[Elecraft] K2 on digital modes.

[Dave Barr]

Hi Dennis

The is a another consideration for digital modes if you are planning to 
work RTTY as well as other digital modes.  In setting up my K2 a long 
time ago, I found much better results with narrow filtering could be 
achieved by using an audio frequency pair (mark and space tones) lower 
than the 2125-2295 standard suggested for most RTTY work.  Using MMTTY, 
I chose 915 for the mark frequency mark, although using 1275 or 1445 
should be fine.  With the high tones I was not able to get flat band 
pass shaping that was similar between the 15 meter-and-up and the 20 
meters-and-down conversion arrangements that the K2 has.   Some will 
warn you not to use low tones because of opposite sideband leak, but I 
have never had that problem, even when checking with a second RX in the 
shack.  I aligned my narrowest filter as low as 40 hz (nominally- it's 
actually much wider than that) and it worked well in crowded RTTY 
contest conditions.  I ended up with nominal filter widths of 40, 75 and 
135 hz.  For working PSK and JT65 and 9 you will probably want another 
filter set up as wide as possible.

73, Dave, K2YG