Shortwave Listening With The K3

I would love to see the K3 receive the attention it deserves from the too-often ignored hardcore shortwave and mediumwave DXers and believe that with a few minor software tweaks the K3 could fill a huge void in the high-performance communications receiver market since it has been all but abandoned by major manufacturers.

Twenty years ago when I first started out in the radio business there were a good number of new desktop shortwave receivers to choose from including the Yaesu FRG-8800 ($639.95), Icom IC-R71A ($799,95), Kenwood R-5000 ($859.95), JRC NRD-525 ($1189.95), not to mention many used late-model receivers such as the JRC NRD-515, Drake R7, Yaesu FRG-7700 and Icom IC-R70. With sadness I've watched as radios like these have been slowly disappearing from the market, replaced by small portable radios aimed at the broader consumer market while serious hobbyists have fewer and fewer choices other than prohibitively expensive mil-com HF receivers, or amateur radio transceivers which more often than not perform awfully in the AM mode.

With the K3, I see hope; a basic 10W K3 costs only $1600 (or $1400 if self-assembled), less than the soon-to-be discontinued NRD-545 is currently selling for, and even with only the stock 2.7 kHz roofing filter the K3 would likely run circles around the '545 not to mention most of the classic receivers mentioned above. However, it will take a little fine-tuning by Elecraft for it to realize its potential as a top-notch SWL receiver.

AM Mode Filtering: There was talk on the Elecraft reflector a while back about the way the filtering works in the AM mode, specifically the 3 kHz maximum "audio" bandwidth. From an SWL's perspective, this makes no sense; it is counter-intuitive and non-standard compared to all other high-end communications receivers (I'll use the NRD-535D as a reference, since I'm most familiar with JRC equipment). With the '535, the filtering in AM mode works like one would expect; no matter which filter is selected, when the passband shift (PBS) control is centered the filter passband is centered on the carrier frequency and shifting the passband shifts tha actual i.f. passband, not the audio passband. So if a 2.4 kHz filter is used, it will pass 1.2 kHz of each sideband when PBS is centered. Offsetting the PBS 1.5 kHz to the right, for example, will move the entire filter passband to pass only the upper sideband while rejecting the lower sideband. This is useful to the SWBC DXer in cases where there is a strong signal 5 kHz below a weaker station that I'm trying to receive and the lower sideband suffers from adjacent channel QRM but the upper sideband is clear. And vice versa, if the interfering signal is 5 kHz above, tweaking the PBS to the left passes the lower sideband while rejecting the upper sideband and the QRM.

I'm not sure what actually happens in the same scenario when using the K3. If I set the filter width to 2.4 kHz and shift the passband to the right, it seems to work as expected - audio frequency response gets higher; but when the passband is shifted to the left, frequency response gets lower, which indicates that the filter passband is either not centered on the carrier, or it is split similar to the way it works in RTTY mode, and passes equal slices of both passbands. Whatever the case, the way it currently works is at odds with what is expected by a true SW or MW broadcast DXer.

Synchronous Detection: There is also the unanswered question as to whether the K3's forthcoming AM Synch mode will allow independent sideband selection. With synchronous AM detection, the ability to select sidebands independently is pretty much mandatory, otherwise the synchronous mode is useless on all but the strong, clear signals which frankly sound just fine without synchronous detection. The NRD-535 selects AM-USB and AM-LSB with the ECSS (exalted carrier selectable sideband) button. Most other receivers that have this feature work similarly. The Sony ICF-2010 does it a little differently - it lets you select sideband by adjusting the main tuning dial up or down slightly, and a little LED indicates which sideband is selected. The Drake R8, by comparison, does not directly allow selectable sideband; its synch mode was DSB, and although you could move the passband shift it isn't as effective as the JRC and Sony systems which totally reject the unwanted sideband.

Joe, W4TV, gets it; in one of his reflector postings on AM filtering he pretty much describes how the JRC ECSS system works in principle (the exception being that JRC doesn't do it with DSP):

Given the DSP demodulation in the K3, it's a shame that there isn't an "offset" option to do "vestigial sideband" demodulation (offset the AM filter to the upper sideband or lower sideband) and demodulate carrier and one sideband for better fidelity.

