Logging errors in contests can exact a steep penalty. Not only will the sponsor remove QSOs containing errors they also assess penalties. On average a removed QSO will reduce your score by at least double that amount. If the removed QSOs are multipliers the cost can become very expensive indeed.
With the advent of computer logging, log submission and log checking the wages of sin will always be paid. In the olden days logs had to be manually checked. This was such a labourious process that logs with scores not high within their entry classes were rarely checked. Carelessness that was once penalty-free for 90% of contesters has evolved and is now a guarantee of score reduction. This is not only embarrassing it can also keep you out of contention for awards.
Is it possible to submit an error-free log? Yes, but it takes a combination of diligence and luck. I'll show you what I mean by luck in a moment, but let's first cover the errors that diligence can prevent. Computer logging is both a blessing and a curse in this regard. Software makes it easy to avoid some mistakes and easier to make others.
Call sign and exchange errors
These are the easiest errors to make and often can be completely eliminated by taking appropriate care. Errors include copying mistakes, typing mistakes and pre-fill oversights. Here are some of the ones I am most familiar with, along with ideas on how reduce mistakes.
Busted calls: This can happen on both SSB and CW. In the former case it is usually due to QRM or difficulty understanding a non-native English speaker. In the latter case the causes of copying errors are more numerous. A sequence of short letters (e.g. E, I, T) or characters with 3 or 4 dot sequences (e.g. B, V, 4, 6) at high speeds will often do it. Although there are some contesters with poor CW skills who get by due the short exchanges, everyone is at risk.
If you're running the other station will most often correct your error since you are sending their call to them. However if you're sending at 30 wpm or faster the other guy may not notice the error. I'm surprised how often I hear this happening while waiting to call someone. Worse, they may not care since in the majority of contests they are not penalized for the other guy's copying errors!
Some stations while in S & P mode make a point of sending the running station's call just to be sure they've correctly copied it. But this can be expensive in time if it is done on every QSO. I would only recommend doing this when there is some doubt about the other's call.
Some logging software will flag calls that are suspect by dint of not being known as having appeared in previous contests -- a so-called master database. Flagged calls should be double-checked, just in case. Be particularly wary of partial call databases, used by you or the other station, that will attempt to pick a likely call from the master database if the call is suspect or incomplete. It is often wrong. I am a regular victim of this feature since the other station often has difficulty copying my QRP signal.
Exchanges: In most contests the exchange is fixed and often predictable from the call. For example, in this past weekend's ARRL DX CW contest my exchange was "599 ON". The RST is of course routinely sent as 599 in every contest exchange. The state/province is a constant and in the case of Canadian calls is strongly correlated with the call sign prefix. Most logging software will analyze the call and pre-fill the exchange field for you, saving you time and potential for a typo. This can also be done for CQ and ITU zones in contests where those are part of the exchange.
US locations in particular are less predictable. It has been many years since a call sign prefix correlated to a state or zone. Logging software makes a best guess but it is up to you to confirm that what the other station sends is what the software pre-fills. It is too easy to get lazy, especially when you're tired, and not confirm the fill before logging the QSO. I can only say that you must be diligent. This is the cause of some of my errors.
If you are uncertain of your copy in contests with a more complex exchange (e.g. Sweepstakes) you should immediately ask the other station for confirmation or a repeat.
Some logging software allows you to use a history file built from previous contest logs (your own or by importing one) to more accurately pre-fill the exchange. The percentage of mistakes will be reduced, but you must still be diligent and confirm what is sent matches what is pre-filled.
Correcting errors on the fly: When I note an error and make a correction on the fly it is not always possible to record the correction in the log. Even if you're highly effective at manipulating the logging software this can take several seconds, during which the other station is wondering what's going on while others waiting for you (if you're running) may QSY. I keep a pen and paper handy to jot down the needed correction since it is sometimes the fastest way to move onward. The log can be updated even just a minute later while your memory keyer or DVM is playing a CQ.
Another technique during S & P is to stick around a few seconds to hear for a second time their call and/or exchange. The call can be quickly corrected this way. However there is a danger if the error is in the exchange. If the running station has a poor rate you could be waiting a while for their next QSO to hear the needed information. Rather than getting into this undesirable situation you should not be shy about asking for a repeat during the QSO.
Not-in-log errors (NIL)
NIL errors are unlike the errors discussed above in that they are not entirely under your control. That is, you cannot be certain that the other operator logged your QSO. You can reduce NIL errors but not eliminate them entirely. This is a topic I previously discussed so you can reference that article for background. What I want to address now is some of the "why" NIL errors are so difficult to eliminate.
I will use a real example. Although the results are not out I am one of the participants in last fall's (November 2014) CQWW CW contest sent a preview log check report (LCR) for review. My error rate is comfortably under 1% so there is little risk of losing my provisional #1 North America position in the SOAB (single op, all band, unassisted) QRP category.
Apart from a small number of busted calls and improperly recorded exchanges there were 3 NIL errors. In trying to understand what might have happened, despite my effort to eradicate NIL during the contest, Randy K5ZD suggested I look through the public logs. He seemed sufficiently confident in their log checking software and processes to punt the question back at me. So I did what he suggested.
Case #1: This occurred while I was running on 15 meters. Getting an NIL while running is odd since the other station would seem to have obviously copied me or would not have called. I have assumed, perhaps mistakenly, that the majority of NIL errors occur while S & P. This is an ongoing risk to those of us operating QRP, and especially so on low bands. Unfortunately the other station's log in this case is uninformative. He was indeed on 15 at the time but his log does not provide the frequency for each QSO, just the band (21000).
Case #2: This one was also while I was running, this time on 20 meters. The other station was multi-single so the log contains the interleaved QSOs of two operating positions. One of those was on 20 at the right time, however that station was running and positioned far from my frequency.
Case #3: Unlike the previous two cases this is one that is easily determined. It was a European on 80 where all of my DX QSOs are marginal. His log confirms he was there and running, and I have some recollection of the QSO. I recall that he did copy my call, with difficulty, though he seemed uncertain and may not have copied my exchange. After a while he moved on, though he first gave me some indication that the QSO was complete. Usually this is a "TU" or something similar before soliciting the next QSO, although I don't remember what it was in this case that decided the case for me that I should log the QSO. I may have been unduly rash since it was a multiplier, something that is very precious to me on 80!
Resolution: As Randy noted confusion often reigns during a contest and some NIL of the sort I had are not uncommon. It is entirely possible for an adjacent QSO (of which you might only hear only one side) can have just the right timing to make it seem that it was with you. This may have occurred in case #1. I have no idea what might have happened in case #2. The call was that of a big gun and not likely to be a copying error on my part, and even if so the log checking software would most likely have determined the correct call from scanning other submitted logs. On this basis there is little I could have done to avoid these two NIL errors.
