Unclear on the Concept: DX Spotting

In the beginning, when we heard a rare DX station we would pick up the telephone and call our friends. They would get on the air and work the DX, and then they might call their friends. These telephone trees were always shallow with few beneficiaries. But there were many of these small trees spread across the globe. They relied on those with the time to spin the dial and find stations, and a smaller number that globally networked with other DXers. This was how groups of DXers found stations and, importantly, knew when and where stations were likely to appear.

The internet changed everything. Now we have a large number of DX spotting clusters networked together so that when a stranger on the other side of the world spots a station we learn about it almost instantly. We click on the spot and our transceiver interfaced PC instantly jumps to the DX station and might even set the correct mode and frequency split. 

It has never been easier to chase DXCC and other operating awards. I've benefitted and it's likely that you have as well. Some laud the technology, exploiting it to the maximum. Others sneer at the ease and simplicity and mourn the loss of the traditional skills of research, tuning and listening. I'll set that debate aside to focus on a different and modern problem: poor and improper use of spotting networks.

First, what is the proper way to spot DX? We can debate which stations to spot, but that's pointless since we will never all agree. It can be rare DX, but it can also be anyone and everyone during a contest, or simply a kind note about a non-rare station who was a pleasant conversationalist. Regardless of your thoughts on this I think we can agree that spots should ideally include the following information:

• Frequency
• Call sign
• Whether the station is operating split, and optionally the offset
• The location of the station if it is not obvious from the call sign; e.g. IOTA, grid square, state/oblast/county/zone, POTA/SOTA, etc.
  

Only the first two are mandatory. The rest depends on how helpful you want to be. It isn't unreasonable to avoid including optional information so that others must do their part by listening. I'm a minimalist when I spot a station.

The list of poor spotting etiquette is long. We can roughly categorize those as careless, inappropriate or malicious. I'll talk about the ones I've encountered that aggravate, surprise and amuse me. And why not? The height of summer is a great time to relax and have some fun. I'll leave the technical topics for another day.

Above are a few examples that I randomly selected for the purpose of this article. They are assembled from screenshots collected from a web-based spot aggregator. In these screenshots I am redacted personal identification even if the spotters are not shy about what they're doing.

Careless

We all make mistakes. The proper way to deal with it is to correct the error. Few do for their bad spots. In the example above, I'm not sure if the correction was distributed out of sequence or whether the error "corrected" the correct call sign.

Careless mistakes that I often see include:

• Automatic spotting while running: Many logging applications include a feature to spot every call sign you type in or log while spinning the VFO. If you forget to tell the software that you're running (CQing on a frequency) the spots will continue to be generated. This is of course irritating for those who click on the spot and find that the station isn't there or not workable because it's the spotter's frequency. A few hams do it deliberately (bragging about their big signal?) though most often it's just a mistake.
• Call sign error: Mistyping a call sign can cause confusion. It can be a dropped letter, transposed letter, changing "0" to "O", or just a typo. Most logging software will let you make the mistake. If I click on the spot, work the station and log it, I should not expect a confirmation! These mistakes are common, so listen carefully.
  
• Propagating an error: I know this one well. Someone copies my call during a contest as "VE3UN" and spots it. Many hams miscount dits when the CW speed is very high in a contest, and this error is very common for my call. The mistake is propagated when callers, drawn in to work a new station, fail to listen and also spot the erroneous call.
• Spotting the wrong frequency: This is common for split operation in a DX pile up. Rather than spot their receive frequency (where the DX station is transmitting) they spot their own transmit frequency. This is worse than simply unhelpful since most logging software give precedence to the most recent spot. You click on the spot and find yourself listening to the pile up instead of the DX station. You either hunt for the DX or manually locate an old spot with the correct frequency.
  

Inappropriate

There is a fine line between careless and inappropriate spots. My criterion is that the inappropriate spot is one whose purpose is not that of informing about a station's call sign and frequency. That is, using the spotting system for communication of other kinds of messages is inappropriate. 

Examples are legion, but here are a few that I regularly encounter:

• No copy: These are variation of "nope, I hear nothing". If that's the case, what is being spotted? Your failure to copy a station not only doesn't justify a spot but also misleads others to believe that you have heard the station. Few hams notice the added comments and solely rely on their band maps and spectrum maps that just plot the call sign at the frequency.
• ESP attempts: The DX station is working a pile up, not reading spots. You cannot effectively communicate with them this way. Pilot stations for the especially rare DXpeditions may, but that's about it, and it still won't help you. Cries of "you got my call wrong!" are not only pointless but non-radio attempts to correct the DX station's log is inappropriate. Do what the rest of us do: work them again. The same goes for spot messages such as: "turn to NA", "I need you on 160 SSB" or "upload your log!".
• Shaming: We all make mistakes. Using the spotting network to publicly shame other hams is inappropriate no matter the reason. Naming the alleged guilty party with a call sign and a message like "UP UP", "20 khz splatter", or "DQRMer" is very rude. Your impatience or frustration are not a valid excuse for your inappropriate behaviour.
• Help me: "Where is he listening?", "did he QSY?" and so forth are inappropriate. Spots are not a chat line. There are venues where assistance can be requested.
• Complaints: There are an awful of spots of this variety. Examples include: "they only work EU", "too much $$$ for a QSL", "he's deaf" and insults for a host of perceived affronts. Public tantrums are not cute after you've passed the age of 3.
• Brag: "DXCC300", "worked with qrp and dipole", "human to human" and so much more. We should be proud of our accomplishments, but not in this way. The implication with some of these messages is that those who operate differently from them or have accomplished less are lesser hams. Bragging is almost always impolite, and it is certainly inappropriate in a spot.
• Skimmers: There are always a few hams who connect their personal skimmers to spotting networks rather than to the RBN.
  

Many of these inappropriate spots should not be sent at all or should be fodder for the announcement feature of the cluster network. But few hams pay attention to announcements -- for good reasons that I won't get into here -- and these are people who want to be heard. But that's a poor excuse to misuse the spotting network.

Malicious

Human beings continue to be human when they sit in front of a radio. Hams are not angels. Those with malice in their hearts or who harbour grudges don't always set them aside when they operate. When these individuals are sufficiently uninhibited they will use the spotting network to expose their inner demons.

I won't give examples of malicious messages since this is intended as a lighthearted article. Consider the following:

• Political and hate speech
• Impersonation of others to post inappropriate messages
• Deliberate frequency and call sign errors to misdirect or confuse

You've probably seen examples of all of these types of malicious message. I suggest that you ignore them and use a cluster that actively monitors for and filters abusers of the network. Which brings me to the next topic.

Filters

Cluster operators do not act independently. They share tools and filters and discuss ways to minimize improper use of the network. They not only filter users but also clusters that permit or encourage bad actors. It is to our benefit that they do. I don't believe enough hams are aware of their efforts on our behalf.

In addition to the filters applied by the cluster operators you can have your own filters. Filter features are provided by most of the cluster software applications. You can configure those with applications such as CC User by VE7CC. 

You can also create filters in your logging software. I have done this for several hams that persistently make careless and inappropriate spots. Don't overdo it since most hams eventually correct their behaviour.

