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Introduction to Scanning
- Part II

Scanning –  Technologies

Scanning –  Technologies

Scanning –  Technologies

Other digital signals on the air

Scanning –  Who uses what?

Scanning –  Who uses what?

More about Trunking

More about Trunking

More about Trunking

More about Trunking

More about Trunking

Scanners – APCO Project 25

Scanners – APCO Project 25

Scanners – What do I need?

Scanners – What do I need?

Scanners – What do I need?

Scanning Resources

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Introduction to

Scanning

- Part II

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End of slide show, click to exit.

Introduction to Scanning
- Part II

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| Trunked and Digital Radio Systems
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| - Terry Stader, KA8SCP

Scanning –  Technologies

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| Conventional signals
| simplex or repeater
| analog – FM & NFM (25Khz/12.5KHz)
| most agencies use this now
| sub-audible tones used
| Digital Coded Squelch (DCS) & CTCSS (PL)
| all new assignments are now NFM (WPD)
| 483.125 versus 482.3875
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Scanning –  Technologies

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| Trunked (frequency hopping)
| multi-agency use
| can be VHF-Hi, UHF or 800/900MHz
| EDACS & Motorola are most popular
| as few as 3 frequencies
| 2 voice, 1 control
| as many as 28 frequencies
| multiple control, multiple voice

Scanning –  Technologies

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| APCO Project 25
| human speech converted to digital
| data & voice can co-exist on the same channel
| enhances use of Narrow-band FM
| provides an option for encryption
| can be conventional single frequency or trunked radio use
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Other digital signals on the air

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| Current modes
| Bo’s favorite!
| Several PARTers do this?
| Paging
| Golay, POCSAG, FLEX
| MDT – Mobile Data Terminals
| DES – Digital Encryption System
| ACARS - Aircraft Communications And Reporting System

Scanning –  Who uses what?

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| Conventional
| Wide-band FM
| NEMLEC, Littleton PD & FD
| Narrow-band FM
| Westford PD & FD

Scanning –  Who uses what?

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| Trunked
| EDACS/Ericsson
| Worcestor
| Motorola - Astro
| MSP, Cambridge, Logan
| APCO Project 25
| NH SP and many communities/counties
| Hanscom MP’s & Fire
| Nashua

More about Trunking

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| 3 trunking technologies
| Logic Trunked Radio (LTR)
| EF Johnson
| SmartTrunk
| Motorola
| EDACS
| GE/Ericsson

More about Trunking

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| Trunking Radio Systems were designed to compensate for the increased demand for public communications, the exponential growth of its users and the limited number of frequencies available in the radio spectrum.
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More about Trunking

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| A Trunked Radio System may contain up to 28 different frequencies, with radio users divided into groups (usually referred to as "talkgroups") with individual ID's. When someone in a talkgroup uses their radio, a brief burst of data is broadcast before each transmission. The Trunking System computer uses this data to temporarily assign each radio in the talkgroup to an available frequency. Once the group using the frequency stops broadcasting or pauses between replies for a few seconds, the computer removes them from the frequency, so that it can be made available to others. If the conversation between the same groups continues, they will automatically assigned a new frequency.

More about Trunking

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| Every Trunking Radio system utilizes at least one Control Channel. This is the frequency that the Trunking System computer uses to broadcast trunking instructions to all radios in the system. The "active" Control Channel is easily identified from the "buzz saw" noise found on the channel. Trunking Systems often shift their Control Channel to another assigned frequency in their system.
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More about Trunking

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| Trunking Radio Systems make use of the concepts of "timesharing", and "if you don't use it, you loose it" as far as frequency retention is concerned. Attempting to follow a trunked transmission on a regular scanner is next to impossible as the computer may assign multiple frequencies in the space of a few seconds. With a Trunk Tracking scanner, you will always be assured that you can follow a conversation between groups regardless of which frequencies they are assigned.
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Scanners – APCO Project 25

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| APCO-25 is a project headed by The Association of Public Safety Communications Officials to create a common architecture for two-way radio digital technology.  APCO-25 defines the standards that digital two-way radio communications networks will use so that interoperability is a success and so effective bandwidth utilization is maintained.   It also defines the technical standards such as Vocoder, bandwidth, signaling, and other features.  The PRIMARY goal of APCO-25 digital modulation is to reduce bandwidth requirements for public safety communications, NOT to prevent scanner listeners from hearing communications.

Scanners – APCO Project 25

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| APCO-25 systems that are totally digital will use a 9.6kb control channel.  This means that ALL radios on the system must be digital capable, and must be totally APCO-25 compliant.  It is VERY rare for a system to use this format.  The State of Michigan is one of the few systems that uses this format.
| APCO-25 capable systems that need ANY backwards compatibility with analog radios or talkgroups must use the standard Motorola Type II 3.6Kb control channel.  Most "APCO-25" systems in place today follow this format, since they need backwards compatibility with analog radios.

Scanners – What do I need?

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| Conventional/Analog
| Programmable
| Search capabilities
| 30 – 1000 MHz
| AM (air), NBFM & FM
| CTCSS and DCS
| Manufactures
| Uniden/Bearcat, AOR, Radio Shack, Yaesu

Scanners – What do I need?

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| Trunked
| Current models will do all modes
| Some will NOT do mixed modes
| conventional AND trunked in same bank a real plus!
| EDACS, LTR & Motorola
| Scanner Manufactures
| Uniden & Radio Shack

Scanners – What do I need?

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| APCO Project 25
| First generation scanners just coming to market
| Only 1 manufacturer today – Uniden BC-785DXLT & BC-250D
| requires optional digital card

Scanning Resources

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| Eastern Mass Trunking System Information - http://lynx.dac.neu.edu/s/stjohnso/ematrunk/index.html
| Scan Massachusetts - http://www.scanmassachusetts.net
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Scanning –  Technologies

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o

Conventional signals

n

simplex or repeater

n

analog – FM & NFM (25Khz/12.5KHz)

n

most agencies use this now

n

sub-audible tones used

p

Digital Coded Squelch (DCS) & CTCSS (PL)

n

all new assignments are now NFM (WPD)

p

483.125 versus 482.3875