Case #3 is a dilemma. When there is uncertainty in a situation like this there is no best choice. If I log the QSO and it is not logged by the other station I lose the QSO and multiplier and get assessed a further penalty. If I don't log it not only I will lose the QSO and multiplier, which the other station might have logged, I could cause the other station to suffer an NIL. That would be inconsiderate of me.
This comes back to suggestions above regarding getting as much confirmation of critical data during the QSO to eliminate these doubts about whether to log it. On low bands where the other station is barely able to copy me this is difficult. That does not rate as a justifiable excuse. You just do the best you can.
Hole-in-One
Getting to a 0% error rate is difficult, as I hope my experience has shown. It is not purely a matter of chance: if you are sloppy I can guarantee you will never achieve 0% errors. Yet even if you are extremely diligent I cannot guarantee you will eliminate all errors. The reason is that what the other operators do, the hundreds or even thousands of them you work in a contest weekend, is out of your control.
At its fundamentals the error rate is a stochastic process, where there are one or more random variables. We can draw an analogy from the game of golf. The top players can never guarantee getting a hole-in-one, not in any particular match and perhaps not in their lifetimes. What they have is a higher probability of doing so than everyone else who has ever picked up a golf club. This is because they can more often hit their tee shots onto the green. If you can't do that, or do it often enough, you will never score a hole-in-one. Unless you get very, very lucky.
Operating a contest is much the same. You may never score a 0% error rate but your chance of doing so dramatically rises when you make the effort to reduce errors. Even if you don't get to 0% you will see a big improvement in the difference between your claimed and published scores, and that will push you up the leader board past those who don't make the effort.
Wednesday, February 25, 2015
Friday, February 13, 2015
2-element Parasitic Ground Plane for 40 Meters
As the solar cycle declines my attention to the low bands increases. This means I have an increased interest in vertical antennas, even though "serious" low-band antennas are impractical on my suburban property. So I instead plan and model in the hope that one day I can start building large antennas.
Experimenting with 40 meters is in some respects easier than doing so on 80 and 160. Antennas are easier to successfully model and prototype at the shorter wavelengths, and then compared to existing antennas. Antennas that work out can then be scaled to the longer wavelengths with predictable results. There are also some things you can do that may be too mechanically challenging on lower bands. The antenna in this article is one of those.
Concept antenna, not a final design
Please keep in mind that this is purely a concept antenna. It is perhaps worthy of prototyping but should not be seriously considered without further work. I did not aim to fully optimize the design. My intention is to play with it to see it if has good DX performance with regard to gain, F/B and match. As we will see there are design aspects that require more work before committing to construction.
Another motivation is to see what can be accomplished with a relatively simple vertical array in comparison to well-tuned, switchable 4-square antennas that many big guns use on 80 and 160. Although this design is for 40 the antenna can be scaled, with some construction effort and expense.
My concern with the 4-square and similar directive arrays is the intricacy of the feed and switching networks. This invites the potential for failure when one or more elements is affected by weather (e.g. snow and ice) or a component drifts in value or fails. That is why 4-squares often have a "dump" resistor and a warning system. The design lacks a degree of robustness.
This is not meant to demean recent efforts at optimum phasing and power division, which can be very impressive. Designs such as those you'll find in chapter 11 of ON4UN's fifth edition of Low-band DXing are so bizarre because the elements are often so closely spaced that mutual coupling dominates. To my mind it is better to use judo rather than brute strength to tackle the problem. That is, to accept mutual coupling as a design partner rather than having to coerce it to behave in a prescribed manner. I try to do that in this article.
Copy and spin
There are many ways to make a parasitic array. You can even do it with λ/4 monopoles with ground planes, if you're careful. Consider the simple 4-radial ground plane mentioned near the end of my recent article on vertical modelling experiments. It is broadband, with low-angle radiation (good for DX), and is a good match to 50 Ω coax.
I proceed in the usual fashion of making a parasitic (reflector) array by copying a resonant single-element antenna and offsetting the copy in the desired direction. To avoid tangling the radials, which are about as long as the inter-element spacing, I spin the radials of one element by 45°.
With the elements mounted 10 meters above ground they a maximum height of about 20 meters. The bases can be light-duty television towers or masts made from aluminum or steel. I prefer the former so that the feed point is easily accessible for assembly and maintenance. Guying is necessary but there is no need for concrete. The radials can do double duty as guys, if you use something stronger than aluminum or pure copper wire.
With a bit of open space this should be an inexpensive and not too challenging antenna to construct. The minimum required area is 500 m² (25 x 20 meters). Even though mounted above ground it is recommended that there be no other structures within 1λ (40 meters) radius, and even farther from towers or other large conductors.
It's a Moxon!
Okay, it doesn't look like a typical (or even atypical) Moxon but it does have the same attributes. The reason is those radials: the way they intermingle causes near critical coupling between elements. Even with the relatively wide spacing between monopoles of 10 meters (close to 0.25λ) those radials keep the coupling high.
You can see this most clearly in the radial currents. Rather than the current in each of the 4 radials being ¼ that of the monopole it varies a lot, depending on the radial's position. One implication is that the parasite must be configured as a reflector. Well, you can try to make it a director but you'll find that task quite difficult unless you can find a way to reduce the coupling.
In the driven element (wires 6 to 10 in the current plot above) the radial currents are 6% and 43% that of the monopole in the rearward and forward radials, respectively. In the reflector (wires 1 to 5) the radial currents are 53%, 34% and 40% that in the monopole in the forward, rearward and side radials, respectively. These values are at 7.1 MHz, near where gain is maximum. No only are the radial currents unequal their sum only equals the monopole current in driven element. The sum far exceeds the monopole current in the reflector element.
The current in the reflector monopole ranges from 60% to 70% that of the driven element across the band. This is typical of a Moxon and higher than in a conventional 2-element parasitic array. As we'll see, gain, F/B and SWR vary less than a 2-element yagi across the entire 40 meters band.
Tuning for optimum performance
Performance is sensitive to element separation (equivalent to boom length in a conventional yagi or Moxon rectangle) and radial arrangement. The thing I found annoying is that although gain would vary a lot when these are adjusted a little, the feed point impedance (and thus SWR) and F/B were far more stable. It's annoying because the latter two are far easier to measure, and would simplify the tuning of this array.
In the model I settled on monopoles 9.95 meters tall and made from 25 mm (1") aluminum tubing. This is an approximation to a real antenna that would use telescoping, tapered tubes. The monopoles are 10 meters apart with bases 10 meters (~λ/4) above medium ground. The radials are 16 AWG aluminum wire, such as the often used (and inexpensive) aluminum fence wire. All radials are 10.525 meters long and slope downward 30°.
I²R loss in the aluminum monopoles and radials is around -0.1 db. The pattern plots are with zero loss conductors, including for the reference single ground plane. The performance chart below includes the loss. Ground loss is calculated by EZNEC to be about -5 db over medium ground.
