours and enticed friends to visit. Things began to move quickly again. First to arrive was Craig VE3OP. Between the two of us and his SUV we lifted three more sections into the air one fine Sunday afternoon, taking me to 110'. His careful handling of the vehicle ensured the smooth lifting and bolting in place three more sections.

I handled all the tower work. With only the two of us I also served as ground crew for the lifts. This involved moving and rigging the next section, riding the tag line and looking out for trouble. Once the section was in position at the top I transformed into the tower rigger. I would climb up, work with Craig to slip the sections together, bolt them in place and finally move the gin pole up a section.

Above 100' the view becomes quite impressive. On lower towers the view is often not great since you are typically not much higher than the trees. Even so I only gave the horizon the occasional brief glance. Time was pressing and my crew was waiting. Sightseeing can wait for another time.

In the picture above right I am seen splicing the tenth section. Aside from splice overlaps this put the tower at 100' (really ~96'). I like to say that a tower is similar to dimension lumber. That is, a 150' tower is 150' the same way a 2x4 measures 2" by 4".

VE3NJ (on the left) and VE3DQN
The next day I completed the third set of guys for the 105' level by lifting them in sections that were not too heavy. I then drew them out to the anchors and got them roughly tensioned and the tower aligned. By then it was late afternoon and no amount of repellent kept the insects from feasting on me. I ran for cover.

Higher yet

I was in a rush to get the 105' guys installed since I had earlier arranged a two man crew to assist me the next day. It was necessary to get the tower tensioned and aligned before they arrived. To my surprise I discovered more settling in the 70' guys so I had to readjust those before finally drawing in the upper guys. This happens. Professionals always make one or two post-installation visits to align new towers. Since I was doing this task myself it takes one or two hours.

The new crew were John VE3NJ and Don VE3DQN. Both are occasional contesters. With their help (and John's car) we raised 3 more sections, taking the tower to 140'. I positioned the gin pole for lifting the final section and called it a day. We were all tired and the sun was going down. The insects once again swarmed in the waning daylight.

Over the next few days I adjusted the guys and tower alignment and then raised the tension in the 105' level guys close to their final value. I had kept them ~500 lb until I was satisfied that the tower was properly aligned and the guys were unlikely to relax any further.
14th section ready
for splicing

Returning the lift rope to the ground became a problem. The weight of the latching hook and tow rope used to connect to the load were not enough to keep it from tangling or being blown over the guys. John suggested tying the tag line to the hook and letting them pull it down. A great idea that worked well.

The tag line on long lifts must be very long. If the person handling the line is too close to the tower the angle of the rope is near vertical and the load cannot be effectively steered. The 200' tag line made it possible to stand far back from the tower to allow control of the load without unwanted stress on the gin pole.

Unfortunately that distance made it difficult for the tag line handler to see how close the load was to the tower, guys and gin pole. The car driver was worse off being further distant. When I was up the tower for the lift I gave feedback on how the lift was going. On the ground I did the same by standing closer to the tower to see what was happening overhead. This is hard hat territory.

The view from 140' towards Japan (north-northwest). South end of that field will be getting an 80 meter array.

Read the fine print

On the top set of guys I added a non-resonant section at the bottom to prevent 80 meter resonance with vertical arrays. When they were attached to the tower I came down to complete the guying. I attached the reel of guy cable to the bottom insulator and my two-man crew pulled the assembly towards the anchor where I was waiting with the come-a-long.

But it was too long! The insulator passed the anchor. How could I have made such a calculation error? The specification for the tower said that the top guys would be 207' and since I attached them 5' lower this should work out to ~203'. Yet I had only ~190' of guy to the bottom insulator. This was embarrassing. I told them to wait while I raced indoors to recheck the manufacturer's dimensions.

It did indeed say 207'. Then I saw the fine print above the table. It was difficult to read since this was a PDF document made from images of the ancient paper document. The note said that all guy lengths include an additional 15'. Ouch!

I removed the pre-forms and bottom insulator and continued with guy attachment. I suppose the lesson is to read the fine print or ignore the table and do my own calculation. The extra 500' reel I ordered was not needed. Perhaps I'll use it on my next tower.


All towers move. Self supporting towers achieve their lateral stability from taper. Think of how much more resistant you are against a push when you stand with your legs apart. These towers will certainly move a little side to side when fully guyed. Lighter duty towers will unsurprisingly experience greater lateral motion for the same force.

