Dana Puopolo’s Guest Commentary, “Let’s Keep AM Sounding Good” (Jan. 19) contains a number of technical errors. Mr. Puopolo’s thesis hinges on the ideas that the thing which causes 5 kHz low-pass ...

There are many ways to disfigure a well-behaved spectrum. One subtle way that can often be overlooked is Group Delay Variation (GDV). There are a few system and subsystem specifications that seem to ...