Microwave Data Systems MDS entraNET 2400 Especificaciones descargar pdf (Pagina 30)

20 GE MDS entraNET Reference Manual 05-4055A01, Rev. D

Invisible place holder

Figure 2-4. Power Connector

(polarity: left +, right –)

The transceiver must be used only with nega-

tive-ground systems. Make sure the polarity of the

power source is correct. The radio is protected from

reverse polarity by an internal diode and an on-board

fuse.

Power Supply

Connections at 28

Vdc

Common 28 Vdc supplies are often high-current power supplies

designed primarily to charge battery banks. The radio can be operated

from these supplies, providing there are no transients on the leads as

power is applied to the radio. Transients can be created that rise above

30 Vdc to a voltage that exceeds the primary voltage rating of the radio

and can destroy its voltage regulators and other components. It is impor-

tant to keep this potential hazard in mind when designing 28 Vdc power

supply connections for the radio.

• Use a two-conductor cable to power to the radio. Then the cur-

rents in the positive and negative wires are equal and opposite,

causing their magnetic fields to cancel. The result is no net

inductance in the connection to cause voltage overshoot.

• Do not connect a radio to a power supply that is already pow-

ered up, unless necessary (that is, when connecting a radio to a

battery bank and charger). When power is applied by switching

on a power supply, the rise time of the supply is too slow to

cause overshoot.

• Typically, there are multiple return paths for the negative side

of the power supply, through the coaxial cable shield and the

chassis, for example. Any imbalance in the currents in the

power cable results in voltage overshoot, so this should be min-

imized during initial power-up if the supply cannot be turned

off.

• Add a 1 to 2

Ω, 2 Watt resistor in series with the positive lead.

This greatly limits voltage overshoot. Since these radios draw

very little current in receive mode, and transmit only briefly,

there is little loss in power efficiency. In transmit, the voltage

drop is minimal and has no effect.

Wire Ports

Lead

Screws (2)

Binding

POSSIBLE

EQUIPMENT

DAMAGE

CAUTION

POSSIBLE

EQUIPMENT

DAMAGE

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