Monday, December 5, 2022

Prop Pitch Direction Pot Updates

When I raised the first of my big towers in 2017 there was no direction indicator for the chain-driven prop pitch motor rotator. I made one using a Bourns 10 kΩ 10-turn potentiometer, a device used by other hams of my acquaintance. 

These components are not hardened for outdoor use and require protection. I built a plastic enclosure on a bracket dangling below the motor platform and hoped for the best. It lasted 5 years, far longer than I expected.

It was time to replace the pot on that prop pitch rotator. The pot had water damage and there might also be internal mechanical wear. The resistance jumped around a lot during rotation and there is evidence of bald spots on the resistance wire.

I went through at least two plastic "hoods" for the pot. The container seen above replaced the original, which was too small to adequately protect against wind driven rain. I repurposed food containers to save cost for what I expected to be a temporary measure . The work great when they're new. Of course they are not resistant to UV and thermal cycling also takes its toll.

As the plastic cracked the silicone sealant around the gaps couldn't block water incursion. Notice the rust at the base of the pot shaft. It was always a danger of this design because the pot shaft points upward, and open to rain and snow without excellent water protection.

An underappreciated problem with ordinary pots in rotator service is wear due to rocking of the mast and antenna system. This is directly coupled to the direction pot, with the pot wiper moving back and forth over the resistance wire where it is resting. 

The wire in a typical pot is not designed for this amount of abuse. They have a limited service life in this application. In contrast, the pot in a Hy-Gain rotator (photo credit: MFJ) is much larger with thicker wire and a wide wiper. It may help to vary the direction of the yagis when they are not in use.

The multi-turn linear pot has its advantages and it is not too much of a burden to replace them every 5 years or so. To better protect the Bourns pot from the elements I undertook a redesign. I had planned this for some time but put it off until the pot failed.

The chain-driven drive shaft is 2" OD with a wall thickness of about ¼". I projects less than 1" below the bottom of the housing that sits on the side of the tower. There is just enough room to fit the Bourns pot. So that's what I did. As you can see it's completely enclosed and well isolated from the elements. There is no opening above the drive shaft where water can enter.

The difficulty with this design, and the reason I didn't do it this to begin with, is that with the pot fixed in place it is the shaft that turns. The wires must turn with the shaft. Alignment of the shaft is critical to avoid bending force that can bind the pot during rotation. As for the first version, the pot is mounted on thin aluminum flashing that flexes to protect against a minor misalignment.

I tied down the wires to prevent tugging on the pot terminals. The 3 wires are coiled around the coupling. The wires are AWG 24 scavenged from stranded Cat5 cable. The plastic insulation is very pliable but it is stiffer than the wire when used in this application. Disciplining the wire coil is therefore not easy. It looks ugly but it works. Now that winter has arrived we'll see how it does when coated with snow and ice. A snow shield might be necessary.

On the other prop pitch motor turning the 15 and 20 meter yagis I encountered a different problem with the direction pot. A few months ago I replaced the temporary rope belt with higher quality ⅛" nylon weave rope. Since little friction with the mast and pulley is needed to drive the pot I kept the tension low. The rope loosened only slightly but that was enough for it to slip. Worse, it preferentially slipped in one direction. 

At first this could be dealt with by adjusting the zeroing pot on the op-amp direction indicator. With the continual back and forth rocking of the mast the pot soon hit the end of its 10-turn rotation and could no longer be adjusted. I climbed the tower and confirmed the nature of the problem. I centred the pot and pulled out the adjustment bolt to increase tension on the rope.

With the higher tension the mechanism has been working well for the past few weeks. I hope that it survives the winter. Another design may be necessary. One example I've considered is a chain drive. It would provide positive engagement without fine adjustment of chain tension.

I have discarded bicycle chains and cogs (½" pitch) to work with. The challenge is that there is no way to slip a cog over the mast. The cog would have to be cut in half and machined and attached to a collar that wraps around and is affixed to the mast. The pulley on the pot shaft would be replaced by a small chain cog. A master link solves the chain wrap problem. It's straight-forward work that I hope to avoid. Time will tell.

The direction indicator circuit described in an earlier article works perfectly well but it is more complex than currently needed. The goal was a circuit to drive either a physical meter or an analogue Arduino GPIO. The needs are different because a meter responds to current and the GPIO ADC responds to voltage. A second gain stage provides the required voltage range without risking the linearity of the differential amplifier.

Since my immediate plan is to use physical meters the second stage has been eliminated in the schematic shown above. I used the freed space on the breadboard to build two of the circuits. A few days before CQ WW CW I discovered that the meter movement of the old direction indicator (for the 40 and 10 meter yagis) had malfunctioned. The single op-amp circuit is a temporary fix since I needed it for the contest. As these things go, I expect it'll be in service for a while yet.

The circuit provides a minimum 10 kΩ load for the op-amp to keep it stable. The pot is tapped with a current limiting resistor to protect the meter movement. The resistance range was selected to support a large range of current requirements and drive ratio at the direction pot. The circuit is simple and works well. Calibration is performed in the same way as for the original circuit. Substitution of the current limiting resistor may be needed for meters other than the ones I have tried.

Because there's just one meter, one of the meter wires must be moved between circuits to monitor the direction of each prop pitch rotator. An SPDT switch would make this job easier. The arrangement is far from ideal but acceptable in the short term while I decide on a final design. 

I may do what some others have done, by repurposing an orphaned Hy-Gain rotator controller. The meter indicates direction and the levers operate the motor. Unused circuitry in the controller can be removed or left in place in case it is later returned to service as a Hy-Gain rotator controller. It also looks good on the operating desk. A home brew professional looking controller is a lot of work.

There is RFI, which shouldn't be a surprise considering the layout. You can see one RF choke at left on one of the pot wiper lines. This was proof of concept to see how it would help. It suppressed most of the RFI but not all. When properly built the lines will be choked and bypassed to suppress RF getting into the circuitry. Lightning protection must also be included, but probably at a connection point far from the shack for maximum safety.

My next step is to find a used orphan rotator controller and build permanent direction indicator circuits. The ±12 VDC for the op amps is not easily built with the stock transformers in Hy-Gain rotators so I may use the existing power supplies and wire them up to the controllers. The motor controls can be implemented at the same time or later.

Wednesday, November 30, 2022

CQ WW CW SO(A)SB40

Of the many types of articles on this blog, the statistics tell me that contest reports are among the least popular. Well, too bad, because this is another one. I decide on articles based on my personal interests in the hobby and while it's great when the reader's interests coincide with mine that is not why I choose a topic. 

Many will skip this article and that's okay. I write them to reflect on these events in written form because it helps me to understand what happened and what I might or might not do differently in the future. If you're still with me, let's dive in.

Picking a category

After my burnout in last year's contest I was not enthusiastic about doing an intense all band 48 hour contest. It's hard on the body and mind. The impact increases with bigger stations (and rare call signs) because the pile ups are intense and they go on for hours. To be truly competitive you must use SO2R and 2BSIQ. As they say, it isn't my cup of tea. These and more lessons are in the article I linked to immediately above.

The alternatives are the Classic 24-hour no frills category or a single band. I wanted to be active throughout the contest period so a single band entry made sense to me. But what band?

I did 15 meters for the SSB contest and the low solar flux did not bode well for 10 meters. Reports by friends that entered as single band 10 meters suggest that I made the right choice.

20 meters is really tough due to the sustained high density of stations and the long openings. There are enough 160 DX contests to scratch that itch and 80 meters can be a painful noise filled slog. I am reasonably competitive on 80 with my vertical yagi but it is inferior to many of the big guns.

Which brings us to 40 meters. Propagation on 40 is quite fascinating since it is open day and night -- though far better at night -- and globe circling short and long path openings are surprisingly common. A middling solar flux is ideal on 40 because the high traffic paths, especially the one to Europe, can last all night long. Peculiar and surprising propagation entices me in much the same way as 6 meters. But outside of contests those openings are not well exploited and the band can seem dead most nights.

It was also my first opportunity to try the new 3-element yagi in CQ WW since it went up last December, a few weeks after the contest. The antenna is very competitive and I thought it would be a lot of fun to see what it could do for me in this premier event. Combined with the XM240 at half the height the antennas offer good performance and operational flexibility. 

