My basic K2 with no options, serial #2198, was assembled in August 2001. I have later added the options that are needed to make all the front panel labels meaningful: the KSB2 single sideband option, KAT2 automatic antenna tuner, KAF2 audio filter and real-time clock, KNB2 noise blanker, and K160 160m/2nd RX antenna.
In November 2002, the K2 was revised, and many modifications have been included in the kit. My K2 has been modified so that it is up to date with the rev B version, the thermistor temperature compensation option, new crystals for the filters, and the CW key click modification.
My K2 has now grown up and is no longer only a 10 W transceiver, but also a 100 W version with the KPA100 and the KAT100 in an external enclosure. As there were fewer and fewer sunspots to help excite the ionosphere and shortwave conditions got worse, I compensated by adding 10 dB of power. I still enjoy QRP contacts, but for that special DX-contact it is nice to have a little extra power. The KIO2 RS232 interface has also been added recently.
Other Contributed Modifications
Five extra LEDs on the K2's frontpanel
- Increased headphone output (Dec 2001) (used with Yamaha HP-2 93 dB/mW SPL headphones, and removed for new Aiwa HP-CN5 with sensitivity 106 dB/mW)
- Trap for increasing 12 m image rejection to avoid broadcast interference from the 19 m band (Dec 2001)
- Low power CW zero-beat indicator (April 2002)
- Wider 10 m bandpass filter by just adding a single capacitor (March 2004)
- Buffer amplifier for audio output (June 2004)
- Remoting the KPA100 (100 W option) without a KIO2 (RS232) module in the K2 (Feb 2005)
- More reliable auto-detect circuit for keyer input using Shottky instead of silicon diodes (May 2005)
- Five extra LEDs and no holes to drill in the front panel (starting Oct 2005) (see YouTube video above)
- Using the KPA100 loudspeaker when the KPA100 is remoted (Jan 2006)
- Remapping of Keyer Speed Pot Range (March 2006)