In truth, I'm rarely annoyed by poor cluster etiquette. Most of the time I find it quite funny. For example, when a busted call is posted and others echo the mistake rather than listening. Their carelessness is mostly undermining their own award chasing and contest scores. I just shrug, smile and move on.

Is the above example of spotting behaviour inappropriate? Sure. Funny? Very. Sometimes you get the right result by doing the wrong thing. Relax, laugh and don't take poor cluster etiquette too seriously.

Note to readers: You may have noticed a longer than usual gap since my last article. Nothing has happened except summer weather and too many projects. It isn't easy to sit in front of a computer and bang on the keyboard when the weather is fine. I'll soon get back to regular blogging to talk about some of those projects.

Musing on a RadioInfo Standard

Standards are peculiar beasts. They typically come about from the collaboration of competitors, whether at their own behest, pressure from regulators or, importantly, pressure from their customers. Standards can permit interconnection of equipment from different manufacturers and connection of third party equipment to any manufacturer's products.

I spent several years of my life, over 30 years ago, working on North American telecommunications standards. It was interesting at first, especially working with competitors and customers in a common forum. The objectives were good, and the work attracted idealists. 

My attitude soon soured. Typical of many companies, my employer saw the work as necessary but a distraction and a nuisance from the more important objective of building and selling products. Unless you loved the work, it did little for one's career prospects. I moved on.

Standards development can be fast or slow. It goes slowly when the products affected are not in production or when customers are uninterested. With strong commercial pressure standards can be developed very rapidly. For example, when the products can't be sold unless they interoperate. Too much of my work was of the former type, hence my dissatisfaction.

We don't often think about standards for amateur radio equipment. Nevertheless, the presence or absence of standards has an important impact on us and our shacks. I use the term "standard" loosely since in many cases there is informal agreement rather than a formal standard. Formal standards require a recognized accreditation authority which does not exist for amateur radio products.

• Connectors and signals: mics, PC audio and control; rotators; band data; and much more
  
• CAT (computer aided transceiver) protocols
• Remote operation
• Computer logging and control software API
  
• Digital modes: FTx; digital audio; PSK etc.
• Peripheral equipment: SO2R; spectrum displays; and more

That is far from an exhaustive list. It is the rare ham who hasn't fussed over connectors and software configurations after purchasing new equipment. We habitually accept these annoyances with hardly a thought. But think how much easier life would be you could plug in all the existing cables and software applications to use a new transceiver.

We don't always get what we want. The lack of standards dooms us to constantly deal with each vendor's proprietary hardware and software interfaces. Manufacturers have little incentive to collaborate, and indeed see value in putting up barriers to interconnection. On the other hand, it give them freedom to develop new products features with a minimum of external dependencies.

Some of these challenges are diminishing as we increasingly interconnect our equipment with standard PC interfaces, including wireless connections. But that only addresses a subset of diverse physical connectors. Software interfaces are another matter, and is what brings me to the point of this article after a long introduction. Setting the context is worth a few minutes of extra reading (and writing).

Longtime readers may recall that I use the RadioInfo UDP broadcasts from N1MM Logger+ in my station automation software. With it I can select antennas, antenna modes and directions, avoid contention between operators, switch BPF, and more. The API frees me from dealing with the diversity of non-standard CAT and band data interfaces of transceivers. N1MM abstracts the functionality so that the RadioInfo UDP messages are almost all I need.

The downside is that I've made myself dependent on N1MM software. My station automation software is now the only practical way to select antenna. It helps that I use N1MM for contests and for daily operating. It is possible to operate the UI in manual mode for when N1MM isn't available, such as when I use WSJT-X or a different logging application.

What if I no longer wish to use N1MM? I am happy with it now but I know that can change -- nothing is forever. The team may disband, become hostile to user input or fail to accommodate future changes to the equipment we rely on. It is also possible that a better or more preferred contest logger arrives on the scene. 

My thoughts on this were driven by a couple of recent events. One was learning that among WRTC competitors, DXLog has rapidly grown in popularity. I know contesters that have switched to DXLog and I'm sure there will be others. It is not my intent in this article to compare them, and indeed I can't because I have never used DXLog. From what contesters are saying and a quick review of its features I can see why it's acceptance is rising.

The other event is that hams I know are trying to working through how to change or replace their station automation to be compatible with DXLog. This led me to wonder whether DXLog has a similar feature to N1MM's RadioInfo broadcasts. It does. While I have no immediate interest or need to migrate to DXLog it is worthwhile to consider how I might use this feature. That is, can it be done and with how much effort? Can I make my software compatible with both N1MM and DXLog?

I began by comparing the RadioInfo message content of both DXLog and N1MM. My comparison is rudimentary since the documentation for DXLog left me puzzled in some instances, and of course I haven't used it. Both broadcast RadioInfo messages using UDP and XML encoding.

If the text in the diagram is difficult to read, click on the image or widen your browser window.

Dots are for data with no correspondence between DXLog and N1MM. Black dots are for data I do not need or use in my automation software; green dots are for N1MM data that I do use. Arrows are for data with correspondence between the applications, although there may be differences that my brief analysis did not uncover. Green arrows are for N1MM data that I use in my software; red arrows are for N1MM data that I don't use.

Some data that N1MM provides, and that I don't use in my software, are needed for SO2R. Equivalent data is provided over a separate interface using the OTRSP protocol. It is used to communicate with the SO2R-Mini in my station, and which I can control with N1MM keyboard commands.

Most of what I need would appear to be available from DXLog's RadioInfo messages. However it is not that simple. A protocol is more than messages and data: there are semantics (meaning) and the process logic that dictates when RadioInfo messages are broadcast. I can adjust how my software behaves but I have little leverage over the behaviour of the logging app.

Questions that occurred to me while reading about DXLog's RadioInfo messages include:

• When a RadioInfo message is sent and why.
• DXLog's focus behaviour in Windows is quite different because there is one window visible to Windows rather than the multiple windows used by N1MM. Returning Windows focus to DXLog is likely easier than I've found for N1MM.
  
• The internal automation hooks for antenna selection, rotator control and other items are likely dissimilar. That doesn't concern me since my software doesn't use those features of N1MM. Station automation software produced by others may be affected.
• I have to wonder whether the difference in data labels in several cases reflects different functionality. For example, <app> vs. <logger>, or <StationName> vs. <Station>.
  

Many of my questions likely have answers in the DXLog documentation, sparse as it is. I have yet to bother since I have no immediate interest in switching to DXLog. There are features of DXLog that appeal to contesters and may one day appeal to me. These seem to include:

• Navigation within a single window can be easier than with multiple windows. For example, to edit the log. This can be quite a problem with N1MM when focus changes erratically when, for example, you try to edit the log while continuing to operate. It's worse with SO2R and two keyboards.
• Extensive scripting support for customization and extension of functionality. Many contesters have their own peripherals and tools that can be difficult to integrate with N1MM using its existing APIs. Large multi-op stations in particular have been receptive to what DXLog offers.
  

I like to keep an open mind on the matter, so I need to consider what it would take to have my software work with DXLog. It may seem straight forward but it never is, as I hinted above. What might push me over the edge is if two keyboard SO2R works better in DXLog. There are anomalies with N1MM's implementation that the developers have shown little interest in addressing. It's critical to my style of operating contests.