So that's what I chose: 40 meters. I opted to make use of spots to maximize the potential for multipliers and reduce the tedium of constant tuning and finding mostly dupes. That's expected for a single band contest or single band entry in multi-band contests.

Sticking with SO1R

SO2R is very difficult to do in a single band entry. Getting antennas far enough apart to prevent receiver damage is rarely practical. The alternative of wiring the transmit antenna through a receive port to the second station limits listening to when the primary station is also receiving. Hunting on the second receiver is constantly interrupted and the operator can't escape having to listen to both receivers while hunting.

I still wanted to try it. One stumbling block is N1MM Logger's lack of support for two keyboards in SO2V operation. In this style of operating the sub-receiver (or SDR slice) in rigs like my FTdx5000 has its own entry window. With one keyboard the operator uses keyboard shortcuts to manage use of the two VFOs. That can be difficult and is why I do SO2R with two keyboard. When the challenges already mentioned are included, SO2V was a step too far.

I stuck with SO1R and manually tuned and switched the VFOs. I've done this before with a K3S and it works well if you are careful. Being assisted helps because you really only have to click on spots. The trick is in timing the VFO switching so that you hold the run frequency and send your call and exchange in sync with both the running VFO and the hunted station's transmissions. 

It did it numerous times when the run rate was low. Doing it when the rate is high is well beyond my ability. A second operator to hunt is better but you still can't listen full time unless you design some way for the sub-receiver to withstand the kilowatt transmitter only a few kilohertz away.

Propagation and antennas

Despite less than quiet geomagnetic conditions the band was very good. There was no noticable attenuation on paths that skirt or cross the auroral zone. That's often a problem for those of us located at a high geomagnetic latitude. In fact, signal levels were very strong at times. 

Many QRP stations made it into my log, including JA6GCE. It is no surprise that a big signal attracts the smaller stations. I did the same when I regularly contested with 5 watts and low wires. I am happy to swap roles to put more contacts in their contest logs.

Relative performance of the high and low yagis made apparent the daily cycle of propagation on 40 meters. You can work the European big guns during full daylight but not the smaller stations due to D-lay absorption. That isn't necessary since they'll still be there when sunset approaches. Getting a few hours of sleep is more important. 

We can easily work Americans throughout the day, if only they were active. Daytime contest activity is high within Europe but not here. There's little point for the Americans in CQ WW when they only have a handful of Canadians to work. They do far better to stick with the high bands. The situation is very different for domestic contests like Sweepstakes and NAQP with high 40 meter daylight activity.

About 2 hours before sunset it becomes possible to run all European stations. At that time the best antenna is the low yagi. It outperforms the high yagi by 1 to 4 S-units. During daylight the ionosphere's D-layer preferentially attenuates low elevation angle radiation since the traversal path is longer than at high angles. A similar effect dims and reddens the sun when it is low to the horizon.

Around 30 minutes before sunset the relative performance of the yagis undergoes a rapid transition. The two antennas become equally effective and then the high antenna easily does the best. That continues until sunrise. The EZNEC elevation plot is of a typical 3-element yagi at heights of ½λ and 1λ. Notice the null in the pattern of the high yagi. It doesn't do well at elevation angles around 30°. 

Of course this is why many contesters stack yagis. You can choose the antenna that does best and combining them for extra gain. My yagis are not stacked so I pick the one that performs best at any given time. When I turned an antenna to work a multiplier I could keep running on the other, even if it was not the best. A kilowatt can overcome much of the deficit. Indeed, many times it hardly mattered where the antennas were pointed: everyone called me and I could work anyone I called.

Activity level and patterns

In single band contests, and Sweepstakes, you can run out of stations to work. Although CQ WW is a 6-band contest the concern still applies to single band entries like mine. Conditions and contest popularity are critical to sustain rate for the duration of the contest.

I am happy to say that I never really ran out of stations to work. However, there is a rhythm to any contest that relates to time zones and personalities. Understanding these factors can improve your score.

Committed contesters are active for most or all of the contest. Most are active on all bands, but they show up on 40 meters often and they are easy to work. If the opening is brief you hope they are aiming for eastern NA at the best times. This is especially true for those in distant zones and rare countries.

Casual operators are the majority and they tend to be active according to their personal schedules and not the propagation or necessarily in a fashion to maximize their scores. Hams, like all people, can be broadly classed as morning people and nighthawks. I am among the latter. That doesn't matter in a contest since I put in the time regardless of my preferences. To contact the casual operators I take account of their operating patterns.

Let's take Europe as an example since it's a rich vein of contacts and multipliers and relatively easy to reach on 40 meters. Most hams are free in the evening to operate and so they do. That's late afternoon for us, which is perfect for the early sunsets this time of year. The rates are high. As midnight comes and goes in Europe only the nighthawks remain among the casual operators. Conditions may remain good but the rate declines.

Sunrise sweeps across Europe starting at about 2 AM in eastern NA. That's when the morning people in Europe appear. The rate picks up and holds until the high bands draw them away or the day is too far advanced and conditions deteriorate.

The lesson for score conscious contesters is that you must be there at the appropriate times to work both groups of casual operators. Their preferences should guide your activity more than your own.

Amplifier

I used the Acom A1500 exclusively in the contest. It is a manually tuned tube amp. Settings for the Load and Tune controls is determined by the output impedance and frequency. The impedance is never the same for two antennas unless the SWR is exactly 1. The CW spectrum commonly used in a busy contest like CQ WW is from 7000 to 7080 kHz. Amplifier adjustments are typically needed for a QSY of about 30 kHZ for optimum performance.

Optimum performance is desirable but not strictly necessary. If you don't adjust the amp, the most common outcomes include reduced power, lower efficiency (higher heat dissipation) and excess screen and control grid current. For my 40 meter antennas and the frequency range it was not absolutely necessary to adjust the tuning after every change. A drop of 200 watts is not that much and it rarely affects my ability to snag a multiplier or work a station in a different direction.

I regularly monitored the screen current and temperature and I never had a problem. I grew comfortable only adjusting the tuning when I changed my antenna preference to target or QSY'd more than about 30 kHz. Exhaust air temperature was never uncomfortably high under worst case conditions, which was CQ'ing for several minutes without a reply.

Perfection has expensive taste. Don't let it seduce you. Good enough is good enough.

Running vs chasing multipliers

A multi-band SO2R operator can very effectively run on one band and hunt multipliers on another. All you must do is time your transmissions to smoothly interlace the QSOs. It is far more difficult for the single band operator since you will have great difficulty receiving on one frequency when transmitting on another. Unless you're an extreme case you cannot receive while transmitting. 

That makes multiplier hunting far more difficult. It is more difficult for unassisted operators. That is why, although I prefer unassisted operation, that I have only one band to work with.

Using the SO2V feature of N1MM can help. The second receiver or slice has its own window. Since the feature doesn't support two keyboards you have to use keyboard commands to switch windows/VFOs for entering data and sending messages, while paying close attention to coloured dots that tell you which VFO is doing what. That's a problem for me and is why I use two keyboards for SO2R.

I did it manually by manually activating the sub-receiver of my FTdx5000 and used the 'A⇨B' and 'A⟺B' buttons to sync and swap the VFOs, respectively, so that I always transmit with the main VFO. There are AF Gain knobs for each receiver. I set the level of the sub-receiver lower to avoid copy errors on the run frequency, which is more important to me. It's awkward and I made many mistakes, such as punching the wrong button or losing the run frequency. Perhaps practice will improve my success, but I don't know how much importance to attach to this skill.

Most logging software will helpfully tell you the marginal value of a multiplier. For example, if you have 100 QSOs in the log at 2 points each the total QSO points is 200. If you also have 30 multipliers the calculated score is 6000. A new multiplier is worth 200 points in addition to the 2 points for the QSO. The marginal value of an ordinary QSO worth 2 points is 60 (30 × 2). Therefore the marginal value of a multiplier is approximately 3.3 QSOs.

If your run rate is 1.5 per minute the implication is that you should not dally with the multiplier if it costs you more than 2 or 3 QSOs on the run frequency. The chase tends to cost more on a single band than with SO2R on two bands due to the challenges described earlier. You have to decide what to do based on your abilities and the trade off of cost and benefit.

