Sunday, July 15, 2018

IARU and WRTC

I did not make a substantial effort in the IARU contest this weekend. Not only do I not enjoy warm weather contesting -- too many opportunities to do things outside -- ongoing cabling and switching work meant I had just the TH7 at 21 meters and an inverted vee for 40 meters. The bigger antennas are not currently connected to the shack.

Despite all of this I did operate for several brief periods as CW LP. If not for this also being the WRTC contest-within-a-contest event I doubt I would have made any effort to be active. With some amusement I note that, apart from 80 meters, my station as currently configured is quite similar to what the WRTC competitors used. By accident I also used the same power -- 100 watts -- which I selected out of habit. IARU, being an ARRL sponsored contest, permits 150 watts in the low power category.

What I will do in this short article is provide my thoughts on how the competition may have played out. Of course I could be completely wrong. It is nevertheless interesting to test my understanding and make a few speculations. Eventually the full story and the facts will emerge. For background on competitor strategies and choices I recommend N3BB's excellent book, Contact Sport.

QSO totals

Compare the WRTC scoreboard and raw scores on 3830 and you'll immediately notice just how much higher the QSOs and scores are for the WRTC competitors. Their modest stations were no impediment. Like rare multipliers in any contest they attracted a lot of attention regardless of signal strength.

For this reason it is no surprise they spent the bulk of their time running. Indeed, despite spending half of my short time in the contest running I did not get called by any Y8. This continued to be true in the final 30 minutes of the contest when I'd expect their rates to be relatively low. Clearly they knew how to best utilize their time and energy.

Since there are 1,440 minutes in a 24-hour contest it is easy to calculate their overall QSO rates. The top placers were all above 4 QSOs per minute (240 per hour) averaged over the full contest period, with two stations and two operators. That's impressive! The high power multi-op stations could not match this level. I doubt the HQ stations (which are multipliers) fared any better.

Activity level and low power

In most contests those with low power and modest stations (especially QRP) usually must go high in the CW band segments to run. Big guns tend to congregate towards the low end of the band where it is difficult for smaller stations to run and be heard. Yet in this contest the low power Y8 competitor stations appeared to be evenly distributed across the band and could even be found hugging the bottom band edges.

Perhaps they could do this due to their starring role in the contest. On the other hand it is summer in the northern hemisphere when many contesters are loathe to spend time in the shack. I know I am. Despite midsummer conditions with its many attenuated propagation paths it seemed that the overall activity level was not high. That makes room available for smaller stations. Of course many of the big gun operators were congregated in Germany, not at their usual operating positions.

SSB

N3BB points out in his book that choosing the split between CW and SSB modes is a key strategic decision in WRTC. CW has the advantage of favouring low power and being picked up and spotted by the global skimmer network. SSB has the advantage of faster rate and a pool of operators who do not operate CW. In 2014 the competitive advantage appeared to favour those who emphasized CW.

From the scoreboard it appears that the CW advantage was suppressed in this year's competition. SSB totals are generally though not universally higher among the top scoring teams. If this is true why might it be so?

In 2014 the competitors were in W1 where the bulk of the valuable QSO points come from Europe. There remains a strong CW culture among Europe's contesters. From Germany looking west towards North America there may be proportionately fewer CW operators due to the now longstanding migration to SSB due to no-code licensing. Outside of the US, Canada and Europe the use of CW is even lower.

From central Europe I would expect that inter-continental QSOs favour SSB toward Central America, South America and east Asia. East Asia does not contribute many QSOs from W1 but it is a productive path from Europe. There are, for example, many non-CW operators in E2 and YB.

Could this have been a factor? I notice that North American teams are lacking among the top scorers. European operators may have better understood the need for SSB for racking up contacts on the available propagation paths beyond Europe and North America.

Low bands

Europe is a hotbed of amateur radio activity, including contesting. Pay close attention to the standings after any major contest and you'll notice that even the QRP participants in Europe work an enormous number of other European stations on the low bands, day and night. Did enough of the WRTC competitors from outside Europe understand the importance of the low bands? Intra-European contacts are worth less but there are so many more available.

In North America the low bands are mostly a wasteland during daylight hours, except in late afternoon and early morning during domestic contests, and then only in the eastern third of the continent. Europe is different.

Time will tell

Don't take my analysis too seriously. It is mostly speculation based on limited data. Time will tell whether I am right on any of my suspicions.

Being wrong does not worry me. In any competitive endeavour it is beneficial to study the competition to see what can be learned, whether to emulate or avoid the tactics they use. Answers may always remain elusive since the competitors themselves may be uncertain about what exactly they did right or wrong. Sometimes it is merely a matter of luck, be it good or bad luck.

For me contests are fun rather than a serious competition. I have no aspiration to compete in a WRTC. It is an opportunity to learn and to watch the masters in action. We should all always be learning.

Sunday, July 8, 2018

Insurance Contact Dilemma

An insurance contact is when you work a DXpedition a second time on a band-mode. This is generally frowned upon since it takes time away from the DXpedition operators to work other stations, stations that may not have worked the DXpedition at all. Sometimes it's done by mistake.

Most often it is done to be extra certain that their call is in the log. Rare DX can cause anxiety! Before the internet became prevalent in the DX sport insurance contacts were more often due to anxiety about whether they got in the log the first time.The uncertainty may be due to QRN, QSB or QRM (deliberate or accidental) that obliterates part of the QSO. The DXpedition operator can contribute to the anxiety by not clearly repeating and confirming the received call before moving on to the next QSO.

There are also less than stellar individuals who do it to show off their big antennas and big power. With computer logging braggarts risk being called out by the DXpedition operator so this behaviour is no longer as common as it once was.

With near real time log uploads to services such as Club Log there is less cause for anxiety. It used to be that you might only learn one or two years later that you weren't logged! That happened to me a few times so I am appreciative of the benefits of modern technology. Since internet access may not be available or reliable from remote locales, resulting in upload delays from hours to days or until after the DXpedition is over, anxiety still occurs.

Which brings me to the recently completed Baker Island DXpedition: KH1/KH7Z. There were two QSOs that caused me some anxiety, and ultimately a pursuit for insurance contacts.

The first was 15 meter CW. Despite the poor solar flux there is a brief propagation peak in the late evening my local time. Signals are quite weak, putting us at a disadvantage to those further west on the continent. Nevertheless I managed to eke out a QSO around 04Z with my TH6 up 43 meters and with my usual 200 watts. Having a kilowatt would have helped get through but with a lesser antenna I may not have heard them.

The QSO was not without drama. It took a few overs until he copied my call correctly. Finally I heard it, sent my report and heard the confirmation. One more band slot in the log. Or so I thought.

The QSO was not in the online log after it had been updated up to and beyond the time of our QSO. This is not necessarily a problem since it often happens that logs from all operating positions are not uploaded at the same time. So I waited another day. Still nothing.

Perhaps I had been wrong when I heard him send my call that final over. I felt (and still feel) it was correct. I could wait and hope for the best or consider trying for an insurance contact. For many this would be simple to resolve: just get in there and do it. My reticence is due to my dislike of bothering the DXpedition operator again or, worse, hearing the dreaded "QSO B4".

Nevertheless I went ahead. Propagation peaked at the same time a few nights later and I made the QSO easily enough despite the weak signals. No incorrect call to correct this time. Lo and behold the QSO appeared online the next morning! It seems I had made the correct decision.

During the intervening time I got lucky one morning and worked them on 80 CW about 10 minutes after local sunrise when signals usually peak. I heard my call clearly above the noise after one extra over to communicate my call sign suffix. There was a smile on my face as the pile up crowded onto my transmit frequency for their attempt to make it.

The smile didn't last. As you can guess the very same thing happened. Again the QSO failed to appear. There was no happy ending this time since I was not able to catch them again on 80 at the right time and mode.