Many find the motion at the top of a self supporting tower. You get used to it or you don't, so it seems to me from my own experience and that of many other hams I've known over the years. Indeed that motion on self supporting towers is a common explanation for why some hams choose not to climb.

Guyed towers move differently due to the use of straight sections. A self supporting tower made from straight sections moves far more than a tapered tower, at a frequency dependent on the tower structure, its height and the weight at the top (mostly you, the climber). Think of it as an inverted pendulum. It can be disconcerting. I know it was the first time I experienced it.

A guyed tower wobbles in this way as it extends above a guy anchor during construction, which only disappears once the next guy set is tensioned. It can be worse above the second and higher guy stations since the top guy station acts as a fulcrum where the tower below bends like a bow and can sustain an oscillation for longer by whipping the upper unguyed segment back and forth. I've known professionals who hate the experience.

The wobble is not a hazard unless it causes you to react inappropriately or you experience discomfort. Avoiding jerky motions reduces wobble, so move slowly if the wobble bothers you. One curiosity I experienced is that the rhythmic operation of a ratchet wrench on the splice bolts can cause an oscillation. This can be remedied by stopping for a few moments or by speeding up or slowing down arm motion to avoid the tower's resonant frequency.

Once the tower is complete there is no wobble, but there is vibration. A steel structure under tension experiences relatively high frequency resonances. These come from the forces of the guys and the tower itself. As you climb lower, with more tower overhead the vibration can take on an almost ominous aspect. Although there is little motion you can sense from those vibrations the tremendous force the tower is dealing with. Respect it.

Final alignment

After pulling in the top set of guys and aligning the tower I called a halt. The misalignment at 70' persisted and I wanted to deal with that before going to full tension on the top guys. The next day I took a slew of measurements and discovered a few anomalies. Most concerning was tension inequality among the bottom guys. One of them was at 1,300 lb. This was unexpected.

My conclusion was that the difficulty might be at 35', not 70'. My hypothesis was that when I tried to pull the 70' level north to get the tower vertical I was fighting the guys at the 35' level, resulting in higher tension in the southward 35' level guy. I did a little more viewing of the tower from various positions and felt more certain of that, but also hesitant to proceed. There is a tremendous force on the lower part of the tower now that it's full height and the guys tensioned. This is not the time to make mistakes.

Instead I emailed someone who would understand the situation and either reinforce my plan of action or suggest an alternative. His advice was pretty good, and I followed it:
  • Starting from the bottom use a transit (or suitable alternative) and get the tower centred on the base (vertical alignment).
  • Don't worry about the guy tension until this has been done for all guys.
  • The tower should now be straight and vertical.
  • Adjust tension of all guys to specification.
At that point the tension of all guys ought to be equal, within the accuracy of the tensiometer. As he reinforced, to do this properly really requires that the tower be vertical and a transit is needed to be sure.

I followed his prescription and had success. One important change from my earlier method was to align the tower by the centre pin, not by the legs. Doing this made the 35' level misalignment apparent. Since I stuck it with my poor man's transit the tower may not be aligned to high precision. But it consistently tests and views as straight and vertical and that's more than good enough to allow me to continue with my project.

Cleaning the rat's nest

At the end of the alignment process there is a bit of a rat's nest at the anchors. This is obviously the work of an amateur!

Notice how the turnbuckles are not equally threaded. When the tower is aligned by the professionals this doesn't happen. The pre-forms don't go on until the tower is fully aligned and the guys at the correct pre-load tension.

Without all those expensive tools more post hoc adjustment is required. The picture was taken with the tower aligned at the 145' guy level and before full tension was applied. There is still a sacrificial pre-form on those guys, and they are not fully wound to allow easy removal. This is not a risk since even without the top guys the tower is strong and stable; without antennas present the tower is only supporting its own wind load, and the weather continued fair.

Steel rods are inserted through the thimbles to prevent the tension in the guys from changing. Turnbuckles and guys can unscrew themselves, and even a few rotations will ruin tower alignment. Once the guys are complete the turnbuckles will be locked with a length of EHS threaded through both the screw eyes and the turnbuckle bodies to prevent rotation. The turnbuckles will be painted or cold galvanized since the galvanizing on these old parts is no longer pristine.

