Cross Band Split for the Elecraft K3



By itself, the K3 does not allow cross band split operation.   It is not possible for the user to enable SPLIT with VFO A on one band and VFO B on another band, even with the subreceiver installed and CONFIG:  VFO IND set to YES.  This would have been a nice capability for running on one band while doing S&P for multipliers on another band via the dual VFO windows in N1MM.  In theory, N1MM can automatically put the K3 into SPLIT mode when you send something from the VFO B window, but the K3 only allows that if the VFOs are on the same band.  It is possible, of course, to manually activate the A/B button, but that requires moving your hand from the keyboard to the K3 to push the button and it also causes N1MM to lose track of which VFO was making the contact (if that happened to be important).

Elecraft has had various requests for a firmware modification to allow cross band split, but they have stated that it would require a lot of relay switching of the low pass filters, among other difficulties, and that such a modification was not likely to occur in the foreseeable future.  I completely understand that, so I decided to see if I could accomplish essentially the same thing using N1MM rig control macros.  Here is what I came up with:

 
{CATA2ASC SWT11;} ~~~~ action {END} {CATA2ASC SWT11;}

where:

"{" and "}" are the N1MM command procedure brackets

"CATA2" designates VFO B

"ASC" designates an ASCII command syntax

"SWT11;" is the K3 macro for the A/B button

"~~~~" are four tildas in a row for a delay to let the K3 bandswitch relays settle (less than four did not seem to give reliable results)

"action"    is the string you want N1MM to send or the action you want N1MM to perform (send your callsign, the other station's callsign, your 
report, etc)

"{END}" tells N1MM that "action" is finished and that whatever follows is another command procedure


CATA2ASC is only executable if the window for VFO B in N1MM is active.  If instead the VFO A window in N1MM is active, N1MM will ignore the 
command to flip VFOs and it will only execute "action".  In other words, let's say that I have entered N6KR in the callsign entry field of Window 
A while running on VFO A, and I have entered WA6HHQ in the callsign entry field of Window B after finding him via S&P on VFO B.  If Window A 
is active, the following N1MM macro will transmit "N6KR" from VFO A, albeit with the delay caused by the four tildas:

{CATA2ASC SWT11;} ~~~~ ! {END} {CATA2ASC SWT11;}

On the other hand, if I make Window B active (such as by clicking on Window B, hitting the "\" key, or by clicking on the Window B bandmap, etc), 
that same N1MM macro will switch the K3 VFOs, wait for the relays to settle, transmit "WA6HHQ" on what had been VFO B's frequency, and then 
switch the VFO's back the way they were.

Since this macro actually performs an A/B exchange rather than a true split, I think that the correct LPF always gets activated so that there 
shouldn't be the usual concern about which bands can work together.  

I'm not sure I'd want to yank the K3 back and forth a lot like this in general (Elecraft was definitely right about the relays), but for multiplier chasing 
on one band while running on another I think it should be practical.

73,
Dave   AB7E