Considering how peculiar an antenna this is its performance is quite good. Not only is it 5 db better than a single ground plane at 7.1 MHz (comparison in the elevation plot above) the gain varies little up through 7.2 MHz. The F/B, while not exceptional, is adequate to my needs. The SWR is particularly nice, staying below 2 across the band.
Compared to various single element and 2-element antennas the 10° elevation gain is very good. For example, it equals an inverted vee (broadside) 25 meters high and even a 2-element yagi up 15 meters. If you don't have a high tower but do have some open land this could be an attractive antenna choice. Don't expect this performance on a suburban lot since vertically-polarized antennas can under-perform the models.
As I stated at the beginning, I did not really design this antenna with the objective of putting in on 40 meters. If I eventually have higher towers there are superior alternatives. This experiment is about getting a handle on antennas for 80 and 160 where, often, towers cannot be high enough to make a horizontal antenna competitive. When scaled to 80 meters the the required towers for comparable horizontal antennas must be twice as high. Scaled verticals for 80 lose relatively little gain at low height (though half as high in wavelengths) but may suffer from additional ground loss and environmental interaction.
Although the monopoles are the same height the reflector element has a base loading coil. It is a very small coil with an inductance of 0.4 μH. Although small this value is critical. Even if only 0.1 μH higher or lower the SWR and gain will noticably suffer. F/B is less sensitive to inductance changes. Small changes to the radials will affect the required value of this coil since their length and position affect mutual coupling between elements.
To give an idea of the dimensions involved, a suitable 0.4 μH coil would be 5 turns with a length and diameter of 1" (2.5 cm). The equivalent shorted 300 Ω open wire stub would be 16" (40 cm) long at 7.1 MHz. The stub is easier to tune (with a sliding shorting bar) but will be exposed to the weather which can alter its reactance.
Direction switching
It is always helpful in a fixed element array to be able to change the direction of the beam. This antenna is amenable to such an arrangement, though with some stringent construction and tuning criteria. This, too, is typical of Moxon (critically-coupled) arrays.
The switching method I describe here has significant differences to the one I used for the various styles of 40 meter wire yagis I described over a year ago. I am assuming that the support masts for the elements allow convenient access to the feed points which are 10 meters above ground. This is why I recommend light duty television towers for the supports.
The switching system requires 2 plastic enclosures, 3 DPDT relays, 2 loading coils, DC switching circuitry and 50 Ω coax for the transmission line and running between the element feed points. One element will be connected through to the transmission line while the other will be isolated from the transmission line and a coil connected between monopole and radials. Relay DC power can be run by separate cable or on the transmission line. In the latter case a DC cable is still needed between the 2 enclosures at the bases of the monopoles.
The recommended arrangement has the transmission line terminate at the enclosure at the base of one of the monopoles. Make it the one closest to the shack to keep the total length of coaxial cable to a minimum. The length of coax between that enclosure and the one at the base of the other monopole is non-critical, except that it must (of course) be at least 10 meters long, the element separation. That section of coax will be fully isolated on both ends when the second element is a reflector. Similarly the transmission line will be fully isolated from the first element when it is a reflector. The outer conductor of the both lengths of coax must not be connected together or to the radials, except when connecting to the driven element. This is why the enclosure cannot be metal. Metal will also alter the coil's inductance if it is inside the enclosure.
One relay selects the element to connect both conductors of the transmission line. The other two relays switch each element between the coax feed and the loading coil. The coil provides the inductance to configure that element as a reflector. A shorted stub can be used in lieu of the coil. Obviously when one element is connected to the transmission line it becomes the driven element and the other is a reflector. The normally-off position of the relays should point the array in the most important or commonly used direction.
The transmission line outer conductor will act as a radial when the first element is driven. To avoid asymmetry and mistuning in that direction it is best to run the transmission line along one of the radials and choke it where the radial terminates, making them the same electrical length and at the same potential. A coax coil choke can be used if tuned to be effective on 40 meters. There should also be a choke where the coax enters the second enclosure to ensure it also does not become a radial when the second element is driven.
The two supporting masts and the isolated connecting coax are λ/4 long and so should not interact with the array. The supporting masts should be isolated from ground to make them non-resonant.
Broadside
It is possible in many vertical arrays to create a feed arrangement (power division and phase) to convert an end fire array to broadside. The idea is that it's often more convenient to come up with an elaborate feed than put up more elements, whether two independent 2-element arrays or a 4-square. With the antenna described in this article this is not possible.
Pattern flexibility requires that the factors under one's control (phase, power division, element tuning) are sufficient to sculpt the desired result. With a near-critically coupled antenna like this one the mutual coupling tends to make any effort in that pursuit moot: the mutual coupling dominates. Coupling can be reduced by moving the elements farther apart, but that would negate the parasitic benefits of the array. More elements can be added, but that too has significant costs.
The best that can be achieved is an omnidirectional pattern by splitting the feed in the centre and running equal lengths of coax to both elements. The resulting feed point impedance is 15 Ω, which would require a 3:1 unun. In the broadside configuration here is less than 1 db of gain in comparison to a single ground plane.
I believe it is better to leave the array as is and use another antenna, even just an inverted vee, to fill the holes in the array's end fire pattern.
Next steps
This is an experimental design that I do not recommend be built by anyone. Because if you do you'll have to deal with its various idiosyncrasies either in your own modelling effort or (literally) in the field.
Before I would undertake construction of this antenna I would model variations in radial deployment to modify coupling in a way that preserves the array's best attributes while making it less sensitive to minor variations in tuning. Another thing I'd like is to find an easily-measured quantity that correlates well with antenna performance. For example, in the various 2-element switchable 40 meter antennas I've discussed in the past this metric was the frequency of maximum F/B.
Of course all of this modelling and planning is contingent on having the space to build it. That is tentatively in my long term plans, although for the present I can only design, plan and model. It's time well spent.
Experimenting with 40 meters is in some respects easier than doing so on 80 and 160. Antennas are easier to successfully model and prototype at the shorter wavelengths, and then compared to existing antennas. Antennas that work out can then be scaled to the longer wavelengths with predictable results. There are also some things you can do that may be too mechanically challenging on lower bands. The antenna in this article is one of those.
Concept antenna, not a final design
Please keep in mind that this is purely a concept antenna. It is perhaps worthy of prototyping but should not be seriously considered without further work. I did not aim to fully optimize the design. My intention is to play with it to see it if has good DX performance with regard to gain, F/B and match. As we will see there are design aspects that require more work before committing to construction.
Another motivation is to see what can be accomplished with a relatively simple vertical array in comparison to well-tuned, switchable 4-square antennas that many big guns use on 80 and 160. Although this design is for 40 the antenna can be scaled, with some construction effort and expense.
