In some embodiments, a radio transmitter assembly comprises a test signal generator module to generate a first instance of a test signal, the test signal comprising a code, a test signal receiver module which receives the code, a signal combiner to combine the first instance of the test signal with a real signal to create a combined signal, a radio signal generator to generate a radio signal from the combined signal, a signal separator to separate a second instance of the test signal from the radio signal, and comparator logic in the test signal receiver module to compare the code with a code embedded in the second instance of the test signal in the test signal receiver module.