NEC5 Test Drive

I have a long to-do list for my station. It reflects a lot of ambition. However, my actual pace of work is at a lower rate. Amateur radio is a hobby after all. Some items linger on the list for a long time indeed! NEC5 was one of them. I say 'was' because I've finally purchased a licence for the software and added it to EZNEC.

EZNEC makes it easy to use NEC5 as an alternative calculating engine. Considering the many advantages of NEC5 over NEC2 and NEC4, and that EZNEC is now free, it is very easy to justify US$110 for a licence. I will not bore readers with what can be learned elsewhere about NEC5 and EZNEC, which you can find elsewhere, including following links provided in this article.

These are perhaps the most relevant resources I read before diving into my initial experiments with NEC5. It helps to know the technology you are dealing with before using it and trusting the results.

• EZNEC and the EZNEC 7 manual
• AC6LA's NEC5 notes (access requires a QRZ.com account)
• NEC5 validation manual
  

Next, a brief summary of why to choose NEC5 versus NEC2. Others cover it better and more completely, but a few points are enough to get you started:

• Tapered elements, including loaded elements -- with NEC2 you need the SDC (stepped diameter correction) in EZNEC, or its equivalent in other modelling software, and also stay within its strict constraints
• Antennas with wires meeting at angles, especially acute angles -- it can be done using NEC2 with fairly complex segmentation procedures, although EZNEC and at least one other package will help you with it
• Wire segmentation is in general not at all strict -- NEC2 requires strict segment alignment between parallel conductors when the separation is small
  
• Antenna elements with loads, lumped or distributed, are handled well -- includes capacitance hats, traps and coils inline with tapered elements and more that are often handled poorly in NEC2
  
• Radials can be on the ground or in the ground, and with more accurate results -- no more having to artificially place radials a short distance above ground, and consequent issues
  

All of these have been important to me at various times. Sometimes there are modelling workarounds and other times I had to mathematically calibrate a NEC2 model with measurements of a built antenna. NEC5 promised a far better modelling experience with less opportunity for errors.

There is a cost to gaining these advantages, and I don't mean the license fee. The greatest cost is segments: you need a lot. A peculiarity of NEC5 is that the calculations converge slowly with increasing segments. That is, you need a lot more segments than with NEC2 to get accurate results. The more complex or large the antenna, the more you need.

That slows the run time and can be a bit of a bother at times. Doubling the segments is frequently inadequate so I double again. I've stopped at 4× the amount though some go further. More on this as I go through my initial modelling experiments with NEC5. 

There are other differences that must be understood. For example, NEC5 does not natively support insulated wires. EZNEC includes an algorithm to allow them when using NEC5.

Luckily for most hams NEC2 continues to be perfectly adequate, especially with the enhancements included with EZNEC. Whether to use NEC5 depends on your interests and needs. This article may help you decide.

40 meter reversible Moxon

The initial experimental model of a 40 meter reversible Moxon was the first antenna I modelled with NEC5. I did nothing more than change the calculating engine, just to see how the results would change without the segmentation and other modifications recommended for NEC5 models. Recall that the model uses constant diameter wires (25 mm) throughout; this is not a physically realistic model, only intended for computer experimentation.

The NEC2 result is at the top and those for NEC5 on the bottom. Resonance shifted downward approximately 1% (~75 kHz). Gain and F/B were similar, after adjusting for the frequency change. Doubling the segments for NEC5 had a negligible impact on the results. 

I tentatively concluded that the difference is more likely due to improved accuracy with NEC5 due to the 90° angles between wires. Even for a straight forward antenna like this we can see where NEC2 is challenged to generate accurate results. 

For those practically minded, you may have more luck getting accurate dimensions from one of the online Moxon rectangle generators (typically based on scaling working antennas) than by using NEC2. I can't guarantee that is generally true, but you ought to keep it in mind should you model a Moxon rectangle or an antenna with similar attributes.

I next tried my physical model for the reversible Moxon. This one uses tapered elements for the antenna I am currently building in my workshop. I won't detail the design in this article since it is an ongoing process. I am trying to build it using only the aluminum tubes and pipes that I have in stock, which imposes interesting constraints. I'll write an article about the antenna when it is built and tested.

