Brian Beezley, a retired software and circuit designer with an interest in IBOC, has taken another look at whether HD Radio stations in the SoCal area are time-aligning their analog and digital signals.
In the year since he last looked at this issue, he says the time-alignment of station signals he can receive from San Diego and Los Angeles from his hilltop in northern San Diego County has worsened.
The alignment wasn’t good for many stations, causing echos and other impairment sounds during the analog/digital blend, he said. Beezley told me that, going by his new measurements, it appears more stations have alignment problems and the problems they have are more audible. (The details are on Beezley’s Web site.)
Beezley developed a DOS program that station engineers can use to time-align their analog and digital signals. Using a few seconds of audio, the program calculates the delay between the transmitted analog and digital signal so they can be adjusted.