How does this happen? As the DXpedition wound down I happened to be chatting with a serious DXer friend of mine and we talked it over. We could think of several possibilities.
  1. My mistake: Skill, experience and diligence can still fail us. Despite my certainty it is possible they copied my call incorrectly and I failed to hear the error and correct it. This happens quite a lot in contests, so I am accustomed to these irritating mistakes. However I tend to be especially careful when working a rare country.
  2. Accidental erasure: Endurance operating takes its toll, whether in a contest or on a DXpedition. A wrong or forgotten keystroke and a QSO can vanish without a trace. Although this certainly happens I don't consider it highly probable in the case of my missing QSOs.
  3. Typo: Operators have many different styles. Logging software can smoothly handle transmission of partial calls that are typed in and re-sending of updated call signs. Some operators are more comfortable sending the partial call by hand. Only after they believe they have the call correct do they type it in and log it. In this way I could hear my call being sent yet not be correctly logged. The likelihood this happening twice does not seem high to me. It's just a possibility.
Frankly the most probable explanation is that the mistakes were mine and mine alone, despite my confidence about what I heard. It is nevertheless a healthy exercise to explore the range of possibilities. Even if errors occurred at their end it does not absolve me: perhaps there are things I could have done to improve the outcome. That is, to make it easier for them to copy and log me. Insurance contacts are a poor substitute for accuracy.

All of this said there remains the faint possibility that my QSOs are correctly stored on the DXpedition PCs. There may be gaps in the records uploaded from the database, gaps that will be filled when they get home and process the logs. I am not very hopeful this will happen

Screen capture from Club Log

I did pretty well despite the lost 80 meter QSO. Unfortunately my 160 meter antenna is down for the summer since I did hear them on that band a couple of times. Baker Island on the low bands will have to wait for another 10 years, which is the earliest another DXpedition will be permitted on the island.

It give me one more thing to look forward to. I'd better get back to work on towers and antennas so that I'll be ready when that long awaited day arrives.

Saturday, June 30, 2018

Making the Move to FT8 on 6 Meters

Six months ago over the Christmas holiday I downloaded WSJT-X to give FT8 a try. Since quite a lot of CW and SSB activity has moved to this new digital mode, in particular on VHF, it seems inevitable that I would take the plunge eventually. Also with a background in software and experience developing commercial applications using DSP and statistical analysis the technology alone was of great interest to me regardless of whether I would ever use it on the air.

On VHF/UHF, 160 meters and the new MF and LF bands the attractiveness of advanced digital communications is readily apparent. For a week I monitored the FT8 watering holes on most bands from 160 through 6 meters just to see what showed up that I might not otherwise notice courtesy of its low SNR capability. The software is easy to use and I was decoding traffic within minutes of installation. The only error I made was at first to connect the sound card input to the rig's microphone rather than the receiver audio. Without thinking I had stupidly connected like to like -- mic to mic -- a common enough mistake

The amount of activity was surprisingly high on every band that was open. On 160 meters there were numerous European stations on 160 meters when there was no CW signals present. Most of the calls were unfamiliar, indicating that FT8 either draws more hams to try top band or that FT8 allows smaller stations to be more successful. On 6 meters stations were copied when I had no particular reason to believe there was sporadic E present. On the HF bands the FT8 windows were crowded.

Based on the signal reports being exchanged the majority of signals would have been comfortably copied on CW. But since you can't predict signal strengths in advance this is not a slight against FT8 versus traditional modes.

Hibernation before a first QSO

First FT8 QSO
After a week of fooling around I pushed WSJT-X aside without having transmitted once or made any QSOs. It was peak DX and contest season and I was not willing to spend more time with it. Its time would come, I knew, when the peak sporadic E (Es) arrived in late spring. The migration to FT8 on VHF has been so profound that it would be that or miss a substantial amount of activity, especially DX, which is my particular interest on 6 meters.

In late May I became serious. After some experimentation I had the FTdx5000 working well with WSJT-X 1.9 and began making QSOs on June 5. I made my first QSO on 10 meters since propagation did not favour 6 meters when I was ready to go. As is my bent the first QSO of course had to be DX!

Now familiar with the software and certain I had everything hooked up correctly I exited HF entirely to focus on 6 meters. Indeed as I write these words that first FT8 QSO is my only one on HF. It may be a long time before there's another in my log.

Motivation and qualms

My sole motivation to try out FT8 is the wholesale migration of DXing activity on 6 meters from CW and SSB. Whether one likes it or not that is where the activity resides. This became very evident in 2017 and was certain to be even greater in 2018. While I had nothing against FT8 there seems something overly artificial about QSOs that fully rely on machine coding and decoding. This is a common sentiment among many hams.

It was therefore with only middling enthusiasm that I took the plunge. The technology itself is fascinating and delightful, and that pushed me along. My appreciation is in part because I have developed commercial DSP (digital signal processing) software. There is an undeniable urge to learn what far better minds than mine have been able to accomplish in developing FT8 and similar digital modes.

But would it work for me? Could I learn to enjoy FT8? Would DX fill my log? That is, would I work DX on FT8 only because that's where the activity is or because it delivers superior results? The only way to know for sure was to become active and stick with it through the sporadic E season. Before continuing I'll tell you now that my expectations were met. However it is not all roses.

What I've worked

No QSO, but how nice that he sent that last message
As I write these words I've been on 6 meters FT8 for 3 weeks. In that time I have primarily focussed on DX, but also North America west coast and Mexico as conditions dictated. A few times I ran shorter distance stations to improve my skill using WSJT-X. It's quite easy, just click, click and click some more, and watch the log fill with QSOs.

Although it can be boring I usually fill the time by browsing the internet, eating or skipping away for a few seconds at a time to do small chores. It's a very different kind of amateur radio than I'm accustomed to!

In these past 3 weeks I've worked close to 170 stations (no dupes), with 40% of those outside of the US and Canada. I haven't counted countries but there are quite a few, many of which are new for me on 6 meters. Stations I've copied or almost worked range from JA to OA to OH to 4X and TY.

For the longest of paths the opening might last no more than one 15-second transmission, never to be heard again. FT8 is a bit of a tease that way. Despite the frustration it is fascinating to watch what is getting through. I often leave the station monitoring 50.313 or 50.323 MHz when I am busy elsewhere and see what the propagation delivered while I was away.

Usually there little to see while other times I am appalled at the opening I've missed. For example, the JA opening seen in the adjacent screen capture. It lasted 7 minutes with over two dozen Japanese stations copied. But I wasn't there to work any of them. Oh well, there's always next time (or next year).

The briefness of so many openings -- shorter than it takes to conduct an FT8 QSO -- may seem unreasonable yet this is not really true. Although it is true that a CW or SSB QSO can easily be completed far faster than FT8 and thus benefit from ultra brief openings you have to be in the right place at the right time to do it. This is quite difficult though I've done it numerous times. It makes me wonder whether one of the fast modes would be more suited to DXing on 6 meters. Perhaps MSK144 that is used for communication via meteor scatter pings.

With FT8 you monitor the entire "band" at once and can see and respond to one of these micro openings in seconds. In a typical east European opening there can be dozens of these in quick succession. Of course one to two minute QSO may be too long to fit into the opening but at least you have a chance. Most often on CW and SSB you would never even notice the openings and so work nothing at all. On balance FT8 wins this contest, in my opinion.

Switching to 50.323 MHz

Birds flocking together in the fall are a good analogy to 6 meter FT8 DXers. After days of false starts somehow consensus is reached and the flock takes off together to begin the migration south. In the same fashion everyone congregates on 50.313 MHz until the unspoken signal is given and we all make the move to the intercontinental DX window.


What is that signal? One that motivates me is exemplified by the above spectrum view. In good openings the standard FT8 window fills with many signals or a few very loud ones. When this happens our receiver's AGC gets busy protecting us against excess IF amplification and distortion. This effectively desenses the front end and can render weaker signals undecodable.

