An apparatus having corresponding methods comprises a signal generator to generate an radio-frequency (RF) signal comprising a ranging signal comprising a component of a television signal; a wireless transmitter to wirelessly transmit the RF signal; and a self-check unit comprising a receiver to receive the RF signal, and to recover the ranging signal from the RF signal, a pseudorange circuit to determine a pseudorange based on the ranging signal, and a self-test circuit to generate a self-test output based on the pseudorange.