RF Neulink NL5000 Rev B0 - Manual (Page 11)

NL5000 User Manual Rev B0 10
5.0 OPERATION
5.1 CHANNEL SELECTION
Via the 15-pin connector, the NL5000 supports one channel if the A/B pin (pin 4) is
programmed for high/low power and two channels if the A/B pin is programmed as
a channel select input. Channel A is set when the A/B pin is activated and the A/B
pin is in the logic high state i.e. above 3.5 volts DC or left unconnected (There is an
internal pull-up resistor on the A/B pin). Channel B is set when the A/B pin is
activated and the A/B pin is in the logic low state i.e. below 0.5 volts DC. If the A/B
pin is programmed for high/low power, channel A is always selected.
Internally, the NL5000 can store eight (8) channels. The first one or two are
selected via the 15-pin A/B pin, but the remaining channels can be selected within
the Configuration Software or via a special channel select command through the
RS-232 connection.
A change in the channel selection in receive will cause the receiver to operate on
the new channel. In transmit, however, the channel selection is only checked only
at the beginning of a transmission. Changes in channel during transmit will not
change the transmit operating channel of the unit until the unit is cycled from
transmit to receive and back to transmit.
5.2
POWER SUPPLY VOLTAGE
Pin 6 is the positive supply input to the unit. The type of module determines the
actual voltage that should be applied to this pin. One should be absolutely sure of
the proper voltage and current requirements before applying power.
Three voltages are used within the unit; +5 volts for the processor and logic circuits
along with most of the receiver, +7.5 volts for the transmitter driver stages, and the
supply voltage for the RF power module which depends upon which module is
used.
The VHF unit and the 3 and 6-watt UHF units use 7.5 volt RF power modules.
Two supply voltage options are available for these units depending upon whether
the modem board has a regulator installed. If a regulator is not installed, the
voltage should be 7.5 volts +/-10 %. This voltage should be “clean” and preferably
regulated since the RF power module is powered directly from this source.
Variations in voltage will cause variations in transmitted output power. Conversely,
if the control/loader board has a regulator installed, the supply voltage can be at
any voltage between 10 and about 15 volts. Although the use of the regulator
allows flexibility in terms of supply voltage, because of the amount of heat
generated by the regulator, significant duty cycle/key down limitations may apply
(see below).