29
With few exceptions, such as the VHF Aircraft and Ma-
rine bands, almost every other VHF or UHF radio system
uses some form of coded squelch. By far, PL is the most
popular mode among non-trunked systems. For most
scanning use, try setting PL mode for all non-trunked
channels. If you operate the bank in open mode, the
scanner will display the appropriate code.
AM Mode
This sets the scanner to receive transmissions using am-
plitude modulation (AM). AM is used for aircraft, military,
some amateur radio, and some government transmis-
sions. When the scanner receives a transmission on a
channel set to the AM mode, it always stops on the trans-
mission.
FM Mode
This sets the scanner to receive transmissions using fre-
quency modulation (FM). FM is used for most public safe-
ty transmissions, as well as broadcast, business, and
amateur radio transmissions. When the scanner receives
a transmission on a channel set to the FM mode, it al-
ways stops on the transmission.
CODED SQUELCH MODES
(PL, DPL, AND TRUNKING)
PL Mode
This sets the scanner to decode subaudible tones that
are transmitted with many FM transmissions. Radio sys-
tem users use these tones to allow multiple users to
share a single frequency and to prevent interference from
other systems operating nearby on the same frequency.
When you select the PL mode for a channel, you can also
set a specific PL tone for that channel.
20-522.fm Page 29 Friday, September 17, 1999 12:46 PM
