Duplexers, Cables, And Antenna Spacing; Duplexers; Basic Specifications - Motorola CDR500 Programming Manual

Introduction to Repeaters and Components

Duplexers, Cables, and Antenna Spacing

Repeater Controller
X X X X
X X X X
X X X X
CDR500
Repeater
X
X
X
accessories with each repeater controller. Table 1-4
shows general compatibility for the other accessories
available with the CDR500 and CDR700 repeaters.
Additional accessories may be compatible if custom
programming is done on the CPS and/or accessory
cables are modified.
Duplexers, Cables, and Antenna
Spacing

Duplexers

The duplexer "isolates" the receive radio from the
transmit radio in the CDR500 or CDR700 repeater.
Without this isolation, the ability of the receive radio to
detect weak signals would be severely degraded by the
output signal of the transmit radio. Isolation may also
be obtained by using separate antennas with proper
spacing (distance) between the antennas. Less vertical
spacing is needed for a given isolation of land mobile
antennas than may be obtained easily with horizontal
spacing.
There are two basic types of duplexers:
• bandpass
• bandreject
The bandpass duplexer has two filters connected
together such that each filter will "pass" or appear
transparent to, a narrow segment of frequencies; the fil-
ters are tuned to different frequencies. Any signal
within the segment is transferred from or to the
1-4
Table 1-3. Accessory Compatibility (Audio & DTMF)
X X X X L3144, L3147
X X X X L3150
X X X X L3151
X X X X X HMN3000_
X X X X X AARMN4026, 4038
X X X X X AAREX4617
Table 1-4. Accessory Compatibility (General)
CDR700
Repeater Part No.
X HSN8145
X RSN4001
HLN9169
X HLN9455
Part No.
Accessory
7.5 Watt External Speaker
13 Watt External Speaker
CDR500 Wall & 19" Panel Mount
CDR700 Battery Revert/Float Maintenance Charger
antenna while frequencies outside of the segment are
"blocked."
The bandreject duplexer has two filters connected
together such that each filter rejects, or "blocks," a
narrow segment of frequencies. Again, the filters are
tuned to different frequencies but any signal outside of
the segment is transferred from or to the antenna
while frequencies within the segment are "blocked."
The choice of which duplexer configuration to pur-
chase may be dictated by the particular application. If
several repeaters and a CDR500 or CDR700 repeater
are to operate at a given location, the bandpass
duplexer might provide additional rejection to the sig-
nals from the other radios.
Basic Specifications
The basic specifications for a VHF or a UHF duplexer are:
• Impedance: 50 ohms
• Isolation: 70 dB minimum
Instead of the term "isolation," the manufacturer of
the duplexer may use the terms "Receiver (or Rx)
Isolation at the Transmitter Frequency" and "Trans-
mitter (or Tx) Noise Suppression at the Receiver Fre-
quency."
• Power handling: 50 Watts minimum
Power handling may be called "Continuous Power
Input" by the manufacturer. If a Lowband repeater
is being assembled with the low band Professional
6864110R66-O
CDR500 & CDR700 Repeater Service Manual
Accessory
Local Desksets
DC Remote Adapter
Tone Remote Adapter
Desk Microphone
Enhanced Keypad and Heavy Duty
Microphones
Telephone Style Handset
March, 2001