What would be ideal is a standard for RadioInfo messages. That would permit station automation software, including my own, to more easily support N1MM, DXLog and perhaps other applications that choose to implement the standard. Agreeing on a standard, and a process to get there, could prove difficult, and perhaps impossible. 

Both applications are free so any customer pressure for a standard will be social rather than financial. But once in place it could encourage other application developers to participate. Of course there are other contest loggers, but they seem to have low or dwindling use. That is true for paid and free applications.

A RadioInfo standardization process led by N1MM and DXLog is not impossible. I am in no position to say whether the parties would be willing. The amateur radio universe has certainly done it with OTRSP, ADIF, Cabrillo, APRS and others. I doubt that there are significant technical barriers even though logging applications are in some respects more complex than other software applications developed for our hobby. 

There would have to be compromises on some points and agreed disagreements on others. Unresolved differences can be managed with permitting proprietary data items in RadioInfo message as is done for ADIF and other protocols. We did the same for the telecommunications standards I once worked on. While regrettable it is occasionally necessary for progress to be made.

Without an early effort to unify the content and behaviour of RadioInfo messages it will become more difficult. As third parties, such as me and my custom software, become dependent on N1MM or DXLog's unique RadioInfo implementations, the contest loggers will get push back if they make changes to make them work the same. 

Perhaps there is more flexibility on the DXLog team since N1MM's implementation of RadioInfo is more established and therefore has more dependent third party users. This, too, is not uncommon in the commercial world I am familiar with. There is an incentive for latecomers to exactly emulate the first movers. But it would be unwise to rely on the hope that it happens in this case.

As much as I'd like a RadioInfo standard, it is not the most likely outcome. The only solution then is to be application sensitive in third party code, and all the work that entails. I am already thinking ahead to do that in my station automation software. I am hopeful that it will not be difficult.

Reflections on IARU HF World Championship

I didn't operate in the IARU contest last weekend. However, my station was active with a guest in the operating chair: Vlad VE3TM. I didn't take a picture of him during the contest so I'll direct you to his QRZ page.

Since I'm not a fan of summer contests, it was an opportunity for Vlad to play with a bigger station than his small one in Ottawa. His station is also plagued with noise, a common occurrence in urban and suburban settings. 

I benefitted since this was the first time someone else operated my station in a contest. It was useful to learn how the station automation, operating desk layout and equipment performed for another contester. My job during the contest was to answer questions and fix any problems that might arise. Luckily, none did. I kept the coffee flowing and otherwise kept out of his way.

I designed my station automation to be intuitive but that is no guarantee that it will make sense to others who sit down to use it the first time. I directed Vlad to my description of it on the blog and that proved to be sufficient. I explained how the SO2R system worked and how to use the many rotators. There's a lot to learn and it can be overwhelming. I'm not the best judge of the learning required because I'm familiar with the station.

Aside from 2BSIQ, which Vlad has never done, the best way to exploit a large station is to always be running on one band and hunting for stations and multipliers on other bands. That takes practice. Propagation was such that only 15 meters delivered consistently strong runs, mainly to Europe. For the most part he kept the stack pointed northeast. Runs were limited on 20 and 40 meters to times when conditions were favourable. Part of that is due to stations migrating to the higher bands to take advantage of the high MUF.

Marginal conditions on the other bands -- 10, 80 and 160 -- proved difficult since he was in the low power category (100 watts). Vlad usually operates low power in contests and that's what he did in this one. Since my amps are manual tune (A1500 and L7) he avoided another point of complexity while operating an unfamiliar station.

At the end of the contest he had a respectable claimed score of over 700K points and more than 1200 contacts. Had he operated the full 24 hours and better able to exploit SO2R he could very well have had the top score in VE/W. Nevertheless, he enjoyed himself and I learned a few things about the station. That's a win for both of us.

Now I'd like to say a few words about the WRTC competition in Italy. It of course is run in concert with the IARU contest. Many participants make a point of working the competitors with their special call signs. There was a live scoreboard so that everyone could follow the competition, but with the operator identities hidden until after the contest.

The format and location of team statistics on the official web site keep changing so I don't know what you'll see when you click on the link. Before the final tally the claimed scores were shown. Those disappeared when the final scores became available a day or two later. First they were in a PDF file and then an HTML table, so who knows. You may have to take my word on a few points since you may find it difficult to check.

The final standings may be a surprise. Operators that consistently place high in major contests have mediocre results in WRTC, and vice versa. There are known and speculative reasons for this. The ones that occur to me include:

• Big scores in major contests most often are done with big stations, from stations that everyone needs for a multiplier, or from favourable geographic locations. Run fast and you'll do well.
  
• Skills to exploit the above benefits are not necessarily the skills needed to do well in WRTC. However, it does require many well-honed skills to do well with a big station, and a mediocre operator won't do well when dropped into the chair at the world's best station. The former include: SO2R; 2BSIQ; knowing where to point antennas, and when; picking complete calls from a pile up, correctly and on the first try; a recognizable call that is easy to copy; etc.
• WRTC rules reduce the value of many big gun skills. Many contesters love to find and call WRTC competitors, but aside from that they are little pistols in this contest. I'll just include one link (out of many) from my blog that enumerates skills you need to do well with a small station. Those accustomed to being a big gun may have rusty little pistol skills that they need in WRTC. You cannot simply point the antennas, cue the CQ machine and keep at it for 24 hours to place well.
  
• It has been said that contesting from Europe requires a local focus. There are more stations to work than, say, from within North America, and you must exploit that by working as many other Europeans as possible, despite the lower point value compared to DX contacts. I failed to understand that for a long time because I've never operated from Europe.
  

There is one point well worth noting from comparing the raw and final scores of the competitors: accuracy matters. The ranking of the top teams did not change but the margins did. After log checking the spread between first and second place dropped from 6% to 1%. They were very close to changing positions.

There are other notable points in the published statistics that I will not bother with. Have a close look and you will learn a few things, both good and bad. I'm sure it will be more interesting when the logs become public. I'll leave that job to others since I'm not that curious!

I have no WRTC ambitions. I enjoy watching many of the world's best contest operators do their utmost in these tests of skill and knowledge, and that's enough. Contest is recreation for me and an incentive to build a big station. That's all. 

My other great passion outside of amateur radio is cycling, and my attitude toward it is the same: it's recreation, and an incentive to hone what talents I may have. But I leave the racing to others. I didn't watch the WRTC but I do watch the Tour de France online. It was particularly enjoyable to cheer on home boy Michael Woods as he won a stage of the great race in grand style atop Puy du Dome that same weekend.

I don't know any Tour de France competitors but I do know several of the WRTC operators. It'll be interesting to hear the stories they have to tell when we next meet.

Re-boxing the Balun Designs 1113s

I repaired and reinstalled the common mode choke (balun) on the TH6. As readers may recall, the PVC enclosure for the Balun Designs 1113s shattered in several places. It was a valuable lesson on the limits of PVC and, of course, became blog fodder. In this article I'll describe how I went about the repair. The same balun on the TH7 was in good condition when I sold the pair this summer.

My first decision was how to mount the balun. The PVC enclosure is not mandatory and, indeed, many hams leave their ferrite toroid baluns unboxed so that they are well ventilated. No balun is perfectly efficient and there is heat dissipation, though small for well designed devices. Without an enclosure the balun is exposed to the elements, and that entails other risks.