Unlike the model with constant diameter wires, the initial model was far off. I doubled the segment count which, unlike for the model with constant diameter wires, did reduce model inaccuracy. For the final design I may again double the segments. That would be 950 segments! That's a lot for what seems to be a modest looking antenna, yet it is frequently necessary for accurate NEC5 models

It was necessary to make a few small changes to achieve the expected performance. One was a slight adjustment to the reflector element coil. The reappearance of short stingers on the elements is due to the material I have on hand and not to a change to my previous conclusion that stingers limit performance for this style of antenna. I am trying to keep them short without resorting to buying more aluminum.

The SWR is only slightly higher after aligning the gain and F/B frequencies with that of the earlier model. It may improve further with another doubling of segments. That may not realistically matter since environmental interactions are likely to be greater: the tower, its guys, and other antennas on the tower. 

With NEC2 the model is far from accurate, worse than the relatively small 1% inaccuracy of the model with constant diameter wires. NEC5 is worth the price if only for this one antenna.

3-element 40 meter yagi with capacitance hats

When I began designing this monstrous antenna I knew that NEC2 would be wholly inadequate. I was less concerned with the impedance than with the frequency of operation. NEC2 typically shifts the resonance downward for antennas of this type, but there is no reliable method for predicting by how much. That is why I built an experimental element to calibrate the model. 

After repeated changes to various sections of the element (position of capacitance hats, length and diameter of select tubes, length and diameter of the hats and stinger), and approximate compensation for ground effects, I trusted that the measurements were sufficient to calibrate the model. Calibration means accurately determining the differences between the NEC2 model and the real antenna. It is not practical to repeatedly raise and lower a 300 lb antenna up 150'. It was critical to get it right.

The extraordinary thing was that the antenna seemed to do pretty well once it was installed and the gamma match and driven element were adjusted. However, small doubts lingered since the calibrated model was imperfect and there is no good way to measure gain and F/B with reliable accuracy. With the NEC2 model and manual calibration, the model's behaviour from 6.55 to 6.85 MHz was calculated to match the real performance between 7.0 and 7.3 MHz.

Then I suffered the effects of a poor mechanical design of the clamps that attach the capacitance hats to the element. One arm of one hat on the reflector fractured and fell off a few months after the yagi was raised. The same later happened to the director. At first I thought it would be disastrous, yet I could not discern a performance impact on air. Even the SWR curve was slightly better.

Modelling of the missing arms using my calibrated NEC2 model suggested that the antenna had its operating frequency range increased by about 70 kHz (1% of 7 MHz). That's not good but it also isn't bad. However the F/B at 7.0 MHz should have measurably declined. That didn't seem to happen. 

Although I redesigned and built new capacitance hat clamps, I've only replaced them on the driven element. That was easily done since it is close to the tower and the tips are accessible by rotating the DE on the boom. Replacing the hats on the parasitic elements is more difficult. I haven't rushed since the antenna continues to work well, and no more capacitance hat arms have failed over the following 2-½ years.

With NEC5 installed, I ran the EZNEC model without making any adjustments to accommodate the unique requirements of the calculating engine. At first glance the results were quite good. Performance between 7.0 and 7.3 MHz was about as expected; no calibration required. Then I took a closer look.

Every yagi design is a balancing act between gain, pattern and match. That isn't easy to achieve for a high Q antenna on 40 meters due to its 4.3% bandwidth. The NEC5 calculation for the F/B at 7.3 MHz was poor. Closer inspection indicated that the optimum range of the antenna was at a slightly lower frequency, by about 50 to 75 kHz. Notice something familiar about that number?

The frequency shift is very close to the higher operating range due to those missing capacitance hat arms. That could explain why the antenna is performing so well. I must quickly add that it is only a hypothesis at this point. It will be necessary to increase the segment count and make other adjustments to ensure that the NEC5 calculations are accurate. It is important not to stop the analysis just because the first hint of an insight conforms with one's subjective experience with an antenna. 

I will do that deeper analysis later, and likely with a lot more segments. For this test drive of NEC5 it is enough to achieve these inklings of enlightenment. I look forward to doing a full NEC5 analysis of this important antenna. I may decide to alter the antenna slightly when I install the new capacitance hats so that it works at its best.

5-element 15 meter yagi

The final model I tested was this long boom yagi for 15 meters. I chose it for two reasons. The first is that I've heard that multi-element yagis are challenging to accurately model with NEC5. The second is that several months ago I sent the model file (including a gamma match) to a ham who requested to see how I modelled the gamma match. He then passed it to someone who ran the model with NEC5. The resulting SWR curve was far from what I measured and successfully modelled with NEC2.