In a pinch you can use a narrow filter. Most of the time that is a poor solution since you may not know the DX station's frequency or you'll miss new ones. When copy of weak transitory signals becomes difficult or uncertain that may be the time to QSY. Like those birds they'll individually rise up and look around and if they like what they find they'll keep flying. Eventually a tipping point is reached and the entire flock of DXers moves.

In my short experience the whole process takes only a few minutes, including most stations on both ends of the intercontinental path. It's a fascinating study in human psychology.

Who's active

One fact that jumped out at me immediately is that few of the call signs I've heard on HF and VHF were familiar. Often one hears many of the same stations every day on CW and SSB. I was intrigued by the presence of many hams I would not otherwise hear. I like that. It gives a DXer like me a whole new set of stations to work.

There are of course also many recognizable calls, hams who are active on CW and contesting. It makes for quite a mix. Obviously this latter group remains active on both digital and traditional modes. Perhaps they are experimenting with FT8, like me, or have made it a regular part of their activity on HF.

Despite criticisms of FT8 as being machine to machine (partly true) if it gets more hams active that's a good thing. Whatever I may think of FT8 from a philosophical perspective it is now necessary to pursue DX on 6 meters. Being stubborn or a curmudgeon about it does not put DX in my log. It is yet too early to tell how this in combination with the aging out of the older generations will change amateur radio.

Quirks, tips and common mistakes

During my short time on FT8 I have learned quite a lot. Some of it is covered by others, such as in ZL2IFB's excellent guide, though oriented more towards HF where propagation lasts longer than mere seconds. Others I have learned on my own, though all are probably documented by others, somewhere, if you know where to look. I find WSJT-X documentation silent on many questions I needed answers to.

The following are a few of the things I've learned. These points are oriented to 6 meters, especially DXing, and so may not be useful to everyone. Perhaps some will be of use to you.

Decode errors: Although FT8 uses FEC (forward error correction) its algorithms are so aggressive that it is not uncommon to see messages such as the one at right. The more aggressive you dial up the algorithms the more of this you are likely to see. The phantom signal usually has a very low SNR though not always. My first experience of decoded noise was RTTY in the 1970s. The random sequences could be hauntingly close to plain English. The resemblance to real messages is especially true with FT8 since the they are in essence just numbers that map to character sequences.

Power: For optimal decoding of your signal at the other end your signal should have the minimum distortion. What is annoying but passable on CW and SSB does not work at all with FT8. From what I see on the WSJT-X spectrum display many haven't figured this out yet. I leave the rig power at 100% (200 watts on my FTdx5000) in SSB mode and use the WSJT-X power control to set the power output to no more than 50% (100 watts). There is no ALC action and the transmitter isn't stressed. Setting the rig power to 50% requires heavy ALC action and some distortion getting through. Since I use audio equalization the power varies with the transmitter offset, which may require fine tuning.

Mode switching: I use SSB for simplicity in setup and tear down of cabling. Using the rig's digital modes and associated attachments can mean less fiddling with transmit controls when switching modes. For example I have to turn on VOX and disable the compressor for FT8 and reverse the process when returning to SSB. Happily I have fixed level jacks on the rig back panel for audio in and out for computer interconnection rather than having to swap cables when switching modes. The mic must be disconnected since it always mixes with the audio input from the back panel jack.

Simplex vs Duplex: Many calling me transmit on the same frequency while I almost always call others on different frequencies. There is no simple rule. When you are confident there you are likely to be the only caller it can be helpful to go with simplex since the other station presumably chose a clear frequency. Otherwise duplex is the better bet.

Respect directed CQs: When, for example, a station called CQ EU do not reply if you are not in Europe. That seems simple enough yet many call anyway. In the intercontinental segment at 50.323 MHz all calls are presumed to be for DX. Because some persist in calling anyway I turn off the Call 1st feature when I make a directed CQ and manually select a station to answer. I learned to do this when calling CQ DX on 50.323 MHz and my station automatically responded to a domestic caller. This brought out an over-enthusiastic policeman who DQRM'd the QSO. Disrespecting the band plan is unethical but DQRM is illegal. Avoid doing both, and especially the latter!

Policemen: Speaking of policemen there are quite a few of those on 6 meter FT8. Who would have guessed. They hound non-DX QSOs in the DX window, harangue splatterers and those in the wrong time sequence, or simply broadcast what they believe are helpful messages. In their enthusiasm they forget to include their call signs. The policemen, too, have migrated to FT8 from other modes.

Timing: There is no consistent use of even and odd slots on domestic QSOs though there are conventions. When DXing respecting time slots becomes important. The simple guideline proposed by the UKSMG (UK Six Meter Group) is largely adhered to and works well. Don't expect to work much DX if you transmit in the same time slots they use! When everyone respects the time convention you'll notice that spectrum display is empty on even slots except for those weak European signals. When they all mix together on 50.313 MHz the QRM often renders weak DX signals unable to be decoded.

Multiple callers: By not using Call 1st the CQing station can choose who to respond to, at the price of having to be nimble with the mouse. If the desired station is using Call 1st, which is most common, it can take multiple attempts to get through, if the propagation holds for many minutes. This can be gamed to get through sooner by noting that Call 1st is with respect to WSJT-X decoding order. From observation the decoding order is determined by frequency and number of required decoding passes. If you signal is reasonably strong you should transmit well below the desired station because you'll be decoded first! When it takes a second pass due to QRM or propagation phase distortion you'll lose out to someone else. Although not a guarantee the tactic does work.

Calling etiquette: When the CQing station responds to another station some keep calling throughout the QSO while others tail end (after 73 or RR73), while still others are silent until a subsequent CQ is sent. Continuous calling seems impolite to me even though it really doesn't cause harm other than to fill the other station's screen with a few extra messages. Consensus on this point seems elusive.

RR73: Many CQing stations use RR73 rather than RRR to complete the QSO to, presumably, speed the QSO. Unfortunately that doesn't necessarily work. RR73 ought to be used only when signals are strong otherwise WSJT-X will resend it if the expected 73 is not received. But after the caller sends 73 and another RR73 is received the 73 message is not automatically sent since the transmitter is disabled. It must be sent manually, which wastes at least another 30 seconds if you are not very quick with your hands. For the present I avoid using RR73 when I respond to callers to my CQ. Another speed technique is to send a signal report as the first message rather than one's grid. It seems to work well for brief DX openings although it may irritate those who collect grid squares.

NA contest mode: There is one, much to my surprise. During the ARRL VHF contest some used it and some didn't, resulting in mass confusion. I hadn't even heard of it at the time and could not understand the peculiar exchanges (I still don't) which I could not find in the WSJT-X manual. So I avoided FT8 during the contest. Some operators forget to turn the feature off after the contest.

Aurora: Forget it. The auroral curtain causes rapid frequency (Doppler) and phase shifts that defeat all attempts to decode FT8 of reflected signals. The decoding algorithms in WSJT-X are impressive but even they cannot "put Humpty Dumpy back together again." Switch to CW.

FT8 and me

After a month of FT8 activity I am prepared to decide whether it's for me. On HF, no. At best I like it as a type of beacon network to tell me if there's propagation. On 160 meters I can see that it could be interesting, so come this fall I will likely give it a try. But DX only. For 6 meters I find it useful, interesting and I almost but not quite have enthusiasm for it. With it I am near certain I am able to work far more DX and capitalize on marginal openings.

Sure, being able to monitor all activity simultaneously is a bit of a cheat. However it is not all that much worse in that sense than using the spotting network. It's like having my own CW skimmer. For a long time ham it only requires some getting used to the difference in operating style. It's hard to argue with a log containing dozens of DX contacts over the past few weeks. I have no doubt they are real QSOs, no worse than what is typical on all bands and modes.

The worst thing about FT8 to my mind is the boredom. Sitting in front of a screen watching the green bar advance one slow second after another is very tedious. Yet you must have quick reactions to respond to a station in the 2 or 3 seconds after decode to hit next 15 slot. Miss it and you lose 30 seconds (or much more if someone else works the station you want), and that can easily mean missing the contact entirely due to the short openings for the longer DX paths.

