User Manual

DIGITAL MICROWAVE SYSTEM 915
8000-0395-02, Rev. B
SETUP AND SERVICE GUIDE 3
Tuning Procedure
The DMS 915 has been pre-tuned at the factory. If
the detector is performing satisfactorily, no tuning
is required.
To tune the detector, do the following:
1. Using the laptop configurator or Psion
programmer, program the Power Pack to
the following settings:
E Generator Frequency - 111.5kHz
System Type - 915
RF Power - 10
Select RF Bank - 903-905
Alarm Settings - n/a
Number of Hits - 1
Tag Too Close - On
RF Frequency - 904.2
RF Modulation - Off
2. Connect the oscilloscope probe to the
“Recovered Modulation Monitor” test point
located in the IF Module (Figure 1). Set the
vertical sensitivity to 1Volt/division and the
time base to 0.5 millisecond/division.
3. Move a tag around in the field and change
its orientation until a signal of two volts
peak to peak is observed on the scope. If
necessary, the amplitude of the E-Field
Generator can be adjusted to achieve this
value.
4. Adjust the variable capacitor on the antenna
side of the Impedance Matching Filter until
the signal on the scope is at a maximum.
Adjust the variable capacitor on the power
pack side of the filter to further maximize
the signal amplitude. Repeat this
adjustment sequence of the capacitors until
the signal reaches its maximum peak value.
Note: If the amplitude of the signal exceeds
four volts peak to peak at any time during this
adjustment, turn the E-Field amplitude down to
two volts peak to peak to prevent saturation of
the amplifiers and consequently false readings.
5. Using the configurator, reset the System
Type to “915HOP” after tuning has been
completed.
Figure 1. DMS Power Pack
Tx/Rx Tx/Rx I F O
RF
Transmitter/
Receiver
I F I
IF FM Detector
Processor
E-Generator
Connect
matching filter
and one RF
antenna here
Connect other
RF antenna
here
Programmer
Input
Recovered
Modulation
Monitor