My first thought was to mount the balun directly to resin backing plate. Mounted below the yagi boom it is shielded from most precipitation and is fully ventilated. 

I reconsidered when I inspected the balun and found that it does not match the device depicted on the manufacturer's web site. A picture of the currently marketed balun is on the right.

The ferrite is wound with small diameter coax. This is teflon dielectric coax that can handle far higher power than you might guess from its size. It's expensive but you need very little of it to wind baluns. Unlike RG213 and similarly sized coax, many turns can fit on a 2.4" toroid and the turns can be tightly wound (small minimum bend radius). This keeps the size of the balun small and able to fit in a standard 4" × 4" × 2" PVC electrical box. The downside is that the loss is high compared to larger coax, but that is not typically a problem at HF if the choking resistance is high (thousands of Ω).

You can see that the 1113s I have is not wound with coax. At some point the manufacturer switched from a wire-wound transmission line balun to coax without changing the product number. In my opinion the change in design is more than enough to require a product number change. Both designs can be perfectly fine but they are not the same. For example, their behaviour when subjected to high SWR or a highly unbalanced antenna (e.g. end fed wire). But let's move on.

As can be seen, instead of leaving the balun unboxed I opted for a replacement PVC electrical box. I had a spare on the shelf so it was a convenient choice that also eliminated my concerns about the weather implications of leaving it exposed. The non-coax design weighed on my decision because water, snow and ice on the bare wires is a concern.

To my surprise, the new box and the old were identical, right down to the manufacturer (Carlon) details embossed on the insides. I measured the positions of the several holes and drilled them in the same places on the new box. Not even a wire had to be bent for a perfect fit. The black cable ties with screw flanges provide support for the ferrite toroid to keep it suspended within the box.

The new box did not easily mount on the resin backing plate. The 4 mounting screws had to be forced through because they were ⅛" farther apart than the enclosure's screw tabs can accommodate. To compare the boxes I positioned the broken off tabs and old enclosure on the plate to check alignment. They were also not aligned to the backing plate holes. 

That made me wonder whether the lateral tension of the forced mounting screws played a role in the breakage. There's no good way to test that possibility. I reamed the holes on the backing plate so that the mounting screws dropped in without resistance.

Before taking it up the tower I did a quick bench test. I swept the SWR from 1 to 29 MHz with two 30 Ω resistors in series across the balun binding posts. The impedance is almost exactly 60 + j0 Ω at the lowest frequency (SWR 1.2) and it degrades, as expected, with increasing frequency. The inductance of the balun output pig tails and resistor leads is to blame.

The test was successful and also demonstrates an important lesson. Where does the balun end and the antenna begin? It's worth a few moments of thought.

The answer should be obvious: the antenna begins where the wires diverge on exiting the toroid (top centre). That must be the case since there is reduced field cancellation when the wires are not parallel, and approaches zero cancellation when they diverge as in a dipole. That is, the wires no longer form a transmission line.

The leads to the studs and from the studs to the physical antenna element are part of the radiating structure. Antenna manufacturers like Hy-Gain (I'm using this balun on a TH6) specify an exact length for the leads from the driven element clamps to the balun terminals for this very reason -- in this case the length is 6". Depending on the internal wiring of the balun the length of the driven element may need to be adjusted. Usually the effect is minor when the leads are short. For this balun that is 2" per side since the box width is 4". That's a small enough effect that I can ignore.

To reduce the risk of PVC breakage, this time I mounted the balun above the boom. It's more exposed but if the mounting tabs break there is less risk of catastrophic failure. I anticipate no weather-related trouble since the seal on the box is quite good. Sealing the coax connector is easier when it is on top so that should also do well despite being more exposed to the weather.

An accurate SWR measurement is difficult because my body was close to the driven element. On 10 meters the SWR was high with my body less than 1 meter from the driven element. The distance was limited by the short coax jumper to the analyzer and how far away I could stand without adjusting my harness. I figured it was good enough under the circumstances, and indeed the SWR measured in the shack was as it should be. Mission accomplished.

It'll be interesting to see how well the new PVC enclosure withstands the weather. It's an exact replacement for the original and we saw how that did after years of exposure in my station and, before that, in the station of its original owner.

I'll make one last observation before I close. Notice how the frequency range of the balun is specified by the manufacturer. The power rating is for 160 through 10 meters while its effective range is less. This is not surprising but can mislead if not read carefully. Also, the usable frequency in the text is 40 to 10 meters, not 40 to 6 meters as shown in the table. Is it carelessness or something more?

I have another of these baluns on the 80 meters inverted vee. I did not read the fine print before installing it or I would have reconsidered. However, although it may not be very effective on 80 that does not mean it is ineffective. For a non-directive antenna far from the house, even a common mode impedance of less than 1000 Ω can be sufficient. I haven't experienced any interaction problems when operating SO2R.

Common mode baluns have a frequency range determined by the ferrite mix, the transmission line and how it's wound. Unfortunately, measuring common mode rejection (impedance) is very difficult and experts often fail to agree on how to measure it and how to interpret the measurements. Be very careful whether you build or buy a common mode choke. The ferrite mix used by Balun Designs is supposedly custom which makes it difficult to judge without an independent measurement.

If you'd like to build your own common mode choke there are many resources. Perhaps one of the best places to learn is provided by K9YC.

High-voltage Antenna Length Relay

There are many ways to design a multi-band antenna. Each has its good and bad points, and all have been discussed on this blog multiple times. Common deficiencies of multi-band antennas are SWR bandwidth on the lowest bands, loss in the loading elements and pattern peculiarities on one or more bands (multiple lobes and nulls).

Examples include:

• Traps
• Fans (parallel elements from a common feed point)
• Adjustable matching network, in the shack or at the feed point
• Frequency sensitive transmission line sections
• Relays
• Motorized, adjustable length elements
  

All can be complex to home brew due to finicky design and construction. It is no surprise that most hams that need or want a multi-band antenna choose a commercial product in which all the complexities have, hopefully, been solved by someone else.

Perfection is impossible so tradeoffs are necessary. You choose an antenna where the tradeoffs are acceptable for your operating interests and what fits within your property and support structures. Many hams make their choice by price and size. Performance claims are either believed, ignored or deemed acceptable. Yet it is possible to avoid many of the deficits of multi-band antennas. That requires careful design, an understanding of antenna and network theory and practice, and test equipment.

It has been quite a long time since I last wrote an article about antenna design. I most often write about what I'm doing, of which there's an awful lot, and for the past year I spent little time designing antennas. I was recently motivated to investigate a multi-band challenge I have in my station. Although you may not have the same type of antenna in mind, the following discussion may be useful.

One of my objectives is to make the 160 meter mode of my 3-element 80 meter vertical yagi more effective without compromising 80 meter performance. Currently I switch in a loading coil and L-network at the antenna base. On air testing suggests a deficit of -6 to -7 db compared to the 160 meter shunt fed tower.

The big shunt-fed tower, which is an excellent top band antenna, is not available year round because I must roll up the radials for several months in spring and summer while the hay is growing and then harvested. Burying the radials is an option that I am unlikely to attempt this year, if at all. It isn't an easy project.

Alternatives that I considered long before I built the 80 meter array were impractical when it came time to build them. Before going further, consider skimming that article since it introduces several issues discussed in this one.

