Analog Mode Of Operation - ASTRO APX 7000 Basic Service Manual

Sec 2: 3-2
Figure 3-1. APX 7000XE Overall Block Diagram (VOCON Board MNCN6202/ MNCN6203)
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 either VHF or 700,800 bands
(see Figure 3-3), VHF or UHF1 bands
UHF2 or 700,800 bands
RMT Port
PER
AUX
SP3T
Antenna
40
Transceiver
Board
(see Figure
SW
DPLXR
2:1
To
RF/Vocon
Connector
Basic Theory of Operation: Analog Mode of Operation
Expander
Board
60
VoCon
Board
60
Option
Board
(see Figure
(see Figure 3-4), UHF1 or UHF2 bands
3-6) and VHF or UHF2 bands
700/800
VHF
2nd
LO
14
External accessory connector
External antenna
50
Front display*
80
Keypad**
30
50 20
Top display
Controls top
30
Note:
* Applicable to model with Front Display and
VOCON Board MNCN6202.
** Applicable to model with Front Display.
3-2), UHF1 or 700,800 bands
(see Figure
(see Figure 3-7).
SW
2:1
ΣΔ ADC Dec.
Filter
LO CLK
Abacus III
3-5),
SSI
18Mhz
CLK