Background
Having previously built a K2, building the K1 was quicker and easier. Design wise the K1 is more "polished" in a couple of ways, firstly there were no "mods" to incorporate in the form of awkwardly mounted components and secondly being a simple radio meant less additional features in the menu making for more straightforward use (without needing to refer to the manual).

There are compromises in several areas with a K1, it doesn't cover many bands and the choice of bands is fairly limited. Mine has an 80/40 metre board and a four band board configured for 40/30/20/15 metres. Swapping boards is fairly simple but does require the reconfiguring of the "bands" within the menu and also re-calibration on 40m as it is available on both boards. If you have the internal auto ATU, this sits on the "band boards" and can be awkward to re-fit due to spacers on long bolts... an easy fix for this problem is to thread a small rubber band through each spacer which still allows for the bolt to rotate but stops the spacer falling off while mounting the ATU board.

An internal battery option might sound appealing, but it makes for awkward re-charging and warm freshly charged batteries may cause additional VFO drift.

Construction
My K1 dates from 2002, so I do not have a good recollection of building it. However, construction of a K1 is fairly straightforward for anyone reasonably good at soldering "through board" components. My K1 has an internal ATU (KAT1), wide range tilt stand and the back light modification (from Elecraft). I have also added a Cumbria Designs X-Lock 3 VFO stabilizer board (details at the bottom of the page).

Performance
On paper the receiver in the K1 looks a bit weak, as it uses an NE602 mixer for low power consumption. In practice the receiver performs very well, with little overload - even during night time use on 40m here in Europe. The two tone dynamic range with 20 KHz spaced signals is 86 dB, comparable to many transceivers from a few years ago and certainly not one of the poorer performers. The transmitter puts out a solid 5 Watts, with more on some bands if the power is turned higher, the maximum output is around 7 Watts.

Image performance varies with band, and is shown below.

Sensitivity is better than 0.25 uV for 10 dB signal to noise, improving to just over 0.1 uV on 15 metres. The K1 doesn't lack sensitivity.

Power output is close to the indicated level at 5 Watts and 3 Watts.

Harmonic output and other spurious signals on transmit are acceptable, but not exceptional at typically -42 dB to -50 dB below peak carrier (varies by band).

The KAT1 internal ATU is useful provided the antenna doesn't present too extreme a load, typical ribbon cable fed doublet antennas and random wires can be tuned although you may need to adjust the antenna lengths. By comparison, the internal tuner in a K2 will tune almost anything. See below for a simple modification that may help on the lower frequencies if your antenna is not a close match to 50 Ohms.

Since adding a "Huff Puff" VFO stabilizer board, drift has ceased to be an issue with my K1. My original drift figures were quite bad with a drift between 100 and 200 Hz per hour that didn't settle after more than 2 hours warming up. Note the K1 display often appears sluggish and doesn't give an accurate indication of slow frequency drift, I suspect this is because the software stops the last digit flickering between two digits. My measurements were made using an external counter locked to GPS.

Use
The K1 is a cute little radio that gives a good account of itself on air. The internal keyer suits my style of keying and the K1 has a pleasant near QSK break-in capability. The side tone is easily adjusted for both frequency and level via the menu. Dial calibration is also easy to adjust via the menu, however the frequency readout does appear to be +/- 100 Hz at times, possibly due to hysteresis in the display.

Playing stored messages and adjusting the internal keyer speed is easy without needing to access the menu system. Adjusting power output needs a visit to the menu, however as the menu has few entries finding the power level setting only takes a few seconds.

Changing band boards is better done at home, rather than in a field as the case and board screws are easily lost. In some cases it will be necessary to re-calibrate the dial (where a dual band board has the same band as a four band board, in my case 40m).

Those who struggle to tune their antenna with the KAT1 (internal auto ATU in the K1) may like to try the following modification in Adobe Acrobat(147 KB)

Another add-on for the K1 is a Cumbria Designs X-Lock, Huff/Puff VFO locking board. For details of how to fit one to a K1 click here (updated version 2 document, April 2013, 1.2 MB pdf)