This is a complicated antenna simply because it has so many elements and each element is tapered with telescoping tubes. EZNEC with NEC2 and its SDC algorithm produced a model that matched the actual antenna with exceptionally good accuracy. However, when I added a gamma match to the DE it was necessary to replace the DE with a constant diameter wire since the SDC algorithm can't deal with the gamma match. This is not ideal since the current distribution on a stepped diameter element is not the same as on the equivalent constant diameter element calculated by the SDC algorithm, even though both exhibit the same net reactance.

When I modelled the antenna with the gamma match using NEC5 the SWR curve closely resembled what the other ham got with NEC5. I then returned to the version with a tapered DE and no gamma match and, again, the SWR curve was far off the one calculated by NEC2 (including SDC) and as measured on the actual antenna. That's the upper of the two charts above.

When I doubled the segments of every wire the SWR curve (bottom) improved, though still not very accurate. This result implies that the person who ran my model on NEC5 did not increase the segment count in my NEC2 model.

I suspect that I'd have to double the segments again to do better. That's not a pleasant job because there are so many wires in the model. There may be a convenient method to do it that I have not yet discovered.

I might yet do it just to satisfy my curiosity. I also did not revise the model to include the gamma match with the tapered DE since there would be little point until the antenna itself si accurately modelled with NEC5.

I then produced the antenna patterns at several frequencies across the band and found that the gain was similar but the F/B exhibited more variation. The deviation was worst at the bottom of the band. The pattern at 21.0 MHz has a F/B that is about 5 to 6 db lower than the NEC2 model. Since high F/B figures demand accurate and precise calculations of each element's current amplitude and phase it might again be a matter of increasing the segment count.

Other than my curiosity regarding accurate modelling of the gamma match on a tapered element, it would appear that what I've heard about multi-element yagis and NEC5 might indeed be true. I won't pursue this topic further for now since it's not a priority and NEC2 handles these antennas well.

Wrap-up

From what I've seen so far, I am pleased with my purchase of NEC5. It integrates easily with EZNEC and it can far more accurately model a variety of antennas that NEC2 handles poorly. Neither calculation engine is a perfect solution. Every antenna model requires a few moments of thought to decide which engine is most suitable. It is interesting to try both even when you know one of them will do poorly.

Now that I've done my initial experimentation, I will begin applying it to the construction and testing of actual antennas. The obvious first case is the reversible 40 meter Moxon. Unlike for the big 3-element yagi, it appears that I can develop an accurate model using NEC5 without resorting to building a sample element and calibrating the model with field measurements. Once I have more experience with NEC5 so that I can confidently trust the calculations it will save a lot of time and effort, and wondering whether the calibration procedure is sufficiently reliable and accurate.

If you enjoy playing with antennas you should consider purchasing a license for NEC5. It's a tool that I can see becoming indispensable for design and building antennas for my station.

Digital Mode Filters and Courtesy

What do we owe our fellow hams? When we have different ideas about who to have a QSO with, whose wishes should prevail? Should one ham's preference impose an obligation on others?

These are not easy questions to answer in social activity like our, yet many have strong opinions. Indeed, ask around and you will find that some have strong opinions of one kind or another, while others may express indifference and some are uneasy with the question.

It's a question of courtesy, or discourtesy if you prefer. Consider the following scenario. You call CQ DX and a decidedly non-DX station replies to you. You ignore the caller and repeat your CQ DX. There are 4 possible ways to evaluate discourtesy in this scenario:

1. You are discourteous for not accepting the call and having a QSO.
2. The other station is discourteous for replying to a CQ DX.
3. You are both discourteous: the other station for replying and you for not accepting the call.
4. Neither of you are discourteous. The caller tried and failed, you both shrug and move on.

I suspect that many of you have an opinion, perhaps a strong one about who, if anyone, is being discourteous. I don't know which of the four categories your opinion falls into and I don't really care. I also don't care which might be the most popular opinion. I would not be greatly swayed to fall in line with the majority, though some might. 

Were I to alter the scenario, opinions would shift. For example, imagine a DXpedition asking for only stations that need them for an ATNO (all time new one), yet those not among their number continue to call.

