If you want to reliably monitor a single TG using a mobile antenna on the SDS100, you'll first need to make sure you're getting solid reception on a relevant simulcast, which for Fairfield I'm guessing your best bet might be West Orange assuming you're in range - the SDS can struggle with a small antenna if there's much distance involved (the town of interest may come through on other simulcasts as well - I'm sure someone can explain that far better than myself). I do this pretty routinely with my SDS100 using the site hold function, and once you know what works best you can also customize a FL to keep the scanner off other sites if you're just scanning from a fixed location. Also worth noting, even with strong reception on NJICS, I've found mine will occasionally lose it's lock on the control frequency and refuse to receive until rebooted. This happens randomly when I leave it parked to record my local PD for weeks at a time. Pretty rare though.