I liken it to baseball where most of the time you stand around doing nothing and a small amount of time moving like lightning. Your vigilance must not waver. When the time comes you must react very quickly and do everything properly despite the need for speed. You often don't get a second chance.

At least the 6 meter sporadic E season is short. I think I can put up with the negative aspects of FT8 for a month or two in order to work the DX. Time will tell. It may not even matter what I think if the mass migration to FT8 on 6 meters holds. One night during a great opening I moved to CW to relieve the tedium. The one QSO per minute I sustained for 20 minutes was a welcome change. Compared to FT8 that's a fast rate.

After the CW run I switched to SSB and worked a few more before settling into a rag chew with an old friend. Difficult to do that on FT8. Each mode has its quirks and benefits. FT8 fits well into the 6 meter operator's repertoire.

Plans for improvement on 6 meters

My 6 meter station is the same as it was last year and changes will not happen until next year. Although the sporadic E season is only a little more than half over I am too busy with other projects to improve my equipment. My antenna is big, high and working well, I've made the move to FT8 and the DX is rolling in. That's sufficiently satisfying for this year.

There are two deficiencies I would like to deal with. The first is the transmission line. It's an ancient 40 meter run of RG213 that is very lossy at 50 MHz. The matched loss for pristine RG213 would be -2 db and perhaps another -0.3 db due to the low SWR. It measures almost twice that loss due to its age-related deterioration. That's a lot!

Ancient RG213 may seem a strange choice since I have ample amounts of LDF5 and AVA7 Heliax. However the Heliax is slated for long runs to and up big towers for HF antennas. I will not allocate a precious 40 meters of it until I have more in hand. HF contests and DX are higher priority.

The second deficiency is power. It is sometimes (and falsely) claimed that FT8 is best suited to low power, even QRP. Of course low power is often all that's needed, but that's equally true for other modes. For the majority of CW and SSB QSOs you could turn your power down to 5 watts and still be solid copy. Of course almost no one does that. When it comes to brief and marginal DX openings on 6 meters power comes in very handy, whatever the mode. Many FT8 DXers on 6 meters run high power and it delivers results.

When I do purchase an amplifier it would be nice if it covers 6 meters. This isn't mandatory. I am willing to delay or forgo high power on 6 meters if the amplifier I want is available at the right price and only covers HF. As an interim measure improving the coax next spring will give me the equivalent of several hundred watts. An amplifier is not my foremost need.

Monday, June 18, 2018

Wind vs. Tailtwister Rotation Lockup

I find it unconscionable that a company can ignore a serious design flaw in a widely used product that has been in production for decades. Namely, the Hy-Gain Tailtwister rotator (T2X). If you have a T2X you have likely encountered this flaw. I'll briefly describe the flaw and how I recovered from one time in an unconventional way.

The flaw is simply this: occasionally the rotator locks up, able to turn in one direction but not the other. The usual method of dealing with this is to briefly turn it in the operational direction, after which it will once again turn in both directions. It is annoying but not a deal breaker. Since the T2X tends to be reasonably priced on the used market the flaw elicits grumbles but rarely more. I got mine for a good price and overhauled it.

I would never buy a new T2X since it is extravagantly overpriced for its features, load ratings and quality. The manufacturer gets away with it since hams keep buying them despite poor reviews and continuing problems. None of this is the direct fault of the current owner of the product line -- MFJ -- since the T2X and its woes go farther back decades. They just keep churning them out to feed the market's appetite. Obviously I decided to accept the good and the bad with this rotator.

Although the picture at right looks perfectly innocent it is not. The antennas are pointed south and, at the time, were not able to point elsewhere. This is the case where the flaw is far more than an occasional annoyance.

When the rotator locks at the clockwise or counterclockwise stop you cannot use the trick to briefly turn it in the operational direction since it stopped in that direction by the limit switches that prevent over-rotation.

Often the only solution is to climb the tower. A helper in the shack releases the brake and you grab a yagi boom and manually jiggle the mast to free the brake. Since this is not a desirable thing to do one tries to avoid the situation by being careful to never let the T2X rotate right up against the stops.

In the heat of an opening or contest it is easy to forget. Other times wind and rotational momentum will put the rotator into the danger zone despite your best intentions.

In this instance I was chasing South American DX on 6 meters and was trying to catch a new one before the fickle propagation could turn against me. My full attention was not on the rotator position. After trying (and failing) to work the DX I discovered that the rotator was locked against the south stop. Until I could unlock the rotator there would be no west coast or European openings for me!

T2X going nowhere fast

I was not pleased. Over the next few hours I would try the rotator, hoping for a miracle. Absent a miracle help was arranged for ground assistance, but not for that day. Meanwhile I fretted. At least the HF bands were available to me with my other antennas and tower.

Later that day a weather front moved through and moderate winds of up to 50 kph were with us for a few hours. I noticed the antennas rocking on the mast as they usually do with Hy-Gain rotators. This due to the play of the brake wedge in the teeth of the outer housing. As I watched I got an idea.

Back in the shack I released the brake and waited a few seconds. I tried turning the rotator. It didn't move. After a brief pause I tried again and this time the rotator resumed working as it should. What I was trying to do, and succeeded at, was letting the small and random rotation due to the wind force do the mast jiggling for me without having to climb the tower. I had never tried this before and was pleased to see that it could work.

With the antennas back towards Europe I phoned to inform my helper that the problem was resolved. He had a good laugh when I related what I'd done. In future I'll have to be more cautious when operating the rotator.

If you have a T2X or are considering one perhaps my story will someday be of use to you.

Thursday, June 14, 2018

Do Animals Climb Towers?

You have undoubtedly read about or seen the raccoon that recently climbed a 25-storey building in Minnesota. To a human it seems kind of cute and interesting, along with some worry about the welfare of the animal. To the raccoon it would have been more about survival and not much fun at all.

Being a ham this immediately brings to mind the question of whether animals climb towers. Yes, they do. This I know from direct experience. Like the raccoon in the story animals don't usually climb for fun (or to work on antennas!) but rather to accomplish some goal related to survival such as shelter or food. I have seen squirrels climb for no discernible reason at all, but that's about what we expect of squirrels.

The only regular animal climbers I have seen on my towers are raccoons and squirrels. The why and how of it are interesting. At my Ottawa QTH where I had two small towers I had frequent opportunities to witness these climbers.

Unfortunately I have to relate the rest of the story without pictures since they never waited for me to find a camera and then pose, and in any case would disappear fast when they caught sight of me sneaking up on them with camera in hand.

Instead I'll include pictures of the towers and explain the rest in words. The tower pictures are taken from blog articles back in 2014.

How?

Rodents rely on their claws to climb. On trees this works well; on steel the claws are useless. Larger animals can grip tower braces with their paws.

The first time I caught a squirrel climbing was on my DMX tower -- this tower is now the driven element of my 80 meter vertical yagi.

The first few times I noticed that the squirrel would hop onto a bottom brace and sit there. Then it would hop off and continue on doing whatever it is that squirrels do. Days later I saw one (the same one?) jump from the lower brace to the next higher one on another faces. Finally one of the brighter ones realized that this thing could be climbed and made it up to about 20' in this fashion, then immediately come down again. It was interested to observe their learning process.

During one of these episodes a second squirrel on the ground watched the one that was climbing and decided to try it. Its first attempts failed, seemingly unable to catch on to the trick of it. When it finally succeeded the two squirrels chased each other up and down the tower the same way you see them playing on trees. After 30 seconds of this they were back to chasing each other on the ground.

I never caught a raccoon climbing the DMX tower. Perhaps they didn't, however it is very exposed and raccoons are shy and mostly nocturnal. I never saw a squirrel climbing in winter. Whether it was a behavioural thing or the tower steel was too cold for comfort I can't say.

Why?

Apart from play animals can find towers useful. Actually play is useful for improving and demonstrating fitness and is common behaviour among most animals, humans included.

