27 September, 2009

K2 Fixed Level Audio Output

I started by making a very simple modification for a low level audio output with level that was independent of the AF pot setting.

The next step was to modify my front panel board by adding an audio output (mic plug) via a 25 x audio buffer and a zero-beat indicator which uses the same signal. The added circuit is built Manhattan-style on the upper right on the back of the front panel board, see image.

In this way three things are achieved:
  1. The amplified audio output is independent of the AF pot setting.
  2. The zero-beat indicator is also independent of the audio pot setting.
  3. The ‘no-wire’ philosophy of K2 is maintained, as there are no wires that need to be run to any of the other boards.
The schematic of the audio buffer and the updated zero-beat indicator is here. Note that the zero-beat indicator’s component values have some minor changes from the original design, that gave a nicer behavior of the display.

I also have added an optional signal from the sidetone circuit on the K2's control board (requires a plugable strap between the boards). This gives a visual check of the zero-beat indicator when you transmit, and it is also nice for demo purposes as both the received and the transmitted CW are output and can be decoded using e.g. a PC.

06 June, 2009

My Elecraft K2 Modifications

When I got my license in 2001, I discovered the Elecraft K2 transceiver on the internet and noticed the excellent reviews that it had received. Its receiver outperforms most, if not all, of the commercial rigs on the market. It combines state-of-the art performance with the thrill of building something yourself. It is also important for me that the kit designers encourage experimentation and modification.

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.

18 February, 2009

Morse lives on

Nice drawing of Bencher keyer by Dutch radio amateur
Dick Kraayveld, PA3ALM
Although morse has been more or less discontinued in a professional context, radio amateurs are active users of morse code. It gives me a kick every time I am able to receive and send morse code, something which a digital 'black box' never can give. The fact that morse has been replaced by satellites, internet and digital communications is as relevant as the replacement of horse transport by cars, sail boats by motor boats or bicycles by motor cycles. People still ride, sail and bike ... and use morse!