A friend of mine told me I'd need to use a "filter" setting for Simulcast systems, I am looking for a filter option for the Central VA Communications System [Lynchburg area], Hanover County, and the Roanoke systems. Thank you.
From what I've read, there's actually no real guidance saying which filters to use for which situation. I think it is trial and error for the individual. My SDS-100 worked on my local simulcast systems using the default filter setting.
One of the two Invert settings generally work the best for me as well.
For 800 MHz systems, I find Invert works best for systems with strong or good signals as this filter attenuates the signals more than the others.
For weaker 800 signals, a Wide Invert works better for me as it has slightly less attenuation.
The 700 MHz band is mostly unused around me. For this band, I can usually set the filter to Off which does not attenuate anything and gives great results.
All bets are off for UHF 450 MHz signals. I usually can't pull a still strong but weaker signal out with an SDS series regardless of filter settings. I'm obliterated by nearby UHF signals and the 8 or 10 MHz wide front end used by the tuner chip simply allows it all in which wipes out all but the strongest. The available filters are way too wide to work for UHF in my environment. So my SDS models are used mainly for trunked scanning in the 700 MHz and higher bands.