K2 and PKS31 Questions and Answers
1. Is the frequency stability adequate for PSK31 operation?
The K2 works very well on PSK31. We have a large number of users running PSK31 and they report the K2's stability is more than adequate for this mode.
2. How easily can the receive audio be picked off ahead of the AF gain control for PSK, SSTV, RTTY, and other modes where it may be desirable to turn down the volume while demodulating the signal?
Most of our users are using the headphone output of the K2 for driving their sound card. (I use this myself at home.) Just insert the plug half way while tuning and then push it in all the way to stop the audio.
You can pick off the audio from the output of the K2's product detector at an internal option connector, but you will probably need to buffer it with a single transistor or op amp stage.
3. How easily can high level (.5 to 3 volts p-p) be fed into the SSB transmit audio by bypassing the microphone preamp?
Just about all of our PSK31 users are driving the K2 via the microphone connector with a small resistive voltage divider to set the level properly. There is a very good article in using the K2 on PSK31 on our web site at: http://www.elecraft.com/Apps/PSK31_2.PDF It includes instructions for all of the hook up.
4. How wide can the SSB bandwidth be set to make most advantage of the popular Digipan PSK31 software, which can see 3.5KHZ at a time?
The stock SSB filter in the K2 SSB option is about 2.2 kHz. The variable CW filter in the K2 can also be widened to around 2.2 kHz with slightly wider sloping filter skirts, so its apparent bandwidth will be a little more. In addition you can switch in the narrower CW filters on the K2 when QRM is near by. (It is important to note that the DSP filtering in programs like Digipan will not help for strong near by signals which will swamp the AGC of most radios in wide filter settings. The K2 gives you the best of wide and narrow settings for PSK31.
5. How will the 10-watt power amplifier, and later on, the 50-watt option withstand sustained full output operation with SSTV and some digital modes?
We recommend the K2 be run at 5W for most digital and SSTV modes. The high PA will also need to be run at lower powers (probably 50%) if you plan to TX for long periods (over 45-60 sec's.)