Analog Mode Of Operation - Motorola APX 7000 Basic Service Manual

Sec 2: 3-2
3.2

Analog Mode of Operation

This section provides an overview of the analog mode receive and transmit theory of operation.
3.2.1 Receiving
The RF signal is received at the antenna and is routed through the Auxiliary and Multi Switch (SP3T)
ICs. The latter contains a switchable attenuator that is enabled at predetermined RF power
thresholds present at the antenna port. The output of the Multi-switch IC is applied to the first SPST
band select switch to select the either the VHF or 700,800 bands
bands (see Figure
and VHF or UHF2 bands
RMT Port
PER
AUX
SP3T
RMT Port
PER
AUX
SP3T
3-3), VHF/UHF1 bands
(see Figure
SW
DPLXR
2:1
To
RF/Vocon
Connector
Figure 3-2. Receiver Block Diagram (VHF and 700–800 MHz)
SW
DPLXR
2:1
To
RF/Vocon
Connector
Figure 3-3. Receiver Block Diagram (UHF1 and 700–800 MHz)
Basic Theory of Operation: Analog Mode of Operation
(see Figure 3-4), UHF2 or 700,800 bands
3-6).
700/800
VHF
2nd
LO
700/800
UHF1
2nd
LO
(see Figure 3-2), UHF1 or 700,800
(see Figure
SW
2:1
SSI
ΣΔ ADC Dec.
Filter
18Mhz
LO CLK
CLK
Abacus III
SW
2:1
SSI
ΣΔ ADC Dec.
Filter
18Mhz
LO CLK
CLK
Abacus III
3-5)