Theory Of Operation; Testing Rf/Microwave Sensors; Operational Tests - NARDA nardalert S3 Operating Manual

6 Cleaning, maintenance, repair
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Theory of operation

The NS3's patented design can be supplied with RF/microwave sensors
(2271/XX) that detect the electric field over an extremely broad
frequency range regardless of signal type or polarization.
The low frequency detector is a low-impedance, surface-area type
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designed to detect the radial fields that are characteristic of low
frequency communications systems. The diode based detection
operates in its "square-law" region to yield accurate results even in
complex, multi-signal environments.
A diode-dipole antenna is added to complement the low frequency
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sensor in the UHF region and to optimize detection of any and all
polarizations.
Higher microwave frequencies (>2 GHz) are primarily detected with
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thermocouple arrays. This detector is a true "square-law" sensor that
will always yield RMS average results, even in a pulse-modulated
exposure environment.
Individual outputs from all three detectors are processed by the NS3
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with their calibration information supplied by the sensor's imbedded
EEPROM. All units are individually calibrated to facilitate field
support.
The NS3's design utilizes RF shielding and absorbers to isolate it from
reflections or scattering produced by the monitor, or the human body. In
general, the monitor cannot detect microwave fields from behind the
body when it is worn on the front of the body. At low frequencies (<100
MHz), however, the body can act as an antenna and introduce energy
into the monitor, even when the source is from behind the wearer.
The sensors field response is by design:
0.1 to 10 MHz
= Radial Only
10 to 1600 MHz = Radial and Vertical
1.6 to 100 GHz = Vertical and Horizontal

Testing RF/microwave sensors

The NS3 includes a menu screen (Sensor Test) that allows users to
generate their own signal to see the monitor respond. Note that your
signal's power and frequency need to be sufficient to register a response
on the monitor. Users may find that a common "family radio" operating at
433 MHz and at least 2 Watts of power can be used as a simple, but
effective test source.

Operational tests

Units should be visually inspected for complete and correct battery
conditions, switches and overall mechanical integrity. Units should pass
the "Turn-on" sequence and indicate full or nearly full battery condition.
After successful completion of operational testing, units should be
connected to a computer through the Fiber Optic port, to verify
Nardalert S3