Methods, apparatus, systems and articles of manufacture to verify radio station watermarking with software defined radios are disclosed. Example apparatus disclosed herein include a notch filter having a bandwidth and a center frequency corresponding to a first radio station broadcast signal, and a software defined radio front-end to downconvert a radio frequency band to a baseband signal, the radio frequency band including a second radio station broadcast signal different from the first radio station broadcast signal. Disclosed example apparatus also include a software defined radio application to tune to a portion of the baseband signal corresponding to the second radio station broadcast signal and to demodulate the portion of the baseband signal to generate audio data corresponding to the second radio station broadcast signal. Disclosed example apparatus further include a watermark decoder to detect a watermark in the audio data corresponding to the second radio station broadcast signal.