On Thu, 22 Mar 2007 18:25:21 +0000, Ron Hardin wrote:
That you don't hear the lightning crash means that the digital
and analog signals happen at different times, by at leash the
length of a static crash.

Perhaps the analog is delayed by the receiver, and the digital by
the transmitter, I don't know.

Both are delayed at the transmitter.

It takes time to do the data compression for the digital signal.

The analog is delayed intentionally, to ensure it comes out at the same
time as the digital so that things don't "jump" if (as you heard) it
blends to analog. I have heard FM stations that didn't get it right, and
did jump when going to/from analog. It's possible on AM too but I haven't
heard that yet.

There is also a bit of delay in the receiver - for decompression of
digital. The receiver also delays the analog to match. At least with the
BA receiver, this happens even if the station isn't transmitting IBOC. It
can be interesting to tune in a non-IBOC AM station on the IBOC receiver,
and simultaneously tune in the same station on an analog receiver. The
audio on the IBOC receiver will be noticeably delayed relative to the
analog set, even though the station isn't transmitting a digital signal.