My concern with the 4-square and similar directive arrays is the intricacy of the feed and switching networks. This invites the potential for failure when one or more elements is affected by weather (e.g. snow and ice) or a component drifts in value or fails. That is why 4-squares often have a "dump" resistor and a warning system. The design lacks a degree of robustness.
This is not meant to demean recent efforts at optimum phasing and power division, which can be very impressive. Designs such as those you'll find in chapter 11 of ON4UN's fifth edition of Low-band DXing are so bizarre because the elements are often so closely spaced that mutual coupling dominates. To my mind it is better to use judo rather than brute strength to tackle the problem. That is, to accept mutual coupling as a design partner rather than having to coerce it to behave in a prescribed manner. I try to do that in this article.
Copy and spin
There are many ways to make a parasitic array. You can even do it with λ/4 monopoles with ground planes, if you're careful. Consider the simple 4-radial ground plane mentioned near the end of my recent article on vertical modelling experiments. It is broadband, with low-angle radiation (good for DX), and is a good match to 50 Ω coax.
I proceed in the usual fashion of making a parasitic (reflector) array by copying a resonant single-element antenna and offsetting the copy in the desired direction. To avoid tangling the radials, which are about as long as the inter-element spacing, I spin the radials of one element by 45°.
With the elements mounted 10 meters above ground they a maximum height of about 20 meters. The bases can be light-duty television towers or masts made from aluminum or steel. I prefer the former so that the feed point is easily accessible for assembly and maintenance. Guying is necessary but there is no need for concrete. The radials can do double duty as guys, if you use something stronger than aluminum or pure copper wire.
With a bit of open space this should be an inexpensive and not too challenging antenna to construct. The minimum required area is 500 m² (25 x 20 meters). Even though mounted above ground it is recommended that there be no other structures within 1λ (40 meters) radius, and even farther from towers or other large conductors.
It's a Moxon!
Okay, it doesn't look like a typical (or even atypical) Moxon but it does have the same attributes. The reason is those radials: the way they intermingle causes near critical coupling between elements. Even with the relatively wide spacing between monopoles of 10 meters (close to 0.25λ) those radials keep the coupling high.
You can see this most clearly in the radial currents. Rather than the current in each of the 4 radials being ¼ that of the monopole it varies a lot, depending on the radial's position. One implication is that the parasite must be configured as a reflector. Well, you can try to make it a director but you'll find that task quite difficult unless you can find a way to reduce the coupling.
In the driven element (wires 6 to 10 in the current plot above) the radial currents are 6% and 43% that of the monopole in the rearward and forward radials, respectively. In the reflector (wires 1 to 5) the radial currents are 53%, 34% and 40% that in the monopole in the forward, rearward and side radials, respectively. These values are at 7.1 MHz, near where gain is maximum. No only are the radial currents unequal their sum only equals the monopole current in driven element. The sum far exceeds the monopole current in the reflector element.
The current in the reflector monopole ranges from 60% to 70% that of the driven element across the band. This is typical of a Moxon and higher than in a conventional 2-element parasitic array. As we'll see, gain, F/B and SWR vary less than a 2-element yagi across the entire 40 meters band.Tuning for optimum performance
Performance is sensitive to element separation (equivalent to boom length in a conventional yagi or Moxon rectangle) and radial arrangement. The thing I found annoying is that although gain would vary a lot when these are adjusted a little, the feed point impedance (and thus SWR) and F/B were far more stable. It's annoying because the latter two are far easier to measure, and would simplify the tuning of this array.
In the model I settled on monopoles 9.95 meters tall and made from 25 mm (1") aluminum tubing. This is an approximation to a real antenna that would use telescoping, tapered tubes. The monopoles are 10 meters apart with bases 10 meters (~λ/4) above medium ground. The radials are 16 AWG aluminum wire, such as the often used (and inexpensive) aluminum fence wire. All radials are 10.525 meters long and slope downward 30°.I²R loss in the aluminum monopoles and radials is around -0.1 db. The pattern plots are with zero loss conductors, including for the reference single ground plane. The performance chart below includes the loss. Ground loss is calculated by EZNEC to be about -5 db over medium ground.
Compared to various single element and 2-element antennas the 10° elevation gain is very good. For example, it equals an inverted vee (broadside) 25 meters high and even a 2-element yagi up 15 meters. If you don't have a high tower but do have some open land this could be an attractive antenna choice. Don't expect this performance on a suburban lot since vertically-polarized antennas can under-perform the models.
As I stated at the beginning, I did not really design this antenna with the objective of putting in on 40 meters. If I eventually have higher towers there are superior alternatives. This experiment is about getting a handle on antennas for 80 and 160 where, often, towers cannot be high enough to make a horizontal antenna competitive. When scaled to 80 meters the the required towers for comparable horizontal antennas must be twice as high. Scaled verticals for 80 lose relatively little gain at low height (though half as high in wavelengths) but may suffer from additional ground loss and environmental interaction.
Although the monopoles are the same height the reflector element has a base loading coil. It is a very small coil with an inductance of 0.4 μH. Although small this value is critical. Even if only 0.1 μH higher or lower the SWR and gain will noticably suffer. F/B is less sensitive to inductance changes. Small changes to the radials will affect the required value of this coil since their length and position affect mutual coupling between elements.
To give an idea of the dimensions involved, a suitable 0.4 μH coil would be 5 turns with a length and diameter of 1" (2.5 cm). The equivalent shorted 300 Ω open wire stub would be 16" (40 cm) long at 7.1 MHz. The stub is easier to tune (with a sliding shorting bar) but will be exposed to the weather which can alter its reactance.
Direction switching
It is always helpful in a fixed element array to be able to change the direction of the beam. This antenna is amenable to such an arrangement, though with some stringent construction and tuning criteria. This, too, is typical of Moxon (critically-coupled) arrays.
The switching method I describe here has significant differences to the one I used for the various styles of 40 meter wire yagis I described over a year ago. I am assuming that the support masts for the elements allow convenient access to the feed points which are 10 meters above ground. This is why I recommend light duty television towers for the supports.
The switching system requires 2 plastic enclosures, 3 DPDT relays, 2 loading coils, DC switching circuitry and 50 Ω coax for the transmission line and running between the element feed points. One element will be connected through to the transmission line while the other will be isolated from the transmission line and a coil connected between monopole and radials. Relay DC power can be run by separate cable or on the transmission line. In the latter case a DC cable is still needed between the 2 enclosures at the bases of the monopoles.
The recommended arrangement has the transmission line terminate at the enclosure at the base of one of the monopoles. Make it the one closest to the shack to keep the total length of coaxial cable to a minimum. The length of coax between that enclosure and the one at the base of the other monopole is non-critical, except that it must (of course) be at least 10 meters long, the element separation. That section of coax will be fully isolated on both ends when the second element is a reflector. Similarly the transmission line will be fully isolated from the first element when it is a reflector. The outer conductor of the both lengths of coax must not be connected together or to the radials, except when connecting to the driven element. This is why the enclosure cannot be metal. Metal will also alter the coil's inductance if it is inside the enclosure.