However that is not the whole story. The marginal value of the multiplier is not the value of the multiplier for the full contest. The multiplier continues to apply to all future contacts. A multiplier's marginal of value of 200 when you have 100 QSOs in the logs grows to a value of 1000 if you expect to make 500 contacts in the contest. In that light the multiplier is really worth 16 QSOs, not 3.3. If you pay attention to this statistic you'll notice that it increases as the contest progresses.

On the other hand if it is indeed early in the contest you can hope to work the multiplier later and focus on running at present. Of course that is a risk. I often took the risk because of the difficulty of single band hunting while the runs were good. Sometimes it worked out and sometimes it didn't. Those desired multipliers don't always reappear.

There were many times that I had to abandon chasing a multiplier to return to rate production. One example is 4U1UN. They are close enough to me that at night all I had for propagation was watery back scatter. I could not get through the massive pile up, and I could not afford more time since it was prime time for Europe.

For a final observation, be aware that CW spots have two sources: human and skimmer. I notice a dearth of human spots from outside of Canada and the US, inside and outside of contests. Most operators now appear to rely on skimmers and no longer bother posting spots. SSB is different but this is a CW contest. The pile up starts seconds after I see the skimmers broadcast my CQs. That typically takes 15 seconds or 2 to 3 CQ's. 

I have mostly relied on human spots and I disable most data coming from the RBN (reverse beacon network). That is a mistake. I plan to change my cluster settings to pull in more skimmer data.

Trouble with dits

Over the years I've become far more proficient distinguishing 'S' and 'H' and other characters with strings of dits at high speeds. Others are less proficient. It is also a frequent problem with skimmer decoding. Few have difficulty understanding 'VE3' since it's common and expected. The 'V' in my suffix is a source of trouble when I send CW at high speed in a contest.

A bad skimmer spot or human spot can cause grief. My call is regularly miscopied as VE3UN. It is so frequent that the call appears in the master database that most contesters use for the SCP feature (super-check partial). Worse, it appears in the list above my true call. So when mistakes occur that's what they pick.

The bad spot draws assisted operators by the droves late in the contest when there are few stations left to work. Working dupes during my run improves no one's score, and it drives away good contacts that, understandably, won't wait in the queue. Telling everyone 'B4' wastes even more time. I have a function key that sends my call with 'VN' at reduced speed, but even with that many operators pay no attention and keep calling. I could try changing my call by battling the federal bureaucracy but I like what I have.

Experienced contesters know that it is better to accept the inevitable and QSY. Don't become stubbornly attached to a run frequency. The minute or two it takes to find another is well worth the effort.

Fatigue and time management

They award no prizes for good time management in CQ WW. Whether I operate 48 hours or 15 hours, all that matters is the final score. There is a Classic category where the time limit is 24 hours, which did not interest me. Only then do you need to pay close attention to off time rules and schedule your time accordingly.

I don't know my official participation time since I didn't look and I don't care. When I needed a break and the time was opportune I stepped out of the shack. The 30 minute rule was irrelevant. Fighting fatigue by taking care of my body and mind took priority. 

I operated right through both nights of the contest because the band was open and productive. That takes a toll. The few hours of sleep I got was at midday. I had to fight the decline of my faculties as the contest wore on. In the final hours I was making mistakes that I rarely when I'm alert. 

One example is short term memory. When I'm distracted my mind records the CW I hear and I then play it back to copy the call sign. When fatigue set in the recording was blank and I had to request a repeat. A second example is that I once hot switched the antennas. The amplifier instantly faulted and went offline, protecting against damage. Hot switching is prevented with my station automation system but it is not yet installed.

As I type these words I am mostly recovered from the contest and my sleep cycle is back to normal. I am taking it easy today and writing this article because following the contest I got a COVID booster shot. That result in one day of minor aches and lethargy. The rain is pouring down so I don't care. I purposely delayed the appointment until after the contest. There was no point going into the contest with an avoidable handicap.

Bottom line

I exceeded my informal QSO goal of 2000 by over 10% (2231, not including dupes). Despite surpassing DXCC before sunrise on Saturday morning my country total hit a wall. The same with CQ zones. There were many multipliers that were almost worked or that were unworkable. 

40 meters is perhaps the easiest band to sweep all 40 zones in CQ WW from this part of the world. I did pretty well by logging 37 of them but the other 3, all in Africa, somehow eluded me. On the other hand, sweeping all the Asian zones is remarkable. The openings over the north pole were extraordinarily good this weekend.

A couple of club members informed me that my raw score is a new Canadian 40 meter record in this contest. That would be wonderful despite my total ignorance of the record and having set no explicit goal. My objectives were to do well and to have fun. Those objectives were achieved. 

My final score and the status of the record will have to wait for log checking and the publication of the results next year. Mistakes are inevitable and my final score will be lower. I don't anticipate a large score reduction.

Lessons learned and station plans

No matter how big your antennas or the skill of the operator there is always a station better equipped. A full-size 3-element 40 meter yagi up in the lower stratosphere is a great antenna, but it pales in comparison to the even bigger antennas and stacks at the largest contest stations. 

I was outgunned more often than you might imagine. Even where my station was superior I could be beat by a more skilled operator or by the unavoidable vagaries of geography and propagation. Life isn't fair, and I'm okay with that.

Can I do better? Of course. Should I do better? Aye, there's the rub.

My preference is to organize multi-ops in the major contests. That way the station is maximally utilized and we can compete at a high level. Repeated high intensity single op entries is not what I want. I will continue doing it for a while longer. 

Although it has been interesting to learn the necessary skills to be a more competitive single op, and thus improve my skill level and results, it is not what I want to do all the time and, frankly, I will never do it particularly well. I am a good contest operator but I will never be a great contest operator. The unplanned long length of this article contains various lessons I hope to learn from.

In regard to the station, I absolutely will not stack a similar 3-element yagi on the tower. I'd need a ring rotator at the least and I'd have an ongoing worry about the tower's ultimate capacity. 30 ft² per antenna is a lot! The incremental load on station maintenance is an additional burden. The stack would have less than optimum performance since the antennas would not be high enough and the ½λ spacing not wide enough. For the predicted improvement it isn't worth the investment and maintenance. Others choose differently. 

What I will consider is a fixed wire yagi or lightweight rotatable yagi. That would give me stacking gain and additional flexibility on this important contest band. Over the winter I'll model alternatives and develop a tentative plan. There are unique requirements for equalizing phase in a stack built with dissimilar yagis.

It seems fitting I am closing what many consider an uninteresting article with a reference to the most read article on this blog. I'll return to technical subjects in the next articles.

Monday, November 21, 2022

Rebuild of the Beverage Antenna Head Ends

Lightning destroyed 2 out of 3 of the Beverage antenna head ends. These home brew devices select the normal and reverse direction. They also terminate the unused direction in a dummy load (resistor) to prevent reflections that would cause a bidirectional pattern. They contain transformers, relays, resistor and a bias-T to separate RF and the DC reversing voltage that share the feed line. 

There are articles for each of these devices and their matching reflection transformers. Rather than sprinkle the text with links to the articles I'll list them here. Refer to them for technical details since I will not repeat that information here. In this article the focus on the rebuild and design differences.

The north-south Beverage head end was taken indoors before the lightning strike so it didn't suffer the same fate. That was because it, too, was malfunctioning. After completing a variety of other higher priority jobs the time had come to deal with the broken units. The top band season is well underway and I need the Beverages to hear stations that my big transmit antenna attracts.

Many of the components in the affected devices were destroyed, even the PCB copper traces. Since there was little to salvage I opted for a complete rebuild of the electronics. The plastic (ABS) enclosures and hardware were okay so I cleaned and reused them. Connectors and their wires were removed from the old boards and reused.

Hoping for good news, I removed the transformers and tested them. Several were okay but the rest had melted or shorted windings. Winding miniature binocular ferrite cores is unpleasant work and I wanted to avoid as much of it if as possible. The Fair-Rite cores are ½" on a side and the holes are ⅛" wide. I did not reuse the cores for the discarded transformers although they are probably okay. Time is of the essence and they're inexpensive.

