Specifications

8
transmission.
What is Searching?
The AE 72 H can search for active frequencies. This is different
from scanning because you are searching for frequencies that
have not been programmed into the scanner. When you select
frequency bands to search, the scanner searches for any active
frequency within the lower and upper limits you specify. When
the scanner finds an active frequency, it stops on that frequency
as long as the transmission lasts. If you think the frequency is
interesting, you can program it into one of the banks. If not, you
can continue to search.
Conventional Scanning
Conventional scanning is a relatively simple concept. Each
group of users in a conventional system is assigned a single
frequency (for simplex systems) or two frequencies (for repeater
systems). Any time one of them transmits, their transmission
always goes out on the same frequency. Up until the late 1980’s
this was the primary way that radio systems operated.
Even today, there are many 2-way radio users who operate
using a conventional system:
• Aircraft
• Amateur radio
• PMR users
• Broadcast AM/FM/TV stations
• Many other business radio users
When you want to store a conventional system, all you need to
know is the frequencies they operate on. When you are
scanning a conventional system, the scanner stops very briefly
on each channel to see if there is activity. If there isn’t, the
scanner quickly moves to the next channel. If there is, then the
scanner pauses on the transmission until it is over.
Simplex Operation
Simplex systems use a single frequency for both transmit and
receive. Most radios using this type of operation are limited to
line-of-sight operation. This type of radio is frequently used at
construction job sites, and with inexpensive consumer radios
such as PMR radios. The range is typically 1.5-12 km,
depending upon the terrain and many other factors.
Repeater Operation
Repeater systems use two frequencies: one transmits from the
radio to a central repeater; the other transmits from the repeater
to other radios in the system. With a repeater-based system, the
repeater is located on top of a tall building or on a radio tower
that provides great visibility to the area of operation. When a
user transmits (on an input frequency), the signal is picked up by
the repeater and retransmitted (on an output frequency). The
user’s radios always listen for activity on the output frequency
and transmit on the input frequency. Since the repeater is
located very high, there is a very large line of sight. Typical