MTL Instruments CA Specifications

• Large bandwidth dc to 2GHz

• Robust — 10kA surge rating

• Range of connector styles to suit all

applications

• DC coupled

• Low insertion loss and VSWR

• Tested in accordance with

BS6651:1999

technical datasheet

CA Series

Wideband, high current devices for protection of radio transmitters and
receivers connected to coaxial feeders

The CA Series of surge protection
devices prevents surges and transient

over-voltages conducted through coaxial
cables from damaging electronic systems
such as telemetry outstations. They protect
vulnerable equipment without affecting
normal operation, passing high frequency
signals with little attenuation while diverting
surge currents safely to earth and clamping
output voltages to safe levels.

Typical applications for the CA Series
include the protection of radio telemetry
systems, mobile communications base
stations and, where high induced voltages
may be present, in aerial systems.

Receivers & transmitters are particularly
vulnerable to damage from the effects of

lightning. Their remote locations and physical
construction make them a likely target for
lightning activity. The use of semiconductors
and integrated circuits in transmitters and
receivers has rendered them particularly
prone to damage from these disturbances.

Excellent performance levels are
achieved using high energy gas
discharge tubes, in precision engineered

compact enclosures, to produce superior
surge suppression and transmission
characteristics. The protection circuitry is
capable of diverting 10kA impulses whilst
the brass bodies and connectors are silver
plated and are designed to meet harsh
environmental requirements.

A wide range of connector t ypes are
available (including BNC, N-type, TNC,
UHF and F-type) to suit all application

requirements. In addition, bulkhead mounting
options are provided for where insertion into
a panel is preferable. Models are supplied
with a choice of working voltage and
characteristic impedance (90V, 150V and
350V) are provided for most units in the range.

Mounting kits and enclosures to
simplify installation, are available for the

CA Series. Panel mounting can be achieved
using the MC range of mounting brackets,
or, for a larger number of units, the MK range
of busbar mounting kits can be supplied (for
mounting up to 20 units). IP65 weatherproof
enclosures are also available to suit every
application.

901-136 Rev F 020510

www.mtl-inst.com [e-mail]

TYPICAL PERFORMANCE

Limiting voltage

When choosing a surge protection device it
is important to determine the limiting voltage
for a given surge level. Figure 1 shows the
effectiveness of the CA350 series for a 6kV
overvoltage. The limiting voltage shows
the level of surge ‘let-through’ the surge
protection device - in this case just over 600V
for a fraction of a microsecond and represents
a very small amount of energy.

Attenuation characteristics

The inclusion of a surge protection device
should have minimal effect on a system other
than to safeguard vulnerable equipment. The
attenuation plot shown in figure 2 emphasises
how little the system is changed after fitting a
CA series SPD.

Figure 1 Typical limiting voltage for the CA350

Return Loss

Figure 3 shows the return loss for the N-type
variant of the CA series.

Equivalent circuit

An equivalent circuit model of the CAxx/N
is illustrated in figure 4. This model gives
reasonable agreement with measured
frequency response to 4.2GHz and return loss
to 2.5GHz.

Figure 2 Typical attenuation plot for N-type CA devices

Figure 3 Typical return loss for N-type CA devices

Figure 4 Equivalent circuit diagram

The give n data is only inten ded as a product de scription an d should not be reg arded as a lega l warranty of pro perties
or guara ntee. In the i nterest of fu rther te chnica l develop ments, we res erve the r ight to make de sign cha nges.

EUROPE (EM EA): [phone] THE AMER ICAS: [phone] ASIA-PACIF IC: [phone]

[e-mail] [e-mail] [e-mail] 901-136 Rev E 020510

INSTALLATION

Figure 5 shows a typical remote telemetry unit
(RTU). Signals are passed to the transmitter via
data cabling, shown here as a 4-20mA loop.
AC power for the transmitter enters the bottom
of the RTU shed.

For optimum protection it is essential to employ
surge protection devices where cabling enters
the RTU building. The antenna feed connects
directly to a CA Series SPD and then into the
tranmsitter using a short cable link. The CA is
mounted onto an MK2 mounting kit and an
earth connection using at least 2.5mm2 cable
is taken from the MK2 earth stud to the RTU
electrical earth, typically the enclosure earth
stud. This cable length should be kept to a
minimum to reduce the voltage drop across it
during surge conditions.

