A comparison of the Elecraft KX1 and K1 rigs
Reproduced here with the permission of
Bruce Prior N7RR and Wayne Burdick N6KR
Updated Jan 18/04
The Elecraft KX1 is best understood as a smaller and generally more refined version of the K1. In many respects the KX1 is superior, but the K1 also has its advantages.
Let's start with aspects where the two rigs are quite comparable:
In the K1, zero-beat spotting can be accomplished with the receiver unmuted using menu item StP, or with the receiver muted via menu item StL. For routine operation, I leave the K1 menu set for StP to make that function readily available. Zero-beat spotting is most convenient on the KX1 using the SPEED function, during which time activating the keyer doesn't transmit RF. The KX1 also has the StL and StP menu items which can also be used for zero-beat spotting, but in both cases the receiver is muted.
The basic keyer features of the K1 and KX1 are identical, offering non-volatile mode A or B keying and with non-volatile programmable keying speeds between 8 and 50 WPM.
Because of fine engineering and very detailed instructions in the manuals, both the K1 and KX1 are easy to build and either one would be an appropriate choice for a builder with only modest experience at soldering and assembling kits.
Here are features which are superior in the K1 compared with the KX1:
The basic K1-2 offers a choice of CW portions of any two bands between 80 m and 15 m (excluding the USB 60 m allocations, of course), or four bands with the K1-4 or on an optional module which is designed for 40, 30 and 20 meters, plus a choice between 15 and 17 meters. The 2-band or 4-band modules can be swapped so that the K1 will cover six bands total. When the KAT1 module is also installed, swapping band modules is about a ten-minute job. I have my 4-band module configured for 40, 30, 20 and 15 m, and my 2-band module includes 80 and 17 m bands. In addition, the K1 firmware also allows 160 m operation with the 2-band module and some operators have implemented it, including W3FPR. See Don Wilhelm's and Wayne Burdick's postings on this subject in the archives of the Elecraft e-mail reflector for 21 November 2003, available through the http://www.elecraft.com/ website. The basic KX1 covers the 20 m and 40 m bands, and the 30 m band can be added with a tiny and inexpensive optional module which is permanently mounted between the main board and the control panel. So, for the number of amateur bands covered the K1 is better, especially with its capability of 80 m operation, which can be important for routine contact through traffic nets on lengthy wilderness treks. Traffic nets are most commonly found on the 80 m band, including the 75 m phone portion. Without that 80 m capability on the KX1, I will have to make a point of breaking a trip at midday to check into the LSB Noontime Net on 7268.5 kHz at noon Pacific time. Another option is the 7th Region Net DRN7, which meets daily on 7238 kHz at 0945 and 1515 Pacific time. The KX1 could be considerably enhanced for wilderness trek operation if the firmware were revised to allow operation on the 80 m band. Such operation with the current hardware version of the KX1 would have reduced sensitivity on 80 m, and an external lowpass filter would have to be added to attenuate second harmonic transmissions originating on that band.
Both RIT and XIT are available on the K1, whereas the KX1 sports only an RIT. A firmware revision could add XIT to the KX1.
Power output is easily programmable from the K1 front-panel from 100 mW to 7 W. The KX1 power output can be controlled via an accessible trimpot using a tiny screwdriver from approximately 100 mW to about 4 W, depending on the input voltage used. The KX1 power trimpot is not designed to be adjusted frequently.
The K1 has a nice-sounding built-in speaker which is muted when a plug for an external speaker or headphones is inserted. The KX1 is designed principally for use with headphones, but the audio level is sufficient for using an external speaker. I intend to carry a speaker with my KX1 in a backpack to free me from having to be tethered to the rig while operating it. It is frequently convenient to listen to a radio while carrying out camp chores. At home I very seldom use headphones with the KX1. It drives a properly-matched speaker very nicely.
The K1 has provision for an optional noise blanker against ignition or electric fences and similar noise sources, whereas the KX1 has no noise blanker option.
The well-designed 4-pole IF crystal bandpass filter in the K1 has three programmable steps, a better design than the 3-pole IF crystal bandpass filter of the KX1 with its analog front panel control pot and noticeable audio attenuation at the narrow end. A slight nod has to go toward the K1 in the audio filter department, but the KX1 filter is convenient and wide-ranging enough for normal CW operation or for listening to AM or SSB transmissions.
The audio stage automatic gain control of the K1 can be turned on and off, whereas in the KX1 the AGC is always active. This is really a safety feature in the KX1, however, since that radio is designed principally for use with earphones.
Both the K1 and KX1 have two beacon-capable message memories, but the K1 has a 90-character capacity in each memory, whereas the KX1 memories holds up to 48 characters each.
The following are the characteristics where the KX1 outshines the K1:
Designed from the start as a trail-friendly radio, the KX1 is lighter and less bulky than the K1.
The K1 has no audio feedback interface system. The basic KX1 has a comprehensive and programmable audio feedback interface system which is the best I've ever experienced. With a smaller encoder knob installed, the KX1 is an ideal radio for a totally blind operator, and KX1 audio feedback is a great backup for sighted hams as well.
