A number of models have been proposed in the literature to predict the propagation path loss in built-up areas (urban and suburban) at VHF and UHF. However, none of these models is applicable at frequencies below 80 MHz. Other models proposed for application at frequencies between 20 and 10,000 MHz are only accurate when propagation is over rural irregular terrain. This paper describes the development of a path loss model applicable to frequencies between 3 and 450 MHz and propagation in urban and suburban areas. The model has been developed from path loss measurements at 3.195, 4.44, 16.08, 26.63, 49.8, and 446 MHz, where little reported data is available. In addition, previously reported VHF and UHF data have also been used to complement these measurements in the development of the model. The measurements indicate that even at frequencies as low as 3 MHz the electromagnetic field in an urban area will exhibit random spatial variations caused by multipath interference. Thus the received signal is best described in terms of mean and median signal levels. The model describes the frequency and range dependence of the median path loss and should be useful in predicting the performance of point-to-point and mobile HF/VHF communications links located in built-up areas and employing low-elevation antennas.