One relay selects the element to connect both conductors of the transmission line. The other two relays switch each element between the coax feed and the loading coil. The coil provides the inductance to configure that element as a reflector. A shorted stub can be used in lieu of the coil. Obviously when one element is connected to the transmission line it becomes the driven element and the other is a reflector. The normally-off position of the relays should point the array in the most important or commonly used direction.
The transmission line outer conductor will act as a radial when the first element is driven. To avoid asymmetry and mistuning in that direction it is best to run the transmission line along one of the radials and choke it where the radial terminates, making them the same electrical length and at the same potential. A coax coil choke can be used if tuned to be effective on 40 meters. There should also be a choke where the coax enters the second enclosure to ensure it also does not become a radial when the second element is driven.
The two supporting masts and the isolated connecting coax are λ/4 long and so should not interact with the array. The supporting masts should be isolated from ground to make them non-resonant.
Broadside
It is possible in many vertical arrays to create a feed arrangement (power division and phase) to convert an end fire array to broadside. The idea is that it's often more convenient to come up with an elaborate feed than put up more elements, whether two independent 2-element arrays or a 4-square. With the antenna described in this article this is not possible.
Pattern flexibility requires that the factors under one's control (phase, power division, element tuning) are sufficient to sculpt the desired result. With a near-critically coupled antenna like this one the mutual coupling tends to make any effort in that pursuit moot: the mutual coupling dominates. Coupling can be reduced by moving the elements farther apart, but that would negate the parasitic benefits of the array. More elements can be added, but that too has significant costs.
The best that can be achieved is an omnidirectional pattern by splitting the feed in the centre and running equal lengths of coax to both elements. The resulting feed point impedance is 15 Ω, which would require a 3:1 unun. In the broadside configuration here is less than 1 db of gain in comparison to a single ground plane.
I believe it is better to leave the array as is and use another antenna, even just an inverted vee, to fill the holes in the array's end fire pattern.
Next steps
This is an experimental design that I do not recommend be built by anyone. Because if you do you'll have to deal with its various idiosyncrasies either in your own modelling effort or (literally) in the field.
Before I would undertake construction of this antenna I would model variations in radial deployment to modify coupling in a way that preserves the array's best attributes while making it less sensitive to minor variations in tuning. Another thing I'd like is to find an easily-measured quantity that correlates well with antenna performance. For example, in the various 2-element switchable 40 meter antennas I've discussed in the past this metric was the frequency of maximum F/B.
Of course all of this modelling and planning is contingent on having the space to build it. That is tentatively in my long term plans, although for the present I can only design, plan and model. It's time well spent.
Monday, February 9, 2015
KX3 Review by a QRP DXer and Contester
I've been using an Elecraft KX3 as my main station rig for 2 years, ever since returning to ham radio after over 20 years of being QRT. I purchased it since it met my needs at the time: high performance, and; low-impact operation. Now that I've added a FT-1000MP to my shack it seems a good time to review how the rig performs, and how it meets my primary interests of DXing and contesting. The latter activity was not in consideration when I bought the KX3 since I didn't realize that I'd return to contesting.
There are ample reviews of the KX3 so there is no need for me to do the same. In any case I do not have the test equipment needed to do a proper technical review. You can find those elsewhere, such as the QST review and user feedback on eHam. My intent is to give an operator's impression of the rig, both its high points and lows, as applied to DXing and contesting.
My review is in some degree going to be unfair to the rig. It was not designed to primarily serve as a base station, or for the most demanding applications. Take this perspective into account as you read onward. For its intended use the KX3 is a superior product. I mean that whole-heartedly.
Overload
The receiver front end is fragile. There are two significant categories of signals that overload the receiver: strong signals within the roofing filter; strong signals farther away, even very far away. This is with the optional KXFL3 roofing filter installed, which I ordered with the rig and is factory calibrated.
My impression from regular use is that the roofing filter does the intended job of reducing IMD from strong adjacent signals. However when very strong signals fall within the roofing filter the rig may turn off the pre-amp. This is reasonable when that signal is from the ham who lives a couple of blocks away, but less so when the signal is from W8. There is a brief message on the display when this happens which I have rarely noticed while tuning across these signals. A minute later I'm wondering why the band is suddenly quiet. When the rig was new I was always puzzled as to why I would occasionally notice that the pre-amp was off. Eventually I discovered what was going on.
The other problem is fundamental overload where a strong signal into the front-end, even if well outside the ham bands, is detected regardless of VFO tuning. This can be very inconvenient when it occurs. For example, there is a shortwave broadcaster in the US with an exceptionally strong signal here. Even with just a dipole that station can push its way through the receiver and be AM-detected no matter where the rig is tuned in the 20 and 17 meter bands. A narrow bandwidth on CW reduces the interference though not enough in many cases. Turning off the pre-amp or using the attenuator will usually cure the problem, but at the cost of sensitivity.
The better your antennas the worse the overload problems since signals presented to the front-end are going to be stronger.
Receiver DSP
As with all electronics the speed and capacity of DSP hardware has remarkably improved over the years. When coupled with effective software there is the potential for superior performance. In my experience the KX3 does very well in this regard.
The continuously variable receiver filter bandwidth (50 Hz steps) is a delight to use. At all settings the audio signals come through very clearly. Even at the narrowest bandwidth (50 Hz) ringing is low. It is also convenient that the roofing filter automatically adjusts in response to the filter setting.
There are limits to what the DSP filtering can accomplish in this direct conversion receiver. Filter skirts are shallow. For example, I typically set the filter to 200 Hz on CW and yet can hear well outside that narrow range. It is how I compromise between noise reduction (local QRN) and not missing much as I tune across the bands. During contests I often narrow the filter to 100 Hz for S & P (search and pounce) and only need to open it up to 300 Hz when calling CQ, and I don't miss much. The APF is pretty much superfluous on this rig.
Multi-pole crystal IF filters are needed to get the steep skirts needed for best QRM and noise rejection. This is not only impossible in a direct conversion design these filters could not fit inside the KX3's small cabinet.
A bigger issue is opposite sideband rejection for single-signal reception. This is another case where the shallow filter skirts limit performance. Elecraft is well aware of the issue but their suggested solution is one that has side effects I don't care for. So I live with it. It is a particular problem in popular CW contests where stations are packed close together. Even middling strong signals the other side of zero beat interfere with the desired signal. It can also be confusing in that a seemingly interfering signal is in fact 1 or more kHz away. I find it necessary at times to jog the VFO to determine whether the signal is really within the pass band.
