OPERATING MANUAL
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ST 401 ‘CAYMAN’ NLJD
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Range of radiated frequencies
2–3GHz
Max. peak radiated power
< 2W
Antenna polarisation
elliptic
Operation modes
‘Manual’
‘Automatic’
‘Audio’
‘Adaptive’
Sensitivity range in manual mode
40dB (5 values with 8dB increment)
Response indication
– visual
three 16-segment gauges
– aural
internal speaker or headphones
Power supply
two 3.7V Li-ion batteries (type 18650)
Time of operation on one battery charge
2–3 hours, depending on operation mode
Battery charging time
< 3 hrs
Operating conditions
– working temperature range
+5...+40°С
– relative air humidity
up to 85 percent (at 25°С)
Weight (with batteries)
< 0.9kg
Dimensions when folded
(length×width×height)
235х160х156mm
Weight of full set in case
3.7kg
1.4. Principles of Operation
ST 401 ‘Cayman’
is a nonlinear junction detector, or NLJD. Instruments of this type employ
active detection, i.e. they emit probing signals and analyse the return. Their primary search targets
are electronic devices, and those typically consist of circuit plates with conductive elements and
various semiconductor parts connected to them, such as diodes, transistors, and microchips.
The probing electromagnetic radiation induces variable electromotive forces in these loops, and
electronic components with a non-linear current-voltage curve transform the initial signal into its
higher frequency harmonics, which come back to the NLJD’s receiver.
Higher harmonics can also be re-radiated by corroded metal or the so-called MOM-diodes,
metal-oxide-metal structures brought about by contacting metal surfaces. However, these
formations return somewhat different spectra than semiconductors.
With
ST 401
one can distinguish with high probability between responses given by real
semiconductors, and those ‘faked’ by MOM-structures or corrosion. Another important advantage
is a confident detection of search targets behind partially screening obstacles, which is achieved
by simultaneously radiating several frequencies within the 2-3GHz band and analysing some
composite picture of the reflection spectrum, rather than merely the 2nd and 3rd harmonics, as is
done traditionally by other NLJDs.
1.5. Operation Modes
The
NLJD ST 401 ‘Cayman’
has the following modes of operation:
• primary search modes (MANUAL and AUTO)
• identification mode (AUDIO)
• adaptive self-tuning mode
• two optional search modes (OPT1&OPT2)
The two primary search modes are intended for the detection of responses from non-linear
components of various categories of objects, and their identification based on readings from three
multi-segment gauges. During search, the device can be operated with either manual or automatic
gain control (in MANUAL and AUTO modes).
In facilities packed with office equipment and other appliances that are certain to contain
semiconductor components, it is recommendable to use the AUTO mode, i.e. automatic gain
control. This provides for better detection against a background of strong interference, but
decreases the pick-up range. In the MANUAL mode, on the other hand, both maximum and
minimum pick-up ranges are obtainable, the latter being handy when looking for the exact
location of a suspect object. It should be noted that setting the receiver gain to its maximum will
increase the chance of ‘false alarms’.
In the AUDIO mode, a demodulated response from the target can be listened to via built-
in speaker or headphones, which may give the user more information as to the specifics of the
target, be it a live electronic device or an MOM-structure. This mode is used upon detection of a
questionable item in either search mode.
The adaptive mode serves to optimise the parameters in a given electromagnetic environment
and thus maximise the effectiveness of search. Engaging this mode is necessary every time the
device is switched on. It is advisable to repeat the procedure every once in a while during and
in between searches. During adaptation, the antenna must be pointed away from electronics and
large metal objects.
1.3. Main Technical Specifications
