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with care. A conservative figure of
1.0dB
, the factory default, is
generally benign.
Composite Clipping
has no effect on either the analog or digital
line outputs, even when they are set to their FM modes.
HD RADIO™ DELAY
The HD Radio digital broadcasting system, employed principal-
ly in the U.S., is a ‘hybrid’ broadcasting system. This means
that the all-digital signal carrier is transmitted ‘on-channel,’
simultaneously with the traditional analog FM (or AM) carrier.
Legacy radios are thus able to receive the program in the usual
manner, and new HD Radio receivers can recover both the ana-
log and the digital versions of the program.
Because there is an obligatory delay of some 8 seconds(!) in the
digital program encoding and decoding process, the analog sig-
nal must be delayed by this same amount to arrive in sync with
the digital signal. The HD Radio receiver first tunes and plays
analog audio to the listener, but then it cross-fades to digital
reception once the digital signal is acquired. If this were not
the practice, then using pushbutton presets would be an ago-
nizing process, much as digital-TV channel-surfing can some-
times be frustrating, though to a lesser extent because of
shorter delay in TV signal decoding.
This time-aligning “diversity delay,” as it is called, is enabled in
the DAVID IV with an optional accessory circuit board that is
simply plugged into a header strip on the main board.
Installing
the Delay
Subassembly
If you are adding the HD Radio delay option in the field, first
disconnect power from the unit. Then remove the top cover
and install the accessory board as shown here. Mounting
standoffs are already in place, just plug the accessory board
squarely onto the header strip so that the screw holes line up.
Fasten the board down with the screws that came with it. The
DAVID IV will recognize the board when it boots, and you can
then access and set up the delay menu.
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