How well you can receive also depends on your location and what you're using for an antenna. If you're in Marysville, the stock rubber antenna is likely ok. But you could be in locations where either your radio's antenna can't "see" the tower you're trying to listen to or perhaps some other strong signal is interfering.
I am in Sacramento county and monitor the entire valley but use an outdoor antenna. It's not just how high in the air your antenna is, but the total elevation. In other words, someone could have an antenna 20 feet in the air but still be down in a canyon (therefore have poor reception).
When it comes to the CT value, I have my radios programmed to "search". When a signal comes in and 118.8 is displayed, it gives me high confidence that I am hearing Yuba county (in this case). As stated, you don't need to program it to listen. As a matter of fact, when you program in that value, the receiver must detect that frequency for it to consider there's a signal present. It's a means to "filter out" other signals on the same frequency that you don't want.
You indicate that you're not picking up Yuba County dispatch; how about Sutter County? How about Marysville or Yuba City PD? They are all in the same band of frequencies and knowing that could help figure out your issue.