I am planning changes to the 80 meter array that will make it mechanically easier to improve its 160 meter performance, and prepare for 80 meter yagi performance improvements. Both depend on replacing the tower with a taller one. That will allow me to get rid of the long and problematic stinger.

A new stinger at the top of the taller tower would only be used for 160 meters. The tower itself, and probably with the help of a short "tuning" pipe at the top, will be a resonant ¼λ on 80 meters. Modest loading at the base of the stinger will resonate it on 160 meters. The base coil will be removed and the L-network redesigned for the measured impedance.

With an acre of radials (almost 2000 meters of wire) under the 5 vertical elements of the 80 meter yagi, the 160 mode of the array will be far more effective with negligible impact on the 80 meter array. Because it will be shorter than a ¼λ on 160 the load cannot be loss free, the new design will likely be 2 db less effective than the shunt-fed tower, but that's a notable improvement over the present design. That will let me be competitive on top band during the summer when the shunt fed tower is unavailable.

The drawings at right show just the essential aspects of the existing (left) and proposed (right) construction. Since the new stinger cannot extend 20 meters above the tower, loading will still be required on 160 meters. Support ropes for the parasitic wire elements would attach to the top of the taller tower rather than the top of the stinger, as in currently the case. That allows the stinger to be lighter duty. If it is 8 to 10 meters long, the 160 meter vertical will be about ⅜λ, so the loading coil can be small and low loss.

The stinger will have to be switched by relay. Use of a trap or parallel (fan) vertical have been discarded due their negative effects on 80 meter yagi performance and narrow bandwidth on both 80 and 160 meters. A switched stinger is far superior in this regard. The primary challenge is with the switching between 80 and 160 meters. 80 meter impacts must also be quantified. 

The design can be done in the comfort of my shack by computer modelling. My tool of choice is EZNEC and its version of the NEC2 engine. I began by building a simple model to investigate switching methods, and refining that until I had a workable design. 

This article focusses on the simple model to investigate switching behaviour. After the tower is replaced and I can take measurements of the new array, I will refine the design.

Modelling the relay

Relays are not perfect devices. The coil requires wires for power, wires to the contacts have inductance, closed contacts have resistance and there is capacitance between open contacts. When the relay contacts are open, as they are in this application for operation on 80 meters, the voltage across the contacts can be very high, well over 1000 volts for legal limit power. This is a case where my relay phobia may be justified.

The EZNEC model ignores the wires powering the coil, assuming they are suitably routed and choked to isolate them from the high adjacent RF field. We'll return to these challenges later.

You may have to expand the picture to read the tables. There are wires for the 80 meter vertical, the 160 meter stinger and a short connecting wire containing an RLC load. The load is modelled as a pure capacitance. A small value for open relay contacts (80 meters) and a short for closed contacts (160 meters). 

Relay spec sheets may or may not show the capacitance for open contacts as measured at the terminals. The capacitance depends on relay construction, comprised of that between the contacts and the wires to the relay terminals, and the housing and other conductors if they are significant. The reactance decreases with frequency so that "leakage" is greater on the higher bands. In this instance the capacitance is only relevant on 80 meters where the contacts are open.

The SWR curves were drawn with a load capacitance of 0.01 pF. Up to 2 pf the R and X components change by no more than 2 to 3 Ω. That is negligible. With a good radial system (which I have) the impedance is low enough that a matching network may be helpful. For a poor radial system the series ground loss would improve the match at 50 Ω without need for a matching network.

I adjusted the wire lengths (all have a 40 mm diameter for simplicity in the initial models) to resonate the 80 and 160 modes where I want them. Relay lead inductance is ignored but they are almost negligible for these long wavelengths and are easy to compensate with length adjustments in the built antenna.

Conducted 80 meter current in the 160 meter stinger peaks in the centre of its length. For 1 pf of relay capacitance the peak current is 6% of that at the base of the vertical. It rises to 7% for 2 pf. That's comfortably small but may impact F/B when the array is operated in its directional modes on 80. I am deferring the exploration of that interaction to a later time.

Differences between the SWR curves and gain on both bands are negligible when compared for single-band verticals; that is, without the relay, and the stinger removed from the model on 80 meters. That is what I expected. So far so good.

Relay requirements

You don't often see antennas like this, using a relay to switch bands. Traps are far more common in this application despite their inherent loss and increasing the antenna Q on both bands. A relay has neither of those disadvantages. This is readily apparent in the EZNEC model's load data with the relay open for operation on 80 meters.

On any antenna with an open end -- which is almost all antennas other than closed loops -- the current at the ends of elements falls to almost zero and the voltage is high. Should you attempt to feed the antenna at one of these locations -- such as an EFHW (end fed half wave) -- the impedance is very high. Matching it to 50 Ω can be done, at the expense of transformer loss and difficult to control common mode current. In our case, it is only the voltage that needs to be tamed.

Relays exist that can withstand over 1500 volts of RF but they are not ones you commonly encounter. Contact flash over voltage is misleading since the spec is typically for DC or the low frequency AC found in power systems. The coil, insulators and conductors behave differently with RF flowing across the contacts. When the contacts are open, some RF current will flow due to stray capacitance or due to humid or polluted air. 

The resistance can be higher than expected when the contacts are closed, and the capacitance higher when the contacts are open. Further, the actual voltage could be higher than in the model due to voltage modelled in the wire segment rather than at the wire tip, and various environment and construction details. I would at least double the relay's voltage breakdown spec to be safe. A properly rated relay can still be destroyed by accidental hot switching. Luckily that's unlikely since a relay for changing bands is only operated when the transmitter is idle.

There are two classes of high RF voltage mitigation: use a relay designed for the application, or design the antenna so as to reduce the voltage where the relay is placed.

The preferred choice for applications like this is a vacuum relay. They are available with breakdown voltage ratings starting at 2 kV and going much higher. Unfortunately they are expensive: starting at well over $100. There is a good market for surplus and used vacuum relays to limit the expense, if you can find those with suitable specs.

There are other considerations: they can be fragile, difficult to mount and protect on a tower, detailed specs may be difficult to locate (e.g. capacitance for power and signal relays), and have inconvenient coil voltage (24 to 28 VDC is most common on the used market). Choose carefully.

Mitigation measures

There are ways to reduce the stress on the relay to reduce the risk of failure, and in some cases it may be possible to use a conventional open-frame or sealed relay. These are the ones I modelled, and all work, though not necessarily very well:

• Capacitance hat below the relay
• Leakage capacitor across the relay contacts
• Large diameter wire (tower) below the relay
  

The models I developed to test these methods are solely intended for the purpose of exploration. I will make no recommendations or provide dimensions for a real antenna. NEC2 and pretty well all modelling engines are not highly reliable with respect to voltage, current and impedance at the open ends of wires. Real antennas and relay terminal voltages will never exactly match the models. But they can come close, and that makes the modelling experiment worthwhile.

The capacitance hat option (left diagram) was a disappointment. The voltage across the relay only dropped by 25% with two arms that are 5 meters long. For an antenna that is 20 meters long the effect is severe and must be corrected by shortening the vertical quite a lot. That's unacceptable since the shorter length would degrade performance of the 80 meter array. I did not bother to dig deeper to quantify the effect because a 25% voltage reduction isn't enough to eliminate the vacuum relay.