I would prefer to redo many of the guy terminations to place the turnbuckles screws at their midpoint. As they are right now there is less adjustment room, and some would argue that more thread should be inside the turnbuckle for safety in case of thread abrasion or corrosion over time. It is not an immediate threat, if a threat at all. I am deferring this task. It is good practice to replace pre-forms that must be unwrapped.

150' in perspective

I'll close with a picture of my 70' (20 m) Trylon from the new tower. It provides an interesting perspective on what being up 150' is like. Consider that a tower of that height with a small stack of yagis is more than what most hams have. Put another way, you have to be a little bit crazy to go this high.

The tower is as yet unadorned, not even so much as a mast. That's coming up.

Thursday, September 21, 2017

Administrivia -- Spam and Other Things

Blogger is free but it isn't problem free. Recently the amount of spam coming into the comments has significantly increased. In a way it's educational since I can study the messages to learn the various techniques spammers use to evade filters, persuade the blog owner to publish the comment or tag their comments to discover which blogs are most susceptible to their efforts. It is also extremely annoying.

To make my life easier I have disabled anonymous comments. That means you must be registered with one of the several identity services Google honours on its Blogger platform. Comments remain moderated. I hope to disable the identification requirement sooner rather than later, in the hope that the spam sources tire of hitting a brick wall.

The reason I allow anonymous comments is that the Blogger platform has bugs in its commenting software and will often fail to recognize identity credentials when they're offered. I myself have great difficulty commenting under my Google credentials when I'm logged into Blogger. That's astounding. I have the same problem when I use their own browser: Chrome.

There's no point in complaining since Google doesn't listen and, well, you get what you pay for: nothing. In any case, close to 100% of my interactions with readers is direct email, not comments. I don't get many legitimate comments. In other words, few would notice the action I've taken if I hadn't bothered to write this article.

In other news, the big tower is up. I have Part 2 of that article appearing soon. With so much to get down before contest season I have been negligent in publishing articles. Be assured that it is not because I've tired of blogging. I'm just tired. For example, today I purchased a large quantity of parts for an antenna switching system and purchased and taken delivery of hundreds of pounds (or kg) of aluminum and steel material.

There are several more articles in draft and awaiting time for completion. It is time I don't have at the moment. I'll be back.

Saturday, September 9, 2017

Pay Now Or Later: The Price of Cheap Fasteners

There are many long pauses during my big tower project. There are many tasks to tackle during those pauses including the preparation of antennas. One example is to redo clamps to fit a 3" (75 mm) mast. Another is to clean and refurbish ancient antennas that have been in storage for some time. It is at times like these I curse my younger self. Case in point is my venerable Hy-Gain TH6.

I bought the TH6 secondhand and put it into service in 1985. It came down in 1992 when I dismantled my station and exited ham radio for many years. I liked the antenna so I stored it in my garage. Even then I cringed at the thought of putting it back into service. When acquired the antenna had the original plated fasteners throughout. This was before Hy-Gain offered stainless steel hardware kits. The boom truss hardware was also plated. Extensive rust was the result.

Before raising the antenna I retuned it since the previous owner tuned it for SSB. The compression clamps on this vintage of TH6 had a screw that pulled tight a steel band surrounding the tube splices on the elements. The rusted screws were easily removed with bolt cutters. The hex head screws used pretty well everywhere else on the antenna snapped in two with the firm application of two socket wrenches turning in opposite directions. So far so good.

As I recall I was in a rush and couldn't bear waiting to order a full set of stainless fasteners for the TH6. Local hardware stores 30 years ago rarely stocked stainless steel. So I took the expedient measure of using ordinary plated fasteners. Worse yet was that the screw heads were rounded and designed for a slot head screwdriver. Although I knew I was making a mistake I judged it acceptable at the time. How wrong I was.

Now, in 2017, I am paying the price of that fateful decision. Only a few of the rusted fasteners could be removed with a screwdriver and wrench. Too much torque and the screw heads stripped because of the mild steel they were made of. Liberal application of penetrating oil liberated several more. The large majority required more labourious methods.

The picture at left is only slightly posed for the blog. I really did have this array of tools lying on the garage floor alongside the partially dismantled halves of the boom.

Notice the collection of split and shattered rusty fasteners removed from the element-to-boom clamps. Rust stains are readily apparent on the clamps, truss and elsewhere on the boom.