Perhaps the most common use of towers by animals is getting from A to B; that is, it's a kind of road. The location of the tower is therefore of utmost relevance to whether it will be attractive for climbing.

In the case of the DMX tower it was eyed by the squirrels as a bridge between trees. Not visible in the earlier picture is an huge though diseased willow tree on the left since it had just been cut down by my neighbours to prevent it falling down. The reach of its branches was ideal for squirrels, allowing them to jump to or from the branches of other trees.

With the willow gone the tower was being eyed as a replacement to cross my yard without touching the ground. It didn't work out, though they did try. One day I watched a squirrel climb to over 30' on the DMX tower and attempt to jump to the spruce on the left. Since the squirrel could not dig in its claws it had to attempt the jump from a sitting position on the brace rather than its preferred method of digging in its hind claws, leaning outward and pushing. It couldn't get enough purchase on the steel to make it work. Luckily it only fell partway, landing on a lower and longer branch.

The bracketed tower was far more useful for animal transportation. With no trees overhanging the house the tower was an easy path to the roof and from there to the overhead telephone and power lines. Utility poles and lines form a transportation network for rodents. Indeed this tower was in use long before they learned to climb the DMX since it is so obviously useful and its braces are comfortably horizontal.

This is where the raccoon comes in. One morning I walked into my home office -- a converted bedroom whose window you see in the picture -- and came face to face with a raccoon. It was heading down the tower and its head was level with mine. Both of us were caught by surprise. After staring at each other for a moment it reversed direction and hopped back onto the roof and sped away.

That's one picture I most regret missing and I never again caught a raccoon in the act of climbing. The only trouble it appeared to have with the tower was its size as it squirmed between and around the tower legs and braces.

The only other animal of note, other than birds, was a lone groundhog that stood up with its front paws on the lowest brace of the DMX tower to have a look around. Like many rodents groundhogs can climb, though not very well and may resort to it only when they have no other means of escaping a predator.

Not here

At my current QTH none of my towers is useful to animals and I have not seen any attempt climbing. This is not unexpected. The bracketed tower only gives access to the roof, which is steel and unfriendly to claws. There are no trees to jump to. The Trylon likewise has little utility since the adjacent trees are short and isolated from other trees. The big tower is in the middle of the hay field is even less useful to animals.

Though unlikely perhaps one day I'll catch a squirrel climbing a tower if only for play. But with so many trees compared to suburban lots I doubt that towers hold the slightest attraction for them.

Monday, June 11, 2018

Tuning Up Tower Guys

Adjusting tower guys is a methodical process. You start at the bottom and work your way to top, guy set by guy set, making the tower vertical and setting the tension. This is done during construction and again once or twice in the following days or weeks after the guys, grips (or clips) and other linkages deform under tension until they reach their final shape.

When done properly there is really nothing more to do except for regular maintenance. Once or twice a year guy tension should be measured and all parts of the guys should be inspected, remotely by binoculars if necessary. Trouble signs include tension differences, fraying, rust, fretting, deformation, and stress fractures.

In this article I'll talk about some of these in the context of maintenance I did this spring. It isn't a lot of work but it must be done to ensure a safe installation. Maintenance is certainly easier than constructing the steel guys and attaching them to the tower! What is needed now is finesse rather than brute strength.

Measuring tension

The tension in each set of (3) guys will be equal unless something is amiss. Problems are typically one of asymmetry of anchor placement, gauge error or tower misalignment.

The first of those should be addressed when the tower is sited, before construction begins. The levelness of the site is easy to overlook but it can result in anchors at different heights and therefore unequal angles between the guys and tower at every guy station.


Measurement error is common with the gauges many hams use. For example, the Loos PT-3 gauge I use (as do many hams) is calibrated for 1 x 19 stainless steel marine cable. For 1 x 7 EHS guy cable the measurement is low by perhaps 10% due to the greater stiffness of EHS. This is easy to deal with by applying a correction factor. What is more difficult is that the larger strands of EHS affect the lay of cable in the gauge guides so that the measurement varies with where the gauge is placed. In my experience with the 5/16" EHS the variation can be 100 lb.

For best accuracy with this gauge I take multiple measurements and shift the position of the gauge a small amount for each measurement. Then I record either the average or the majority measurement.


I strongly recommend recording the measurements. Not only will you instantly spot problems that you might miss if you solely rely on your memory you will easily notice changes over time. I put the measurements in a spreadsheet. I do not replace the old data when new measurements are made. Looking at the trends over time can be valuable to keeping your tower in good condition.

Notice that I record the raw figures from the gauge, not the conversion to real units. This keeps the data evergreen should you discover at some point that the gauge is off by, say, 15% rather than 10%. This way you never have to guess which correction value you used in the past, and measurements are more easily compared.

Weather impacts measurements. In extreme climates tension can increase 10% or more in January from July due to temperature induced contraction. Record the date or temperature to avoid surprises. Although light wind is no impediment to tension measurement you should not do so in high winds. The wind load of the tower and antennas will raise the tension in the windward guy(s) and lower it in the others. The tension will also change second by second. Out of interest I tried this in a wind storm (80 to 90 kph plus gusts) and found the tension rose 100 to 200 lb in the windward guys and dropped up to 300 lb in the two leeward guys.

Add notes for anomalous observations you can refer back to later. Examples include suspected distortions from perfect vertical alignment by height and tower face and rust spots that need attention.

Rust

Turnbuckles, thimbles, EHS guy cable and other hardware rusts. Galvanizing can delay rust for many years but will not do so forever. Surplus parts will rust sooner due to their previous exposure to the elements. Rust on the surface of large diameter steel is not immediately urgent since it is so thick and, if specified for this application, often has more strength than needed. No matter the degree of urgency it is strongly advised that rust be repaired so that a negligible problem does not grow into a serious one.

If you're going to paint over the rust it is necessary to first remove the loose material. Some coatings are designed for rusty steel while others are not. In the latter case all the rust must be removed. A steel brush or sandpaper may suffice while in difficult cases a rotary steel brush mounted on a drill speeds the work. With power equipment be sure not to be so enthusiastic that you weaken the base metal or remove more galvanizing than absolutely necessary.

Galvanized steel often requires a special primer before the finish coats. That is how I refinished the LR20 tower sections before raising the tower.

For the turnbuckles and attached hardware I followed the advice of a tower pro to thoroughly clean them once they're installed and adjusted and liberally spray them with cold galvanizing paint. Two coats recommended, then again in future should any rust appear. All parts are hot dip galvanized but the turnbuckles and some of the other hardware are used and needed some refinishing to protect against rust.

In Canada as in many countries the quality of consumer grade oil based (alkyd) paints is often not what it once was due to environmental regulations that severely limit VOC (volatile organic compound) content. Better quality high VOC coating are still available here but are only sold to professionals with safety certifications. When you hire professionals to do your tower work there is a good chance they'll use the better products.

Deformation and stress

Guys and the towers they support are under tremendous and continuous stress.  Each guy on my big tower has a pre-load of at least 1,000 lb (450 kg). That not only stresses the guy cable and every insulator, grip, thimble, shackle and turnbuckle the tower and anchors experience the stress due to the sum total of the attached guys. Then there's the live load due to wind and ice. Deformation (metal yield) and stress risers are risks to tower safety.

At each guy station on the tower there are three guys attached. The tension is trying to pull apart the tower while also putting a vertical force on the tower and the base. I have seen tower guy stations deformed by excessive force, whether due to wind, poor design, poor maintenance or fatigue. This is subject all its own which I won't cover here. Suffice to say that regular inspection is mandatory, never optional.

As an example of what can be done with problem areas I inserted thick, wide washers under the nuts holding the guy yokes to the tower girt. The purpose is to distribute the load over a greater area of the girt which avoids stress risers due to the nuts alone since the design is such that the nuts are not flush to the girt for low and high guy angles. I omit the details since this problem is unique to the (now obsolete) LR20 tower. The point is that there may be potential problem areas in your choice of tower that should be dealt with before it goes up, especially if the tower has previously been in service.

