Service manual

3-1
March 2000
Part No. 001-3139-502
2000 SERIES RECEIVER DECODER MODULE (RDM)
SECTION 3 2000 SERIES RECEIVER DECODER MODULE (RDM)
3.1 GENERAL
The 2000 Series Receiver Decoder Module
(RDM) is designed for either operation with the 800
MHz or 900 MHz receivers. Refer to the Summit
®
QX Repeater Service Manual, Part No. 001-2008-102
or Summit QX Repeater Service Manual, Part No.
001-2009-100 for detailed information on the circuit
description. The RDM is powered from 15V DC and
operates in the temperature range of -30°C to +60°C
(-22°F to +140°F) with 10%-90% non-condensing
humidity.
The RDM decodes the subaudible data and four
levels of Received Signal Strength Indication (RSSI)
plus the condition of the squelch line, open or closed,
from the receiver. In the Remote site information is
then passed from the RDM, to the RMM, to the Local
Site CDM and then to the RVM. In the Local Site, the
RDMs are hard wired to the RVM.
The Multi-Net System is capable of handling 30
channels and the Voter System is capable of handling
32 voted receiver sites, the maximum number of
RDMs is 960
.
3.2 INITIAL RECEPTION
The RDM RSSI is squelch plus four additional
levels to the squelch settings. The opening squelch
setting is 6 dB SINAD plus four squelch settings at
10 dB, 15 dB, 20 dB and 25 dB, ± 2 dB.
The initial RSSI level is determined by averaging
the RSSI during the initial decode time. The averaging
is done by sampling during the subaudible “Word”
transmitted continuously from the mobile. The
“Word” is 225 milliseconds in length, the RSSI is
sampled every 10 milliseconds during this “Word”
period. The initial reception will be sent directly to the
Receiver Voter Module (RVM) via a 1200 baud FSK
blank and burst signaling on the main audio line. This
also indicates what Home, Group ID, Unique ID, Pri-
ority and Status has been received.