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Setting SSB filter BW with / shifts high pass below carrier - why?

dg7landg7lan
edited August 2022 in Configuration and Operation

Usually I change RX filter bw like this: Press "g" to jump to the frequency field, then type in "/4k" to listen to some wider SSB stations.

This seems to be relative to the center frequency of the filter, not to the tuned frequency. So the result is a filter that has the highpass at -650Hz and the lowpass at 3350. What I expected at first was a filter that starts at 0Hz and ends at 4k.

I know if someone tries to narrow in on a CW signal, things would be different.

So my question is: Can I change this behavior somehow? At least there is no good reason to let the filter flip over to the other sideband when increasing bandwidth.

I thing this might be on purpose but I just don't get the reason :-)

73s,

Andy, DG7LAN

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Comments

  • G8JNJG8JNJ

    Hi,

    It seems to be relative to the centre of the passband, as you have found.

    Try /-4000,0 for LSB or /0,4000 for USB etc. for asymmetrical filters, that works for me.

    A single numerical value may only work for double sideband signals such as AM, NBFM, DRM, I/Q etc.

    A better option for SSB may be to use shift and +/- magnifying glass zoom buttons, this also shifts the passband about the centre, but in a slightly different way.

    Regards,

    Martin

  • jksjks

    Starting a sideband filter at 0 Hz makes no sense at all. There is no reason any of the passband setting options should do that.

    Like Martin says, if you want a specific sideband filter then just specify it with the "slash comma" notation:

    /300,3k /100,4k /200,4.5k

    From our documentation, the full passband specification options are:

    /width (relative to pbc)

    /pb_lo, pb_hi (absolute lo and hi freqs)

    :pbc (use current pbw)

    :pbc, pbw

    Where pbc = passband center, pbw = passband width

  • dg7landg7lan

    Thank you both for the quick response!

    Yes, true, 0Hz doesn't make sense. Thanks for clearing things up! Next time I will look at the specific section in the manual more carefully.

    I really love how thinks can be handled from the keyboard in KiwiSDR

    73 and best regards,

    Andy / DG7LAN

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