frequency spacing
frequency spacing

Microwave RF Repeaters use bandpass filters to separate the transmit and receive signals from the radio terminals that pass through the repeaters. There are rules on what frequency spacings are permitted. When a repeater is detail designed in a radio relay network, these rules must be understood and followed. In general, the rules conform to those used by terminal radios. There are exceptions from time to time.

The two basic repeater specifications that apply are the Transmit to Receive (T-R) Spacing and the Transmit to Transmit (T-T) Spacing (same as Receive to Receive Spacing). Simple duplex equipment configurations are easy to understand as only T-R spacing applies. The more complex 1+1, 2+1, 3+1 and other multiline configurations demand more study before being able to reach a rule conclusion. Please see the following diagrams to understand more about the spacing definitions.

Configuration Drawings, Standard Duplex and 1+1 FD Duplex

Table 20, MW RF Repeater - Frequency Spacings
RF Repeater Repeater
Bandwidth, MHz
T-R Spacing
MHz, min.,
Common Feeder
T-T Spacing
MHz, min.
Common Feeder
RF-1500E 16 49 28
RF-2000E 20 50 28
RF-2000EW 30 80 42
RF-2500E 20 50 28
RF-4000 40 80 80
(with digital radio)
RF-4500 40 80 80
(with digital radio)
RF-6000E 30 80 56
RF-6000EW 40 100 80
RF-7000E 30 80 56
RF-8000E 30 80 56
RF-11000 40 130 80

The term Common Feeder refers to a single coaxial cable or waveguide used to connect all the signals under consideration to the microwave antenna. Configurations where Separate Feeders are used may have closer system frequency spacings.

Examples:

Separate transmit and receive feeders when dual polarized antennas are used.

Separate transmit and receive antennas, dual polarized T-R, T-R with adjacent channels on opposite polarization.

These Separate Feeder configurations require consulting with engineering for semi-custom work. The work is relatively easy but is not in normal documents.

V = Vertical Polarization. H = Horizontal Polarization
Channel Pairs: 1, 1' ; 2, 2' ;...6, 6'.