Lisha,

If you want to tap into local police and fire bands, you'll need to get
a radio scanner which supports trunking. The easy way to get started
is to run down to Radio Shack and buy one -- they range between $80 and
$250 for handheld and base units.

There are a few things you should know first, however. There are
typically several police frequencies allocated for each district. You
should start by trying to find these out. Radio Shack sells a guide
which covers tri-state areas and is an excellent source. There are also
some good database references on the internet. Anyway, once you find
out these frequencies, you'll want to make sure you get a scanner which
can listen in on these.

Usually around the 866 MHz range or 155 MHz range, most scanners will
pick these up. You'll be able to tune in the scanners for a specific
channel. However, most scanners are not usually used in this fashion
(listening to only one frequency at a time). This is okay for listening
to one-way weather advisories and such. However, most of the time you
will scan through many frequencies and listen in on active ones. When
it becomes inactive (conversation silence), you can stay put or keep
scanning. However, you should know most most public organizations will
not simply broadcast a single conversation back and forth on a single
frequency; instead they use a different scheme.

With about a dozen frequencies allocated to them, a police station will
often implement what's called trunking. Special units are placed in the
trunks of police cars so that when an officer wants to make a call, the
unit finds an open frequency in the set and broadcasts on this. In the
transmission it also includes a special group ID code which uniquely
identifies the broadcast group. The problem with only using one
frequency is if many cops are sharing the same single frequency, it's
quite common to have to wait in order to broadcast. With trunking, they
can seamlessly broadcast without worry and without waiting for the line
to clear.

Therefore, to a person listening on one frequency, they will only hear
sporadic conversations. This is because it's possible for a
"conversation" to initiate on Freq A, be replied to on Freq B, be sent
the third time on Freq C, et cetera.

To tune in to a single conversation, it's important to get a trunking
compatible scanner. When you program in a group of frequencies for a
fire or police department into a trunking set, you can scan through the
whole set. This will allow you to listen to all the conversations on
this trunking set. When you find a particular conversation you want to
hone in on, you can HOLD DOWN a trunking button (at least that's how
you do it on the Radio Shack Dual Trunking model) and it will detect
the group ID being used and subsequently filter all conversations down
to only this group ID. Then you'll be able to hear a cop radio to
dispatch and vice versa, following an entire conversation thread end to
end.

One more thing, for trunking to work, each trunking set needs a
dedicated control frequency to send control messages. You can find out
which is the control by listening to the loud modem-like noises or
reference a comprehensive guide.

Also, there are two main types of trunking protocols, Motorola and
EDACS, as far as I know. Make sure your unit can support what your
local area uses. Happy scanning!

- D

Indexing topics: Want to access police or fire frequencies with a
scanner? How does police scanning work? What is trunking and how does
it work? How do I get started with scanning?



Lisha wrote:
This might sound like a stupid question but I never understood what trucking
actually mean???

Lisha
"Celt Chic" wrote in message
...
Hi everyone,

I'm sure everyone is going to sigh in boredom when they hear this
question, but I just bought a Pro-95 Scanner and I'm completely lost
to the whole trunking thing. I've read the manual three times, I've
checked out trunking web sites, and even read a site that pretty much
rewrote the manual. None of these help. I think my brain is in a
stage of rot. Can someone start me off from the beginning, say, by
teaching me how to program a basic Mot II trunking system in my
scanner? What all do I need to do? Please give it to me step by
step, and maybe then I can advance on to Edacs, and then possibly to
Mot I where it also requires fleet maps. They need a trunking book
for dummies because I really have no clue and would appreciate the
most basic help I can get.

For example, here is a set of frequencies that is published on the
trunkedradio.net for Radioland in Floyds Knobs, IN. What would I do
with it starting from the beginning?

System Name: Radioland 900Mhz (Indiana)
Location: Floyds Knobs, IN
County: Floyd
System Type: Motorola Type II Smartzone
Last Updated: 03-16-02 17:01
Hits: 14

System Frequencies
Site Description Freqs
001 Site-1 936.6875 936.7125 936.7250 936.7375 936.7500 937.6375
937.6500 937.6625 937.6750 937.6875

Thanks so much! Once I get the hang of this I know I could do
everything else on my own!