Tools I've been using to remove those rusted fasteners:
  • Penetrating oil (not visible): Applied to all the rusted nuts, hoping that they'll be loosened enough to allow removal, or at least backed off enough to provide room to fit the bolt cutters or hacksaw.
  • Bolt cutters: This is my favourite tool for this job. Unfortunately the jaws are wide and rarely could fit into the awkward contours of the clamps and bite between the nut and lock washer. The recoil of a rapidly severed screw is immensely pleasing. Be sure there's nothing valuable in the projectile's path.
  • Hacksaw: As with the bolt cutters there was rarely room to fit a hacksaw. It worked in a few cases where the bolt cutters didn't fit and there was a narrow gap between nut and lock washer. Care is required to avoid sawing into the clamp.
  • Cold chisel and steel mallet: This was perhaps my worst choice since aluminum clamps bend under the force of the mallet. Damaging the clamps is not recommended since bending them back into shape is not only difficult it will weaken the clamp. Aluminum fatigues easily.
  • Wrenches and screwdriver: This was always my first choice. It was also my second choice after the application of the penetrating oil.
  • Vise grips: Needed to grip stripped screw heads or to wiggle and break partially severed screws.
  • Hand drill with a thin cut off wheel: Placing and holding the wheel in position between lock washer and nut was the big problem. When it worked it work very well indeed. In other cases it would kick out and gouge the clamp.
The job is hours of drudgery and frustration. This is despite choosing to leave alone some of the hardware that does not absolutely require removal. Examples are the truss clamps and most of the inside screws and boom set screws on the element-to-boom clamps. Consider that there are 60 screws alone for the element-to-boom clamps (8 on the clamp faces and 2 preventing clamp rotation on the boom on each of the 6 elements).

After removal I replaced the fasteners with hex head stainless fasteners. I've had good success with a local store that specializes in fasteners. Even so so care must be taken since stainless steel comes in many varieties of alloy mix and strength. Cheap stainless is a poor choice since it can gall, break or corrode (yes, really). Unless the grade is known stainless steel is best avoided where high strength is a primary requirement. Lubrication can help avoid galling and protection against the elements.

I am no expert on fasteners so I will stop with those above cautions. When in doubt you can often opt for grade 5 steel fasteners since they rust more slowly and will survive many years when liberally dosed with grease before assembly. I have had success with white lithium grease even though it is not the ideal choice. There are greases out there for every imaginable metal alloy, however choosing and finding them can be difficult.

The point is that even if you do not make the ideal choice of fasteners you can achieve good results by selecting more expensive fasteners to ensure their easy removal in future. Hy-Gain sells stainless steel kits for many of their antennas. Although you can spend less by hunting them down on your own the kits are convenient.

Cheap fasteners can seem attractive. Just remember to add in the cost of removal before you buy. You'll pay that price in future drudgery, or when no one wants to buy your rust encrusted antenna.

Friday, August 25, 2017

Raising the LR20 150' Tower (Part 1)

Raising a 150' guyed tower is a major endeavour. There really is no comparison to self-supporting towers half that height. It is far more than 2x the work! For the vast majority of hams big towers are nice to look at but you wouldn't want to own one. After all, not only is there the expense, difficulty and danger of raising it you must also maintain the tower and all the antennas and associated equipment that it supports.

For myself I judge the effort worthwhile. Even so it is daunting. I've helped others put up and work on big towers, but that is no real comparison to owning one. The ground work is hard enough, and it only gets worse once you get up high.

This article is a progress report. I'll describe much of what I had to go through just to reach this stage in the project. Things are moving along well enough despite the many questions that needed answering and the obstacles I had to overcome. Part 2 will cover the rest of the project to completion.

Lifting the base section

A guyed tower with a pier base presents a challenge. At the beginning there are no guys. Yes, the base section with its bearing plate will stand on its own when placed on a level surface and will have some lateral stability when sitting on its pin, which is still not enough to raise sections onto it. There are basically two ways to go about it:
  • Assemble on the ground enough tower sections to reach the first guy station, lift it and place it on the pin with a crane or lift truck, then attach the first set of guys.
  • Manually lift the base section onto the pier, temporarily guy it, then lift sections until the first set of guys can be attached.
I chose the second method. It is certainly cheaper and it provided an opportunity to test my newly designed and constructed gin pole comfortably close to the ground. Two strong men could place the base section by muscle alone but in my case it would mean calling in a favour to convince someone to drive out to my isolated location for 10 minutes work.

