Analog Cell Phones and
Frequency Bands

Photo courtesy Motorola, Inc.
Old school: DynaTAC cell phone, 1983 |
In 1983, the analog cell-phone standard
called
AMPS
(Advanced Mobile Phone System) was approved
by the FCC and first used in Chicago. AMPS
uses a range of
frequencies between 824 megahertz
(MHz) and 894 MHz for analog cell phones. In
order to encourage competition and keep
prices low, the U. S.
government required the presence of two
carriers
in every market, known as A and B carriers.
One of the carriers was normally the
local-exchange carrier
(LEC), a fancy way of saying the local phone
company.
Carriers A and B are each assigned
832 frequencies:
790 for voice and 42 for data. A pair of
frequencies (one for transmit and one for
receive) is used to create one
channel.
The frequencies used in analog voice
channels are typically
30 kHz
wide -- 30 kHz was chosen as the standard
size because it gives you voice quality
comparable to a
wired telephone.
The transmit and receive frequencies of each
voice channel are separated by
45 MHz
to keep them from interfering with each
other. Each carrier has 395 voice channels,
as well as 21 data channels to use for
housekeeping activities like registration
and paging.
A version of AMPS known as
Narrowband Advanced Mobile Phone Service
(NAMPS) incorporates some digital technology
to allow the system to carry about
three times as many calls
as the original version. Even though it uses
digital technology, it is still considered
analog. AMPS and NAMPS only operate in the
800-MHz band and do not offer many of the
features common in digital cellular service,
such as e-mail and Web browsing. Read
about
digital cellular
service.
Let's take a good look inside a digital cell
phone.
Learn how to protect yourself from harmful radiation