I have manually turned off all filters, primarily due to my not seeing any difference in reception. I set them all it off as a starting point and tried various filters to determine any differences. Finding none, I left them all off. But as these filter settings are contingent upon your location at any given time, I expect they are more useful when the scanner is stationary, when the SDS100 or SDS200 is used as a “base station”, meaning the scanner has been dedicated to one location. And since I use my SDS100 as a portable, a scanner I use when I leave my vehicle, filters don’t do much for me at all. (I’m not about to check each and every location for a filter setting I am at when I leave my vehicle.) As for close call, where the scanner’s reception is attenuated, it’s detrimental if I set a filter, which may cause its reception to be further reduced… so I don’t use them… at least that’s my take on it. But you can experiment if you choose. You may use your SDS100 in the same location routinely and find there is an advantage.
Its my understanding the filter settings were originally used by the bench techs at Uniden when they troubleshooted problems and Uniden decided to push them out to users as one of the promised software updates (which so far seem to be few and far between). All I’ve gleaned from this is Uniden’s ability to get input from users, turning us into beta testers when we report our results on the forums.
Bottom line, “Your results may vary”. My take is filter settings should be mostly detrimental when using close call. You can determine this yourself by experimenting. Uniden’s giving us this ability is appreciated but as stated, for myself, not useful.
As others have said - it's 100% location dependent.
And... there have been multiple, detailed posts here, on how to experiment with them.
Use search to read them and explore filters further...
That said, filters are to mitigate RFI - Radio Frequency Interference at a specific location.
Basically a strong signal close to the desired frequency, interfering with the reception of the desired frequency.
A close cell tower, another transmitter - even a bad florescent ballast or a badly made, cheap power supply - RFI can come from anywhere.
Filters are changing the IF in the receiver. In Unidens other scanners there's a separate special chip that works as a frequency counter and it most probably have to be the same in SDS scanners as using the receiver chip to cover all bands doesn't seem possible to do in such a short time as a second or two.
So CloseCall should not be dependent of any filter settings. Specification says it needs a signal of -55dBm to trigger a hit. The user manual for UBC3600 (BCD436EU) says it needs -70dBm to -60dBm, so slightly more sensitive.