I took the adjacent picture when the job was mostly done. You can see the basic elements involved.

A standard section with my newly constructed gin pole attached was braced against the pillar. Guy ropes stabilize it. My trusty old hand 2 ton winch (come-a-long) provides the muscle to lift the base section (~150 lb). The two sections leaned towards each other when the base section left the ground. Rope stretches. It was all very stable despite the leaning.

Lowering the base onto the pin took some sweat since I machined a very close tolerance for the 1" pier pin into the base plate hole. This is not at all necessary. I simply chose to stop when the existing hole was barely sufficiently enlarged since reaming a 1" hole in ⅝" steel plate with hand tools and a tiny drill-mounted grinder is not at all enjoyable.

Eventually I got the base section sitting on the pillar. I removed the gin pole and the section on which it was mounted. I noted several gin pole deficiencies which I proceed to correct.

Temporary guys

The pin alone is sufficient to hold the base section in place until temporary guys are attached. Just don't try to climb it!

The top of the base section was guyed with scraps of old steel cable I had lying around. Rope is not good enough since it stretches too much to be safe for lifting 3 sections onto the base section. The greater length of each temporary guy is ¼" EHS taken from an old tower. To this was attached ¼" aircraft cable to loop through the holes guy yokes holes at the top of the base section. At the anchor end I spliced on 3/16" aircraft cable to reach the turnbuckle and anchor plate. An abundance of clips and pre-forms holds it all together.

The temporary guys were tensioned to between 400 and 500 lb. More would have stressed the cable clips and the smallest cables more than I felt was wise. This tension worked well to keep the tower vertical and stable for lifting sections. Shaking the tower at the 40' level did induce some movement in the guys, which was expected and is not a safety concern.

Notice the ladder. This became a regular fixture at the tower base since only on the higher rungs is there a sufficiently large opening for a boot (or two) to fit.

Making the base section vertical

This presented more of a challenge than I expected. A level doesn't work well since the legs aren't vertical and the horizontal members are not reliably horizontal. I used the common trick of placing a spacer at the bottom end of the level so that when place either on a leg face or vertex the level is vertical. The turnbuckles are adjusted (or clips moved) until all legs are at the same vertical angle.

That took some fussing but was eventually done. Getting this right is very helpful to safely raise the section and then have the tower in good position to confidently set up the first set of permanent guys.

At this point a potentially serious problem appeared. The bearing plate was neither horizontal nor flat. I checked and rechecked yet the error remained. I learned from the previous owner that the flaw was always there. He had a custom bearing plate made and welded to the base section and it was not properly done. He never experienced any problem despite the flaw.

That may also explain why the bearing plate isn't flat. Consider that for my tower I calculate the pressure on the bearing plate due to tower and payload static load and the guy tension load to total close to 10,000 lb (4,500 kg).

I next consulted by email with a ham having the requisite expertise (and who has several towers of the same type). He eased my mind on the scope of the problem but strongly recommended that I grout the base. I proceeded to do that. A bag of non-shrink grout designed for bearing plates is inexpensive, widely available and easy to use (it's a common building material). The job was straight forward since I have experience grouting landscaping stonework and doing concrete repairs.

Lifting the base for grouting proved no great difficulty. A large cold chisel was inserted into the gap and used as a pry bar aided by a pipe as a snipe. A conventional pry bar was tried but was not up to a lift of 500 lb, the sum of two sections and the downward force due to tension on the temporary guys. Scrap ¼" angle stock kept the bearing plate elevated for the grouting.

The pillar was thoroughly wetted, swept clean and the semi-liquid grout mix shoved underneath with paint stir sticks. When the space was pretty well filled I used the pry bar to remove the angle stock and let the full weight fall on the grout. Because of the tight fitting pin I had to use a wood block and a small sledge hammer to pound the bearing plate down into place. The pressure would have filled most of all on any voids in the grout.

The grout that squeezed out the sides was removed and the edge shaped to give it a professional look. When dry the grout provided a perfectly mated surface for the distorted bearing plate. Note that the grout bonds to the concrete but not the steel; the bearing plate can still tilt as it should. In fact we could tell when the tower wasn't perfectly vertical by a seam appearing between the grout and base plate.

