drivers like to listen in to police communications as they are
driving. Either the local police or that of the more interesting highway
patrol communications. This (amongst other things), can alert the
driver to issues ahead of them on the road. To do this you need
what is called a "scanner". These scanners need a sensitive
antenna. The cleanest arrangement is to connect it up to the
antenna you already have in your car, the one in its windscreen.
This is not the place to explain the different
types of scanners. There are many types. One type has a
technology that sounds an alarm when you are within about 1 mile of
a Highway patrol car. One is the Uniden Bearcat BCT7 scanner
Fig 1 Bearcat
Scanner beside seat in 99VT
- How do these scanners work?
Well it turns out that the FCC has designated a very precise band of
frequencies that is used for highway patrol communications. The
actual frequencies can vary from state to state. The other
limitation is that the signal power is limited so as not to spill
over into other areas of the radio spectrum. For police cars
in remote areas this is a problem because they could not make
contact with the distant central office. To get around this the signal
is bounced from one police car to the next. It is "repeated" so an
officer talking to the central office bounces the signal from one
car to the next all the way back. This repeating process is
done completely transparent to the user. So at any one time, it
is common for many police car radios to be communicating with each
other - to pass on signals. Even though there may be only one car actually
talking to the central office.
The key factor is that this repeating of signals comes at a very
fixed frequency (different for different states) and can be picked up by a "Repeater Scanner". When the scanner picks up the
signal from a nearby car it will let the driver know (by a series of
beeps) that there is a
police car nearby -- in case you are looking for one for help!
Clearly such a system is not much use in a city, but it is on
highways or in remote areas.
OK so much for the theory! Now one critical
requirement for these scanners is a good antenna. In theory you
could attach a CB radio like antenna to one and get a great signal. This
is not an option for cars like this. Most manufactures supply a
wire that you string somewhere around (preferably outside) the car.
This I found leads to a weak signal ranging from somewhat helpful to
totally useless. The ideal way would be to connect the antenna up
to the radio antenna currently in the car. This antenna is located
at the top of the windscreen of most cars and gives a strong signal.
To do this will vary from car to car. I describe here how I did it in a
1999 Diablo VT and a 2001 Diablo 6L.
Attachment in a 1999 Diablo VT
Most cars have an Alpine radio system. It can be
just a radio and CD/tape player or the Alpine Navigational system.
In theory pulling out the radio should be simple. There is a plastic
Basel around the radio that snaps off exposing two latches on the sides
that holds the radio in place. If these latches are flipped up the radio
should slide out. Unfortunately this is often not the case. There
is a metal bracket that surrounds the radio preventing it from sliding
out easily (fig 2). After spending much time trying to get the radio out
this way, I realized that a simpler way is to remover the whole metal
panel that holds all the central instrument panel controls. This metal
panel is held in place with 8 screws. The removed tray is shown in
figure 3. There is a maze of wires under the panel. All the
connectors to the AC control unit, the suspension settings control, the
lights etc have connectors that allow the complete panel to be removed.
While you have this metal panel take a close look
at it. I have found that the flat black paint gets scratched over
time in the car. Keys etc being placed on it often scratch it. It
seems to have a very soft paint. Fortunately it can be re-sprayed
quite easily and effectively (fig 4). If the car interior is black, I
use Rust-Oluem High Professional Enamel Low Gloss Spray paint. (DE1634).
This paint when dry, stands up better to scratches etc during normal
use. Be sure to spray the tops of the nuts as well. It appears to
exactly match the color Lamborghini black color and texture exactly.
Ok lets get started. We need to locate and
disconnect the car radio antenna cable going to the back of the radio.
It simply pulls out on Alpine units. It is a black standard coax cable.
Cut about 6 inches from the end of this cable (fig 5) and peal back the
copper braded wire. With the central copper wire protruding insert a
standard coax cable connector (fig 6). These are available at any
electronics components store (e.g. Radio Shack). Also at the same
store obtain a "TV coax cable splitter box". This is a component that
allows one coax cable to be split into two outputs (fig 7) The
antenna coax cable from the cars windscreen in attached to the input
side of the splitter box. One output then goes to the short 6"
cable cut off above (now also with a coax cable connector) and to the
radio input. The other output of the splitter box goes to
the coax cable antenna connection of the scanner. So we have two
devices (Radio and Scanner) sharing input from the cars antenna.
The diagram is like this:-
| -----------> Radio
- Car Antenna
| -----------> Scanner
The reason we go through these elaborate lengths
to encase the splitter in a splitter box is that if one simply cuts the
coax wires and splices the new antenna connection with insulation tape
etc. we get an unshielded connection with severe loss in signal
strength. This way we get good signal strength on both devices.
Note do not use this approach to hook up a CB
radio. These send out signals to the antenna. The strength of such a
signal can burn out the input of a radio on the same wire.
Attachment in a 2001 Diablo 6.0L VT
The setup is similar for 6.0L Diablos. The
difference is that the radio antenna comes in to the a unit behind the
drivers seat. The reason for this that these cars have in fact Alpine
equipment to receive TV signals. They are outlined in the 6.0L shop
manual. I have never seen them used. Perhaps a project for a later date.
Anyway the coax cable needs to be split as described above. Figure 10
shows the splitter box in a 6.0L Diablo. This shows the setup
after the panel behind the drivers seat is removed. This can be easily
done by moving the seat full forward. Removing the 2 screws that hold
the panel to the floor and the 3 screws that attach it under the
"storage box cover" to the rear firewall.