Noise Blanker (NB) and Noise Reduction (NR)
I have a lot of noise to contend with throughout the day when neighbours are awake. Most seems to come from LED lighting power supplies, which is added to by various appliances and computers. The worst band is 80, followed by 30, and lesser noise on 20 through 10 which varies with the yagi's direction. For some reason 40 is mostly quiet.
Since I can't change the world or hope to track down every noise source and convince my neighbours to fix the problems the receiver must have effective noise control features. NB and NR are important features.
The NB in the KX3 sometimes works well and sometimes makes matters worse. The NB was not adjustable until a firmware version that came out in (I believe) 2013, after I'd owned the rig for a while. Unfortunately the variability helped little so I typically keep it at or near maximum (15).
The major problem with the NB is its susceptibility to signals outside the filter bandwidth and within or near the range of the roofing filter. Even if those signals are of middling strength the NB is heavily modulated and pretty much renders the desired signal unreadable. This appears to be a case of where the DSP filtering is unable to make up for the limitations of the basic receiver design.
The NR sometimes works, though as with most rigs with NR it typically works best on SSB, and not so well on CW. This is especially true with weak CW signals, where the NR is of no benefit. In my experience adjusting the NR doesn't help on CW.
When the noise is making a CW QSO difficult I often try the NB first. In the majority of cases I get a better result by tightening up the filter to 50 or 100 Hz. In contests where most of my QSOs are S & P (search and pounce) I use a narrow filter of 100 to 200 Hz to contend with the noise and QRM while ensuring I miss few signals as I tune across the band.
VFO Attributes Memory
Every rig associates a variety of controls with each VFO-band pairing, though not always the same ones. On balance I feel that the KX3 does better at this than some other rigs I've used. For example, the KX3 remembers these important settings with the VFO-band pair: attenuator, pre-amp, NB, NR, mode, frequency, and perhaps some others. Since noise and signal levels are band and antenna dependent the first four of those are very welcome. Other rigs often don't associate these with the VFO-band pair, requiring some button pushing on every band change.
What I wish the KX3 would remember is the filter bandwidth. It associates this setting with the mode but not the VFO-band pair. Yet like the items mentioned above the filter is also a control I set differently per band, for reasons of noise and activity level. At least that's how I operate.
VFO, RIT and XIT tuning rates
These features work pretty well aside from the small size of the controls. The problem I have is one of tuning rate. It can take many turns of the knob to effect the desired offset.
The VFO rate is less of a concern to me than RIT and XIT. When I am scanning the band, either in a contest or in daily operation, the VFO tuning rate is fine. For larger frequency excursions it is too slow. Tuning rate can be sped up with a long press of a button, but then the steps are quite large and unsuitable for tuning in a station. Alternative rate settings in the menu are less than ideal to my style of operating. It's easier to use the rig control pane of logging software for large QSY steps.
RIT and XIT tune so slowly that they are very cumbersome for use in split operation. It is almost always better to use both VFOs for split and leave the RIT and XIT for minor adjustments on ordinary QSOs.
QSK and VOX
The QSK (CW break in) and VOX (SSB) work very well. I have heard some complaints about the rig's QSK though that is the opposite of my experience. I use it full time on CW, and I use CW for over 95% of my QSOs. At well over 30 wpm I can hear clearly between dots. There are no annoying switching transients.
When I decided to enter a SSB contest last year I had planned to use PTT with a foot switch, just as I did years ago. I ran into some difficulty wiring in a foot switch and time was pressing, so I decided to try VOX. It worked so well that now I only use VOX when operating SSB with this rig. It was easy to adjust, reasonably immune to inadvertent or extraneous sound, and never cut enough of the first syllable to cause copy errors at the other end in rapid-fire contest exchanges.
ATU-free operation
I did not purchase the optional ATU (automatic tuner). This could have been added later if I got tired of manually adjusting an external tuner. But once I transitioned from my eaves trough antenna to resonant outdoor antennas I found that tuning was not necessary.
At 10 watts output I rarely triggered the protection circuitry even when the SWR got as high as 4. The only serious problem I encountered was common mode from my eaves trough antenna that was easily cured with a coax choke. It similarly was happy putting out 5 watts on 160 meters when feeding the coax centre pin of my 80 meters half sloper. In this case the measured SWR was close to 5.
Buttons and ergonomics
The KX3 is really small and lightweight. This makes it an ideal portable rig, it's designed purpose. As a base station -- how I any many others use it -- size is a problem. When I describe the rig to others I like to say that I can cover the entire face plate with one hand. It's no exaggeration.
The majority of controls are on one of the main circuit boards, which is mounted directly underneath the face plate. When you press a button you are pressing on the circuit board. Although the physical support for the board is quite good I worry that it is prone to eventual failure. If a button breaks or the board cracks the repair implication can be dire. Further, even with my relatively light touch (I'm not physically abusive with my rigs!) the entire rig will slide backward. The rubber feet don't help since the KX3 is very light.
Another problem with its small size is the overlaying of features on the available controls. In addition to a primary use each button or knob can access (presumably less-used) features by long press, pushing knobs, or by pressing another button first. While necessary in a compact design it does cause operating grief. For example, I have several times managed to QRM a DXpedition when trying to operate split since the A=B key is also a split selector on a long press. Playing back a CW memory requires 2 button pushes making it almost useless due to the delay involved between action and result, and the potential for error.
For some reason the normal CW mode operates on the lower sideband (LSB). This is opposite to most other rigs, requiring that I set the mode to CW-R (reverse, or USB) to suit my operating style. In N1MM Logger+ I had to locate the option to use CW-R rather than the default CW mode, otherwise every clicked (self-)spot reverses my preferred mode. It's a solvable problem though not one I find convenient.
Microphone flexibility and SSB
As originally designed the microphone gain could not be set to accommodate a dynamic microphone element. For some reason Elecraft was reluctant to change this despite numerous requests. I was surprised since, as it turned out, it was correctable with firmware alone. To their credit they did relent and I was able to use my venerable Heil headset with the KX3.
Despite the company's protestations about noise and hum that can come with high gain I have experienced no such problem. Ultimately I am happy with the outcome and the KX3's flexibility in regard to the variety of mic elements and handheld controls they support.
After adjusting the gain and ALC in accord with the manual I also added compression for more SSB talk power. The feature itself is standard on every rig on the market although not always done well. From numerous solicited requests on the air I feel confident in saying that when properly adjusted the KX3 produces a high quality, easily-copied SSB signal. This is with the Heil element that emphasizes the mid-range; I set the KX3's mic equalization to flat.
Computer integration
This was trivially easy: just plug one end of the supplied cable to the rig and the other to a USB port. When I first purchased the KX3 not all popular software supported it since it was relatively new, a lack that has since been filled. I have no issues with any of the standard and contest logging software. At least not since setting communication speed to its highest setting of 38,400 bps. Otherwise the logging software was slow to track mode and frequency changes.
