[Elecraft] K2 filter center frequency shift with band?

[Don Wilhelm]

Chris,

I see that Julian has given you some information already - the sideband 
reversal thing is correct..
I must ask just how much you need to move the mark frequency.  If it is 
only a few tens of Hz, then it is simply a matter of adjusting the BFO 
for LSB.  If it is in the range of kHz, then it is due to operating with 
the wrong sideband.  You must adjust the mark frequency in the 
application to match the filter center frequency in the K2 to use narrow 
filters.

I highly recommend that you activate the RTTY filter set because it 
allows the compression to be set independently of the setting used for 
SSB.  I usually set the RTTY FL1 filter the same as that used for SSB 
FL1, but also set FL2 thru FL4 to 1.0, 0.7, and 0.4 kHz with the filter 
center at 1000 Hz.  Greater audio frequencies may exceed the K2 BFO 
range capability, and 1000 Hz is a compromise that is easy to remember.  
Tune the desired signal to 1000 Hz (with the VFO) on the waterfall 
display and you are ready to switch in a narrow filter when that 
rock-crusher comes on close to your desired signal.  The same applies to 
all other digital modes, not just to RTTY.

73,
Don W3FPR

Chris Kantarjiev wrote:
> I'm playing in the RTTY Roundup this weekend, using a simple AFSK setup
> with my K2. For some reason, when operating on 15m I need to shift
> the Mark frequency to get the signals to fall inside the filter.
>
> This doesn't match up with how I understand the K2's filters to work;
> I expect the center frequency of the filter to be the same regardless
> of the band.
>
> What am I misunderstanding?
>
> 73 de chris K6DBG
>   
>