Now I'll add an additional wrinkle: the mode. I suspect that for traditional modes like CW and SSB, when you receive a caller from out of area (e.g. non-DX responding to your CQ DX) you are less likely to ignore them than for digital modes like FT8. I respond to them even though I'd rather not. They "feel" more personal to me, and probably for most hams. Usually they just want a signal report, which can be quickly accomplished.

By contrast, on digital modes I regularly ignore non-DX callers when I send a CQ DX. They can take some time, more than on CW and SSB, and time is precious during a 6 meter opening. Am I being discourteous? You be the judge. As I've already shown, there will be a diversity of opinions. I make no apology for my choice.

My use of the digital modes helps to explain my behaviour. It is limited to the following operating activities, in chronological order of my gradual migration to digital mode operation:

1. 6 meters: My primary interest is DXing and digital modes are very effective for the propagation found on the magic band, and sporadic E in particular. I regularly work non-DX on 6 meters but when I do so I send a simple CQ to solicit calls.
   
2. 160 meters: As the amount of CW activity declines outside of contests, I increasingly resort to FT8 to work DX. When I CQ it is always CQ DX, and I mean it.
3. Rare DX: An increasing number of resident operators and DXpeditions to rare entities include no CW operators. A recent examples is FT4GL (Glorioso). So I worked them on FT8. I also worked FT8WW (Crozet) on FT8 as "insurance" in case I was unable to work him on CW.

I have not yet taken to routine use of FT8 and other digital modes. I may change my mind if CW activity outside of contests continues to decline. However that won't happen soon. I can't say how I'll handle non-DX callers in that future world.

As you can see, my digital CQ'ing on 6 and 160 meters is almost exclusively for chasing DX. Anything that interferes with that is cause for annoyance and, where feasible, mitigation. Until recently I avoided using filters so I was not inconvenienced by the lack of filters in WSJT-X.

Instead of switching to JTDX, which has long had filter features, I chose a different option: WSJT-X Improved by DG2YCB. He includes a variety of features not in WSJT-X and that may never be included. One of those is filters. By choosing his "bleeding edge" version of WSJT-X I retain the familiarity of the original and can select from among the additional features. It is exceptionally easy to do the migration since it installs like any version of WSJT-X and keeps the settings common to both and the log file.

After installing the software and experimenting with its novel features, I looked more closely at its filtering capabilities.

My needs are simple so there was very little that I needed to do. I may never use filters other than the blacklist. Obviously I obfuscated the call signs.

It can be occasionally useful to temporarily disable the filters to get the full picture of what stations are being received. The "BP" checkbox does that. I don't use the "Ignore" feature so I'll say no more about it. You can read about all the additional features of WSJT-X Improved in the documentation.

At this point you might be wondering why I filter stations. I ignore callers manually, which only requires that I do nothing. I don't often program the software to auto-respond to callers, and when I do I can easily click the CQ message button.

The blacklist would grow large indeed were I do enter every non-DX caller that replies to my CQ DX. Besides, I might want to work them, just not when I am hunting DX.

I am not even inclined to put many suspected robots in the blacklist. In most cases they don't really bother me. Again, I ignore them. To repeat a point that I made earlier:

A station's desire for a QSO, whether by human or robot, does not create an obligation on my part.

In the past I would occasionally work a robot just so that they would never again bother me. In a few cases I did not log them. I now believe that it's more honest not to work them than not to log them. Filters help me to do what I believe is the right thing, in accord with my needs and interests.

Well then, who goes into my blacklist? I am not driven by anger, to "get back" at anyone or to smugly deal with stations that operate in a manner that I disapprove of, or stations that splatter or QRM others. I do not engage in vendettas or pointless battles. My true reasons are more mundane.

The stations I typically want to eliminate are those that I'll describe as digital mode spam. Those are stations that flood my screen with endless CQing (often an hour or more), that respond to everyone whether they've worked them before or not, hound stations that obviously don't want to work them, and that are sufficiently local that I can't avoid them. Not all are robots though many are. I am rarely annoyed enough to filter a station that is only heard when propagation is favourable to their location.

Of the 4 calls in the filter screen above, 3 of them are local to me (VE2 or VE3 regions) and one is a nearby US station. This time of year I monitor 6 meters whenever I am not doing anything else with the station. I'll leave it monitoring when I'm out of the house and sometimes overnight. Having the monitor screen overflow with their "spam" means that I can easily miss the occasional message from a distant station, either because it scrolled off the screen or, during periods of heavy activity, it is difficult to spot amongst the clutter.