I'm not sure if Joe is talking about syncing the carrier and replacing it with an internally generated one, but that is what a good synchronous ECSS system does in a nutshell. Without selectable sideband capability, synchronous AM detection is like tits on a bull.

SWL Mode: Another easy software mod that would be welcome for people who wish to use the K3 solely for SWL purposes would be to include a setting to disable the transmitter, similar to the TX TEST mode but without requiring it to be set each time the radio is turned on. This can be done by at least making the TX TEST mode persistent so that the K3 would remember it was in test mode when it was last powered up. Preferably there would be an additional CONFIG menu parameter that would put the radio into SWL mode in which the TX indicator will be turned off (not flashing like in Test mode); if the PTT line is keyed while in SWL mode the K3 would display a message like "SWL MD" and there will be no RF output - basically extending the out-of-band transmitter disability to K3's the entire frequency coverage while in SWL mode.

And that's it - just modify the firmware code and send a K3 off to Larry Magne for testing! The rest will be history.

K3 vs. JST-245: The Road To Victory

With the addition of a stereo line splitter to feed K3 audio into two separate channels on the Multi-RX, it is now far easier to compare the two rigs. The following observations refer to SSB mode only; testing in CW and data modes to come as time allows.

Audio Quality: The most obvious thing is, the K3's audio is much more crisp than that of the JST-245. By "crisp" I mean it has a bit more high frequency response, while the '245 has more punch at the low frequency end. Which is better is more a matter of preference than science. My ears generally find the weakest signals more easily readable with the K3, while signals S9 or better tend to have a more natural tone with the '245. But the differences are subtle, neither radio sounds dramatically better than the other when using a common audio system (in this case, the Multi-RX feeding a pair of small Sony speakers left over from my home theater surround sound installation, as well as a pair of JRC ST-3 communications headphones). The K3's stereo audio effects (AFX) settings can tremendously improve the quality of reception and reduce listening fatigue, and works equally well with speakers and headphones; the AFX feature gives the K3 a slight edge.

Noise Reduction: Most notable is the DSP Noise Reduction (NR). Even at it's lowest setting, the NR removes so much background hash with the push of a single magic button that I find myself turning it on and off just to come to grips with the fact that it actually works. There are several NR settings selectable by holding the NR button and dialing in the level. Lyle Johnson KK7P, Elecraft's DSP genius, says:

NR is more properly Signal Enhancement rather than Noise Reduction. The distinction is subtle but important if you wish to understand how it works and how to best apply it. If ti were noise reduction, the implication is that it passes everything until it figures out what is more likely to be noise, which it then attempts to suppress. Since it is signal enhancement, it tends to pass nothing until it figures out that which is more likely signal, which it then attempts to pass.

With this understanding there is one more concept I must explain: correlation. This is the degree to which a signal is similar to itself; conversely, it can be used to figure out how noise is dis-similar to itself (more random). This is the basis on which NR works.

In the current implementation of the K3, we have four (4) basic NR filters. These are displayed as F1..F4. F1 is the gentlest, F4 the most aggressive. Recalling that the filters tend to suppress everything until they can sort out what is probably a signal, there is some time delay involved in their application. Further, especially with voice signals, some components of the signal may not be recognized as well as others. THis gives rise to distortion.

So, we added a second field to the NR. This is the -1..-4 which specifies a certain amount of "bleed through" of the original signal. This reduces the apparent distortion and delay, but limits the ultimate S/N improvement. -1 provides the least distortion but limits the S/N improvement on weak to moderate signals to about 6 dB. -4 provides no "mixing" whatsoever and can result in dramatic S/N improvements, but at a cost of slight time delays and increased distortion.

NR is not appropriate for very weak signals, so a -1 or -2 is best if you wish to hear them.

Having said all this, the correct way to use the NR is to listen and adjust it for the best compromise between noise reduction and distortion. Everyone is different in this regard. Some tolerate noise better than others, while some don't tolerate distortion very well at all.

I live in a quiet location, and use NR1-2 as my most common setting. This is low in distortion, allows me to hear weak signals, and shows no apparent delay as I tune through the bands. On the rare occasions when things get noisy here, I crank it to higher values.

