1. Radio 101 for ESF #2 Webinar Presentation for ESF #2
2pm EST, Monday, February 28, 2011
Ross Merlin
DHS Office of Emergency Communications
The author is a senior telecommunications specialist with the DHS Office of Emergency Communications. His Federal emergency communications experience includes disaster response with the National Disaster Medical System, FEMA wireless management, DHS spectrum management, and now the OEC Technical Assistance branch. He is the author of the National Interoperability Field Operations Guide (NIFOG). You may contact him via .
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2. Public Safety Radio Bands
VHF-Low Band: 30 MHz to 50 MHz
VHF-High: 138 MHz to 174 MHz
UHF: 406 MHz to 512 MHz
700 MHz (new)
800 MHz
4.9 GHz (new)
These are the most common frequency ranges used by public safety agencies in the United States.
The lower the frequency, the farther the signal travels – less path loss.
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3. Can we talk? Most radios only operate in one band!
Multi-band radios are rare and expensive
If Agency A uses VHF and Agency B uses UHF, they can’t talk to each other unless they:
Use runners
Have face-to-face interoperability – co-locate at Command Post
Swap radios
Relay through dispatchers
Connect through a gateway
Even if direct contact by radio is possible, what is the procedure? Who do you call? How do you identify yourself on their system?
“I don’t know you – I’m not going to talk to you.”
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4. Propagation & Band Characteristics
VHF Low Band (30-50 MHz)
Best propagation in undeveloped and hilly terrain
Poor building penetration
VHF High Band ( MHz)
Very good propagation in undeveloped and hilly terrain
Moderate building penetration
UHF ( ; some areas or MHz; Federal Government MHz)
Good propagation in undeveloped and hilly terrain
Good building penetration
700/800 MHz
Poor propagation in undeveloped and hilly terrain
Very good building penetration
4.9 GHz
Microwave propagation used for short range (WiFi type) or point-to-point links
Better building penetration at higher frequencies due to ability to more easily pass through small openings, not to penetrate through solid walls.
Lower frequencies generally penetrate walls better (except for metal).
MHz, the UHF T-band – frequencies available in Boston, MA; Chicago, IL; Cleveland, OH; Dallas/Fort Worth, TX; Detroit, MI; Houston, TX; Los Angeles, CA; Miami, FL; New York, NY/NE NJ; Philadelphia, PA; Pittsburgh, PA; San Francisco/Oakland, CA; Washington, DC/MD/VA
Frequencies in the 421–430 MHz band are available in the Detroit, Mich., Cleveland, Ohio and Buffalo, N.Y. areas
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5. Frequencies vs. Channels
A frequency is a point in the radio spectrum
Part of what describes a channel
A channel is a set of parameters that can include one or more frequencies, Continuous Tone Coded Squelch System (CTCSS) tones, bandwidth, modulation, name, etc.
Example: VCALL10 is a channel with transmit and receive frequency MHz, transmit CTCSS tone of Hz, no receive CTCSS tone, bandwidth kHz
The terms “frequency” and “channel” are often used interchangeably.
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6. Continuous Tone Coded Squelch System (CTCSS) Tones
PL stands for Private Line, a Motorola trademark
Other names include Code Guard, Tone Squelch, Call Guard, Channel Guard, Quiet Channel, Privacy Code, Sub-audible Tone, etc.
Generic (vendor-neutral) term is CTCSS – Continuous Tone Coded Squelch System
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7. What Are CTCSS Tones Used For?
CTCSS tones are used to MASK interference
They DO NOT remove interference
Useful for masking interference caused by computers, electronics, etc.
Useful for masking interference from “skip”
Should NOT be used to block out traffic from neighboring (nearby) departments
This is OK for taxis, etc., but not for public safety
Creates “Hidden Interference” problem – missed calls possible
If two neighboring departments use different tones, department A will not hear department B when they are talking. This might sound like a good thing, but it is not!
Example:
Portable radio from department A wants to talk to the fire station of department A. The user keys up and calls for the fire station, but unbeknownst to him, the dispatch center for Department B is talking on the same frequency at the same time. The portable radio user doesn’t realize this because his radio doesn’t open the speaker unless the correct tone is received. Fire station A never hears the portable radio talking because the neighboring dispatch center’s signal is much stronger than the portable signal and overpowers it. The radio at fire station A never makes a sound because the overpowering dispatch center signal is transmitting the wrong tone. The result? The call goes unheard.
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8. Radio Programming
Programming a radio is not like programming a microwave oven
Oven: Universal programming tool (fingertip) works with all brands. Graphic User Interface (touchpad) similar
Radio: Every brand has their own tools: cables, adapters, software. No standard for frequency (MHz or kHz), CTCSS (frequency or code), Network Access Code (NAC) (hex or decimal), etc.
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9. Results of Improper CTCSS Programming
If Radio 1 is set for transmit (TX) tone only and Radio 2 is set for transmit/receive (TX/RX), both radios will hear each other. Radio 1 will hear any interference on the channel
If Radio 1 is set for TX tone only and Radio 2 is set for no tone, both radios will hear each other. Both radios will hear any interference on the channel
If Radio 1 is set for TX/RX tone and Radio 2 is set for TX/RX tone, both radios will hear each other.
If Radio 1 is set for TX/RX tone and Radio 2 is set for no tone, Radio 1 will not hear Radio 2. Radio 2 will hear Radio 1
ANY radio programmed with an incorrect TX tone will not be heard by radios using a RX tone, even though it can hear traffic from other radios
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10. Results of Improper Frequency Programming
You can hear other stations but can’t be heard
You can’t hear other stations but they can hear you
You can’t hear other stations or be heard
You can hear other stations when they are close to you, but can’t hear them when they are far away (via a repeater)
You are transmitting on an unauthorized frequency, causing interference to a different radio system
You are listening to a different radio system but think it is yours – you are very confused
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11. Simplex Very Reliable Limited Range Radio Channel uses 1 frequency
In Simplex communications, radios take turn transmitting or receiving on the same channel.