When I put those stations on the blacklist, my band monitoring experience is more pleasant and effective. The monitor window stays empty while the endless CQ's scroll down the waterfall. This is not about hate, disapproval or philosophical differences. I just don't want the screen filled with their clutter. 

I use the blacklist like an email spam filter. I am not even too bothered by distant "spam" since those stations at least inform me that there is propagation in that direction. I only filter the local spam.

I have only ever blacklisted stations heard on 6 meters. For my limited digital mode operating on other bands, I've never had cause to filter anyone else.

The bottom line is that if I don't respond to you it is almost certainly not because you're blacklisted. Either I'm ignoring you or simply not copying your signal. If you wish, you can judge me as being discourteous. I won't care.

I expect my blacklist to remain short. I might even delete entries since people's habits change. Perhaps I'll do that each spring at the start of 6 meter season. I can always add them back if their bad behaviour persists.

Your reasons to filter stations may differ from mine. Indeed, filters are used by few stations: they either don't use them or they stick with WSJT-X which does not support filters.

Many fervent 6 meter DXers use area filters to silence all callers out of the area they are interested in. For example, European DXers that filter all callers from Europe. There is no need to blacklist every station. I have yet to use one of those filters despite the temptation, since I consider it discourteous for a station in Canada or the US, unless they are very far away, to call me when I send CQ DX. 

Sometimes nearby friends answer my CQ DX. I usually reply to them when no DX calls me. I don't blacklist friends! With the limited message diversity on digital modes this is their way of saying hello. Custom messages are a bit of a bother and I've never used them.

I was averse to the use of filters for a long time. Times change. Perhaps the reasoning I've provided in this article can be food for thought as you consider whether and what to filter. I don't expect everyone to agree with my choices.

With the increasing number of hams attracted to 6 meter digital modes -- generally a good thing -- some bring behaviours antithetical to those of us DXing on 6 meter. The small step I've taken with selective filtering is helping to restore my 6 meter summertime experience to what it once was. Now if only propagation were better!

Between a Rock and a Hard Place

I am accustomed to sharing the towers with wasps early in the fall. Their job is done and most are doing little more than waiting to die. For some reason they are attracted to the cool steel of the towers. They are not a danger since they have no hive to protect. Leave them alone and they leave you alone, even when you're nose to nose with them. Above 10 meters their numbers rapidly diminish.

July is not that time of year. Wasps are now very active and several species are easy to antagonize if you do nothing worse than walk beneath their hives in the tree branches overhead. The occasional sting is painful but usually nothing to worry about. Then one day about 25 years ago, while mowing the lawn, a few stings from wasps protecting a nearly invisible hive 5 meters overhead sent me to emergency room. 

Doctors informed me afterward that I had developed an allergy to wasp venom. I learned that isn't unusual. The risk increases after repeated assaults because the immune system learns the wrong lesson and eventually reacts inappropriately, with a risk of anaphylactic shock. I was fortunate not to become a statistic.

There is immunotherapy available for a variety of allergens. I never got it for wasp and bee venom since it can be unpleasant. Instead I carried an Epi-pen. Years later I had successful immunotherapy for an unrelated allergen that gifted me with a side benefit in that it also reduced, possibly eliminated, my sensitivity to wasp venom. The immune system pathways are largely identical, with small differences for each allergen. 

I was surprised by this in the following year when wasp stings only elicited what can be called a normal response: pain and swelling for a couple of days. However the risk remains and living in a sparsely populated rural area there are daily encounters with wildlife in all of its variety. I am not fearful of the wildlife, even wasps, but it helps to be observant and not take due care. Several days ago I was not observant and I paid the price.

As mentioned in the previous article, I have a lot of outstanding maintenance and new construction to catch up on. One of those tasks is to diagnose and repair an intermittent in the coax going to the upper 5-element yagi of the 20 meter stack. It was a fine warm morning so I gathered my tools and gear and headed over to the 140' tower sitting amidst the growing hay. I mow narrow paths to the big tower and around the bases to ease access during late spring and early summer.

I did my usual rapid visual inspection of the tower and antennas and started up. I didn't get far. I should have taken the warning of an unusually dense cloud of flying insects at the tower base. 

