still ticking, although it suffers from
some limitations. These are, for the
most part, about to be eliminated by
the digital versions of radio. The question is why go digital when AM/FM
analog radio is still so popular? There
are several good reasons.
First, broadcast radio is very
competitive. Stations need to do
something exceptional to retain their
listeners and advertisers. Improving
sound quality digitally is one good
way. The success of the digital
satellite radio services that have
already been offered has, no doubt,
also spurred the industry into action.
Second, the technology is now
available to do it. Yes, I know — just
because we can do something with
technology doesn’t necessarily mean
that we should. Yet, that happens all
the time in electronics. PC technology
is a good example. Who actually
needs a 3 GHz, Pentium-based PC?
Few do, but we get them anyway.
Digital radio is now at that stage.
Finally — and this is the good
part — digital radio offers some real,
positive benefits. For example, both
AM and FM will have greatly
improved sound quality. AM will
sound more like the higher fidelity
FM, while FM will sound more like
CD quality audio. Music lovers will
appreciate this, as we have certainly
become accustomed to the superior
quality music and sound of CD, DVD,
and MP3 players; it is about time
radio catches up.
A key benefit — especially for FM
listeners — is the greatly minimized
degradation of the signal due to
multipath effects, which are caused
by signal reflections. There will be
less fading and drop out as you are
driving. This is not such a problem
with FM, but AM is affected by atmospheric effects, like lightning. Digital
transmission virtually eliminates all of
the pops, clicks, static, and other
noise associated with AM and FM
reception as we know it today.
Other benefits are new features
and data services. With digital
transmission capability, the radio
stations can now transmit station ID
information — such as call letters
and frequency — for display on the
receiver’s LCD or fluorescent output.
It can send the name of the artist,
album, and song digitally for display.
That’s a great feature and, with an
alphanumeric display, many other
items can be displayed.
A station may even have a
program guide. Short news briefs,
weather, traffic, and even financial
information can be transmitted, when
appropriate. Of course, if you have
digital data transmission capability,
there is always the potential to transmit
images, such as digital camera-like still
images. That remains to be seen.
There are a few downsides to this
new system. Aside from the extra cost
of a new radio, one potential problem
is adjacent channel interference.
There may be instances when a
station on an adjacent frequency can
interfere with the signal that you are
trying to pick up. The system has
been designed to reduce adjacent
channel interference, but, in some
high density population areas with
many stations, you may occasionally
hear some interference.
A second problem is interference
from distant AM stations. At night,
AM signal propagation changes
dramatically. During the day, the sun
ionizes the lower layers of the ionosphere, making radio wave refraction
such that only short distances are
viable. Without the sun, ionized layers
appear at a higher level, permitting
long range skip propagation; at night,
it is often possible to hear AM stations
from thousands of miles away.
Such signals could interfere with
the station you may be listening to.
Again, adjacent channel interference is
minimized by the system electronics,
but it could still be a problem. Initially,
the FCC is permitting IBOC AM operation during the day only.
How It Works
The new digital broadcast radio
service is referred to as high
definition radio (HD Radio). It is also
known by the name given to it by its
Circle #114 on the Reader Service Card.