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In the Forum: Off Air Audio
In the Thread: What to do in office?
Post Subject: The stations that broadcasting in digital.Posted by Romy the Cat on: 5/28/2009
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The fact that they are broadcasting digital streams over web has no impact over FM reception of cause. The problem is not “digital” but with the stations the embrace HD Radio. The HD Radio is very popular here in US and many do FM/HD simulcasts. To get a FM signal “clean”    from a station that does HD your multiplex decoder in your tuner shall have a filter that would sharply kill the garbage over 53kHz or 65kHz. You might look at the web for posdetection filters… Some tuners have it some not. Those that do not have it will be a problem with HD …

If the posdetection filter is simple to fix there is something else that is the bigger bitch. They sold a lot of HD radio in cars and they want the cars to have a reliable connection. If you run FM and driver into a bad reception area then you just pick a noise. If you are in bad reception area with HD then you completely loose the signal (like telephones). So, if you lose HD then they automatically switch you to FM (any HD receiver has FM logic). To do so the FM and HD feeds need to be synchronized and here is where the major problem arrives. The run one feed as a master and another as slave and the slave feed constantly delayed or run ahead of the master feed. So they in REAL TIME jerk the slave feed back and forth, synchronizing it with master. If the FM feed is the master then it is not a problem (the HD listeners are deaf anyhow) but if the FM feed is a slave then it is a huge problem as you can hear the artifacts of the feed jerking… So, it is all depends what kind listeners your station considers revealing and depends of how much the people who work at the station care about Sound.

I do not know anything about the DAB+ format. The FM/HD is all that we have here in Boston.

The Cat

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