Do you have any 5-pole roofing filters? In particular, is your wide filter a 5-pole 2.7 kHz filter or an 8-pole 2.8 kHz filter? The 5-pole filters have an offset, which is written on the filter and which is entered into the firmware with the CONFIG:FLx FRQ menu entry (or by using the K3 Utility). When a filter with an offset is selected, the IF changes by the amount of the offset. For example, if you have a filter with an offset of 1.0 kHz, then when that filter is selected, the centre of the IF bandpass is actually moved by 1 kHz relative to where it is when using a filter with no offset. If your panadapter takes its input from the IF Out port, input signals will move when you switch the receiver between filters whose offsets are different from one another.
There is also a per-mode offset between SSB modes and CW, AM or FM. This is not actually a change in IF frequency, but rather a change in the way the radio's dial frequency is related to the receiver's bandpass. In CW, AM and FM, the receiver's bandpass is centred on the dial frequency. In FSK D or AFSK A, the receiver's bandpass is centred between the mark and space tones, i.e. 85 Hz away from the dial frequency. In SSB or DATA A, the receiver's bandpass is centred above (USB and DATA A) or below (LSB) the dial frequency by approximately half the audio bandwidth (more accurately, by the DSP filter Fc setting). If the panadapter uses the dial frequency to label frequencies in the display, simply changing modes will result in a shift in the displayed signal relative to the frequency markers. There are a couple of other things that affect the relationship between the IF Out signal and the frequency displayed on a panadapter. One is the filter Shift control (or Hi-Cut and Lo-Cut controls) - when the filter Fc is moved, so is the IF relative to the signal frequency. Another was mentioned by Wayne in a recent post on another thread: in CW, with some combinations of sidetone pitch (low) and DSP filter bandwidth (high), the firmware moves the IF centre frequency to ensure that the low edge of the audio bandpass stays away from zero. Both of these effects are usually quite a bit smaller than the mode-to-mode or crystal filter offset differences, but they can be seen easily enough when you zoom in the panadapter display. There is a radio control command specific to the K3/K3S that software and the P3 can use in order to adjust the frequency display markings to compensate for these offsets, but generic software like HDSDR doesn't use that command. 73, Rich VE3KI VE5UO wrote: Hi, I have a K3s with a 400hz filter. I am using an SDRPlay (HDSDR) connected to the IF out port. When the 400Hz filter activated using the xfil button or tuning the DSP), the signal on the panadapter shifts up approximately 1.5khz. It seems to happen on all bands/modes. ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