I started with the north-south RG6 Beverage since it had no lightning damage. I removed and tested the transformers and they were both good. That was fortunate. The fault appears to have been one of the SPDT reed relays. It had a lot of material between it and the PCB from an insect infestation. A thorough cleaning did not resolve the problem. By holding my ear close to it while applying voltage (they switch very quietly) I could tell it wasn't healthy. They're sealed so I'll never know. The coil resistance tests normal.

I selected new parts and ordered them. The proto boards come from my stock. On a cold and miserable day I got down to work.

The new proto board happens to be designed to fit the Hammond 1590 enclosure. It's quite a common enclosure and it is available as plastic or cast aluminum. Plastic is easier to work with and unlike many other RF devices there is negligible benefit from an RF tight enclosure. Please note that the relay has a wiring error in this picture that I discovered during testing. Don't use it as a template! I was lazy and didn't bother to take another picture after correcting the error. You might find it educational to refer to the schematic (earlier linked article) and try to find my mistake.

Unlike many proto boards, the copper traces only connect two adjacent holes. To simplify the wiring there are several soldered joints above the board. Where I could stuff two wires into one hole I did. I am using the same type of RF choke and low voltage bypass capacitor in the bias-T. The new DC blocking ceramic capacitors are rated for 630 volts. They replace the 40 volt devices that lightning destroyed. Of course lightning induces a far higher voltage but these will have a fighting chance if the pulses are short enough. The difference in price is small and worth the experiment.

Reed relays are small and very good for small signal switching. But they're relatively expensive and two are needed since DPDT reed relays are rare or nonexistent. I decided to go with the larger and cheaper Omron G5V DPDT relay. It's small and sealed, and it is found in many commercial receive antenna products. That's good enough for me.

There is no flyback diode on the relay coil. I was in a rush and it can be easily added later. Alternatively, the diode can be placed in the shack controller, either on each control line or the positive line from the power supply.

Wiring and layout isn't critical for receive application below 2 MHz. The proto board is larger than what I used for the first Beverage head ends, which leaves lots of room. The wider separation of components eases construction.

When fully wired the head end is tested. I constructed a test jig on a small "push in" proto board, The analyzer or VNA is connected on one side and the head end on the other. A blocking capacitor protects the analyzer from the applied +12 VDC. The alligator clips connect to the power supply. 

To reduce stray inductance use shorter wires to the power supply or, better, insert RF chokes. For rough testing this setup worked well enough, but don't expect accurate reactance measurements. Resistors are placed across the antenna terminals to simulate the common (normal) and differential (reverse) modes of the Beverage. 

This isn't a perfect test since there is no true antenna, with a long wire (transmission line) and reversing transformer. The 75 Ω load resistor should see a matching resistance at its port via its transformer to minimize inaccuracy on measured mode. Again, for a rough bench test it isn't strictly necessary, but it may be helpful when interpretting measurements that differ from perfection. We'll see shortly that it did lead me astray in one instance.

The rebuilt RG6 reversible Beverage head end was reinstalled. The wiring error was discovered that evening. It was retrieved and repaired the next day. The next evening it worked as it should. That was one head end down and two to go.

If you refer to the article where I twinned the northeast Beverage to make it reversible you'll notice in the schematic that there is only one of the transformers connects to the Beverage wires. The other takes the common mode (normal direction) from the first transformer's centre tap. 

It was no surprise that when the transformers were removed from the lightning damaged head end that the first transformer was dead. The windings were burnt and shorted. The other transformer tested good and was reused.

Unfortunately the 4:12 transformer is more difficult to wind that the others. This is due to the large number of turns (16 in total) and care in construction to achieve best balance in the centre-tapped primary winding. I used a new binocular core and teflon sheeting. Teflon liners prevent wire abrasion by the hard ferrite (it's a ceramic). 

I purchased a small roll of 28 AWG magnet wire rather than the scavenged enamel wire I used previously. The enamel coating may have been abraded when it was removed from an old transformer and a few transformer failed due to shorted turns.

In retrospect it would have been better to use 24 AWG magnetic wire because the thinner wire is difficult to handle. It is also easy to damage the wire when stripping the enamel off the wire ends. For the number of winding turns needed for Beverage transformers there is no need for very thin wire. I often use insulated wire from discarded Cat5 cable for windings with only a few turns. When I do that I can often make do without the teflon liners.

I must be getting good at winding these tiny transformers because I got it right the first time. The impedance transformation of 9:1 (the turns ratio of 3:1 is squared) took the 330 Ω resistor to 37 Ω, which shows as a flat SWR of about 1.4 on the analyzer.

The new transformer was mounted on the PCB. The old transformer is also in the picture. After a bench test the head end for the northeast-southwest Beverage was reassembled and installed. It was tested that evening and although it worked there was a problem with the antenna itself that made it bidirectional. Nevertheless it was nice to have it back.

Suspecting lightning damage to the reflection transformer I trudged through the newly fallen snow to retrieve the transformer. It tested okay so I soldered it back in place and trudge back to reinstall it. I took the opportunity to replace the hastily repaired ground wire that an animal had torn off sometime over the summer months.

The next step was to retrieve and test the head end. After removing the cover it took less than 15 seconds to spot the problem. Instead of a wiring error it was a wiring omission. The picture above was taken before the repair so, again, you have an opportunity to troubleshoot it yourself. If you decide to take the challenge, stop reading now because I'm about to tell you what it was.

One of the two Beverage wire wasn't connected to the transformer. I had cavalierly dismissed a puzzling R component of the impedance measured while bench testing the reverse direction (differential mode). I was sloppy and I paid for it. 

The wire was installed and, without further testing, installed. An SWR sweep looked good and that evening it performed perfectly. That was a relief since CQ WW CW is this weekend.

I have yet to rebuild the east-west Beverage head end because I depleted my stock of proto boards. More will be ordered. With my temporary head end I now have 5 out of 6 directions working. It is east that is missing, and I can live with that for now since there are not many stations in that direction.

I plugged the weep holes I had drilled in the old plastic enclosures. The enclosures seal well on their own and the weep holes only encourage insects to make their homes inside. The moisture and detritus the critters introduce cause corrosion. We'll see how well this works. In any case, next summer I will likely remove the electronics. I want to be prepared for a third(!) lightning strike.

Saturday, November 12, 2022

Re-aligning the 40 Meter 3-element Yagi

Here's a retelling of an old joke:

Riddle: Where does a 300 lb antenna sit?

Answer: Anywhere it wants to.

When I raised the 3-element 40 meter yagi last December I omitted a step. The plate for the boom-to-mast clamp was firmly tightened on the mast but not too tight. Getting the boom to sit flat on the plate when the tram line was slacked might require twisting it, and I wanted to be able to respond quickly. 

Our team did such a great job that it was positioned perfectly. All I had to do was slip on the u-bolts and thread the nuts. I was so happy that I skipped a critical step. My mistake became apparent a few months later in the aftermath of a wind storm with gusts of 90 kph. That's when I remembered.

The antenna was no longer aligned with the 10 meter yagi above since it had turned on the mast. The difference was 30°. I confirmed that the 40 meter yagi was responsible when I climbed the tower and saw the marks on the mast and the skew of the boom truss cables. I thought back to December and could not recall tightening the several clamps holding the mast to the clamp plate. Sure enough, that was the mistake I made.

The antenna wasn't going anywhere so I put it on my to-do list and mentally adjusted the true bearing of each yagi when rotating them. During late summer I stepped the mast in preparation to hook the top of the mast -- it rises 10' (3 m) above the top plate -- and attach it to a tensioning device and a harness for the boom. I wasn't satisfied with my first mechanical design so I delayed the job. 

It is no trivial matter to take the 300 lb weight of the antenna and being able to freely rotate it on the mast without also having it slip down the mast. I kept putting off the job since it wasn't urgent. My preference was to come up with an alternative design that would be easy and foolproof.

This is the contraption I discarded. The weather is cooling and we've had high winds, neither of which is conducive to mast climbing. That was one point against it. Another was the difficulty of holding the hook firm on the rim of the mast pipe until there was tension on the cable, especially since it would have to lever out over the mast clamp and boom of the 10 meter yagi located less than 1' below the top of the mast. 