Data lines should be protected using an SD
series surge protector. These mount onto DIN
rail and provide an automatic, high integrity
earth connection via the DIN rail. Mains
powered equipment can be protected using
the MA Range of AC power SPDs.

Figure 5 Protection of a remote telemetry unit (RTU)

CA SERIES MOUNTING KITS AND ENCLOSURES

The CA series has a full range of mounting kits and enclosures to simplify installation. Telematic offers a choice of enclosures to suit every applica­tion. Panel mounting can be achieved using either the MC range of mounting brackets or, for a larger number of units, the MK range of busbar
mounting kits.

MK mount MC mount WP enclosure

Mounting options

MC1 mounting bracket for 1 CA device
MC2 mounting bracket for up to 2 CA devices
MK2 mounting kit for up to 2 CA devices
MK5 mounting kit for up to 5 CA devices
MK10 mounting kit for up to 10 CA devices

Weatherproof enclosures

WP3 Polycarbonate to IP65, holds 3 CA devices
WP5 Polycarbonate to IP65, holds 5 CA devices
WP12 Polycarbonate to IP65, holds 12 CA devices

The give n data is only inten ded as a product de scription an d should not be reg arded as a lega l warranty of pro perties
or guara ntee. In the i nterest of fu rther te chnica l develop ments, we res erve the r ight to make de sign cha nges.

EUROPE (EM EA): [phone] THE AMER ICAS: [phone] ASIA-PACIF IC: [phone]

[e-mail] [e-mail] [e-mail] 901-136 Rev E 020510

SPECIFICATION

All figures typical at 77°F (25°C) unless otherwise stated

Maximum discharge current (inner to
screen)

10kA 8/20µs pulse (to IEC 61000-4-5)

Maximum power rating (VSWR = 1, no AM)

DC

Sparkover

(V)

90 45 30

350 784 523

Limiting voltage

600V (6kV/3kA)

Bandwidth

2GHz

Maximum transmit

Power (W)

Zo=50 ohm Zo=75 ohm

Style Voltage Impedance Maximum

Frequency

(MHz)

BNC

N-Type

90

350

90

350

50
75

50
75

50
75

50
75

1000 <0.1

1000 <0.1

2000 <0.2

2000 <0.05

TNC

90

50
75

1000 <0.1

Typical

Insertion

Product

Name

CA90/B/50
CA90/B/75

CA350/B/50
CA350/B/75

CA90/N/50
CA90/N/75

CA350/N/50
CA350/N/75

CA90/T/50
CA90/T/75

De-rating for VSWR

Derate the applied power by a factor of

where r is the reflection coefficient

Additional de-rating for AM
Derate the applied power by a factor of

where D is the modulation depth

Inner to shield capacitance

< 1pF

Ingress protection (BS EN 60529)

IP65

Temperature Range

-40°C to +85°C
Weight
BNC 95g
N-Type 130g
TNC 95g
UHF 100g
F-type 95g
Bulkhead N-type 150g

Dimensions

See figure 6

Corrosion resistance

Silver plated connectors and bodies are
standard and stainless steel nuts, screws and
washers are used throughout.

UHF

90 50 2000 <0.1 CA90/U/50

350 50 2000 <0.05 CA350/U/50

F-Type

90

Bulkhead N-Type

90 50 2000 <0.2 CA90/N/50/B

350 50 2000 <0.05 CA350/N/50/B

*Information available on request.

75

(nominal)

1000 <0.1 CA90/F

Please note

All products are supplied with female connec­tors as standard.

There are a number of variants within the CA
range. Detailed technical performance data
for each device can be supplied on request.

EUROPE (EM EA): [phone] THE AMER ICAS: [phone] ASIA-PACIF IC: [phone]

[e-mail] [e-mail] [e-mail] 901-136 Rev E 020510

Connector A B C

Bulkhead N-type 27.0 19.0 18.5

Figure 6 Dimensions (mm)

The give n data is only inten ded as a product de scription an d should not be reg arded as a lega l warranty of pro perties
or guara ntee. In the i nterest of fu rther te chnica l develop ments, we res erve the r ight to make de sign cha nges.

BNC 18.5 20.0 18.5

N-type 18.5 19.0 18.5

TNC 18.5 20.0 18.5

UHF 17.0 24.0 17.0

F-type 16.5 19.0 16.5