Gin pole

Since I can't weld I prefer fabricating devices from common metal stock and parts that can be found in hardware stores. It can be challenging at times. Devising a gin pole for the LR20 was just such a challenge.

First I had to deal with 3 different styles of tower sections and small variations within the most common style of section. These were the base section, one section with curved members between legs and 13 sections with angle stock members. Despite the differences all sections meet the same splicing spec and fit together perfectly.

The girts on all but one section have holes on the top surface for attaching support plates and other fittings. The positions of the diagonals was the greatest worry since this made the position of the lower attachment point variable. The base section also has non-vertical faces to be dealt with.

In the picture at right the completed gin pole is at the 50' level, ready to lift the next section. Two stacked heavy duty construction L-brackets comprise the upper hook. On the upper surface (not visible) is a short bolt that slips into a bolt hole on top of the girt (matching holes on the other sides of the girt are visible). A retaining nut is optional.

For the lower attachment I took a short length of 2" schedule 40 pipe that slips over the 1.9" OD of the gin pole 1.5" pipe. A U-bolt and machined angle stock clamps the sleeve to a diagonal member. A short bolt at the center of the angle stock (not visible) increases the bearing surface by bracing against the inner surface of the diagonal. Two drilled and tapped holes in the sleeve lock the gin pole to the sleeve.

To move the gin pole up one section the sleeve locking bolts are loosened. From the top the gin pole is lifted until the upper attachment is above the tower. The pole is lowered into the sleeve below (I made two to make this process safer). The bolt in the upper attachment is fit into the girt hole. Finally the sleeve locking bolts are tightened. The sleeve on the lower section is then removed, to be used later on the subsequent section.

For the section without bolt holes on the upper surface of the girts the gin pole is rotated so that the long bolt that secures the L-brackets faces the tower. It fits into a bolt hole on the outer surface on the girt. The retaining bolt in this case is mandatory. The pulley must be moved to opposite side of the gin pole so that it is always facing the tower.

The gin pole was given a few improvements to correct shortcomings I discovered during use. It is lengthened 18" with a schedule 40 aluminum pipe, making it easier to lift 10' sections while not becoming too top-heavy for one person (me) to safely lift and position.

Since the lifted section can easily snag on the gin pole bottom and protruding bolts I constructed ramps (shields) so that it can slide over these obstacles. The sleeve locking bolts are placed out of the way by rotating the sleeve so that they face inward.

The shields successfully reduced the incidence of snags that inevitably occurred even with tag lines to pull the lifted section away from the tower and gin pole at critical moments during section lifts.

Lifting power

My original intention was to use my lawn tractor to lift the sections. Unfortunately, as I feared, this didn't go well. The tractor is too light and the tire tread too smooth to gain enough traction to pull a free weight of 120 lb. There are solutions to these difficulties but that could not be quickly implemented.

I resorted to the winch used to build the Trylon tower. It's a more tedious but proven method. I used junk box angle stock to construct pinch clamps to secure the winch to the base section and allow the handle to turn unencumbered just beyond the tower leg. The winch must be operated from a short ladder since I was unable to attach the winch lower where the base section is very narrow.

The tower reached 70' with the winch. At that point I'd had enough with the painfully slow lift speed and tired arm muscles. My ground crew became restless as well since the slowness was boring. How I chose to resolve the problem will be covered in Part 2.

Pulling guys

Sacrificial pre-form as a cable grip on first guy level. It is not
fully wound so that it's easy to remove. The guy is at full
tension so a new pre-form is wound on the turnbuckle.
The temporary guys are still attached for safety.
Weight of 5/16" guy cable, strain insulators and pre-forms is considerable. For the first guy station at 35' I attached the guys to the tower section on the ground and lifted them as a unit. The trade off is that wrapping the pre-forms on the ground is easier than in the air but the lift is more work on the manual winch due to the additional weight. The gin pole is however up to the task.

With more guy weight at the 70' and higher guy stations it is not practical to attach them on the ground. The guys were individually lifted and attached in the air.

After the section with the guy station is attached to the tower the guys must be drawn out to the anchors in preparation for attachment and tensioning. This is a muscular job that must be done in stages to avoid undue bending stress on the tower.

Before raising the guys I built them out to the lowest strain insulator. A single span runs from there to the anchor turnbuckle. Partially used and therefore lighter cable reels were carried into the field by wheelbarrow. The cable is attached to the strain insulator and unreeled back to the anchor. One person pulls moderately hard on the cable to get the rough distance and a second marks a point about 2 meters out from the turnbuckle. That's where I attached my cable grips for pulling the cable with the come-a-long.