Noise Blanker: The K3 Noise Blanker (NB) is also a masterpiece - between the separate IF and DSP blanker settings I've been able to remove all sorts of crap that would otherwise make it impossible to hear any but the big gun signals. It's as simple as this: When I hear any sort of electrical noise, I first crank the DSP NB up to see if it has any effect. If not, I try the IF DSP. Usually one or the other does the trick, I haven't found any noise that requires both at the same time. The '245 NB is useless by comparison; if it works at all it must be against a very specific type of impulse noise that I've never encountered, because I've never found it to be of any use at all (unless distorting a desired signal is of use to anyone).

Notch Filter: With the '245 I almost always use the manual notch filter as a mid-cut to tailor the receive audio to my liking. I find this technique to be a bit more effective with the '245 than the K3 as the latter takes an awful lot of dial turning to adjust the notch range from 200 Hz to 3.92kHz in 20 Hz steps. Also, the K3 notch width is much sharper than the '245 so the effect is more subtle. Of course the K3 has built-in graphic equalization for the purpose of shaping the audio response, so this issue is pretty much moot and leaves the notch filter to be used for its intended purpose - to remove heterodyne interference. To this end, the K3's Auto Notch is superb. The manual says it will, in some cases, remove multiple carriers although I've yet to find a situation that will confirm this. The '245 does not have an auto notch function, but it has Notch Tracking which will offset the manually adjusted notch filter when the VFO is tuned slightly; this is useful but not nearly as effective as a fully automatic system. Notch depth is adequate on both rigs.

Ergonomics: Both of these radios are a joy to use. The '245 has a solid feel and a heavy, balanced main VFO knob that spins like a top. All of it's buttons have a nice positive 'click' when pushed, and the smaller knobs and controls feel good and not overly 'plastic'. And the color LCD! - it's about the finest looking display of it's generation and, in my opinion, better than anything even today short of the newer Icom color TFT displays of the IC-7800, IC-7700, etc. Because JRC took the time and effort to find out what amateur radio operators really wanted and where things were supposed to go on the front panel, all of the most commonly used controls are assigned to individual buttons or knobs with very few alternate functions or hidden menus to toggle through; outstanding ergonomics was a chief goal during the JST-245 design review, especially after the JST-135 got raked over the coals by Dave Newkirk in his QST review (and deservedly so). So although I may be biased as a member of aforementioned JST-245 design review team, I find the JST-245 to be a more enjoyable radio to sit in front of and operate.

The K3, however, is no slouch. Elecraft had different design criteria, one of which was to make the K3 compact and easily transportable. Neither of these adjectives can be applied to the '245, therefore JRC had a whole lot more front panel real estate to work with than did Elecraft. Consequently many of the K3's controls are doubled up, several often-accessed settings are menu-driven, and some things which take a single button push with the '245 take two or more with the K3. But by and large I think Elecraft got it right, the K3 has just the right amount of compromise between keeping the size of the radio down, making it attractive to the field user and people with limited space, and including all the high-performance features demanded by discriminating users such as contesters and DXers. So while I may have to toggle through different modes to set the K3 instead of pressing a single button, it's not a big deal to me. The K3's buttons have a soft feel to them which reminds me of the Drake R8 receiver's front panel buttons. While the main tuning dial does not have the same flywheel feel of the JRC it still spins nicely. The main liquid crystal display is very sharp and has a wide range of backlighting levels (including OFF), though it must be viewed at a fairly straight-ahead angle. All in all, from a usability perspective, the K3 is a nicely designed little rig.

The one area in which I find the K3 to be deficient is in its selection of memory channels - unlike the '245 which has a dedicated Memory Channel knob that lets the user dial through channels one by one, the K3 has a more convoluted process of pressing the M>V button, dialing up the memory channel with the VFO knob - without being able to hear what's going on at that channel's particular frequency! - then pressing M>V again to set the rig to the stored frequency, mode and other parameters. If I could change one thing with the K3 it would be to let me hear what's on each channel as I dial through the memories, before I hit the M>VFO button. This should be an easy firmware fix.