The reason I expected better from the capacitance hat is that it partially mimics a large diameter wire (as in the right diagram) which is known to reduce corona effects found with sharper antenna tips. Instead it behaved as if the voltage was measured inward of an ordinary element or T-top vertical.

To model the "fat" lower wire (right diagram) I increased the diameter of the 40 mm wire to 200 mm (8"). This is quite close to the top (#1) Delhi DMX tower section I am currently using, and will be again when two larger bottom sections are added to the tower. Tower taper can be ignored for the experimental model since we are interested in the voltage at the top of the tower and not its exact height. The model's wire containing the relay (again, a low-value series capacitance load) was made 2 mm (AWG 12), while the 160 meter stinger diameter remained at 40 mm (1.6").

This option is promising. The voltage across the simulated relay contacts dropped from 1500 to 850 volts, which is more than 40%. The resonant frequency on 80 meters barely changed. The voltage reduction is enough to consider using an inexpensive relay with contact and wiring isolation voltage of 2000 volts or more. The model is not definitive since there are factors to be considered in a physical antenna. For example, the relay is likely not close to the tower top plate because a tuning stinger may be required for height adjustment. There are also the effects of humidity, pollution (dirt particles in the air) and precipitation.

Despite the concerns, it may be worth the experiment when the antenna is rebuilt. Flea market open-frame relays are inexpensive enough to risk destroying a few! Since I am designing for high power it is highly recommended to do the experiment using an amplifier with fast-acting fault protection. Luckily I have one of those.

A capacitor across the relay contacts (middle diagram, above) may be an unusual option since until now we've been trying to minimize stray capacitance due to the relay. The trick is to increase the capacitance to pass enough current to cause the voltage to fall to a value where a conventional relay can be used. Reactance decreases with increasing capacitance.

The 80 meter resonant frequency drops since the series capacitor electrically lengthens the anteanna, and that can be a problem. There is no effect on 160 meters because the capacitor is shorted by the closed relay contacts. We need to know how much capacitance is needed to substantially lower the voltage across the relay while avoiding excess lowering of the 80 meter resonant frequency, as we saw for the capacitance hat.

The result is not good. It took 30 pf to reduce the voltage by 25%, and the resonant frequency dropped ~10% to 3.2 MHz. This is very similar to the 5 meter long capacitance hat described above. I suppose that should be expected since a capacitor and a capacitance hat are close relatives. Current in the 160 meter stinger peak at just under 25% of that in the 80 meter wire (tower). Gain of the vertical on 80 meters dropped by -0.1 db, which is negligible. However, the stinger current could be a problem in the array's yagi modes, but I have not run the model as yet.

The only promising mitigation measure is the "fat tower" option; the others have too many deficits. I may play with the model further to see if I can improve it beyond what I did for this article. It would only be for curiosity since I now know enough to proceed.

Further considerations

Whether a vacuum relay or the ordinary kind is placed atop the top, wiring it to the switching system at the base of the tower must be done with care or the wiring itself will modify the antenna's behaviour. The usual way of doing this is to run the cable inside the tower. Skin effect is our friend in since the antenna currents primarily run on the outside of the conductor. It is more complicated with a lattice tower than a solid cylinder (wire or tube) but the current flowing along the inside of the tower should be much lower than on the outside.

Spacers must be used to keep the wires several inches from the tower surfaces. The tower is not grounded so two wires are needed, one being DC ground. RF chokes should be placed on both wires at both ends of the cable and another set midway. That will detune the relay wiring on 80 and 160 meters and keep RF out of the switching electronics. The cable will have to be carefully routed around the top tower plate. Check the relay specs to ensure that the minimum voltage breakdown between the contact wires and the coil wires is at least as good as we need between the relay contacts and wires.

If the stray capacitance of the relay is very low and the loading elements on the stinger keep it far from resonance on 80 meters, there should be little enough current on the stinger to keep it from disturbing the 80 meter yagi modes. This was modelled and discussed earlier, but I have yet to model the full 80 meter yagi to confirm that the stinger current does not degrade the yagi pattern. It probably won't but it would be foolish not to check.

That said, there is reason to add a capacitor across across the relay contacts. We want a small value that does not appreciably load the 80 meter vertical. Perhaps no more than 5 pf. Its purpose is to damp corona effects at the relay that can amplify the voltage across the relay contacts when the humidity is low. A high value resistor should be added in parallel to bleed static charge on the tower and stinger when it rains or snows. Vacuum relays can't do the impossible so we should do what we can to reduce the stress on this valuable device.

The top of the tower can be made wider with a wire cage between the top plate and the base of the relay to lower the voltage across the relay's open contacts. A capacitance hat won't do that, as we've seen, because it is too thin. The cage complicates construction and may not be worth the trouble just to avoid a vacuum relay. The structure would also make working at the top of the tower awkward and possibly dangerous. Out of curiosity I may model it regardless.

Attaching the 160 meter stinger to the tower has its own challenges. It will be quite tall with substantial bending stress at the bottom. There are a couple of ways it can be done: A) inline at the top of the 80 meter vertical's short tuning pipe, or B) bracketed to the tower. The loading coil and relay should be close to the bottom of the stinger. High quality and mechanically strong insulators (red) are needed since, as we know, the voltage can be very high. 

I believe the best approach is to bracket the stinger to the tower. The mechanical demands on the insulation are far less than placing it inline, especially for a long stinger. For example, one or two layers of PVC pipe can be placed over the stinger where the tower bracket clamps to it. One layer may be enough if excess voltage due corona and static are managed as see above.

Next steps

While this article is about my particular antenna, it is applicable to other vertical multi-band antennas of the same design. The technical challenge to incorporate a relay is modest and may be well worth the effort to achieve maximum performance. This can be particularly welcome on the low HF bands where a higher Q method such as traps significantly reduces the SWR bandwidth.

I am undecided whether to begin working on the 80 meter array this year. I am behind with other projects and I am trying to take a rest from major projects this year. The earliest it will happen is this autumn after the insects die off. The project will proceed in stages to avoid finding myself without a good 80 meter antenna when contest season begins in earnest. 

The 160 meter change described in this article is more likely to be undertaken in 2024. Replacing the tower and guy anchors must be done first, and that requires taking the tower down and doing a lot of digging and concrete work. After the tower is replaced I can attach the wire elements to the top of the new tower and not have to change any of the existing switching electronics and matching networks. 

Unlike the models in this article, the physical stinger height for 160 meters will not be full size (20 meters). That will lower the SWR bandwidth on 160 but not on 80 meters. Loading is irrelevant to the characteristics of the relay and mitigation methods.

One item I'd like to revisit for the blog is a survey of the alternative methods for multi-banding vertical antennas that I listed but did not delve into at the start of the article. It may be worthwhile to compare and contrast them in more detail. I've done all this work in the past but my perspective has changed. Perhaps this winter.

New Zealand on 6 Meters

The first half of the summer sporadic E season has not been the best in this part of the world. DX openings have been weak and brief. I haven't seen it so poor for several years. We're hoping for improved conditions in the second half of the season.