I use "sacrificial" pre-forms as my cable grips. They are far cheaper than the proper tool and work perfectly well. I call them sacrificial since pre-forms are not designed for reuse. I selected old stock 5/16" pre-forms from my junk box, using 3 on the guys and 3 on the turnbuckles. Only when near to full pre-load tension was reached did I use a new pre-form to attach the guy to the turnbuckle.

Each guy was pulled part way with the come-a-long then tied off with a sacrificial pre-form. With just the one come-a-long it takes well over an hour to make the circuit of the anchors a few times until the tension was high enough and the tower adjusted to vertical that the permanent pre-forms could be attached. It wouldn't do to find that a final adjustment is beyond the range of the turnbuckles.

Professionals use 3 sets of grips, tensiometers and come-a-longs plus one or more transits to do the job quickly and easily. A few of the sacrificial pre-forms had to be discarded during the tower raising when they fell victim to overuse.

Poor man's transit

The tower must of course be made or kept straight and vertical as the guys are pulled to full pre-load tension. It is easy to have the tower lean or bend when there's 1,000 lb of tension on the guys. The professional tool to do this is a transit (theodolite). Unsurprisingly I don't own a transit and although I can rent one I also do not have the training to use one properly.

Instead I used what I call my "poor man's transit". Although totally ridiculous it does surprisingly well if you use it carefully. My crew at the time, Brian VE3CRG (on the left) and Geoff VE3KID, show how it's done. A new aluminum tube (surplus but never used 2.5" aluminum tube) is the straight edge that is tilted to vertical with levels 90° apart (or one if you trust your arms to steady the tube). Do this standing near a guy anchor. You then sight along the tube towards one leg of the tower. Deviation from vertical can be estimated from the width of a tower leg, as sighted at the guy station on the tower. Later I attached the tube to a fixture so that it didn't need to be held in place during use.

Brian VE3CRG (left) and Geoff VE3KID using the poor man's
transit. The "hazmat suits" supposedly protect them from the
multitude of ticks and biting insects in the wet hay field.
To correct deviations from vertical the opposite two guys are adjusted the same amount in opposite directions. That is, if you loosen one turnbuckle 3 full turns the other is tightened 3 full turns. Done this way the tower will move in the desired direction without changing the guy tension. You can calculate the number of turns per the turnbuckle thread pitch (keep in mind there are two screws, not one, so the rate of change is double the thread pitch) or guess and then correct your guess after rechecking with the transit.

You must repeat the process with the transit at the other two anchors. It doesn't have to take long if you go about it methodically and don't rush.

Let me interrupt here to warn you about shortcuts and to bust a common myth. Do not use a level on the tower itself to test for vertical. It doesn't work. Although the splice tabs at either end are usually exactly where they ought to be the tower members in between may not be. Welding, shipping, previous usage and abuse can add deviation and ripple that will fool a level. Move it from place to place on a seemingly straight section and you'll see. Small deviations can trick you.

Even if the tower steel is perfectly straight the level itself is often not adequately calibrated. Use each side in turn and if they do not agree the level is not calibrated. A perfectly calibrated level is still inadequate since the tower is many times longer than the level and an imperceptible deviation will be greatly amplified.

The myth is that a guyed tower or mast is vertical when the tension in the guys is equal. A tower can lean quite a bit out of vertical before any measurable amount of tension differences among the guys appears. This is because the guy tension is far greater than the horizontal force of a leaning tower. In fact if you tighten one guy you'll find the tension in all the guys increases the same amount.

Tension differences are often due to incorrect use of the tensiometer when attached to the cable. A persistent 100 lb difference in one guy was corrected by reducing the tension in the temporary guys. This discrepancy is in general a sign that guys at multiple levels are either not properly adjusted or there may be a flaw in a tower section or a section splice is misaligned.

Another source of error is the lay of the guy strand. With only 7 strands in EHS each is quite large gauge. Move the tensiometer a short distance along the guy and remeasure. A high or low point on the EHS where it contacts the tensiometer can affect the reading. That small amount of cable deflection difference on 5/16" EHS can be 50 to 200 lb in my experience.

