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Field strength indicator and bug detector
ZAP Checker is an sensitive field strength indicator
that detects and displays electromagnetic RF signals over a wide
frequency range, developed around 2002 by Alan Susals of
Alan Broadband Co. in Fair Oaks (California, USA).
Several upgraded models were introduced over the years.
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The device responds to nearly any type of RF signal in its vicinity,
and has an adjustable sensitivity. Furthermore, its analogue meter
scale can be switched from logarithmic to linear, making it extremely
useful for bug finding.
Apart from the large and clear analogue meter, its provides a visual
indication by means of two LEDs, a red one and a green one, plus a
vibrator that can be switch on when needed. The image on the right shows
the initial basic model 180 which features a 10 MHz to 4.5 GHz frequency
range. The unit is housed in an ergonomic case.
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Later models had an extended frequency range and also provided an
acoustic feedback, allowing the nature of particular signals to be
identified more easily. In addition, some of the later models featured
a socket for connection of an external (directional) antenna,
such as a log-periodic one.
Unfortunately, ZAP Checkers are no longer in production as the manufacturer,
Alan Broadband, went out of business around 2012.
They are sometimes being offered on auction sites like eBay.
The device is only suitable for finding narrowband continuous wave (CW)
transmitters and wideband burst-type transmitters, such as WiFi base stations
and GSM phones. The presence of such signals in a room is easily detectable
and the device is quickly found. It is not suitable for finding
pulse-based bugs, such as the
CIA's SRT-56 transmitter,
due to the extremely low energy density of its 350 MHz signal.
Even when held against the antenna, ZAP produces no reading whatsoever.
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The ZAP Checker has very few controls and is extremely easy to use. Yet
it provides a quick and reliable way to check for the presence of RF signals.
The device is switched ON by turning the rotary knob away from the zero-position.
The same knob is used to adjust the sensitivity (30dB).
Once switched ON, the analogue meter shows the current signal level, assisted
by two LEDs (a red one and a green one) that provide a very useful feedback when
operating the device in the dark.
A slide switch to the left of the sensitivity knob, is used to select between
a logarithmic and a linear response of the meter, whilst another slide switch,
to the right of the meter, can be used to turn on the internal vibrator, which
can be useful for concealed operation. It provides a physical feedback, that
consists of a intermittent vibration that is proportional to the signal strength.
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The case of of the ZAP Checker can be opened by removing two small screws
from the battery compartment and separating the two plastic case shells.
This can be a bit tricky as there are three notches that hold the two
case halves together.
The image on the right shows the PCB, which is mounted to the rear of
the analogue meter. The big coil at the center is a non-resonant
helical antenna.
At first sight ZAP may seem a simple device, but
the real beauty is hidden under a
black epoxy blob just behind the antenna...
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180 10 MHz - 4.5 GHz 185 3 MHz - 5 GHz 190B 1 MHz - 8 GHz 300 1 MHz - 8 GHz with socket for external antenna 126 1 MHz - 14 GHz 270 Yellow with directional antenna
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Frequency 10 MHz - 4.5 GHz Length 128 mm Width 55 mm Weight 132 grams (including batteries) Antenna Internal Sensitivity 100µV (at the lower frequencies) Batteries 2 x 1.5V AA-size, 80 hours life (50 hours when vibrator is on)
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© Crypto Museum. Created: Sunday 21 May 2017. Last changed: Saturday, 06 October 2018 - 15:10 CET.
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