When a suspected problem is noticed deal with it immediately. If you're not sure of what you've found a useful technique is to take pictures of the area and email them to an expert. Cracks, fractures, metal bowing, fraying and similarly highly visible flaws are evidence of serious problems. Other flaws may be less visible. For example, some hams expose the top couple of feet of anchor rods every year or two to check for rust and other below ground damage.

Turnbuckle safety and redundancy

For an installation as major as a guyed tower it is good engineering practice to reduce or eliminate single points of failure (SPOF). That complete redundancy is impractical is no excuse to not do all we can to protect our towers from component failures. Guys are also popular targets for vandalism which, unfortunately, does happen to some hams as it does commercial towers.


The simplest and most effective protection for guys is to install safety loops at the turnbuckles. A typical method is show in the diagram produced by Rohn. The loop has two functions:
  • Prevent unscrewing of the turnbuckle. Despite the high tension constant vibration and cycling of wind and temperature can and does loosen turnbuckles.
  • Turnbuckles can be weakened when they are adjusted under tension due to thread wear, torque on the body and infiltration of moisture and rust. The EHS loop mechanically couples the guy and anchor should a turnbuckle fail. It can keep a tower standing when disaster strikes.
There is more than one way to do this, depending on the anchor design. Many hams use back-to-back L-angle or U-channel steel (¼" thick or more) rather than rounds for the anchor rods since they can be built in a home shop without welding. However round rod is more robust when the anchor is not perfectly aligned, horizontally and vertically, with the tower, as often occurs.

The safety loop is run through the gap between the steel members to additionally protect against equalizer plate failures which could develop stress fractures at the upper sides of the turnbuckle attachment holes. With round rods this may not be possible so the loop is run through the lower attachments, as shown.


On my anchors the equalizer plates are welded to the rods. This leaves the lower hole in the equalizer plate unused. (Welding the plates is not uncommon for large commercial towers, which requires careful engineering and construction to correctly set the rod angle.) I therefore used this hole to provide protection for the equalizer plate.

It only takes an hour to install the safeties on all 3 anchors. Only a few things are needed: ¼" EHS cable, bolt cutters and a wrench to tighten the clips.

Notice the uniform gray colour due to the liberal coating with cold galvanizing paint, discussed earlier. The unequal threading of the four turnbuckles wouldn't happen in a commercial installation because the tower alignment and guy tension are set before the bottom grips are attached to the guys. This is not so easy for a ham to accomplish with simple and limited tools.

The safeties must be removed to adjust the guys. To avoid the extra work I delayed installing them until I was satisfied that the tower was about as perfect as I could make it. The 10M rebar on the right was used as temporary though imperfect protection while the tower was aligned and guys adjusted.

Sunday, June 3, 2018

Going Underground: Burying Wire and Cable

There is rarely any reason to bother with burial of coax and other cable in most ham stations. Towers (if any) and other supports are of modest size and close enough to the dwelling to allow direct entry to the building wall. The one or two antennas that may be further away can usually be services with overhead runs from the support to the building.

When the towers and antennas get big they are typically further distant and burial is often needed to avoid eyesores and to reduce interactions between antennas and the the long horizontal runs of cable. Ground mounted verticals benefit from burial of radials and coax to eliminate hazards to people and lawn mowers, and to help prevent the feed line from becoming part of the radial system.

Until now I have kept cables overhead or on ground in my present station. Some was intended to be permanent while others were temporary solutions when weather prevented burial in the frozen ground. The time has come to deal with the problem.

For the present I have buried the control and transmission lines from the big tower to the rock wall surrounding the house area of my property, and the feed line, control cables and radials for the 80 meter vertical yagi array currently under construction. Once the coax and control lines are out of the hay fields they run overhead to the switching system at the base of the Trylon tower located near the house. This was done to ease maintenance and avoid dealing with tree roots and other obstacles incompatible with going underground.

Other than the radial wire all the buried cable is rated for direct burial. No conduits are used. Trenches are dug, the cable laid down and the soil replaced. Many hams swear by conduits while others swear at them. Water, moisture and condensation are always risks with conduits other than in arid climates.

Perhaps the only good reason for conduits is to avoid digging when cables must be added or removed. This can be troublesome in many cases. I have always found it best and easiest to go with direct burial. Should I ever need to add cable in future I can easily dig another trench. In this article I'll show how I've gone about it.

Radials

Radials are the simplest to put down out of the way, except that there's so much of it! My 80 meter array will have up to 2,000 meters of radial wire when complete. Since the radial field must be mowed -- haying is banned in the area since the machinery will disturb on-turf or wires pushed up by frost heaving -- burial was chosen rather than turf staples. With that much wire and uneven ground there is a near certainty of radials finding their way into mower blades from time to time.

I did initial testing of the 80 meter antenna with radials on the surface. This is done immediately after mowing to maximize the time to test the antenna and then bury the radials before the next mowing. Then I do it again to add more radials. As I write this I have 12 radials buried and 8 more on the ground for the driven element. My objective is at least 32 for the driven element and 16 for each of the four parasitic elements this year. Even that may be too much to achieve this year with all the other antenna and tower work to be done.

To bury the first 4 radials I built a manual sod cutter. This is supplemented with the sharp end of a pick axe to widen the narrow furrow. The latter is necessary since the gap in the sliced turf is so fine that it can be difficult to find in places to push the 18 AWG wire into it with a light push so as to avoid zigzagging up and down and side to side around hay roots.

The turf slicer is a length of hard wood with a couple of common steel construction straps that are filed to an edge. This is pushed into the sod alongside the radial and pulled backward. It works quite well although tight tangles of vegetation deflect the blade a small amount. Having two blades allows placing the blade on either the right or left side of the wire (used as a guide), whichever works best. There is little risk of the blade slicing the wire.

After cutting the sod the furrow is widen by dragging the pick axe through it. Even with this done it can be frustrating at times to find the furrow and insert the wire. This is so much not enjoyable that it is necessary to constantly remind myself how wonderful an antenna this will be!

Since that wasn't enough to sustain me I built a plow attachment to my lawn tractor. With it I can sit and relax while I plow a furrow. It must still be done slowly but it is much less effort.


As you can see it's very simple, merely a length of ½" threaded rod through a pre-existing hole on the left side of the mower deck. With the tractor in position and the rod alongside the radial wire the mower deck is lowered and the tractor driven forward. The rod digs into the ground after only an inch or two of forward travel. The threads must be cleaned afterwards so the nuts can be unscrewed and the rod removed.

Unfortunately the furrow made this way proved imperfect. Where the ground dips the plow doesn't dig deep or at all. Dragging the pick axe through the furrow is still necessary, after which I went along it on hands and knees to fit the wire into a furrow obscured by infalling dirt and sod that hinged back to where it was before plowing. This is the best I can do for now so I proceed a few radials at a time to avoid being driven crazy with the tediousness of it all. Tick and fly protection is strongly advised.

Coax and control cables

Radials are easy to deal with since they are largely immune to ground conditions and mostly only suffer by injudicious future digging or abuse by burrowing animals. While control cables are nearly as hardy the same cannot be said of coaxial cable. These must be handled with care if they are to survive underground for long, preferably a few decades.

Hazards include but are not limited to:
  • Ground frost bending and deforming coax
  • Water infiltration through cracks or holes in cable jackets
  • Rocks abrading cable due to motion induced by ground frost
  • Burrowing animals gnawing or exposing cable
  • Farm equipment snagging cables too near the surface
  • Tree roots which will move and grow over the years and destroy cables
To dig the long and deep trenches for the coax and control cables I rented a trench digging machine. The small one you see in the picture alongside the driven element of the 80 meter array is positioned to begin the third of four shallow trenches for the control cable to the base of the parasitic elements. These trenches are shallow (4" or 10 cm) to speed digging and ease maintenance. Deeper trenches (12" or 30 cm) are dug for the coaxial cables.