And the winner is...: In the tweakability department the K3 has a few bells and whistles that are missing (or ineffective) in the '245. In practice I find that I am able to get similar reception with both rigs by using each radio's tools to maximize the desired signal and minimize the junk. I am still amazed at how well the JST-245 holds up to the latest and greatest in DSP technology, and it is such a pleasure to use. Therefore I've abandoned any thoughts of selling the '245 to finance the acquisition of a second K3; it is simply too good a rig to let go of.

That said, the K3 is clearly the future of HF transceivers, and it looks to be a pretty bright future at that. While the above observations are subjective and based narrowly on SSB reception under less than perfect antenna and propagation conditions I think it's pretty clear that the K3 is a gem of a rig. Of course many of the design elements that on paper put the K3 in the league of the mega-buck rigs from JA-land do not come into play with my limited antenna system - for example, I rarely see a signal stronger than S9+10dB, and have yet to find two such signals close together as in a contest situation, therefore the benefit of the narrow roofing filters and strong front-end performance remain untested by me in any real way. In any case, others (ARRL, Sherwood*, etc.) will confirm or deny Elecraft's published dynamic range and IP3 specs soon enough, so I'll leave it to the pros to do the scientific evaluations.

If held at gunpoint and told to choose one of these two radios, subjectively, emotionally, and based solely upon my ears, fingers and eyes... it would have to be the K3. But barely.

* Update 09-Feb-08: Serendipitously, Rob Sherwood has released some of his K3 test results which were promptly passed on to the Elecraft reflector by Wayne Burdick:

Rob Sherwood, NC0B, an independent and well-known receiver performance specialist, has completed his K3 receiver tests. We're pleased with the results, which will place the K3 at the top of his comparison chart.

Rob will be updating his web site in a few days. For now, I'll just mention a couple of his numbers (with his permission).

Elecraft K3, S/N 00149, 20 meters, preamp off:

Dynamic Range 20 kHz 104 dB
Dynamic Range 5 kHz 102
Dynamic Range 2 kHz 101*

* with 200 Hz 5-pole filter

Blocking above noise floor at 100 kHz spacing, AGC On: 140 dB
Phase noise (normalized) at 10 kHz spacing: 138 dBc/Hz

Rob performs some tests differently that we (and the ARRL) do, but in general we're all in close agreement. Note that the unit under test had only Elecraft 5-pole filters. Our tests show the 8-pole filters to be as good or better, and we sent some of them to Rob to test when he gets a chance.

73,
Wayne
N6KR

Back in business...

The K3 is in place, the Multi-RX is back in action, the MFJ-267 watt meter/dummy load finally arrived, the antennas still suck...

With the playing field level - both rigs hooked up to the same antenna and speakers - I can do some fair and honest comparisons between the K3 and the JST-245. I must still fine-tune the system a bit - an adapter to split left and right channel audio from the K3 speaker output is first on the list, and I think I can do something with an antenna that is somewhat temporary yet still effective (and quiet) and will tide me over until I get to the new QTH later this spring.

Assorted junk...

Fifty years later, Jimmy Mulligan still lives with his mother and has never been laid.

Words of Wisdom

FCC's Riley Hollingsworth (K4ZDH) channels my sentiments precisely in his Dayton HamVention address.

To the Nets: Just because you have been on the same frequency for 75 years, that doesn't mean you own it. All frequencies are shared. If you vary your frequency, or even if you don't have a net one night, the radio world isn't going to end.

To repeater owners: Just because you are coordinated doesn't mean you own the frequency. Coordination is a recommendation, not a frequency assignment. It's your call sign on the repeater and it's your station and your responsibility ...just as if you had left the door open to your station at home. If there is abuse, lock the door. Don't ask us to be baby-sitters or hall monitors of your repeater. That's what control operators are for. Nobody asked you to start a repeater. If you shut it down tomorrow, what would happen? People would use OTHER repeaters!

To the contesters: be more courteous. You are responsible for the frequency you are operating on and realize that's true even when you operate split. All frequencies are shared.

To those who don't like contesters: lighten UP!! Contests are short lived. Use the WARC bands. Wash the car. Cut the grass. Learn from the contesters - and this applies to you Traffic net folks too - learn from the contesters. They pass information a lot faster and more efficiently than you do. Contesters are some of the best radio operators on planet Earth. If the contesters operated at the same pace as some of the emergency traffic nets, the contest would be over after the first few dozen signal strengths were exchanged!

