Actually, there is more to it than just the 5-pole filter offset. The panadaptor offset between the carrier and the IF center can shift as filter width increases because the K3 doesn't let the lower edge of the filter fall below 200 Hz. In CW mode for example, using a pitch of 600 Hz, there is a change in the offset required when the filter width exceeds the point where the IF center can be offset by the CW pitch frequency (where (200 + width/2) > 600).
I noticed this when hacking PowerSDR/IF-Stage here to make some improvements. The definition for command FI in the K3 Programmer's Reference states: FI * (I.F. Center Frequency; GET only) RSP format: Finnnn; where nnnn represents the last 4 digits of the K3’s present I.F. center frequency in Hz. Example: If nnnn = 5000, the I.F. center frequency is 8215000 Hz. Intended for use with panadapters, which need to keep track of the exact I.F. center frequency as filter bandwidths and shifts are changed by the operator. If you don't account for all this the position of the filter passband relative to the carrier frequency isn't displayed correctly on the panadaptor. Bob NW8L PA3CW wrote: > > Hi all, > I recently completed a small SDR receiver called PM SDR. I am using it > with HDSDR software. Currently i have it connected to the IF out on my K3 > to use it as panorama view. In the software HDSDR i have to set some > offset values in the different modes to have the PMSDR and K3 in sync. > That is going fine, however, when i switch my filters i.e. in CW from > 400Hz to the standard 3,7 kHz the synchronisation is lost and i need > completely different offset values. Why is the offset changing if i > change filters? Is there any way i can correct this in the settings of my > K3? > Thanks > Dick PA3CW > I'm sure you meant to say standard 2,7 kHz...not 3,7 kHz. The reason for the difference is that 5-pole filters (e.g. 2.7 kHz) have a large offset compared to 8-pole filters (e.g. 400 Hz). You can either install a 2.8 kHz 8-pole filter or compensate for the offset in your software. Unfortunately it is not possible to correct for this in the K3 itself. 73, Bill ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