The final concern was the turnbuckle. I liked it because it's lighter than alternative mechanisms. However, it is difficult to adjust when it's on the mast since the upper and lower eyes must both be fixed in place and there is no good way to do that. When using them on tower guys the lower screw is bolted onto the anchor rod plate (or equalizer plate) so you only need to hold a rod or big screwdriver in the eye of the upper screw while turning the turnbuckle.

Shackles on the boom cradle would help to secure the lower screw. I tried that with several sizes of shackle and none of them fit in the small triangular gap between the boom pipe, u-bolt and mast clamp plate (there are no saddles under the u-bolts). In light of these deficits I decided to try something different. 

We had several days of unseasonably warm November weather and I wanted to take advantage. The morning of the arrival of the rainstorm remnant of hurricane Nicole I draped 30 lb of steel equipment on and over my safety gear and climbed 150'. I had about a 2 hour window for the job before it began to rain. I was probably lifting 40 lb in addition to my own weight! That isn't fun but I can do it. It was another win for brute force over ingenuity.

On the left, ¼" aircraft cable is threaded through the narrow gap under the boom clamp u-bolts. The ½" u-bolts are a strong anchor point. A chain or belt around the bottom of the boom clamp is easier to attach but it would be heavier and might slip out while awkwardly setting up the lift.

Rather than climb the mast with the aforementioned hook, a scavenged mast clamp that came with the LR20 tower is attached to the mast below the boom truss clamp (middle panel). To make room for it I cut the ties binding the LMR400 coax to the mast. The ½" u-bolt and heavy gauge steel angle will withstand more than the required vertical force required to support the yagi. A 5/16" chain is looped around the mast above the clamp with the ends connected by a shackle. 

The movable hook of my 40 year old 2-ton come-along (hand winch) slips onto the shackle and the fixed hook snaps onto the aircraft cable. This arrangement is easiest for operating the winch without interfering with my fall arrest gear and permitting clear access to the mast clamp. In seconds the winch had the weight of the yagi and I loosened the 8 nuts on the ½" bolts of the mast clamps.

With the yagi free all I had to do was rotate the yagi. That's easier said than done!

Developing sufficient leverage at the centre of this behemoth isn't easy. It's particularly difficult at the top of the tower where you have limited options for where to brace your feet and how far out your hands will reach and be able to push. Think about it for a moment and you can perhaps understand. My solution was to loosen my positioning belts, lean out from the tower, crouch and plant my feet on opposite sides of the tower. I could then pull the boom and push the driven element, or vice versa.

Once the antenna starts moving its momentum keeps it moving. When the boom was approximately aligned I tightened a few of the mast clamp bolts. I rechecked the alignment and found that the yagi had rotated back several degrees. Only after the second attempt did I look around to find the reason for the backlash. 

It was the boom truss mast clamp. It is fixed to the mast so that rotation past its neutral point increases tension on the truss cables. The tension gradient in torque turns the boom truss into a spring.

This is more difficult to fix and I didn't have the time with Hurricane Nicole literally on the horizon. I gently nudged the antenna to minimize backlash and gradually tightened the bolts. As you can see the alignment is out by a few degrees. For a 3-element yagi, and a 5-element for that matter, there is little practical impact. The yagis' beam widths are pretty broad.

As long as they align I can be flexible on where the yagis point because the prop pitch motor direction indicator permits setting of the zero point. A tweak of a pot in the controller and it's all done.

Next year I'll redo the alignment. I'll let the 40 meter yagi come to rest with the boom truss cables orthogonal to the mast clamp, which is exactly where it wants to sit. I'll then step the mast, climb up and align the 10 meter yagi with the 40 meter yagi. An inspection is in any case timely and I may take the opportunity to lift it the final foot to the top of the mast.

Wednesday, November 9, 2022

Big Station QRP in Sweepstakes

ARRL Sweepstakes draws me for its nostalgia. When I started contesting in the mid-1970s domestic (North American) events were more appealing than DX contests. Operating during a solar cycle minimum from the edge of the mid-continent auroral zone (VE4) the potential for DX contest success was bleak. Sure, we tried, but it was hopeless. It is no surprise that Sweepstakes was for us the premier event on the contest calendar.

I got as high as Top Ten in both the CW and Phone events (low power category) in 1978. The next year I moved to VE3 and transitioned to multi-op DX contests. The DX potential was excellent in eastern NA and the solar cycle was just passing its maximum. In any case, I had no station of my own so I did the contests the station owner preferred. When I built my own station a few years later I barely gave Sweepstakes a thought.

I dabbled in Sweepstakes in the years following my return to the hobby in 2013. When I built my current large station I continued to dabble in it. In 2020 I got more serious about it but in the QRP category. I thought it would be more interesting that way and I believed, wrongly, that the slower rate would avoid the Sunday doldrums.

I operated SO2R as before with the absurd attenuator on the FTdx5000 I built for a previous QRP contest. This year the towers and antennas are substantially complete, and everything works. Some of the controls on the operating desk are slapdash but it's usable.

Results

From the claimed scores posted to 3830 I am pleasantly surprised to find that I am, at least for now, in first place. It's unlikely that there are higher unreported scores so it will come down to log checking. My claimed score is over 119,000, with 721 contacts and 83 sections. I missed the clean sweep by not working Newfoundland.

In the QRP Unlimited (assisted) category W2GD had 10% more contacts and a clean sweep. He's easily the superior operator though part of the difference may come from finding more stations faster by clicking on spots. It's just curiosity since we are not in the same category. I am encouraged that the gap is smaller than in 2020, even if my improved station is the reason.

Winning often comes down to picking a category that better operators and those with bigger stations ignore. Some contesters deliberately pick their category where they believe they have a good chance of winning. Plaques are not my motivation and, indeed, all the plaques I've won are gathering dust on a shelf. Displaying them is not important to me. If I win a first place plaque in this contest it will suffer the same fate. I value the experience, not the prize.

For those who enjoy contest reports I'll now dive deeper into this weekend's contest experience.

Activity level

From skimming some of the post-contest reports on 3830 there is a widely held view that activity is lower this year. That is also my sense. Nostalgia motivates those in my cohort of older contesters. More younger hams are entering Sweepstakes that I'd have once believed, but it is not enough. Maybe I'm being too pessimistic and next year will be better.

When you can only work a station once, regardless of band, you soon run out of stations to work. When I went to bed late at night I had over 400 contacts in the log. All of Sunday garnered only another 300. The Sunday grind in Sweepstakes is dreadful. As an unassisted operator the constant trawling of the bands is fatiguing. Many quit, and I don't blame them. I stuck with it because I was doing reasonably well and I wanted to see if I could beat my score from two years ago.

As I said, nostalgia is at play. To increase rate the band rule would need to change or the contest duration reduced. The chance of that happening is quite low since ARRL strongly believes in preserving tradition. It is arguable that today's premier North American contest is NAQP.

All you can do on Sunday is keep the CQ machine going and scour the bands so that you can work casual operators who briefly appear to make a few contacts. Most casual operators S & P so you must run or they won't find and work you. QRP doesn't change that. That many operators ignore weak signals is no excuse.

SO2R

SO2R is difficult in Sweepstakes. The long exchange and frequent requests for fills requires greater skill to coordinate active QSOs on two radios. I am getting better but I am still clumsy. The lower rate you have with QRP also lowers SO2R mishaps. But even the top competitors have a low rate on Sunday!

S & P on two radios is challenging because you are constantly listening and copying in both ears. It is easier to run on one radio and search on the other. You must S & P more with QRP but I still recommend the mixed strategy. I would run on both radios when the rate was really slow or I needed a rest. It's important not to be lazy and persist with low rate dual running. You must spin the knob in this contest.

Run vs. S & P

You must both run and hunt in any contest to be competitive. The question is where and when to do each. With SO2R you can do both, which helps but that is not a full answer.

At the contest start I tend to S & P a lot. In Sweepstakes I do the same but I focus on just one radio. That is, I ignore the second radio for a short time because SO2R in this contest is awkward when the rate is high. And the rate is high at the start.

