We have experienced the following on stations, usually right after a major change is made such as returning to HD service or adding an HD2 or 3. It goes on for a few days or weeks until the engineer in charge figures out that something is wrong and probably gets on the horn with the manufacturer. Our receiver starts out in analog, in the usual way until it locks onto the HD1. When it eventualy loses the HD signal, it goes silent, popping between the HD-1 and silence, never to return to the analog mode. We cannot even force it to remain analog. What can we tell or Email the engineer?