Going higher

I'll end Part 1 at 70' where the second guy station is located. This is almost halfway. The tower is vertical (using my "improved" poor man's transit), the guys are tensioned and the temporary guys are gone. The next sections to go are parked alongside the base.

Although the Trylon tower is only a foot or so taller I am still looking up at it from the 70' level of the LR20. The Trylon sits on the higher grading surrounding the house. The hay field undulates, with high and low points, and a general downward slope toward the swamp behind the tree line. Terrain matters when it comes to height.

The top half of the tower has challenges unlike the lower half and will require changes in technique and equipment. For example I am retiring the winch since it is too slow and difficult for the longer lifts. I'll discuss this and more in Part 2.

I'll close with a picture I took at the edge of the hay field while taking a break from working on the first set of guys. It is always refreshing to occasionally take in the scenery. Putting up a big tower is a lot of work so frequent breaks are mandatory. Fatigue causes accidents. Stop when you no longer feel 100%.

"Bring me milkweed or I start a tornado to blow down your tower!"

Sunday, August 20, 2017

Solar Eclipse 1979

In early 1979 I was finishing my graduate degree at the University of Manitoba in Winnipeg and preparing for the move to Ottawa later in the summer. Just my luck that a total solar eclipse was about to make a visit. This was a rare opportunity since no travel was required; few have the pleasure of seeing this phenomenon in their lifetimes unless one travels to the path of totality. One came close in 1963 when I was very young and impressionable. Throughout my youth I looked forward with great anticipation to the real deal in 1979.

As is usual for February in VE4 the weather was virtually guaranteed to be cold and clear. That held true for the morning of February 26. Although I had the desire to drive north to get a longer view of totality, or even just stay home for the day in the north district of the city, I decided that an eclipse extension of 15 or 20 seconds wasn't worth it. As per routine I drove to the university campus in the south of the city where totality would be just shy of 2 minutes duration. I had an enormous workload to get through if I intended to graduate.

Thoughts of radio were far from my mind. Going back to my logs from that time of my life it was pretty clear that my on air activity was extremely limited. I didn't have the time. Although I had an interest in the eclipse's impact on propagation I was infinitely more interested in witnessing the event with my eyes, not through headphones.

Word got around by mid-morning that staff were getting access to a number of building roofs for improved eclipse viewing. Students were welcome. A few friends and I joined a small group on top of one of the science buildings. The view was great even though we were only up perhaps 6 stories. There were no taller buildings, prairie trees tend to be short (leafless in February) and the landscape was flat out to the horizon in every direction.

It was also painfully cold. Few of us were dressed for an extended stay in -20° C or worse temperatures. The breeze above the rooftops increased our discomfort. At intervals each of us would duck inside to warm up. Waiting for totality is not very interesting; there's only so much I could stand of staring at a slowly encroaching shadow over the sun through the viewing filters that were passed around.

As totality approached the temperature was already noticably dropping in the dimming sunlight, already quite weak from a winter sun low in the south-southeast sky. I tried to look for the rapidly moving shadow edge sweeping over the prairie from the west but failed to see anything very distinct. Then it was dark and all eyes turned toward the main event. For a moment I saw Baily's Beads.

The next thing I noticed was the expansive corona. This was the time of a solar maximum, and historically quite a fairly strong one. The corona expands under these conditions. At about the same time everyone noticed and pointed at a large arcing prominence on the upper left limb. It was quite spectacular. This linked photo shows a reddish glow but not the prominence. Possible the photo was taken later during totality when, as I recall, the encroaching moon blocked the prominence from view. Also visible was a smaller prominence and other evidence of high solar activity.

Stars were visible though not as many as I'd expected. The sky was as dark as twilight and grew darker then lighter again as totality progressed. Then it was over. After a couple of minutes the crowd began to disperse. The repeat viewing of the the partial eclipse in reverse couldn't keep an audience in that bitter weather.

Over the following weeks I heard reports of hams experiencing some interesting low band conditions with paths crossing and along the path of totality. Although the internet existed and I had even used it a few times it played no role in connecting hams or distributing news of operations during the eclipse.

I have never travelled to view a solar eclipse and I won't be for this one either. If I have the time I will turn on the rig and listen on the low bands. It's unlikely that I'll bother to transmit. I will only be a spectator. For those of you in the US lucky enough to experience totality on Monday be sure to get outside and away from the shack for at least the several minutes of the main event. It's very worthwhile.