Signal strength is usually measured on your satellite receiver by the RSSI voltage (Received Signal Strength Indicator) coming out of the satellite signal de-modulator, this voltage can be any DC voltage depending of the incoming signal strengths, the voltage is then translated by the recivers software to provide an indication on the screen as the "S" signal.
dB is used for a determination of loss or gain in a system, in the RF world dB is usually indicated as dBm, (dB plus or minus at 1 millivolt)(or lower voltages like uV or pV) a standard RF signal 2 way signal splitter used for TV or satellite is around a -3 dBm per port, this is equal to 1/2 the incoming RF signal at each port.
Normal RG-6 coax used for satellite work has a loss of about a -6.2 dBm at 1 GHz per 100 feet, this loss can be higher or lower depending on the frequency used, at 1 MHz it would be about .2 dB, at 10 MHz it would be about .6 dB, at 100 MHz it would be about 2 dB, so you see the higher the frequency the higher the loss. Also the coax has a bandwidth frequency rating, the normal coax used for TV or cable has about a 5 to 900 MHz operating bandwidth, the coax used for a satellite system needs to have a higher top end, usually around 2.5 to 3 GHz.