Every running station you tune in as you scan the band is a new one. That's pretty well guaranteed. A higher rate than running is typical unless you are a rare multiplier or you have a big signal from a perfectly positioned location. I did S & P for most of the first hour, taking advantage of propagation on the high bands. After that I ran on 40 meters and continued to hunt on the high bands. The running was slow so switched back to running on the high bands. 

In this part of the continent 40 meters is usually more active during daylight. The excellent high band conditions that persisted well after sunset was likely responsible. It certainly influenced me. QRP can go a long way on the high bands where the noise level is lower.

After those first hours I tried to keep running on one radio. That can be slow with QRP in the first hours of the contest since, like me, everyone had ample strong stations to work. They lost nothing by skipping my weaker signal. Running became more productive as the evening wore on.

What to do on Sunday when both running and hunting deliver low rates? There really is no good answer. The better strategy is regular band changes to catch more casual operators. In Sweepstakes you can, in theory, work stations on any band so it may seem as if it doesn't matter. It does matter since many operators tend to focus on a particular band and you must go there to work them. I probably should have spent more time on 10 meters.

West coast stations favour the high bands to work the masses in the densely populated east. Those with low power and poor antennas do the same since they don't fare as well against the atmospheric noise on the low bands. That is not an absolute rule so you have to be flexible. This weekend the low bands were fantastic. Signals from the south and west edges of the continent were strong on 40 and 80 mters and the noise was low. 

The high bands were notable for unusually strong back scatter signals. I was able to work a surprisingly large number of east coast stations with my big yagis pointing west. Most times that is only possible with high power. S & P was better than running to work back scatter due to my weak signal.

On Sunday nothing worked especially well and my rate plummetted. I had to keep spinning the knob to find stations, and the run radio might only garner a QSO every 3 to 5 minutes. Even so it helped to keep running to catch the small number of casual operators yet to be worked. 

Running caught many of the rare multipliers I needed since they were S & P.  Casual operators in rare multipliers often avoid running because they don't enjoy dealing with an unruly pile up. Pile up behaviour deteriorates when everyone is chasing one of the final multipliers needed for a clean sweep.

Benefitting from spots

Every so often the silence on the run radio was replaced by a wave of callers. I couldn't see when I was spotted but I sure could hear it! The giveaway was that those callers sent a precedence of U or M in the exchange. That is another good reason to have one radio always running. 

An amusing effect of the spots is that I am frequently called by stations that can't hear me. It happens to me every time I operate QRP in contests. They click on a spot, hear silence and toss in their call. Only after doing this a few times do they realize they can't copy me. Then they click another spot and they're gone. I suppose it wastes my time but in Sweepstakes that's rarely a problem because the rate is so low.

The mouse that roars

This is typical of what many of my QSOs sounded like:

Me: "...Q VE3VN 72 ONE"
Them: "Pr?"
Me: "Q"
Them: "Q?"
Me: "QQQ"
Them: "TU..."

When one of my 5-element monoband yagi (3 elements on 40) perched in the lower stratosphere is pointed in your direction you will hear my 5 watt signal. I am the mouse that roars. I wonder how many of them suspected me of slipping in a few extra watts. Most QRPers go small in all aspects of their stations, and 5 watts into a wire hanging from a tree is never very strong. 

I've operated QRP on 160 meters in contests and worked a surprising amount of DX. As I was setting up the station on Saturday afternoon I called one of the current DXpeditions on 20 meters and logged them within a few minutes. 5 watts can do pretty well with big towers and antennas.

There is no substitute for power. QRP is -13 db and -23 to -25 db compared to low power and high power contest participants, respectively. You can't make up for that deficit with big antennas. But every decibel helps! I was routinely working the west coast on 40 and 80 meters. More than a few operators commented on my big "Q" signal.

There are the inevitable downsides of a signal weaker than most others. My run frequency was regularly stolen. Perhaps they couldn't hear me or decided to muscle in anyway. Half the time they didn't send "QRL?" before punching the CQ button. This is expected with QRP and I didn't fret over it. I would QSY, often less than 1 kHz. The only concern was that if I had been spotted I might lose a few contacts.

Whither QRP redux

I keep telling myself that contesting with QRP is too painful and I should stop doing it. Yet it can be a lot of fun, especially with big antennas. I expect that I'll keep doing it occasionally when I have an itch that needs scratching.

Thursday, November 3, 2022

CQ WW SSB: Preparation, Operation and Contemplation

I am not especially attracted to SSB single op contests. I made no attempt to join a multi-op and my station is really not ready for it. Since I was going to do it alone I narrowed my focus so that it could be enjoyable and not a time burden. There was also the state of the station to be considered, which is a never ending work in progress.

After considering options I decided on the same category I entered last year: single op, assisted, 15 meters, or SO(A)SB15 HP using the most common abbreviation.

Unfortunately it was not so easy. There were outstanding problems with the 15 meter stack that had to be resolved. When I considered 10 meters to take advantage of the vastly improved conditions there were similar problems to resolve. Besides, I have the option of focussing on 10 meters in December's ARRL 10 Meter contest. 

When I considered the other bands, 80 and 160 meters are difficult on SSB due to the noise level, the 40 meter phone segment is very crowded and split operation is bothersome, and 20 meters would require too many hours of operation to be competitive since it is now open long into the night.

Preparation

There were two problems to be solved with the 15 meter stack:

  • SWR was 2 rather than below 1.5
  • The wiring of the direction pot wiper was open

With ~100 meters of coax between the outdoor 2 × 8 antenna switch and the stack switch on the tower there is a lot that can go wrong. The problem was isolated to that long length by testing the feed line at the antenna switch and at the stack switch. After doing that, I was relieved to find that the antennas were working properly.

I was concerned that the fault might be in the 50 meters of buried LDF5. I've never had a problem with directly buried Heliax where the jacket was in good condition, but there's always a first time. Since the other cables buried alongside it in the trench were fine I was hopeful that wouldn't be the case.

I tried to find the fault location with my old RigExpert AA54, by sweeping the cable in the frequency domain and using math to convert to the time domain. This model does not have a TDR (time domain reflectometer) feature and my VNWA3, which does, is difficult to use in the field. The plot of the fundamental reflection only told me the length of feed line. There were interesting squiggles on a wider sweep that were difficult to interpret. Some day I'll have to learn how to properly perform a TDR analysis.

I climbed the tower and disconnected the connectors that spliced the main run to the tower run of LDF5. The upper run was fine but the buried cable showed a fault. This test was done with a small 50 Ω load termination where the cable would plug into the antenna switch. I opened the lower connector and found corrosion.

One of the nice features of large hard line connectors is that there is no fussing with coax braid and soldering. The connectors are entirely mechanical. But because they're large so are the wrenches. They had to be carried up with me. That's a fair exchange for connectors that are easy to work on high up the tower. 

A bad connector on ordinary coax can be far more difficult to repair. This week I spent a few hours on a friend's tower diagnosing a feed line problem that was due to a misbehaving N connector on RG213. Eventually we gave up on it. I cut the coax and I installed a UHF connector. That solved the problem but it wasn't fun.

The left panel shows the upper half of the male N connector and the centre pin. The corrosion on both the outer and inner couplings is readily apparent. A few drops of water dripped from the connector when I pulled off the shell, which explains the corrosion. It's repairable but that's a job for another time.

What puzzled me is that the Heliax inside the connector was in pristine condition, with shiny copper and no debris on the dielectric. The connector and female barrel connector for the upper length of Heliax was similarly clean. The removed weatherproofing tapes were also clean on the inner surfaces.

Perhaps it was condensation? It also might have been snow or ice that I didn't clean out when I installed the Heliax two winters ago. Who knows. I descended the tower to get another half shell and centre pin. Up I went and wrenched them on. When I connected the analyzer I read a clean 50 Ω from the load back at the antenna switch.

To get rid of the barrel connector and have a simpler coupling the replacement connector is a female N. That left a 1" gap between the connectors. With the Heliax well tied to the tower that posed a challenge: hard line doesn't stretch! I had to climb to the top and coax the coax through the plastic ties on the way down. I couldn't get more than ½" doing this so it took two trips.

When I was done the SWR was back to normal. I taped it up and moved on to the next job.

