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AID TX-602D →
The system was used by
law enforcement and intelligence agencies
like FBI and CIA in the years before GPS and GSM became
mainstream. It requires a VHF transmitter to be covertly
attached to the bottom of a suspect's car by means of a strong magnet,
with a small antenna hanging down. A nearby surveillance vehicle
was then able to track the car's movements unobtrusively.
The surveillance vehicle must be fitted with four identical antennas
that are mounted on the roof. They are connected to the RX-360
directional receiver which is mounted inside the vehicle.
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When driving, a digital compass near the dashboard shows the
direction to the target (i.e. the beacon).
The best results are obtained when using a compatible Bird Dog tracking
transmitter like the TX-602D
that is supplied with the kit.
These beacons transmit a modulated pulse train with adjustable
interval.
As a result, they can operate for six days on a single set
of three 9V alkaline batteries. In addition, the beacon
transmits a status signal that indicates whether the vehicle
is in motion. Using the system with regular Continuous Wave (CW)
transmitters
is also possible, but without the motion detection capability.
The RX-360 receiver can also be used for monitoring
regular listening devices in the same VHF-H band, but without
direction finding capability.
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Note that the remote control features of the TX-610 and TX-612 cannot be
controlled from the RX-380XT.
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The diagram below shows the basic setup of the Bird Dog 360XT.
At the far left is the target transmitter (beacon) that transmits an
intermittend signal. This signal is picked up by four antennas
that are switched in quick succession to simulate a rotational
movement. The receiver delivers its signal to a controller,
which converts it into an Angle of Arrival (AoA), which is
then displayed on the external display unit (the compass).
More about this under 'operating principle'.
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The diagrams below show the position of the four antennas on the roof
of the surveillance vehicle. for a proper and homogeneous radiation pattern,
the cross should be placed at the centre of the roof, with the arrow
pointing in the forward (driving) direction of the vehicle.
The four coaxial cables should be guided through one of the windows
into the car, and must be connected to the four antenna inputs (marked
1-4) at the rear panel of the receiver. Each cable is labelled (1-4),
and it is important that each antenna is connected to the corresponding
input.
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The complete direction finding kit is stowed in a large black plastic
Halliburton transit case that measures xxx × xxx × xxx mm and weights
xxx kg. The antenna base (i.e. the cross) is stowed inside the case
lid, behind the protective foam.
The receiver, the display, the beacon and all other
accessories and spares, are stowed in the bottom case shell.
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An external display unit shows the direction to the target.
It must be connected at the rear of the receiver and
must be mounted near the dashboard, within reach of the driver.
At the right is a circle with LEDs that indicate the angle to
the target. At the centre of the circle is a 3-digit display
that shows the angle more accurately. At the top left is a 1-digit
display that shows the signal strength.
The brigthness of the LEDs can be adjusted with the knob
at the bottom left.
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For an accurate reading of the angle to the target (the bearing),
the system uses four ¼λ antennas, arranged in a square and
spaced ¼λ apart. For this, an antenna mount with four strong
magnets is stowed in the lid of the transit case. It most be placed
at the centre of the rooftop of the surveillance vehicle.
The four antenna rods are stowed at the front of the bottom section
of the case.
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A telescopic arm with a large suction cup is provided for mounting
the display unit near the dashboard, with the suction
cup attached to the front window.
At the other end of the telescopic arm is a tapered plate which
mates with a shoe at the rear of the display unit.
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Although the receiver can be used with virtually any covert transmitter
that operates in the same frequency band, it works best with one of the
compatible tracking transmitters (beacons) that were available from AID.
It is powered by three 9V alkaline batteries and can be attached to the bottom
of a suspect's car (the target vehicle) by means of three magnets.
➤ More information
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The beacon is supplied with the short unobtrusive centre-loaded antenna
shown in the image on the right. The length of the antenna and the extension
coil near the centre are carefully calculated to match the transmission
frequency of the beacon.
Depending on the application and the situation at the target, other antenna
designs were available on request.
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The receiver is designed ot be powered directly from the 12V DC network
of a regular car. For use in trucks are large vans, it may be necessary to
use a 24/12V DC/DC converter.
For connection to the cigarette light socket that is available in most
cars, the power cable shown in the image on the right was supplied.
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Device Radio Direction Finder Purpose Vehicle tracking Model Bird Dog 360XT Manufacturer Audio Intelligence Devices (AID) Years 1995-2004 Receiver RX-360 Beacon TX-602D Frequency 150-174 MHz 1 Channels 6 2 Method Crystal-based Spread 1.5 MHz 2 Modulation CW/USB, Narrow-band FM Modes see below Motion Motion tracking only with Bird Dog compatible beacons Power 12-15V DC Dimensions ? Weight ?
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136-150 MHz on special order.
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All 6 channels are crystal-controlled and must be within a single 1.5 MHz band segment.
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The RX-360 receiver is our collection (S/N 0226002) is populated with the following
channels:
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Alpha 164.460 MHz Bravo ? - -
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- Pulse DF
- CW DF
- Voice 1
- Audible search 1
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No direction finding capabilities in this mode.
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© Crypto Museum. Created: Friday 19 January 2024. Last changed: Monday, 22 January 2024 - 13:06 CET.
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