User's Manual

800MHz-900MHz Off-Air Repeaters (OR Series) Page 91 080 0716F – Rel.06
CHAPTER 3
3
• Tunnels with a length in the 300-meter to 600-meter range.
Also in this case, one single Off-Air Repeater is sufficient. The repeater is located at the entrance to the
tunnel and equipped with a leaky cable. This cable can be combined with a directional antenna to
irradiate a portion of the area in front of the tunnel exit (Figure 4).
FIGURE 4
• Tunnels with a length of more than 600 meters.
The signal can be enhanced in two ways:
a) By an Off-Air Repeater at the entrance to the tunnel, connected to a cascade of bi-directional
amplifiers inside the tunnel which re-generate the signal with amplification steps at a distance of
250mt. ÷ 400mt. from one another (Figure 5).
FIGURE 5
UP
DOWN
DOWN
UP
D
O
W
N
L
I
N
K
U
P
L
I
N
K
Power Supply
(230Vac)
48Vdc Power Supply
and external signals
OFF-AIR
REPEATER
POWER
SUPPLY
DC
DC
BF
RF
BF
RF-DC-BF
RF
UP
DOWN
DOWN
UP
AMPLIFICATION STEP
RF-DC-BF
BI-DIRECTIONAL
AMPLIFIER
RF-DC-BF
RF-DC-BF
RF-DC-BF
D
O
WN
L
I
N
K
U
P
L
I
N
K
BI-DIRECTIONAL
AMPLIFIER
Bias-T
OFF-AIR
REPEATER