Reciter - Tait TB8100 Installation And Operation Manual

Frequency Bands
and Sub-bands
2.1

Reciter

Receiver RF -
VHF Reciter
16 Circuit Description
Much of the circuitry in the TB8100 base station modules is common to
both VHF and UHF frequency bands, and is therefore covered by a single
description in this manual. Where the circuitry differs between VHF and
UHF, separate descriptions are provided for each frequency band. In some
cases the descriptions refer to specific VHF or UHF bands or sub-bands, and
these are identified with the letters listed in the following table.
Frequency
Identification
B band
C band
H band
K band
L Band
a. The actual frequency coverage in this band is:
Transmit: 762MHz to 776MHz, and 850MHz to 870MHz
Receive: 792MHz to 824MHz
The reciter comprises three boards: an RF, a digital, and an optional system
interface board. These boards are mounted on a central chassis/heatsink.
Figure 2.2 on page 18
and the main inputs and outputs for power, RF and control signals.
The incoming RF signal is fed through a low pass filter, then through a
band-pass "doublet" filter, and finally through a high-pass filter. The signal
is then amplified and passed through another band-pass "doublet" filter
before being passed to the mixer, where it is converted down to the
16.9MHz IF (intermediate frequency). A VCO (voltage controlled
oscillator) provides a +17dBm input to the mixer, and a diplexer terminates
the mixer IF port in 50Ω.. The signal from the mixer is fed through a 2-pole
crystal filter to the IF amplifier which provides enough gain to drive the
digital receiver. Note that there are two 2-pole crystal filters, one for narrow
bandwidth and one for wide bandwidth. The appropriate filter is selected
by software-controlled PIN switches, according to the bandwidth selected
Frequency Band and Sub-band
B1 = 136MHz to 174MHz
B2 = 136MHz to 156MHz
B3 = 148MHz to 174MHz
C0 = 174MHz to 225MHz
C1 = 174MHz to 193MHz
C2 = 193MHz to 225MHz
H0 = 400MHz to 520MHz
H1 = 400MHz to 440MHz
H2 = 440MHz to 480MHz
H3 = 470MHz to 520MHz
K4 = 762MHz to 870MHz
L0 = 850MHz to 960MHz
L1 = 852MHz to 854MHz, and 928MHz to 930MHz
L2 = 896MHz to 902MHz (receive only)
L2 = 927MHz to 941MHz (transmit only)
shows the configuration of the main circuit blocks,
TB8100 Installation and Operation Manual
a
© Tait Electronics Limited June 2005