One thing I particularly like is that only the one interface is needed for contesting since it can be used to send CW and play rig-resident message memories. That is, no additional serial port is needed for PC-generated CW. However when used in this way there are some things to be kept in mind.
In N1MM Logger+ a macro can be used in the function keys to tell the KX3 to send CW. For example,
closes off one QSO and invites others to call. The KX3's KY command converts the following text to CW, delimited by the ';'. CW speed is determined by the setting on the KX3.
A problem arises because once the macro is executed and the command sent to the rig the software does not know the ongoing progress of the message since there is no feedback from the rig. In N1MM Logger+ (to give a particular example) the following must be kept in mind:
Wrap-up
There are other things I like and don't like about the KX3, though those are relatively minor items that I won't spend time writing up. Features I don't use I can't report on at all, including everything related to digital modes and battery operation.
I plan to continue using the KX3 for contests in the coming months. Although I have the FT-1000MP it requires some work to be ready for the demanding requirements for contesting (CW filter and various mods), and I do not want to risk neighbourhood RFI. That is, my contesting will remain QRP.
Every rig has its problems, including the KX3, so the negative points I've made should be kept in context. There is also the matter of personal preference, where my preferences can be very different from that of others. The KX3 is well regarded in the ham community, a reputation it deserves. Be sure it meets your needs if you are thinking of getting one.
There are ample reviews of the KX3 so there is no need for me to do the same. In any case I do not have the test equipment needed to do a proper technical review. You can find those elsewhere, such as the QST review and user feedback on eHam. My intent is to give an operator's impression of the rig, both its high points and lows, as applied to DXing and contesting.
My review is in some degree going to be unfair to the rig. It was not designed to primarily serve as a base station, or for the most demanding applications. Take this perspective into account as you read onward. For its intended use the KX3 is a superior product. I mean that whole-heartedly.
Overload
The receiver front end is fragile. There are two significant categories of signals that overload the receiver: strong signals within the roofing filter; strong signals farther away, even very far away. This is with the optional KXFL3 roofing filter installed, which I ordered with the rig and is factory calibrated.
My impression from regular use is that the roofing filter does the intended job of reducing IMD from strong adjacent signals. However when very strong signals fall within the roofing filter the rig may turn off the pre-amp. This is reasonable when that signal is from the ham who lives a couple of blocks away, but less so when the signal is from W8. There is a brief message on the display when this happens which I have rarely noticed while tuning across these signals. A minute later I'm wondering why the band is suddenly quiet. When the rig was new I was always puzzled as to why I would occasionally notice that the pre-amp was off. Eventually I discovered what was going on.
The other problem is fundamental overload where a strong signal into the front-end, even if well outside the ham bands, is detected regardless of VFO tuning. This can be very inconvenient when it occurs. For example, there is a shortwave broadcaster in the US with an exceptionally strong signal here. Even with just a dipole that station can push its way through the receiver and be AM-detected no matter where the rig is tuned in the 20 and 17 meter bands. A narrow bandwidth on CW reduces the interference though not enough in many cases. Turning off the pre-amp or using the attenuator will usually cure the problem, but at the cost of sensitivity.
The better your antennas the worse the overload problems since signals presented to the front-end are going to be stronger.
Receiver DSP
As with all electronics the speed and capacity of DSP hardware has remarkably improved over the years. When coupled with effective software there is the potential for superior performance. In my experience the KX3 does very well in this regard.
The continuously variable receiver filter bandwidth (50 Hz steps) is a delight to use. At all settings the audio signals come through very clearly. Even at the narrowest bandwidth (50 Hz) ringing is low. It is also convenient that the roofing filter automatically adjusts in response to the filter setting.
There are limits to what the DSP filtering can accomplish in this direct conversion receiver. Filter skirts are shallow. For example, I typically set the filter to 200 Hz on CW and yet can hear well outside that narrow range. It is how I compromise between noise reduction (local QRN) and not missing much as I tune across the bands. During contests I often narrow the filter to 100 Hz for S & P (search and pounce) and only need to open it up to 300 Hz when calling CQ, and I don't miss much. The APF is pretty much superfluous on this rig.
Multi-pole crystal IF filters are needed to get the steep skirts needed for best QRM and noise rejection. This is not only impossible in a direct conversion design these filters could not fit inside the KX3's small cabinet.
A bigger issue is opposite sideband rejection for single-signal reception. This is another case where the shallow filter skirts limit performance. Elecraft is well aware of the issue but their suggested solution is one that has side effects I don't care for. So I live with it. It is a particular problem in popular CW contests where stations are packed close together. Even middling strong signals the other side of zero beat interfere with the desired signal. It can also be confusing in that a seemingly interfering signal is in fact 1 or more kHz away. I find it necessary at times to jog the VFO to determine whether the signal is really within the pass band.
Noise Blanker (NB) and Noise Reduction (NR)
I have a lot of noise to contend with throughout the day when neighbours are awake. Most seems to come from LED lighting power supplies, which is added to by various appliances and computers. The worst band is 80, followed by 30, and lesser noise on 20 through 10 which varies with the yagi's direction. For some reason 40 is mostly quiet.
Since I can't change the world or hope to track down every noise source and convince my neighbours to fix the problems the receiver must have effective noise control features. NB and NR are important features.
The NB in the KX3 sometimes works well and sometimes makes matters worse. The NB was not adjustable until a firmware version that came out in (I believe) 2013, after I'd owned the rig for a while. Unfortunately the variability helped little so I typically keep it at or near maximum (15).
The major problem with the NB is its susceptibility to signals outside the filter bandwidth and within or near the range of the roofing filter. Even if those signals are of middling strength the NB is heavily modulated and pretty much renders the desired signal unreadable. This appears to be a case of where the DSP filtering is unable to make up for the limitations of the basic receiver design.
The NR sometimes works, though as with most rigs with NR it typically works best on SSB, and not so well on CW. This is especially true with weak CW signals, where the NR is of no benefit. In my experience adjusting the NR doesn't help on CW.
When the noise is making a CW QSO difficult I often try the NB first. In the majority of cases I get a better result by tightening up the filter to 50 or 100 Hz. In contests where most of my QSOs are S & P (search and pounce) I use a narrow filter of 100 to 200 Hz to contend with the noise and QRM while ensuring I miss few signals as I tune across the band.
VFO Attributes Memory
Every rig associates a variety of controls with each VFO-band pairing, though not always the same ones. On balance I feel that the KX3 does better at this than some other rigs I've used. For example, the KX3 remembers these important settings with the VFO-band pair: attenuator, pre-amp, NB, NR, mode, frequency, and perhaps some others. Since noise and signal levels are band and antenna dependent the first four of those are very welcome. Other rigs often don't associate these with the VFO-band pair, requiring some button pushing on every band change.