During the several weeks since my last climb up this tower the wasps had built a large and growing nest about 15' above ground. It wasn't visible during my brief inspection of the tower because it was inside one of the wide girts on the climbing face of the tower. It would have been difficult to spot regardless since it's gray and shadowed by the girt in the bright sunshhine.

The density of rapidly flying insects increased until my hands unknowingly almost directly contacted the hidden hive. That's when they attacked.

Which brings me to the title of this article. On the one hand, I'm allergic to wasp venom and the stings were adding up fast. On the other hand, I'm on a tower where the only immediate escape is to jump. I'll leave you to choose which of those options is the rock and which is the hard place.

What would you do? There really is only one correct answer: climb down. Whenever you get into a tight situation there is the risk of panic and the classic fight or flight response. But you can't fight the wasps nor can you fly (literally or otherwise). Besides, if you do jump, the wasps will follow and you will suffer from both the fall and the stings. So start descending and endure the attack as well as you can. It'll feel like forever even though it may only be seconds. Luckily the local wasps don't build their hives very high.

I started running when I hit the ground, burdened as I was with my climbing gear, tools and heavy boots. Many of the wasps pursued and continued stinging me. They let off when I was about 200' (60 m) from the tower. The immediate threat had abated but it wasn't over. From experience I knew that it could be 10 minutes or more until the severity of the venom reaction could be assessed.

I won't bore you with the excruciating details. One picture of my hand will suffice. My face and arms looked about the same. It was a warm day so I was only wearing a tee shirt and a small cap to protect my head and eyes from the sunshine. There were few stings below my chest. The greatest worry was having to breathe through my mouth for an hour because the swelling completely blocked the air passages in my nose.

I recovered remarkably well.  When I attended a social gathering two days later, the swelling had diminished enough that few remarked on my appearance. But it did give me a story to tell!

In the end, the wasps fared worse than I did. Although difficult to reach, I went out at night when the wasps huddled inside the hive and drenched them with a high pressure insecticide canister. I always keep a couple of them in the house. 

When the survivors returned the next day, I made a 20' pole out of antenna tubing and wrecked the hive. That drove them off for good. It is to be expected that I may be slightly nervous when I resume tower work after I've fully healed.

Perhaps you found this story amusing, frightening or instructive, or a little of all three. It can happen to any ham doing tower and antenna work. In warmer climates the danger can be worse. What an unpleasant surprise it would be when wasps swarm from a hive hiding behind a rotator 50' up the tower!

What lessons can we learn from this experience? That assumes that I haven't frightened you so much that you've taken a vow to never climb a tower again!

• Know the risks: Mid-summer is prime time for insects building nests. While there isn't much shelter on a tower, competition among the critters for the best spots can lead some to choose your tower.
  
• Inspect: Inspect the tower, from all sides. That probably wouldn't have helped me in this case because the hive was well shaded. But I should have paid closer attention to the insect activity at the tower base. The danger signs were there. I typically only inspect for structural anomalies before each climb.
• Don't panic: Jumping will leave you disabled on the ground and at the mercy of the merciless wasps. Panic almost always leads to poor choices. As difficult as it may be in the moment, think clearly and act appropriately. Mitigate the attack if possible and then get out of there, but safely. The attack may continue but you will survive. 
• Get help: Seek out family or neighbours immediately if you are working alone, or whoever happens to be nearby. Get medical help in case the worst happens.
• Prevention: Build your towers and antennas away from trees and foliage. It is safer for the tower and for you. This year I worked on a repeater tower where the site owner allowed adjacent trees to grow to a large size. I had to climb through the branches. Insects blend into their surroundings and when the leaves are in bloom it is likely you'll spot the hive too late.
  

There are towers that are less likely to host hives. The wide C-channel girts on the LR20 towers that are used by many large Canadian ham stations provide more shelter than I'd have guessed. Thin tubular legs and struts like those on Rohn towers commonly used in the US provide little protective cover for hives. The underside of rotator and bearing plates on all makes of tower often host hives but you'll see them in time, if you're paying attention.

My hand grip is not yet back to full strength so I haven't resumed tower work. Another couple of days should so it, and in any case we're about to be drenched by the remnants of hurricane Beryl. Better to fall behind schedule than to take unnecessary risks.