To the widebanders: If you want to be a Broadcaster, apply for a broadcast license. Using extraordinarily wide bandwidth on crowded frequencies at peak operating time is rude, selfish and inconsiderate.

To the QRP'ers: Thank you, thank you, thank you for your vitality, inspiration, enthusiasm and for being BUILDERS again! I wish I could take your enthusiasm and spread it over all segments of Amateur radio. When I watch you folks, I see the excitement and magic of my first contact.

To those who don't like QRP'ers: Lighten UP. ANYONE can use a linear amplifier as a crutch.

To the rag chew nets: 4 or 5 people meeting on the same frequency every night for 50 years using 1200 watts to talk a few hundred miles when 100 watts would do just fine is not a net. It's an informal roundtable. It ain't going to hurt you either to vary your frequency or skip a night. And the so-called "net" on 75 that bills itself as an "Oasis of Amateur Radio": Give us all a break. You are an ordinary roundtable. And no net is an "Oasis of Amateur radio."

To those of you who don't like DXpeditions: Lighten UP! If a group of people want to spend a lot of money to go to a rock or sandbar in the ocean, live in a tent and swat flies and scorpions for a week and talk over Ham radio 24 hours a day, SO WHAT: LET'EM DO IT!!. DXpeditions, too, are short lived, and such operation must be important to SOMEONE. Scarborough Reef drew over 50,000 contacts didn't it. And weren't over half of them CW, by the way? Nobody would have even known about it had it not been published in popular radio magazines.

When I'm elected President my first act will be to appoint Hollingsworth as FCC Chairman.

No, Virginia, CW is NOT Dead.

On February 23, 2007, the Morse code requirement for amateur radio licensing will be gone. The debate over whether this should be done has been going on for years - opponents have claimed, correctly, that CW is an antiquated mode that no other radio service uses or requires, and that it is an unreasonable hurdle that keeps many otherwise dedicated and valuable operators out of the hobby at a time when we need them most, as other services seek to grab up amateur frequency allocations that are sparingly used; meanwhile, proponents of code testing cited tradition and warned of the floodgates opening, the HF bands tuning into CB radio, and.... well, damn it, I had to pay my dues and pass a code test, why shouldn't you?

I can appreciate both sides of the argument, but when I weigh the pros and cons, I find myself dancing on the grave of the code test. It's demise will not mean the end of CW on the ham bands; the only thing that will kill CW will be if hams choose to stop using the mode. I doubt this will happen, as CW is very popular among DXers and contesters.

The slippery slope argument is tenuous. It might have been a concern in the 70's during the CB craze, when CB radios were at the cutting edge of personal communications. But today the CB substitutes of choice are the internet and text messaging; ham radio won't capture the nitwit market because, 1.) It's expensive, and 2.) Even without the code test, getting licensed takes a good deal of effort. These are major obstacles to people who aren't serious about the hobby.

Amateur radio has always appealed to people who are fascinated with the science of radio, generally a brighter demographic than your typical chat room inhabitant. I can't see how these people will go through the whole licensing process, and the trouble and expense of building an amateur radio station, then suddenly devolve into a hoard of freaks shouting "Breaker Breaker!" into their echo mics on 20 meters.

So I welcome the FCC's decision to end the code requirement for licenses with HF privileges. I doubt most of the old curmudgeons that bitch and moan about it ever tune their radios off their 75m phone frequency, and probably fail to notice that the average age of US amateurs is quickly creeping up to the Geritol and Depends age bracket, let alone understand that that's a really bad thing. The hobby is in desperate need of a transfusion of new, younger blood, and telling kids that they need to learn CW, the telecommunications version of Aramaic, is the surest way to drive them back to their text messages and MySpace pages.

Do you like all those fancy modern HF rigs with spectrum scopes and DSP filters? Me too. Do you think companies like Kenwood, Icom and Yaesu will continue to devote R&D yen to continue producing these rigs while the market shrivels away? People on Social Security are not going to be buying many IC-7800's and FT-9000's, and sooner or later, if the number of hams dwindles, no one will be making these rigs.

So I say good riddance to the code test. And to celebrate it's death, I have downloaded every W1AW code practice MP3 file to my iPod so I can get my CW chops back.

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