Rf Coax Connections - Ametek UPLC-II System Manual

5.2.4 RF Coax Connections
The RF connections to the chassis are made using
the J1 and J2 female BNC connectors. The cable
used to make this connection must be a 50 Ω or 75
Ω coax cable, depending on the line tuner input
impedance. A knife switch is sometimes placed in
the rear of the cabinet housing the UPLC-II™ in
order to service it.
If the carrier is set for two-wire mode:
both the TX and RX would go through J1.
If the carrier is set for four-wire mode:
J1 = TX output & J2 = RX input.
5.2.4.1 Coaxial Cable for RF Connections
A coaxial cable is required for a shielded, low-loss,
path between the UPLC-II™ and the Line Tuner (in
the switchyard).
The type of coaxial cable we recommend is
RG-213/U (50 Ω, 29.5 pf/foot):
• #12AWG, (7–strand of #21AWG)
copper center conductor
• Polyethylene insulator
• Copper shield
• Vinyl jacket (nominal O.D. 0.405 inch)
We also recommend changing from RG-213 cable
to the smaller diameter RG-58 coax cable at a ter-
minal block once entering the cabinet. Alternately,
you can connect directly to a hybrid or some device
with a UHF type connector that can accept the RG-
213 coax. The inputs of the hybrid would then be
connected with RG-58 coax.
If the coaxial cable is to connect to related cabinets
enroute to the switchyard, you should connect the
RG-58 cable from J1 or J2, of the UPLC-II™, to the
related cabinets, and RG-213 from the cabinets to
the switchyard. Keep the coaxial cable as short as
possible and ground the outer braid of the coax only
at the end connected to the UPLC-II™ and not at
the line tuner end.
CAUTION
!
The UPLC-II™ does not ground the coax shield. It
must be externally grounded to prevent surge-
related failure to the UPLC-II™.
January 2016
Chapter 5. installation/Commissioning Procedure
Figure 5–1. Coax Connections
(ground at terminal block)
H 1 S B - R o r H 3 X B
R F H Y B R I D
(Female UHF)
Mounting
Screw
Ground
Figure 5–2. Coax Connections
(ground at hybrid)
In order to ground the coax braid (shield), you can
use an intermediate terminal block (Fig. 5–1) or one
of the UHF connector's mounting screws on the
hybrid (Fig. 5–2).
CAUTION
!
NEVER DISCONNECT THE CARRIER LEAD-IN
BETWEEN THE LINE TUNER AND THE COU-
PLING CAPACITOR UNLESS THE LOW POTEN-
TIAL END OF THE COUPLING CAPACITOR IS
GROUNDED. BEFORE DISCONNECTING THE
CARRIER LEAD-IN CONDUCTORS, CLOSE THE
GROUNDING SWITCH AT THE BASE OF THE
COUPLING CAPACITOR. IF THIS GROUND IS
NOT PROVIDED, DANGEROUS VOLTAGES CAN
BUILD UP BETWEEN THE LINE TUNER AND
COUPLING CAPACITOR.
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