[Elecraft] Elecraft K2/100 in RTTY and PSK31 Modes

[Julian, G4ILO]

I have been very happy using my QRP K2 for PSK31 for almost 4 years. But 
there are a couple of issues which make it difficult to consider the K2 the 
best transceiver for these modes and be completely impartial.

The main issue is the limited VFO and BFO frequency resolution, which leads 
to a slight audio shift when you change selectivity. Unless you do 
something about it, this causes the audio AFC in the data mode software to 
compensate for this, with the result that the receiving station thinks 
you've changed frequency. If his AFC is also on you can chase each other up 
or down the band. I have worked around this using the macro facility in 
MixW to lock the transmit audio frequency before selecting a narrow filter. 
But it *is* a workaround, and one that isn't available to users of other 
digital mode software. (You can lock the frequency manually, of course, but 
you have to remember to do it. And to undo it, if you don't want to 
inadvertently end up working split...)

The other apparent issue with the K2/100 is drift, due to the higher 
temperatures if the PA is mounted internally. There's a mod to compensate 
for this, but I don't know if it stops it sufficiently to be satisfactory 
for data use. Others will have to comment on this, since I don't have the 
PA. All I would say is that it isn't necessary to run more than 10 or 20 
watts in PSK31, so the PA shouldn't warm up too much anyway. But if you 
want to compete with the big-gun RTTY guys, that's another matter.

The KDSP2 is, I think, literally redundant in RTTY mode as it is disabled 
in that mode. If it were enabled, I would say that it is unnecessary since 
the sound card won't be fazed by signals other than the one you're trying 
to copy. Additional filtering at audio will only increase the chance of 
distortion and degrading copy. The only useful filtering for digimodes is 
at IF. You can use a narrow filter to attenuate strong signals so you can 
still copy the weaker ones with good SNR. 

I've never needed to use the KNB2 in anger, so I can't comment on that.

For me, once the novelty of a new rig has worn off I lose inteerst in going 
on the air using pre-built appliances. The excellent general performance 
and unique design of the K2, the great sense of community among K2 builders 
and the fact that I built it myself add a great deal to my enjoyment of it, 
so that I'm prepared to live with this minor annoyance when working my 
favourite modes.

73,
--
Julian, G4ILO. (RSGB, ARRL, G-QRP)
G4ILO's Shack: http://www.qsl.net/g4ilo





  ==== Original message ====

> I am thinking of purchasing the Elecraft K2/100 for use in RTTY and 
> PSK31
> modes. I am a beginner in these modes. Can anyone help me with the 
> following
> questions?
> 
> 1. Is the K2/100 a good transceiver for RTTY, PSK31 and other digital 
> modes?
> 2. Does the KDSP2 DSP Filter help during digital operation, or does the
> soundcard perform the same function? I am wondering if the soundcard 
> makes
> the KDSP2 redundant.
> 3. Do you recommend the KNB2 Noise Filter for digital modes?
> 4. Any other comments are welcome.
> 
> Thank you very much for your help!
> 
> 73, Phil, WB6TQG