Despite the lack of fireworks there has indeed been DX to work. It just takes more work. You have to monitor the band, watch what others are working and spotting, and have the antenna pointed in the right direction at the right time when that rare DX signal rises out of the noise. I started the year with 122 DXCC worked and I now have 130. That's pretty good but I am never satisfied. I want more.

Let's roll back to the evening of June 23 when I worked #130, since that was a good one. There was periods of very good propagation to W6 and XE during the day, often quite strong even with the yagi towards Europe. That made me hopeful for propagation over the Pacific Ocean in the evening. It's a not uncommon pattern. But with so few hams over that vast expanse I could only monitor, occasionally CQ and hope for actual activity. Surprises happen.

When I saw US stations working New Zealand I paid close attention. The path slowly crept my way, moving from W0 to W9 and W8, and then in the Toronto area, which is about 300 km to the southwest. Soon enough I decoded weak FT8 messages from a couple of ZL1 stations. 

This was my first time hearing New Zealand on 6 since March. That opening was very brief and I missed out. I flipped on the amp, starting its 3 minute warmup. It was a warm day and I didn't want to heat up the shack unnecessarily by turning it on sooner.

By the time the amp warmed up there were no ZL decodes. So I called CQ and was quickly answered by ZL1RS on the North Island, north of Auckland. On my one visit to New Zealand over 30 years ago I was in that area so I could picture the scenery. Signals were painfully weak but we quickly completed the QSO. I was very happy to log him.

I notified my 6 meter buddies (we're a foursome now) and hunted for more, and CQ'd when there were no signals from across the Pacific. I heard only one other ZL that evening, albeit too briefly to attempt a QSO.

You have to anticipate the propagation to maximize your chances. I had pointed the yagi to ZL well in advance because there was strong propagation to W6 earlier in the day, and then XE came rolling in. As you can see from the PSK Reporter map below that these bracket the great circle path to New Zealand.

After the contact I received a nice email from Bob ZL1RS. It must be quite the challenge to operate 6 meters from that corner of the world due to the distance from there to the most active corners of the globe. On the other hand, almost every QSO is DX!

None of my friends in the area had the same luck as me. However the scales soon tip the other way, and the next day one friend worked 3B9FR while I came away empty handed. That day there were other long haul "almost" QSOs in Asia, and I did manage to work 9K, but that's it. There are enough new and promising signs of DX propagation to suggest that the second half of sporadic E season will be better than the first. Hope springs eternal.

Win or lose the chase is exciting and I'm having fun. I wanted to share that experience by deferring completion of a long delay technical article so that I could publish this one while the propagation continues to be good. 6 meters is truly the magic band.

Perils of PVC

PVC products are plentiful and inexpensive in hardware stores. There is pipe, conduit, weather-tight electrical boxes and much more. It is very tempting to this ham. I have used it in endless places throughout my station. The following images taken from my blog will give you an idea just how pervasive it is.

You can see enclosures for baluns, matching networks and switching systems, coil forms, open-wire spacers, wire antenna spreaders, gamma match supports, supports for Beverages and other antennas, and there are more that I haven't included. Flexible PVC is abundant in our stations as wire insulation and coax jackets. I would be surprised if you could not find many examples in your own station.

Despite its utility, there are important considerations before choosing to use PVC. There are many types of PVC and you can't easily know the characteristics of the material you're looking at. There are questions of rigidity (flexibility), dielectric constant, insulation qualities, UV resistance, thermal stability and fatigue life.

Flexible PVC conduit pipe can support my Beverages only because of the wire tension. The pipes would bend if they had to support all the wire weight. The pipes hold the wires in their correct positions and harmlessly bob back and forth in the wind. When the pipe is under load, as it is, for example, at the top of the stinger for my 80 meter yagi driven element (which must not be conductive), a wood dowel is inserted to give it the strength to withstand vertical and horizontal forces.

Depending on additives, PVC can be a very poor dielectric at RF. I use it for coil forms, but only for 80 and 160 meter antennas. As the frequency rises, loss in the PVC coil form can be substantial. 

UV resistance can be difficult to predict for PVC material bought at your local hardware store. I have seen PVC that has weakened in the Sun and I have seen PVC that endured many years outdoors. For example, the PVC jacket of RG213 has additives that give it excellent UV protection. 

Rigid PVC electrical boxes may be less UV resistant but can last a long time. It depends on the manufacturer, of which there are many and I couldn't tell you which are the best. I have seen discolouration and breakage that are due to a combination of UV and thermal cycling in our extreme seasonal cycle. They are also not immune to animals since some like chewing on them, much to my dismay.

With so many variables and uncertainties, many hams eschew PVC entirely while others believe that it's a miracle plastic. The truth is more nuanced. You can avoid PVC, and the convenience and economy it brings, in favour of less available and more expensivematerials. It is difficult to provide good guidance, so I won't.

All of this brings me to the point of this article: PVC structural failure. While doing work at the top of the 150' tower supporting the 3-element 40 meter yagi, I passed the side mount TH6 about halfway up the tower. I wasn't paying it any attention other than to climb past its tower support struts on my way up and then down. It was only on about the third trip down that I noticed something was amiss.

For those of you who don't recognize it, that is a ferrite balun made by Balun Designs. I used these to replace the ineffective Hy-Gain BN86 balun on both my TH6 and TH7. The TH7 (and balun) have been sold so I have two of these products left in my station -- the other is on the 80 meter inverted vee.

I can't say for certain that the discolouration is due to UV damage, but it is suspicious. The other two baluns have a similar appearance -- check the pictures in the link above for the 80 meter antenna -- as does an outdoor electrical junction box. My assessment of what transpired is that the 4 tabs of the standard PVC electrical box snapped off, and later the enclosure shattered at the coax connector due to the cable tension. I have had the mounting tabs snap on other PVC boxes mounted outdoors, and those were of different manufacture. The PVC must have been weakened by UV or thermal stress to break so easily.

I am amused that the reason I hadn't noticed the problem until then is that the antenna continues to work perfectly well. The wire windings on the ferrite core that are connected to the UHF jack and wire studs are holding it together. A corner of the ferrite toroid is visible through the crack in the enclosure. 

I'll have to replace the box, at the very least. It won't be difficult to transfer the ferrite core and hardware to another PVC electrical box. The question is whether I should do that. Won't it just happen again in a few years, or sooner?

Many hams keep their ferrite toroid baluns open-air since they are not perfectly efficient. With a kilowatt there can be 10 watts or more of heat in a choke in which small diameter coax is wound around the toroid or wound with wire as a transmission line transformer. Weather-tight is also heat-tight. Heat build up is unlikely the cause of PVC failure in this case because the TH6 only sees intermittent use, even in contests -- it's my multiplier antenna, and is rarely used for more than a few QSOs in a row.

I may forgo the PVC entirely and mount the balun directly to the underside of the resin plate on which the PVC box was mounted. That provides weather protection and ventilation of the balun without the risk of using PVC. The back plates of all the Balun Design baluns appear to be in good condition. When I come up with a suitable solution I'll write it up for the blog.

Accessibility for repair

Go ahead and use PVC in your station, but do so with an understanding of its merits and demerits. PVC can be more fragile than you may believe. This is particularly true when the PVC is deployed outdoors where it is difficult to repair. 

An example is my use of PVC conduit pipe in gamma matches and coax chokes on the driven elements of long boom yagis. Repair would require lowering the antennas to the ground. I hope that won't be necessary but it is a possibility.