Despite being about the smallest trencher you can find the machine weighs in at 270 lb (120 kg) and must be moved manually. It's hard work for someone like me whose weight is half that of the machine. After starting the engine the cutter is lowered and begins digging. The depth lever is locked when the cutter reached its target depth. You then stand on the foot pedal which uses a cleat to pull the machine backward. A front cleat (mostly) prevents the machine from kicking forward when rocks and roots are struck.

The deeper the trench the longer it takes. One nice feature of this machine is that it will kick out rocks up to ~6" (15 cm) diameter and eat through modest sized roots. It just takes some patience and enough muscle to hold the cutter in position. The carbide bits are incredibly tough.

You'll likely notice in the pictures that the trenches are not perfectly straight. There is a torque on the machine due to the cutter not being centred so it tries to turn left (as seen from the operator position). Once I realized this a few minutes after starting it up I took to manually shoving the machine slightly to the right every few feet. That mostly solved the problem. But it doesn't shove easily.

Partial back fill over control cable & radial
Once the trench is dug prepare to get dirty. It is rarely enough to simply dump the cable in and back fill. Try to have the cables sit flat along the bottom of the trench. There's a reason you dug them to that depth. Hard line should be carefully straightened before lowering into the trench since the weight of the dirt alone won't cure rippling.

Coaxial cable in particular should be carefully inspected for nicks, abrasions and cuts. A breached jacket will result in water infiltration. If you must use a cable with jacket damage use a liberal amount of a professional grade sealing compound and then rubberized sealing tape and an outer abrasion coating of high quality electrical tape. Don't skimp! Even burial grade coax with a cut in the jacket will succumb to water within a year or two. Hard line such as Heliax with a damaged jacket will survive longer but will eventually fail as well as the copper outer conductor corrodes.

When directly buried cable must be replaced or added it is always better to dig a new trench rather than attempt to uncover previously buried cables. Mark the trench if possible so that when you dig a parallel trench years later you do not dig into the older cables.

Back filling

Putting the dirt back into the trench when you're done is mostly straight-forward and quick. For best results there are a few items to keep in mind.

The first is to keep sharp-edged and large stones away from the buried cables. Either dispose of these elsewhere or put them aside until the cables are well covered with granular material. I use a heavy gauge rake to fill the trenches which also serves to filter out stones.

Avoid voids under the cables which will fill with water and reduce the risk of section of cable rising to or above the surface where they are prone to damage from mower blades or deer hooves. Sod staples on radials can help but may not be a forever solution.

Big tower trench: cable first laid (left) then fully buried and trench back filled

Finally, you may discover that you don't have enough dirt to back fill the trenches. Usually it's the opposite, that you seem to have more dirt than the hole will hold. The reason for the latter is that without compacting the excavated dirt will occupy more volume. This is common in larger excavations such as tower bases. For low volume trenches the machine grinds the soil into smaller grains that tend to be lost in the sod beside the trench. It can be very difficult for the rake to find it all. Find soil from elsewhere to level the surface if you can't otherwise easily level the surface.

Look carefully and you'll see that the back filled dirt over the trench from the big tower is higher than the adjacent ground. It is better for the buried cables to let the rain transport to compact the dirt and transport it into voids than to aggressively compact the dirt mechanically. Soon the field will be safe for haying.

As I write this article I have back filled all but the coax and control line trench to the 80 meter array. I have to do more work before it is ready to be back filled. Once you back fill a trench it is not easy to undo so be sure to do it right!

Going overhead

Trenches are nice but not always possible or desirable. I only use trenches over open ground. When I get near large trees and other obstacles I run the cables overhead. Doing so avoids a lot of work, reduces future risk due to root damage and eases maintenance. When convenient I place connectors on cables at either end of the trench to make it easier to isolate problems and to replace buried cable that has deteriorated.

There are a few places that are currently overhead that I plan to bury in future. One example is the short distance between the Trylon tower and the house entry point. All antenna switching and control cable terminations are at the base of the Trylon. Burial must wait until I have a permanent switching system design in place.

The coax from the Beverage antenna remains on the ground along the tree line from the feed point to a point near the yard where it proceeds overhead to the tower. Eventually I will raise it off the ground where it is easier to maintain and to reduce the risk of animal damage.

Wednesday, May 23, 2018

NIL, Again: Contests and DXing

Getting a NIL (not in log) penalty in a contest can be exasperating. It's one of those things that cannot be entirely eliminated since it is mostly dependent on the other end of the QSO. As I perused the final LCR (log check report) from the CQ WW CW contest last fall I felt some frustration since I thought that I'd been making progress reducing these errors.

Consider the ways in which a NIL can occur and you'll understand the difficulty avoiding them:
  • The QSO was logged with your call incorrect and the log checker software failed to match the erroneous record with that in your log. Software isn't perfect so this will happen. There is little you can do about it other than to be certain the other station has your call correct.
  • You are running on the same frequency as someone else who you cannot hear and you think you have worked someone who instead worked the other station. Yes, this really happens and you may not notice what's going on for several minutes. All you can do is QSY and hope for the best.
  • User error results in your QSO not being entered into the other station's log. Every contester makes mistakes so this will happen occasionally. I know I've done it myself and unless caught instantly there is no recovery possible, and indeed you may be unaware of the mistake.
  • The other station gives up on you because you're too difficult to copy -- happens a lot when you run QRP -- but instead of telling you sends "TU XX9YYY" and continues onward. You think the QSO is good and log it. In my opinion this is unsportsmanlike behaviour.
When you make thousands of QSOs in a contest you should expect a number of NIL penalties. While it is possible to reduce their number with care if you want to get to zero you will also need very good luck! As one contest director once told me: don't worry about it too much, it happens to everyone. Yet it still bothers me.

I was surprised to find that I could remember a few of those NILs in this most recent LCR. A couple of them I was sure were good. But as noted above the log checker may have gotten it wrong. Although I didn't bother this time a couple of years ago the CQ WW contest director at the time suggested looking in the public logs for these NILs. It was both enlightening and perplexing. By comparing logs you can sometimes see where the software may have mismatched records but you can not see into the other operator's mind if your QSO is absent.

Learn what you can, do your best to ensure your future logs are accurate and hope for the best. Since many of your competitors are seeing similar penalties the score reduction is only a problem if you are especially negligent, in which case their lower error rate will hurt you. Perfection may be impossible but you will surely not attain it if you don't try. Accurate logging is a valuable skill for contesters to practice. I can do better.

But what if you're not a contester? Are you a DXer? The possibility of NIL still applies to you. Let's examine this with a real situation I encountered, but without revealing call signs.

A few weeks ago there was a DXpedition from a moderately rare country, one I've worked many times before. When they showed up on 40 meter CW I jumped in if only to practice my pile up skills.

After just one minute I got through -- having a yagi up high helps! The band was noisy here and presumably there as well (warm weather in both places) with the usual QRM from poor operators who keep calling regardless of the station being answered. As a result he took a few tries to correctly copy my call. Then without having ever sent my correct call (one letter was wrong) he sent "TU UP" and moved on to the next QSO.

I may have been in their log with my call correct, my call incorrect or perhaps he gave up and erased the QSO. There was no way for me to be sure. What would you do in this case? In a contest I would most likely have logged the QSO, risking a NIL, and perhaps duped him later if it was a needed multiplier.

However this was not a contest. If you are a DXer you'll have been in this situation many times and faced the question of whether to log the QSO. From my experience I know that many would log the QSO and either hope for the best or check the DXpedition's online log and try again if the QSO doesn't appear.

What would you do? Be honest. Think about it for a moment before you continue reading to discover what I did.

I erased the QSO from my log. To me that was the ethical choice since I did not hear him send my call correctly. In effect I assumed NIL or copying error, making the QSO invalid. Had this been a new country or band-country I admit I would have been tempted to log it and hope. When I hit "delete" I was motivated by the disgust I felt at the poor operating practice that left me in doubt.