The K1 uses an analog varactor diode tuning system which yields a maximum total range of about 170 kHz per amateur band, whereas the KX1 has a more convenient DDS rotary encoder tuning system which not only allows full amateur band coverage, but non-transmitting receive coverage considerably beyond the specified amateur bands. In addition, the KX1 tuning speeds are 5 kHz, 1 kHz, 100 Hz and 10 Hz per encoder step. This makes large or small frequency excursions very convenient with the KX1.
Although
the K1 has an optional 10-element internal tuner KAT1, and the optional internal
tuner KXAT1 for the KX1 has only 7 elements, a firmware revision for the KXAT1
allows it to be controlled manually to accommodate the expanded receive range
outside of the amateur bands. The
KAT1 only operates in automatic mode.
Both rigs are considerably enhanced by these well-designed options.
The K1 can be equipped with a versatile, but heavy optional wide-range tilt-stand, whereas the controls-on-top KX1 design make such a tilt stand completely unnecessary.
While the K1 has a single-step RF attenuator, the KX1 sports a more versatile analog RF gain control.
The only K1 option which I would not recommend is its 8-cell optional internal battery holder. The reason I don't like it is that it is very awkward to access in the shack, to say nothing of the field. A 6-cell internal battery holder comes standard in the basic KX1. It is considerably more convenient than the K1 version. Its only disadvantage is that with only 6 cells, the KX1 produces lower output power than when using a 12 to 14 Vdc external power source. The KX1 internal battery holder can be operating from an external power source while batteries are in the internal batter holder, and the radio will draw from whichever source produces the higher voltage. For outdoor operation, I prefer to carry 6 AA lithium cells inside the KX1 but normally operating with an 8-cell external AA holder available from RadioShack. In cold weather or on lengthy trips I always use AA lithium cells in the external holder. For an overnight trip in the summer, 8 alkaline AA cells would do fine to power the KX1. An even tinier and lighter-weight external power supply can be constructed from a single-cell AA holder (RadioShack #270-401A) loaded with two 6 V Duracell® 28L lithium batteries in series.
The KX1 is very well designed for CW-to-LSB or CW-to-USB cross-mode operation, while on the K1 cross-mode operation is only practical on the with LSB stations on the limited portions of some phone bands which the K1 covers. Since my life was once saved by just a cross-mode contact on the Canadian calling frequency, 14.140 MHz, I'll admit a personal bias strongly in favor of the KX1 because of this feature.
Only on the 7.1+ MHz band are a few shortwave broadcast stations receivable with the K1, whereas the KX1 has extensive shortwave receive coverage, especially with the optional 30 m adapter (KXB30) installed, and the KX1 produces surprisingly good audio quality for SSB or AM reception. With the addition of the KXB30, the KX1 will receive from 5.0 MHz to 16.505 MHz.
The K1 has a scrolling non-illuminated liquid crystal display which is difficult to read in some conditions, but the KX1 has a variable-brightness low-current LED display which is not only easy to read in varying conditions, but it can be programmed to turn off after a period of inactivity.
The K1, like the K2, comes equipped with a hard plastic tuning knob, while the plastic tuning knob on the KX1 is rubber-ringed for better grip, especially using gloved fingers.
The K1 requires the use of an external key or keyer, but optional detachable iambic keyer paddles are available for the KX1. The KX1 is also compatible with an external key or keyer.
A frequency memory on the K1, if it could be called that, is only possible by retaining the position of the 10-turn tuning potentiometer on a given band. The KX1 has one non-volatile last-stored frequency/mode memory per band plus three more non-volatile frequency/mode memories per band.
No lighting is available on the K1, but an independently-switchable LED logging light on the KX1 can also be used as an emergency flashlight. Some users may wish to replace the standard white LED with a red one to discourage neighboring insects from joining the party for CW lessons.
The base model K1-2 (2-band version) price is $289 + S&H; the K1-4 (4-band version) is $349 + S&H. The K1 with all options starting with the K1-4 is $621 + S&H. The K1 with all options starting with the K1-2 is $631 + S&H. The basic KX1 costs $279 + S&H, or $456 + S&H with all options.
I own both a K1 and a KX1 and I don't intend to sell either one, but if I had to choose between them, I'd go for the KX1.
J. Bruce Prior N7RR
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Addendum by Wayne Burdick N6KR
Hi Bruce, Thanks for posting this comprehensive comparison.
I would add just one further point. Since the K1 has an analog L-C VFO, its spurious-free dynamic range is larger than the KX1's DDS VFO. The same would be true in comparing any L-C vs. DDS implementation.
In typical field operating circumstances, the KX1's DDS VFO does very well; the simplicity, wide tuning range, and low current drain of DDS is ideal for a trail radio. But the K1 receiver would have the edge in some cases, such as in a major contest where most of the stations were operating at high power levels. The better the SFDR, the less likely you are to suffer from a general increase in IMD. This is one reason we consider the four-band K1 to be an ideal home QRP CW rig.
Wayne N6KR