Another question, do all of the trunked systems have to start on
channel 00 in the banks, or can I have multiple trunked systems in
the banks? I believe I can only have motorla in one band and edacs
in another, but can I have multiple systems in each bank? For
instance, since edacs must be in order, can I have 12 frequencies of
edacs starting from channel 400 going to channel 411, and then have
another edacs system starting from channel 412 to channel 430?

Muchas gracias!

--
~~~~~~~Surfing Radio Frequency Waves~~~~~~~
Celt Chic - WA9012SWL
email me at (but first remove nospam)
In the process of moving my web page from http://www.ius.edu/sdean to
http://home.att.net/~monster-masher/
Web page last updated March 20, 2003.

System Name: Radioland 900Mhz (Indiana)
Location: Floyds Knobs, IN
County: Floyd
System Type: Motorola Type II Smartzone

System Frequencies
Site Description Freqs
001 Site-1 936.6875 936.7125 936.7250 936.7375 936.7500 937.6375
937.6500 937.6625 937.6750 937.6875

First off, I have never programmed a PRO-95 in the 900 MHz range, but
it should go like this:

First pick a scanner bank that's empty or at least doesn't have
anything important. Load the above freqs as if they were conventional
channels. In my case, Bank 9 is free so I'd store them in channel 900,
901, etc. Now scan those channels and listen for the one that emits a
continuous data stream (buzz or roar). That's the control channel.
When the PRO-95 stops there, press MODE until the mode indicator in
the upper right part of the screen says MO. (Available choices are FM,
MO, ED, AM.) If the PRO-95 is reading the data ok, you'll see MOT:
CNTRL appear at the bottom of the screen. (If people are talking,
you'll also see their talkgroup numbers on the screen.) Lock out the
other channels you entered.

Press PGM then TRUNK. Then press MODE until MOT appears in the bottom
line of the screen. (Available choices are "not trunked", MOT, and
ED.) You'll see some other stuff on the screen; ignore it. MOT is the
important setting.

Finally press SCAN and you should be in business.

You could delete the other channels instead of locking them out, but I
wouldn't, since some systems rotate the control channel among the
assigned freqs. If you turn on the scanner some day and find the
control channel dead, it's probably been moved to one of those other
freqs.

Note that there's a difference between setting a *channel* to trunked
mode (described in my second paragraph) and setting a *bank* to
trunked mode (third paragraph). These are two independent things.

You can set a channel to trunked mode even if it's stored in a bank
that's not set for trunking. Why would you do that? Well, suppose you
have a freq that sounds like a trunked system control channel. For a
quick check, just store it in any free channel. Try setting the
channel to MO or ED mode as you watch the display. That'll immediately
reveal if it's carrying Motorola or EDACS trunking data. For this, the
bank's trunking setting doesn't matter.

It also doesn't matter if a channel is set to a non-trunked (FM or AM)
mode. Such a channel is scanned like a conventional channel,
regardless of the bank trunking setting. In theory a bunch of
conventional channels can share a bank with a trunked system. In
practice I have found that doesn't work so hot. There's no quick way
to focus the scanner on the trunked system if an incident is breaking
there. I have to keep punching the lockout button to silence the
conventional channels sharing the bank. Then later I must remember to
unlock them. The whole business is such a hassle that I don't share
banks, though it means several hundred channels aren't available for
conventional use.

A Motorola control freq doesn't have to be stored in the first
channel of a bank. There can even be more than one active control
channel in a bank. (You might set the scanner up that way if a trunked
system has more than one repeater site within receiving range.)
HOWEVER, the PRO-95 will lock onto only one control channel and ignore
any others in that bank.

With EDACS, I think the last 2 digits of the channel number in the
PRO-95 must match the LCN (the EDACS channel number). For example, the
freq for LCN 3 could be stored in scanner channel 103 or 203 etc., but
not in 153.

--
Paul Hirose
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