[Elecraft] K3S DSP filter plots

[Don Wilhelm]

Charles,

I believe most operators use the RIT control rather than IF Shift to 
tune for off frequency stations.
The IF shift is normally used to reduce interference from an "offending 
station".  That along with the Width control can isolate a single 
station with ease and with the 50 Hz minimum DSP bandwidth, operation in 
a crowded band segment can actually be a pleasure - unless an extra 
strong signal gets past the roofing filter passband and activates the 
hardware AGC.

When you get your K3S, give it a try and I think you will find the use 
of RIT to be more effective.

Of course, if you ordered the KRX3, you can always go to SPLIT and 
eliminate the need for using RIT.  Split will cover a much greater range 
than RIT.
The KRX3 is not required to operate SPLIT, but if you want to 
dynamically listen to your transmit frequency and the desired signal at 
the same time, the KRX3 is the only way to do that.  Without the KRX3, 
you can use the REV button to temporarily listen to your transmit 
frequency, but you will not hear both frequencies at the same time with 
the REV button.

Yes, I realize this is a bit different than the discussion of filter 
shapes and the interaction of the roofing filter with the DSP 
filtering.  If it is not relevant, then please ignore my comment.

73,
Don W3FPR

On 11/16/2015 12:35 PM, charles at k5ua.com wrote:
>   
>
> Thanks for the reply Guy.
>
> I understand your rationale for aligning IF and DSP filters for
> additional out-of-passband rejection in crowded contest conditions.
>
> My concern stems from using IF shift to move the DSP filter within the
> roofing filter passband. The Elecraft rep I spoke to last week told me
> that the 8 Mhz IF roofing filter and the DSP filters do not track. The
> roofing filter is fixed and will present a fixed bandwidth in which the
> DSP filter can operate. Therefore, there will be an interaction between
> the two filters, the fixed roofing filter, and the DSP filter which can
> be moved higher or lower with the IF Shift control. If the roofing
> filter and the DSP filter have the same bandwidth, the interaction
> between the filter skirts creates a high cut or low cut condition
> depending upon the direction of the IF shift. If the IF can be shifted
> enough, a stop-band condition occurs and all signals disappear.
>
>