A day or two later I was talking to a friend who congratulated me on working this station on 40 meters -- we tend to check up on each other in DXpedition online logs so that we know when to call each other when we hear them on. I had to tell him that, no, I didn't log the QSO and proceeded to explain why. He had a good chuckle over that one.

All of this leaves us with an ethical viewpoint on the NIL problem. During contests we expect to hear our call correctly before logging the QSO, although some don't care because it's the other guy's score that will suffer, not theirs. Indeed when you're running it is common for callers to never send your call so you can never know if you're in their log or logged incorrectly. Some always send the running station's call to remove doubt, which annoys some operators due to the two seconds it consumes.

For DXing both stations do try to ensure correct copying of our call since the penalty for a NIL is arguably greater for the rare ones. We all notice the sloppy DXpedition operators who do not strive for accuracy, leaving us in doubt and annoyed. We also notice the sloppy callers who pay little attention to whether their call is being correctly sent in their enthusiasm to work the DX.

In DXing as in contesting it pays to be accurate and to confirm or correct what has been copied.

Friday, May 11, 2018

Radials: Resonant to Non-resonant

We all know -- or should know by now -- that for ground-mounted vertical antennas the more radials the better. Specifically, more and longer radials reduce the near field ground losses by confining antenna return currents to the highly-conductive radials rather than the lossy ground below. That is, a good radial system forms a low loss ground plane.

This is highly desirable since ground loss can be substantial. This is a shame since vertical antennas can be excellent radiators at the low elevation angles needed for effective DXing on the lower HF bands which is difficult to achieve with horizontally polarized antennas. A lot of wire and ground area is required to construct a good radial system which is impractical for most hams, and so they must compromise. That compromise may be short radials, few radials or avoid vertical antennas entirely.

But for this exercise let's assume you are building a ground-mounted vertical and radial system. I'll do this for 80 meters since that's the antenna currently of interest to me. The data can be scaled to other bands if that's your interest. I will further assume that you are comfortable with the data and theory regarding near field and far field ground loss associated with verticals and vertically polarized antennas. If not there are ample and excellent resources available to you. Perhaps some of the best can be found on N6LF's web site and in ON4UN's book Low-Band Dxing. I addressed a few of these elementary items in my own small way, such as here and here.

In this article I want to focus on the effect of radials on the resonance of a ground-mounted vertical. The reason is that I am currently dealing with this issue and I have not found any easily digestible material out there that describes just what happens. In particular what it means when we say that radials tend to "resonant" when there are few and "non-resonant" when there are many.

Developing a model

Modelling a ground-mounted vertical with the NEC2 engine has drawbacks. In case this is unfamiliar to you here are some of the issues to be aware of:
  • Even with the real ground models used in EZNEC there are ground loss and velocity factor inaccuracies with on-ground radials. As the radial count increases the effects will diminish but are still difficult to quantify.
  • Ground is not homogeneous yet the model must assume that it is. At low frequencies the antennas fields can penetrate many meters into the ground, so what you can't see can hurt you.
  • Radials cannot touch the ground or be placed below the surface. They must be placed a small distance above ground for the model to work, which contribute to inaccurate calculation of ground loss and radial velocity factor.
  • Monopoles constructed with an open lattice tower cannot be directly modelled and must rely on a substitute "effective diameter". Determining the effective diameter is difficult and is more difficult yet for tapered towers, such as the one I am using in my 80 meter array, where a stepped diameter correction is impractical. It almost inevitably requires post-construction measurements and adjustments to the height to achieve the desired resonance.
  • The feed point of a real tower vertical is located within the tower base. Since the model can't deal with that there will a difference in effective lengths of the radials and monopole.
Despite these challenges a NEC2 model will still deliver excellent insights into vertical antenna design when developed with care. Although there will certainly be inaccuracies in the results the general trends and behaviours can be correct and useful.

For my model I am using the following parameters. You can adjust these as necessary to suit your own requirements for design and construction. Better yet, if you can afford it, use NEC4.
  • Monopole height of 19.9 meters and effective monopole diameter of 50 cm (20").
  • AWG 18 insulated wire for radials.
  • Radials and monopole raised 10 cm (0.0012λ) above EZNEC medium ground.
  • Segment length of ~1.0 meters. It is desirable to equalize the segment length of radials and monopole for model reliability.

Running the model

The model was run for a range of lengths and numbers of radials. The data collected is resonant frequency (X = 0) and feed point resistance at the resonant frequency. Radial length is varied from 10 through 25 meters, which covers lengths that are both above and below the resonant frequency. Radial counts are: 2, 4, 8, 16, 32 and 64. Doubling radials at each step is most illustrative since the effects are not proportional to the number of radials.

The only quirk I encountered was with 64 × 25 meter long radials which exceeded the1,500 segment limit in my version of EZNEC. For that one case I was compelled to use just 58 radials.


In the left chart the transition from resonance to non-resonance is plainly obvious for all radial lengths as the radial count increases. Notice how in all cases the resonant frequency regardless of whether the radials are shorter or longer than resonance. However the greater the radial length departs from resonance the more radials it takes to converge to the ultimate resonance that is approximately 3.680 MHz.

I added the 18 meter length radial data since that is the closest integral value that keeps the antenna resonance static with respect to radial count. The true value is closer to 17.5 meters, which would have required violating my rule of keeping segment length constant at 1 meter.

The implied velocity factor for the radials due to ground proximity is ~0.89 plus a further 0.02 reduction due to wire insulation. The true velocity factor is almost certainly lower when radials rest on or slightly below ground. As discussed above this cannot be fully modelled with NEC2. Expect the measured velocity factor be no higher than 0.75: radials resonant at 15 meters length or less.


The story for feed point impedance is more complicated. N6LF addresses this matter in detail so I will not delve into the topic too deeply. High feed point resistance is a indicator of excessive ground loss, which is not surprising to see for short radials even when there are many of them. Many radials can only partially compensate for short length.

For long radials the lower feed point resistance is not a reliable indication of lower radiation resistance or ground loss. As N6LF demonstrates the current peak moves outward from the feed point when the electrical length of the radial is greater than ¼λ which changes the character of the entire antenna.

By expecting a final feed point impedance for your vertical antenna or array you will be better equipped to plan ahead for a matching network, rather than merely hoping for a perfect match or stopping when one is reached despite it being a symptom of high ground loss or less than optimal radial currents. Requiring an L-network for a vertical network should be seen as a nice problem to have.

What does it all mean?

When your chosen radial length is substantially unequal to a ¼λ you should expect unusual resonant frequencies when you first attach a few radials and then large changes as you add more. Forearmed is forewarned so the charts above can help you to anticipate and to avoid surprises. Certainly this happened when I first lit up my 80 meter vertical a few days ago!

Had I chose shorter radials the effect could have been the opposite of what I measured, with resonance occurring above my design frequency and then falling lower as radials are added. To give a more concrete example, when I attached a long on-the-ground length of RG213 back to the antenna switch the resonance shifted upward to 3.5 MHz from 3.4 MHz. With only 4 radials the outer surface of the coax acts as a unreasonably long fifth radial and that disturbs the symmetry of the other 4. This resonance effect would largely disappear with a radial count of 16 or higher. However this is distinct from common mode current on the coax surface, a separate though related problem.

It was these experiences that motivated me to run the models and write this article. Nowhere that I could find was there a quantitative or visual presentation of the precise migration of vertical resonance with radial length and count. My thought is that if these models are helpful to me it may be helpful to you for the design of vertical antennas and the gradual deployment of radials. I certainly won't wait until there are 64 radials before I try an antenna. I doubt that any ham would!

Rely on those referenced resources and others to plan your vertical antennas to achieve the optimum number and length of radials for your individual circumstances and performance objectives. Models will help as well, provided that you take account of modelling software constraints and limitations. It is my hope with this article that I've provided one point of insight into the process.