Operation; Channel Selection; Power Supply Voltage - Ritron DTXM II Series User Manual

4

OPERATION

4.1

CHANNEL SELECTION

Via the 15-pin connector, the DTXM 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 2.0 volts DC or left
unconnected (There is an internal pullup 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.
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.
4.2

POWER SUPPLY VOLTAGE

The DTXM-160, DTXM-260, DTXM-360 units and the 3 and 6-watt DTXM-460 units use 7.5 volt RF
power modules. Two supply voltage options are available for these units depending upon whether the
control/loader 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 11 and 16 volts. The RF power module in the 10 watt DTXM-460 unit requires at least 12 volts to
achieve 10 watts, although voltages as high as 15 may be used. Since the module is powered directly from
this voltage, the supply should be "clean" and, preferably, regulated. The output power will vary with
supply voltage. Switching power supplies can be used, but in models without the internal regulator, care
must be taken that the output waveform is low noise. Also, the module antenna should never be placed
near an unshielded switching power supply.
4.3 CURRENT DRAIN VS SUPPLY VOLTAGE
The current drain of the module is a function of the supply voltage, the RF output in transmit and the
regulator option. The internal 7.5-volt regulator is a switching type such that the current drain actually
decreases with an increase in supply voltage. Typical current drain values are shown in the table below:
Receive Mode
Supply Voltage
7.5 V
11.0 V
12.5 V
16.0 V
Transmit Mode – 1 watt output power
Supply Voltage
7.5 V
11.0 V
12.5 V
16.0 V
Internal Regulator
No
Yes
Yes
Yes
Internal Regulator
No
Yes
Yes
Yes
Current Drain
130 mA
100 mA
90 mA
75 mA
Current Drain
1.2 A
0.9 A
0.7 A
0.5 A