User's Guide

DANIELS
ELECTRONICS LTD
TM
3-6 CI-PM-3 Paging Modulator Instruction Manual
3.12 Simulcast Delay Setup
A typical Simulcast system is depicted in Figure 5-2. To correctly determine the differing
propagation path delays to each transmitter in a Simulcast system and compensate for them, signal
delays in both the transmission medium and the equipment must be known. For the purposes of
this manual, it is assumed that only Daniels MT-3 radio equipment will be utilized at each paging
site, and that each radio subrack will be identically configured with CI-PM-3 Paging Modulator
modules.
Signal delays from the base transmitter to any paging transmitter are calculated as follows:
Delay = t
(Link)
+ t
(Eqpt)
Where: t
(Link)
= Propagation delay from Base TX to Paging TX
t
(Eqpt)
=t
(RX)
+ t
(PM)
+ t
(TX)
t
(RX)
= Delay through Receiver
t
(PM)
= Delay through Paging Modulator
t
(TX)
= Delay through Transmitter
d = Distance
The delay through the equipment at each paging transmitter site, t
(Eqpt)
,will be identical for each link,
and can therefore be eliminated from our calculations. As such, the only delay variable(s) of
interest will be the distance from the base transmitter to each paging transmitter. Since radio waves
propagate at or near the speed of light (3x10
8
m/sec), the delay calculation becomes:
Delay = t
(Link)
= d (km) × 3.33 µ sec
or
= d (mi) × 5.37 µ sec
For the Simulcast system depicted in Figure 5-2, the signal transmitted by PAGING TX #1 will not
be delayed, as this is the furthest site from the BASE TX. However, to ensure identical signal
processing characteristics at each site, the DATA DELAY circuitry of the CI-PM-3 at PAGING
TX #1 will be enabled, but with zero delay selected. PAGING TX #2 will have its paging signal
delayed by a value proportional to the difference in distance between PAGING TX #1 and
PAGING TX #2 to the BASE TX. The delay for PAGING TX #2 is therefore calculated as:
Delay
(Link B)
=(d
(Link A)
(km) - d
(Link B)
(km)) × 3.33 µ sec
or
=(d
(Link A)
(mi) - d
(Link B)
(mi)) × 5.37 µ sec