The development of the wideband quasi-coherent detector described in this paper resulted from the need for a low noise, very low delay FM detector for use in power line protection systems. At NTC-1975, Klapper and Kratt described the new detector and presented the results of their analyses of output distortion and performance in the presence of sine wave interference. Recently they have published a more detailed analysis. These previous authors showed that under usual operating conditions the detector output contains distortion components that are relatively small. They also found that in the presence of weak sine wave interference their detector performed approximately the same as the limiter discriminator. However, with a strong interfering carrier the Klapper-Kratt detector performed much better than did the limiter discriminator. The detector's performance in the presence of strong interference led to the inquiry whether the new detector might possibly provide threshold extension. The detector (without limiter) has now been analyzed with noise and found to perform identically to the limiter discriminator above threshold. However, threshold occurs at a higher CNR than that of the conventional limiter discriminator. The results of this analysis were confirmed experimentally by assembling and testing a version of the new detector family. It was also verified experimentally that the Klapper-Kratt detector preceded by a limiter prforms identically to the limiter discriminator.