Sorry if I wasn’t clear enough.
In Discovery Mode without SSID broadcasting, my Time Capsule would display intermittently and show zero signal strength.
In Discovery mode with SSID broadcasting, I can consistently see my Time Capsule (about -58 dBm) and only one of two Airport Expresses (about -40 dBm). The visible one is a floor above me; the invisible one is about 10 feet away from laptop running NetSpot.
Airport Utility connects to all three APs.