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Building a CHP detector box
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So...you're driving down the freeway and you want to go faster than
55mph? Well I can tell you how to do it without worrying about the CHP.
This idea is NOT a radar detector. And it does NOT work with local police,
only the CHP. It is a cheap version of the CHiPs detector you may have
seen advertised in Car and Driver for upwards of $300.
First...how it works. You may have seen local police with a two-way radio
clipped to their shirt pocket. They like this because they can immediately
call for backup if they get into trouble. These radios work on the same
frequency as their car radios and allow communication with the station
house (the base station). The CHP has similar personal mobile radios, but
they work on a different system. The reason for the difference is that
CHP officers may roam many miles away from their base station, unlike
the local police. A portable radio would not have the range to call back to
their base. So what the CHP personal mobile radios do is they work on a
different frequency than their car radios. This frequency is called a
mobile extender frequency. Their portable radios transmit to their car
radios, and their car radio takes the signal, changes it to it's own
frequency, and relays it back to the base station. The mobile extender
frequency radios that the CHP officers carry on them only have a range of
3 miles.
So, if you have a common police scanner (perfectly legal to own and
operate), and tune it in to the mobile extender frequency, whenever you
pick up anything on that frequency you know that a CHP officer is within
three miles of you. The stronger the signal, the closer he is. This idea
isn't perfect. You only can pick up the signal if the officer leaves his
portable radio on while he is in his car (they always do) and you can only
pick something up when something is being transmitted. Fortunately, CHP
officers constantly talk to their base.
So, to implement this idea in the cheapest manner, go to your local Radio
Snack store and get their cheapest scanner. Barring any sales, that would
be their two channel portable scanner that uses crystals. Buy it, and order
a crystal for the frequency 154.905 (it must be exactly this). A better
idea is to get a non-crystal using scanner for about $100. This scanner
can pick up any of thousands of frequencies without any add-ons being
required. Don't be confused if it is called eg. a "10 channel scanner". In
this case the ten channels are equivalent to the preset buttons on you car
radio. And like your car radio it can still pick up ALL frequencies within
the specified bands. The two channels of the crystal-using scanner really
refer to only two frequencies that it can receive. As you can see, the
more expensive scanner is vastly more useful, though the cheaper scanner
will work fine. Scanners more expensive than $100 usually only add bells
and whistles that you probably don't need. The $100 scanner does have
other useful features over the $50 one. You can plug it into the cigarette
lighter of your car and therefore you won't need to rely on batteries; you
can use your more sensitive car antennae instead of the one built into the
scanner, and you have the option of letting the more expensive unit scan
between the mobile extender frequency and the regular CHP frequency to
get a better feel for the officer's range and what he's up to. As with the
crystal-using scanner the frequency to tune into is 154.905.
Now you can drive at the speeds that the freeways were designed for. But please, if you use this id your seatbelts!
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