What I wish the KX3 would remember is the filter bandwidth. It associates this setting with the mode but not the VFO-band pair. Yet like the items mentioned above the filter is also a control I set differently per band, for reasons of noise and activity level. At least that's how I operate.
VFO, RIT and XIT tuning rates
These features work pretty well aside from the small size of the controls. The problem I have is one of tuning rate. It can take many turns of the knob to effect the desired offset.
The VFO rate is less of a concern to me than RIT and XIT. When I am scanning the band, either in a contest or in daily operation, the VFO tuning rate is fine. For larger frequency excursions it is too slow. Tuning rate can be sped up with a long press of a button, but then the steps are quite large and unsuitable for tuning in a station. Alternative rate settings in the menu are less than ideal to my style of operating. It's easier to use the rig control pane of logging software for large QSY steps.
RIT and XIT tune so slowly that they are very cumbersome for use in split operation. It is almost always better to use both VFOs for split and leave the RIT and XIT for minor adjustments on ordinary QSOs.
QSK and VOX
The QSK (CW break in) and VOX (SSB) work very well. I have heard some complaints about the rig's QSK though that is the opposite of my experience. I use it full time on CW, and I use CW for over 95% of my QSOs. At well over 30 wpm I can hear clearly between dots. There are no annoying switching transients.
When I decided to enter a SSB contest last year I had planned to use PTT with a foot switch, just as I did years ago. I ran into some difficulty wiring in a foot switch and time was pressing, so I decided to try VOX. It worked so well that now I only use VOX when operating SSB with this rig. It was easy to adjust, reasonably immune to inadvertent or extraneous sound, and never cut enough of the first syllable to cause copy errors at the other end in rapid-fire contest exchanges.
ATU-free operation
I did not purchase the optional ATU (automatic tuner). This could have been added later if I got tired of manually adjusting an external tuner. But once I transitioned from my eaves trough antenna to resonant outdoor antennas I found that tuning was not necessary.
At 10 watts output I rarely triggered the protection circuitry even when the SWR got as high as 4. The only serious problem I encountered was common mode from my eaves trough antenna that was easily cured with a coax choke. It similarly was happy putting out 5 watts on 160 meters when feeding the coax centre pin of my 80 meters half sloper. In this case the measured SWR was close to 5.
Buttons and ergonomics
The KX3 is really small and lightweight. This makes it an ideal portable rig, it's designed purpose. As a base station -- how I any many others use it -- size is a problem. When I describe the rig to others I like to say that I can cover the entire face plate with one hand. It's no exaggeration.
The majority of controls are on one of the main circuit boards, which is mounted directly underneath the face plate. When you press a button you are pressing on the circuit board. Although the physical support for the board is quite good I worry that it is prone to eventual failure. If a button breaks or the board cracks the repair implication can be dire. Further, even with my relatively light touch (I'm not physically abusive with my rigs!) the entire rig will slide backward. The rubber feet don't help since the KX3 is very light.
Another problem with its small size is the overlaying of features on the available controls. In addition to a primary use each button or knob can access (presumably less-used) features by long press, pushing knobs, or by pressing another button first. While necessary in a compact design it does cause operating grief. For example, I have several times managed to QRM a DXpedition when trying to operate split since the A=B key is also a split selector on a long press. Playing back a CW memory requires 2 button pushes making it almost useless due to the delay involved between action and result, and the potential for error.
For some reason the normal CW mode operates on the lower sideband (LSB). This is opposite to most other rigs, requiring that I set the mode to CW-R (reverse, or USB) to suit my operating style. In N1MM Logger+ I had to locate the option to use CW-R rather than the default CW mode, otherwise every clicked (self-)spot reverses my preferred mode. It's a solvable problem though not one I find convenient.
Microphone flexibility and SSB
As originally designed the microphone gain could not be set to accommodate a dynamic microphone element. For some reason Elecraft was reluctant to change this despite numerous requests. I was surprised since, as it turned out, it was correctable with firmware alone. To their credit they did relent and I was able to use my venerable Heil headset with the KX3.
Despite the company's protestations about noise and hum that can come with high gain I have experienced no such problem. Ultimately I am happy with the outcome and the KX3's flexibility in regard to the variety of mic elements and handheld controls they support.
After adjusting the gain and ALC in accord with the manual I also added compression for more SSB talk power. The feature itself is standard on every rig on the market although not always done well. From numerous solicited requests on the air I feel confident in saying that when properly adjusted the KX3 produces a high quality, easily-copied SSB signal. This is with the Heil element that emphasizes the mid-range; I set the KX3's mic equalization to flat.
Computer integration
This was trivially easy: just plug one end of the supplied cable to the rig and the other to a USB port. When I first purchased the KX3 not all popular software supported it since it was relatively new, a lack that has since been filled. I have no issues with any of the standard and contest logging software. At least not since setting communication speed to its highest setting of 38,400 bps. Otherwise the logging software was slow to track mode and frequency changes.
One thing I particularly like is that only the one interface is needed for contesting since it can be used to send CW and play rig-resident message memories. That is, no additional serial port is needed for PC-generated CW. However when used in this way there are some things to be kept in mind.
In N1MM Logger+ a macro can be used in the function keys to tell the KX3 to send CW. For example,
{CATA1ASC KY tu {MYCALL};}
closes off one QSO and invites others to call. The KX3's KY command converts the following text to CW, delimited by the ';'. CW speed is determined by the setting on the KX3.
A problem arises because once the macro is executed and the command sent to the rig the software does not know the ongoing progress of the message since there is no feedback from the rig. In N1MM Logger+ (to give a particular example) the following must be kept in mind:
- ESC can't be used to interrupt transmission. You must tap the paddles.
- CQ auto-repeat interval is from when the command is sent to the KX3, not from end of the transmission. It is best to disable this feature and press F1 as needed.
- Sending speed cannot be easily adjusted from the software. For example, the "<" and ">" speed change commands don't work, nor do the PageUp and PageDown keys.
- If you operate SO2R or switch rigs the CATAASC macros must be swapped out. I have this problem now that I have a FT-1000MP, as soon as I start using it in a contest.
Wrap-up
There are other things I like and don't like about the KX3, though those are relatively minor items that I won't spend time writing up. Features I don't use I can't report on at all, including everything related to digital modes and battery operation.
I plan to continue using the KX3 for contests in the coming months. Although I have the FT-1000MP it requires some work to be ready for the demanding requirements for contesting (CW filter and various mods), and I do not want to risk neighbourhood RFI. That is, my contesting will remain QRP.
Every rig has its problems, including the KX3, so the negative points I've made should be kept in context. There is also the matter of personal preference, where my preferences can be very different from that of others. The KX3 is well regarded in the ham community, a reputation it deserves. Be sure it meets your needs if you are thinking of getting one.
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