I previously mentioned that the new direction indicator electronics require that the direction pot wiper not be grounded. But when I disconnected the grounding wire at the top of the tower there was no continuity back to the shack. There are several splices and cross-connections among the multitude of Cat5 control cables in the path and I had to trace the wire through all of it.

It took a few hours until I found that a wire in a crimp connector at the tower base had snapped off. I had to remove the crimp connector to see what had happened. It's possible that I was overly aggressive with wire stripped and the thin AWG 25 wire was nicked. It took only a minute to repair.

Ugly, isn't it? What mattered is that it worked. In the picture is the prototype direction indicator with an extra current limiting pot and wired into the ±12 VDC supplies in the old controller. The upper yagis of the 15 and 20 meter stacks are shown pointing NNE right after I worked VK9CM on 20 meters after the contest. The controller was problem free during the contest so I never had to run to the window to see where the antennas were pointing.

Operation

For a change there were no equipment problems during the contest. The ionosphere was another matter. I am far enough north that the geomagnetic disturbance blocked many potential contacts in Japan, the far east and Europe. US stations several hundred kilometers south did better since they could "see" around the disturbance to the right and to the left. It was frustrating but there was nothing to be done about it.

This is a regular complaint and I admit that it sounds like a gripe. Yet it is a real concern and one that is not always appreciated. It's just the way propagation works:

  • This time of year daylight is longer as you go south, and that enhances and extends openings
  • At the slightest sign of a geomagnetic disturbance, we see attenuation or complete blockage of signals between northeast and northwest

In Canada we have advantages that counter those challenges:

  • We have few mode restrictions so we can operate SSB where the Americans cannot
  • The high ratio of Americans to Canadians gives us far more stations to work

For these reasons Canadian and American scores are not comparable in CQ WW. Yet we habitually do compare our scores despite our respective advantages and disadvantages. This is unsurprising since category plaques for North America often lump us together.

On Sunday the conditions were far better. In an unusual twist I worked more stations in the second half of the contest than the first. But I was still outgunned when chasing particularly attractive multipliers in Africa and the far east. Some of this is geography and some is my station. Big as my towers and antennas are there are far larger. Add in the different power limits and I am dealing with several decibels of disadvantage. Many of the southeast Asian stations I couldn't work Saturday would have been workable on Sunday had they been there. But for them it was Monday morning and a work day.

I worked a similar number of stations as last year but with 10% fewer zones and countries. Despite the lower solar flux, last year I could run JA. Not this year. My runs were solely to Europe and the US. Nevertheless, by pointing the big antenna south and west I was able to garner quite a few callers from South America and Oceania, respectively.

One frustrating miss was zone 2. VE2IM's usual big effort was absent because he went to the Caribbean. VO2AC and VE2IDX were single band and neither of those bands was 15 meters. When VO2NS showed up late Sunday the skip was long to the east and he was unworkable from here. Many North Americans worked him easily.

The dearth of Ukrainians and Russians reduced QSO potential but that had little impact on multipliers.

There were many multipliers, zones and countries, that I heard but could not work. In some cases I had only to wait for conditions to improve but in others the wanted stations moved on before that happened. As is typical with a big signal, many valuable multipliers called while I was running. Most casual operators never run and only call others. That's as true for rare DX stations as it is for those of us in common locales. It is vitally important to run to give them a change to find and call you. 

Lingering in hopeless pile ups lowers your score even when you eventually get through. Experienced contesters learn to balance running and multiplier hunting to maximize their score. Working other stations while the big guns and those with more favourable propagation work the wanted multiplier is usually an effective strategy, but not always. They may leave before the pile up thins enough for you to have a chance.

There are many old articles in the blog that discuss the above points in more detail. Rather than select one or two of them, use the search box at the top left of the page.

When 0000Z rolled around on Sunday evening my final score was respectable but not impressive. I was moderately satisfied and also disappointed. There were many "what ifs" to ponder, which bring me to the final section of this article.

Contemplation

Amateur radio is a hobby and contests are fun and exhilarating events. Winning is great but, for me at least, it is not the primary motivation. I enjoy designing and building a competitive station, learning new skills and pushing myself to see what I and my station can accomplish. I rarely win and that does not discourage me.

My towers and antennas are so far above the norm that I can crack most DX pile ups without an amplifier. Indeed, the amplifier had gone unused since August. I turned it on and used it the day before the contest to reassure myself that it still worked!

Many stations have more and bigger towers and antennas. There really is no limit if you have the time, motivation and resources. The question I keep asking myself is: how far should I go? I'd like to be more competitive, but that comes at a price. Also, while I'm in excellent physical and mental condition, I am not young and I will only get older. VE3VN is over the hill and it's all downhill from here.

I know where to acquire more large towers at a reasonable price. I have not and will not pursue these opportunities. Dealing with the two big towers and their antennas is enough of a challenge. I have perhaps another 10 good years of tower climbing in me. Hiring riggers when my climbing days are over will not be cheap. It's important to keep the future burden managable.

Nevertheless, I can do better with the towers I have. There is also the possibility of a small tower to host a tri-band or better antenna to replace the TH6 that is side mounted on one of the big towers. I've reluctantly concluded that trap tri-band yagis are not up to the demands of competitive contesting.

The possibilities I am currently contemplating include, but are certainly not limited to:

  • Swing gate for the fixed, side mounted lower yagis of the 10 meter and 15 meter stacks. That would offer 300° rotation to have more stacking power when chasing multipliers outside Europe. That would prove especially useful for running stations in Japan and southeast Asia, along with multiplier hunting in Africa and the Caribbean.
  • Move the XM240 to the current location of the TH6, but put it on a swing gate so that I can use it for more than just NA and SA. I can of course leave it on the Trylon, at about the same height and 360° rotation. The move would free the Trylon for more VHF antennas and small yagis for 17 and 12 meters. I would like more effective DXing antennas for those non-contest bands.
  • A swing gate for the lower 20 meter yagi is unlikely due to the antenna's large size and weight and relatively low height. However I would like a 3-element rotatable 20 meter yagi for multiplier hunting. The possible locations for it are limited but I would like to squeeze one in somewhere.

What's missing in this list are tri-band yagis. I would like to find a place for the TH6, perhaps fixed to the south or southwest as a rapid option for easy to work multipliers. I have to ponder this one further.

What does not fit in my plans is the TH7. There simply is no place for it and, as already stated, though it is quite good it is nevertheless a compromise antenna. Another problem is that it cannot be side mounted because the driven elements are close together. It is only suitable for mast mounting at the top of a tower, and I have none available. It can be converted to a TH6 but I don't really see the point. I will hold on to it for a while longer, just in case. 

I have other antenna plans for 80 and 160 meters, most of which have been described in earlier articles. All antenna plans are for 2023 and beyond. My 2022 antenna season is wrapping up. 

The major project remaining is to rebuild the extensive lightning damage to the Beverage. That was one reason I chose a high band focus in CQ WW. I want to be fully operational in time for CQ WW CW. CW Sweepstakes is this weekend and I have yet to decide which category to enter and how serious an effort to make. We are having unseasonably warm weather and I might decide to turn off the radio to spend time in the great outdoors.

Thursday, October 27, 2022

Shallow Dead Man Anchor

Our antenna towers need help to stand upright. Gravity alone can't provide stability since it can only pull them against the ground but cannot provide lateral stability. Ground anchors are what give the tower stability to withstand the forces they must face: vertical, horizontal and torque. One big anchor if it's self supported and several if it's guyed.

In most cases the anchor is a solid mass of reinforced concrete. There is one directly under the tower. A guyed tower has several additional anchors. 

Anchor specifications depend on tower load and soil conditions. To get a building permit for a tower you may be required to have a soil test done by a professional. Those without the need to acquire a permit should not skimp on the anchors or a thorough soil inspection or test. Nature and the laws of physics pay no attention to pieces of paper, or hope.

There are articles in this blog that go into some detail of the anchors for my several towers. They require siting, excavation, reinforced concrete and alignment. I used heavy equipment and hired skilled labour when it made sense to do so.

Anchors are not only for towers. Sometimes we use trees or a convenient rock to hold the ends of wire antennas. A house bracket can anchor a light duty tower. The demands on anchors for non-tower use are often less strenuous. 

