I've seen smatterings here and there that basically indicate "choose what works best for you" - however I as well have yet to see a well put together technical reference or article that describes each of the filter settings and what they actually do/mean etc.
It seems appropriate that for advanced users an article or explanation should exist. Each filter setting should have a description of what the developer's intended result was (why invert vs normal) and other (why wide vs non-wide) and why normal vs off might be appropriate, as well as what each filter is actually doing internally.
Unless I'm missing something, right now we're just in trial and error mode.
In my #1 case of problematic receiving, which were several 800 MHz conventional police frequencies that were close in frequency to a strong control channel for the local smartzone of our state police TRS, I found that using the IFX with the invert filter worked superbly. The filters alone did not make an overwhelming difference for me by themselves. I too would like to see a detailed description of what the actual intention of these filters are. There is some description of a few of them at this link:
http://info.uniden.com/twiki/bin/view/UnidenMan4/SDS200FirmwareUpdate
But I think it would be helpful to understand the filters in a little more detail.Unfortunately, trial and error. Try each setting, the one that works best is the one to use (at that location).
Global means it is set to whatever the global filter setting is set to.
Normal is high pass. Invert is low pass. Wide is wider pass frequency.
Normal is high pass. Invert is low pass. Wide is wider pass frequency.
The right combination of filters and IFX if necessary does work, but it is interesting to read this. The hardware filters I have used, such as the ones from Par Electronics, are high pass, low pass, or notch. But in each case there is an actual frequency that signals above or below can pass, or a frequency or area of frequencies that can be notched out, such as the FM broadcast band. How does the SDS200 know where to start I guess for lack of better wording? My offending frequency is a strong Mot Type II control channel at 855.5375, and my frequencies that are affected by it were 855.4625, 855.2375, and 855.1125. So, if the SDS200 magically knows this I understand why the invert setting works (but with help from the IFX which is what really made the difference as I previously stated).
Other than that I'm completely missing something, which is entirely possible, or it truly is hit or miss. But as said the right combo DOES work, most importantly. This is why I'm curious as to a more in-depth description at some point about how they work. Thanks Paul.
Normal is high pass. Invert is low pass. Wide is wider pass frequency.
What on the display should I watch to see if there is an improvement when changing the filters or is it all by ear listening. Why would Uniden add the feature with no explanation, not everyone has attended Uniden University!