RF Neulink NL5000-T - Manual (Page 16)

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High/Low Power
If RNet compatibility mode is not programmed into the unit, high and low power levels can be
programmed into the unit on a channel by channel basis. High power is selected by placing the
CSN input at a logic high state. Placing the CSN input at a logic low state chooses low power.
The CSN input has an internal pull-up resistor; it will assume the high state i.e. high power when
left unconnected.
Specialized Modem Operation
Modems designed to achieve the highest data rates possible in a radio channel may require a direct
DC connection to the modulation path and the removal of the limiter-filter. In order to receive
FCC Type Acceptance, the NL5000-T module must either be tested and approved with a specific
modem connected to the transmitter, or a modulation limiter and limiter-filter must always be
present in the transmit modulator audio path with the modulation inputs AC coupled. To allow for
the most flexibility for the end user, the unit was type accepted as a stand-alone unit. It is
possible, with hardware modifications and special programming software (not supplied with the
unit), to DC couple the AUX IN input and/or defeat the limiter-filter. The modulation limiter
would still be in place, but the deviation of the NL5000-T module could be set such that the
modulation limit within the NL5000-T module is never reached. The deviation would be set by
the modem level and the AUX IN gain setting. The end user/system integrator would then bear
the responsibility of obtaining type acceptance or operating in a frequency band where type
acceptance is not required. Contact RF Neulink for details. Note: Most modems will connect
directly to the NL5000-T without requiring any special modifications or programming.
Antenna Placement
The NL5000-T module is enclosed in a metal housing for RF shielding. However, RF emitting
sources located very close (less than 12 inches) to the unit can at times affect its operation. It is
not recommended that an antenna be connected directly to the module’s BNC connector unless the
RF output power is set for less than 1 watt or the module is placed within another RF tight
enclosure.
5.5 RNET COMPATIBILITY MODE
The NL5000-T module can be programmed to mimic some of the behavior of the RNet 450 radio.
In the RNet compatibility mode, the CSN input is used as a channel selector line. A logic low
selects channel 1 while a logic high selects channel 2. The channel select lines, CS0, CS1, and
CS2 have no effect. Also, the DCD output is held in its true state during transmit. It would
normally be false in transmit.