User Guide

Technical Documentation
NHD–4
System Overview
PAMS
Page 3–9
Original 11/97
Cellular Frequency Band
Phone
TX RX
Base Station
RX
TX
AMPS_7
824.040MHz
848.970MHz
869.040MHz 893.970
MHz
Figure 7. AMPS: Cellular Frequencies
The 800 MHz cellular band consists of two 25 MHz wide frequency blocks. The
individual channel transmit and receive frequencies are spaced 45 MHz apart and
each channel is 30 kHz wide. Note that the transmit frequencies for a Base Station
are the receive frequencies for a cellular phone and vice–versa.
AMPS_8 A = A system provider channels
B = B system provider channels
Figure 8. AMP: Ch # & usage
Cellular Frequency Band
Phone
TX RX
Base Station
RX
TX
AMPS_7
824.040
MHz
848.970
MHz
869.040
MHz
893.970
MHz
The 800 MHz cellular phone band was divided into two parts by the FCC for
competitive reasons. When cellular phone service was first started channel
numbering was from 1 to 799. Later when the bottom 33 channels were added a
nonconsecutive channel numbering scheme was used. Cellular phones that were
in use when only 799 channels were available would have tuned to an incorrect
frequency if the channel numbering had been changed when the new channels were
added. Close examination will show that both “A” and “B” providers have an equal
number of channels.
When cellular phones were first introduced they scanned all available channels.
Present day cellular phone’s scan only the Control Channels. Most phones will
scan only the “A” or “B” control channels even though they are capable of scanning
all 42 channels. Air time is less expensive if only the phone’s Home channels are
used.