In contrast, the busted balun enclosure on the TH6 is close to the tower and therefore convenient to remove and repair. May all your PVC repairs be as easy as that.

Outing Robots

As I mentioned in a previous article, I don't like FT8 robots. I don't dislike them on principle or because they're new and less "human", but for practical reasons: they call others when they shouldn't and they consume valuable spectrum. I steer clear of robots when I can positively identify them. I might a robot just to silence it, and then forget to log the QSO.

Identifying a robot is not as easy as you might believe. Human operators can exhibit behaviour almost indistinguishable from robots, robot algorithms are frequently changed, or the operator alternates between live and robot operation. Although I'm not obsessed with robots, identifying them is useful for avoiding them. But how?

For illustrative purposes consider this fictional conversation with what may, or may not be a robot:

Human: Are you a robot?
Other: No!

H: You call CQ for hours on end, and only a machine would do that.
O: I like making lots of contacts and earning awards.

H: When you call stations you annoy them by always transmitting on their frequency.
O: That's because they choose frequencies that are free of QRM at their end.

H: You also answer a CQ from every station you haven't work before.
O: They send CQ because they want others to call them. Nothing's wrong with that.

H: Even when they call CQ DX or CQ JA?
O: That may be what they prefer but often they will answer me.

H: But you call them 20 or more times in a row.
O: A lot of stations don't hear well so I have to keep trying.

This is deliberately written to mimic the most common form of the Turing test, where a interrogator interviews a subject via text messages and has to determine whether the subject is human or an AI (artificial intelligence). It is a difficult challenge and, to be blunt, most people are easily fooled. Many humans already have difficulty correctly identifying text responses from a LLM (large language model), which is not intelligent.

The question remains: how can an FT8 robot be identified? There are three major areas of inquiry:

• Self identification
  
• Behaviour pattern
• Stimulus-response

Self identification

Robots sometimes identify themselves. This might be surprising unless you know where to look. For example, digital stations connected to PSK Reporter will dutifully identify the software application. Bring up a map in PSK Reporter and hover the mouse over the location marker over the suspected robot station (you can narrow the search by noting its grid square).

Unfortunately this no longer works as well as it once did. I tried this for many likely robots while writing this article and I didn't find one. Robot operators have learned the hard way that they need to be less obvious because some hams took to tracking them down and telling them what they thought of what they were doing.

There are two ways to mask the software. One is not to not connect to PSK Reporter. The second is to use a feature of most (all?) of these applications to misidentify as WSJT-X. For this latter method it is possible to root out likely robots in a subset of cases. Look at the software version being reported. Negligent robot operators may not notice that the version being reported raises suspicions.

I located one station connected to PSK Reporter that by its longtime behaviour is almost certainly a robot most of the time its on 6 meters. I redacted the call sign and grid in case I am wrong. Is there anyone still using this ancient version of WSJT-X? A scan of other connected stations on the map will soon convince you that the use of this ancient software is rare.

Behaviour pattern

Since I discussed robot behaviour in the previous article I don't need to say much more. I would only caution robot hunters that behaviour patterns can be quite complex depending on the operator's configuration of the software. In many cases they keep it simple, opting to CQ or respond to CQs using mostly default parameter choices. Those are the easiest to spot, especially when they endlessly call CQ.

Don't be too certain that endless CQs or answering every CQ are sure signs of a robot. Human operators do that too. Cancel the watchdog timer and you can call CQ forever, and that's what some hams do. They use the auto-answer features of WSJT-X and JTDX and glance at the monitor from time to time in case there is a QSO in progress. When it's done they log the contact (or make logging automatic) then manually re-enable the transmitter to resume CQing.

Quite a few human operators pounce on any station they haven't worked before (those CQs have a distinct colour code). When the contact is logged they pounce on another. Most hams are more discriminating about who they call, so it may see robotic to see stations that call anyone and everyone they haven't worked before.

Stimulus-response

If you suspect a station is a robot it is possible to give it a poke and see what happens. This is analogous to the Turing test described earlier. The best way might be to call CQ with an unusual call sign that almost every human operator would react to differently than most robots. 

Before I continue, I must caution you that to do this deliberately can be unethical and even counter to the regulations for your country. I've never done it but I have seen it done inadvertently. When it occurs the results can be quite educational. I will give you an example that I recently encountered.

There was a station in the Caribbean that was very popular for DXers. Many common countries are often not so common or easy to work on 6 meters. The station in this instance was VP2MKP, and it was a new one for me when I worked him. 

Apparently he wanted to work stations faster so he composed a couple of custom messages to announce that he would move to FT4 on 50.318 MHz. This is a good idea and I wish more stations would do it. When conditions are good, doubling the QSO rate is worth a few decibels of sensitivity. But let's put that aside since it is not the point of this article.

There were two free form messages that were each transmitted several times. There is a strict limit to the length of these messages so they are often somewhat cryptic.

• CQ VP2M/FT4
• CQ VP2M/50318
  

The following screenshot captures only part of what ensued. It is enough to help you to see how different reactions of humans and robots. Call signs of suspected robots have been redacted, but not their grid squares.

The robots instantly reacted to the CQ message that appeared to contain a portable indicator for what was interpretted as a call sign. Although not real call signs, WSJT-X (at my station) tagged the messages as valid CQs. The port of the same software used by the robots did the same. Obviously the robots have never worked these call signs and so they went to work.

Would a human have clicked on the messages and answered, and do so in the very next period? That is highly unlikely, and it appears that none did in this instance. I can say that I stared at the screen for several seconds until I understood what those blue labelled messages from VP2MKP signified, and there is no way I would have replied, instantly or later, since that would have been foolish.

Not only did the suspected robots call, and call instantly, most stopped calling at almost exactly the same time! A lot of robot operators clearly stick with the default software parameters. There were variations. For robots that were in QSO at the time there was a 30 to 60 second delay before calling the false CQs.

How would you have reacted at the time. I can tell you how I reacted: I laughed. Then I scrolled back and forth and to confirm what had occurred. I knew I had a great idea for a blog article so I took the above screenshot.

There are many ways to deliberately provoke robots without waiting for chance to deliver what I've shown above. I'm sure most readers can come up with at least one. However, almost all are as unethical as the robots themselves since they require the transmission of deceptive messages. I won't do it and I would discourage you from trying it. Two wrongs don't make a right.

What should you do?

I don't know. What do you think you should do? If you really hate robots, my advice is to proceed with caution. Without walking in to the suspect's shack and inspecting their station, you cannot know. Never assume that you have found a robot with any of the methods discussed here or elsewhere. Being 95% certain is not 100%. Everyone deserves the benefit of the doubt.

In this and the previous article, I hinted at how I typically deal with robots. They are an annoyance but not a capital offense. I will not allow the presumed faults of others to become my obsession. If you are emotionally incapable of that, don't expect help from any regulatory authority, club or operating award sponsor. Avoid confrontation! That also applies even for (what you believe is) a friendly approach.

Most robot operators give it up after a while. Watching a machine make contacts is ultimately pointless and boring. Of course, others will come along and give it a try but they, too, will soon stop. In my opinion it isn't worth worrying about. I'll now give it a rest and not soon talk again about robots on the blog.