I ran into a case recently that I believe is worth an article. It wasn't for a tower but for my overhead run of cables from the hay field trenches to the switching system and cable connections at the base of the Trylon tower near the house. 

Looking back in the blog I find that I never really discussed that feature of my station. That's a gap I'd like to fill. However, right now I'll leave that and focus on the ground anchor that supports the overhead messenger cable and the multitude of coax and control cables that hang from it.

The weight of all those cables is substantial. There is also the tension to reduce sag and allow people to walk safely underneath. The existing messenger cable from the tower to a 10' aluminum post at the edge of the hay field is ~60' of ⅛" aircraft cable. Two intermediate posts take up much of the sag without requiring the higher tension required for an uninterrupted span. Tension on the messenger cable is perhaps a few hundred pounds,. That's less demanding than for a tower but should not be treated lightly.

A leg of the Trylon tower base section anchors the cable at one. At the other end is a screw anchor and diagonal guy to the top of the post. A wide wood base and steel peg pounded into the ground keeps the post from leaning sideways. It's ugly but it works. Or at least it has worked until now. 

An accidental collision with the mower several weeks ago exposed a weakness with the screw anchor. Despite no damage from the mower, the screw anchor was dislodged a few inches. Over the past several years I've occasionally had to screw the screw anchor back in a few inches as it pulled from the soil and the turnbuckle bottomed out. It has become too unreliable to ignore. 

The post that supports the messenger cable (a salvaged 10' long Hy-Gain boom section) is creeping and the cables are creeping down the sagging messenger cable. The bend in the post was there all along, due to high impact with the ground when the tower it was on failed. That was over 30 years ago and this is the first use I've found for it!

Although not in immediate danger of collapse, the time has come to rebuild. I had intended the overhead run to be a temporary measure until I could trench the cables to the Trylon. Due to the constant addition of cables and the horizontal roots sprouting from the surrounding birch trees the overhead run will have to be permanent. So I need to do it right. I stabilized the post with a long rope back to the tower and proceeded to design and install a better ground anchor.


Let's review basic facts about ground anchors. The mass of the anchor does not support the tension load. The load is supported by the resistance of the soil on the anchor. The larger the surface area of the anchor and the deeper it is placed the greater the mass of soil that must be displaced by the load. Undisturbed soil can withstand a greater load than top soil. 

The anchors for my large guyed tower are 2' × 2' × 8' blocks of reinforced concrete sitting 6' below grade. That provides ample resistance for the 4000 lb static load and 3× that amount of dynamic load. The attributes are responsible for the "dead man" moniker. Concrete forms for the anchors are often called coffins. Aside from this little joke I'll stick with calling them ground anchors.

The concrete is reinforced with steel rebar so that the anchor behaves as a rigid block. There is tension across the forward and upper faces as the rod is pulled towards the load (red arrows). Tension is greatest at the rod and diminishes as you move outward. Without reinforcing the anchor will eventually crack from the tension. Reinforcing rods across the front and top faces (large black dots on the left) give the anchor strength in tension. Unlike a large tower anchor, there is little shear force in a small anchor so that there is little benefit from constructing a rebar "cage".

The requirements for the anchor to support the overhead cable run are not severe. The tension is unlikely to ever exceed 500 lb. The wind load is not a large factor since the mass of cables are low to the ground and sheltered by trees. A small and relatively shallow reinforced concrete anchor is sufficient, and it will be superior to the screw anchor it replaces.

The main problems with the screw anchor are that screwing it in disturbs the undisturbed soil and it may not penetrate deep enough for the relatively small area of the anchor plate. Proper installation requires a tractor with an auger driving attachment. This is the preferred method since it disturbs the soil far less than doing it manually and you can power through dense subsoil and stones. That is, if the anchor has the strength to withstand the forces involved.

The 2' screw anchor that held the overhead run also shows how the auger end (which doubles as the anchor surface) is bent from screwing past rocks in the soil. The steel grade of these farm oriented anchors is not great. It is cheaper to use more steel than to make the steel higher strength.

The screw anchors I manually installed for the 80 meter yagi's small tower are holding well but they are longer and penetrate deeper than the one above. They were very difficult to install and the newly disturbed soil had to "rest" over the winter and spring thaw before they were safely set in the soil. They, too, will be replaced when I rebuild the 80 meter yagi tower. That job is scheduled for 2023.

The new overhead run will have a stronger messenger cable and the post will be a 10' steel pipe. The pipe is visible above, alongside the aluminum post it will be replacing. The top of the post is guyed to the new anchor. 

The anchor is placed a few feet behind where the screw anchor was located so that there is more headroom underneath. People are less likely to walk into it. The excavation fit neatly between the two trenches to the 150' tower. The roots of the nearby spruce trees go down rather than spread horizontally and were not in the way.


The rod is 4.5' of ⅛" × 1.5" bare angle steel. I have 3 identical lengths set aside for the future work on the 80 meter yagi. I cleaned the loose rust, drilled a hole for the guy attachment and coated the steel with rust paint. The few inches to be encased in concrete are not painted since many coatings don't bond well to concrete and even rusty steel will bond. 

The purpose of the paint is to slow, not prevent, corrosion due to soil, water and moisture. The rod can be uncovered occasionally to check for corrosion. The anchor is not affected by removing soil from around the rod.

The hole was dug with a small shovel and garden trowel to keep it from becoming too large and consuming more concrete than needed. A concrete brick serves as a chair for the rod. Hole depth is 30" (75 cm), which is well into undisturbed soil. If you live in a cold climate you should place the anchor below the frost line to prevent shifting due to frost heave.

The rod is aimed at the tower. You can see a large concrete block being used as an emergency repair to the existing screw anchor. The angle of the rod is low because it is further back of the steel post than the post's height. That lowers the rod's angle so that the rod must be longer than usual to rise above grade. A string pulled tight from the top of the steel post is used to align the rod's direction and vertical angle. This ensures that the rod does not twist or bend under tension.

Mixing concrete is a lot like baking. Make a well in the centre of the dry ingredients, add just the right amount of water and mix it until you have a consistent viscous goo. I used two 30 kg bags of pre-mixed concrete (cement, sand and stone). I've used electric or tractor driven mixers for large jobs where concrete delivery was impractical or expensive. For a small job like this a wheelbarrow and shovel will do the job. The total volume of concrete was slightly more than 1³ ft, which is enough to make an anchor 8" × 8" × 27". There is enough room to encase the rebar by the recommended 3" (7.5 cm) of concrete.

At left is the coated rod sitting on the chair. It is loosely pierced by a few inches of rebar to fix the rod in the anchor. Digging a narrow and deep hole is sloppy work. I used stones to fill unwanted cavities to preserve the anchor's shape and avoid the need for a third bag of concrete.

In the middle panel the anchor is half done. I have just laid an 18" length of 10M rebar to reinforce the upper face of the anchor. Its twin is more forward and buried below the rod to reinforce the front face of the anchor. See the diagram further above. At right all the concrete is in place. A small trowel was used to smooth the surface. Although a buried anchor doesn't need to be pretty it is good practice to eliminate gaps and cavities where water can collect and freeze. Over the years the concrete will crack from repeated freeze and thaw cycles.

Before walking away I rechecked rod alignment. After several days the hole was ready to be back filled.

Notice how the 1ft³ of soil displaced by the concrete has miraculously vanished! Of course it's all there but has been used to level the uneven ground at the edge of the hay field. Small stones were buried in the excavation so they didn't need to be carted away. The sledgehammer was used to compact the loose soil as it was shovelled into the excavation. No further subsidence is expected. There was a lot of displaced soil and rock from the excavations of the big towers. The backhoe moved it out of the hay field.

I will wait at least another week before putting tension of the anchor. Concrete is typically rated by its strength after 28 days of curing. In this case that's 3000 lb, and of course strengthened by the rebar. I am happy to start work on a tower after only a few days since the concrete is strong enough in compression to build upward. It is better to wait for the concrete to cure more completely when it is to be placed in tension.

More on the winter prep work keeping me busy is still to come. But now my focus is shifting to the CQ WW SSB contest this weekend.