2-5 mile range for portable to portable communications is typical; up to 20 miles between mobiles or mobile to base.
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12. Duplex
Radio Channel using 2 frequencies: Frequency 1 to talk from radio A to radio B, and Frequency 2 to talk from radio B to radio A
Each user must be line of sight with each other
Examples: Cordless Telephone systems, which both parties can talk at the same time and listen at the same time. f1
Duplex is possible without a repeater, but this is not often used in public safety (few exceptions). f2
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13. Base Station – Height Improves Range
Some units don’t hear transmission because of obstructions
In this case, when Unit 2 talks, Unit 1 and the dispatcher can hear the transmission. However, Units 3 and 4 are out of range of Unit 2 because of the obstruction (mountain). In order for Unit 2 to communicate information to Unit 4, the dispatcher must relay the message.
Unit 1
Dispatch Center
Unit 4
Unit 2
Unit 3
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14. Base Station – Height Improves Range
Dispatcher relays message – heard by all units
When the dispatcher talks, all units hear the message because the base station antenna is elevated.
Unit 1
Dispatch Center
Unit 4
Unit 2
Unit 3
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15. Remote Base Operation Remote Link Dispatch Center Unit 1 Unit 4 Unit 2
Microwave, Phone Line, etc.
Remote link connects dispatch center to base station. Link can be via a phone line, microwave link, UHF link, etc.
Unit 1
Unit 4
Unit 2
Unit 3
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16. Conventional Repeater
Receives a signal on one frequency and retransmits (repeats) it on another frequency
Placed at a high location
Increases range of portable and mobile radio communications
Allows communication around obstructions (hills, valleys, etc.)
User radios receive on the repeaters transmit frequency and transmit on the repeater’s receive frequency
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17. Conventional Repeater
Dispatch Center
All units within range of repeater hear all transmissions through the repeater f2 f2 f2 f2 f1
When a user keys the radio microphone, the radio automatically switches frequency from its receive frequency to its transmit frequency. The repeater’s receive frequency is the same as the user’s transmit frequency, so it hears the transmitted signal. It instantaneously retransmits that signal out on the frequency that the rest of the users are listening to (their radio’s receive frequency).
Unit 1 f2 f1 RX TX
Unit 4
Unit 2
Repeater
Unit 3
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18. Conventional Systems
When one user is talking, other users on that channel cannot talk, even though other repeaters in the area may be idle.
Communicating
PD 1
PD 4
Idle
PD 3 cannot talk to PD 4 because PD 1 is using the repeater
PD 2
PD 3
If many groups need their own repeaters, it can tie up a lot of resources (e.g. towers, channels), especially if some groups only use their repeater infrequently.
Idle
Public works repeater may be idle 90% of the time, which means that frequency is largely wasted
FD 3
FD 1
PW 1
FD 2
PW 3
PW 2
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19. Trunking
Trunking is a method of combining repeaters at the same site (often multiple sites) to “share” frequencies among users
Spectrally efficient
Allows many more “virtual” channels (called talkgroups) than there actually are frequencies authorized to the system
Computer controlled
Trunking systems can be more efficient and cost-effective than conventional systems when more than about 5 channels are needed. Instead of having to install 15 repeaters, only 5 trunked repeaters may be needed (depending on traffic volume).
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20. Trunked System f1 f3 f4 f2 f2 f2 f1 RX TX f4 f3 RX TX f6 f5 RX TX PD 1
FD 1 f4
FD 2 f2
PD 2 f2
PD 3
Frequencies are dynamically assigned by system controller
User radio may be on a different frequency every time it transmits
Talkgroups are “virtual” channels
Possible to have many more talkgroups than actual frequencies
Statistically, not all talkgroups will be active at the same time
Multiple user groups utilize the same tower sites and frequencies. The system controller assigns frequencies as they are available on a priority basis. f2 f1 RX TX f4 f3 RX TX
System Controller f6 f5 RX TX
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Shared Repeater Bank

21. Trunked System Operation
User radios continuously monitor a dedicated “control channel”
When a user wants to transmit, the user’s radio makes a request to the system controller
If a repeater is available, the system controller temporarily assigns that repeater channel to the talkgroup making the request
Transmitting user’s radio will give a “talk beep”, indicating that a repeater has successfully been assigned…then the user can talk
All user radios monitoring that talkgroup automatically switch to the frequency of the assigned repeater and hear the transmission
When the transmission is complete, all radios return to monitoring the control channel
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22. Multi-Site Systems Conventional Trunking
Repeaters on same output, different input
Linked repeaters on different frequencies
Remote Receive Sites
Voting
Simulcasting
Trunking
Roaming
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23. Repeaters on same output frequency, different input frequency (or CTCSS tone)
Only one repeater active at a time
Users must manually change channel to different repeater depending on their physical location
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24. Repeaters on same output frequency, different input frequency (or CTCSS tone)
Only one repeater active at a time
Users must manually change channel to different repeater depending on their physical location
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25. Linked repeaters on different frequencies
Both repeaters active at the same time with same traffic, but on different frequencies
Link (microwave, phone line, etc.)
Users must manually change channel to different repeater depending on their physical location
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26. Voting Receivers
Voter (comparator) chooses best received signal and sends that signal to the transmitter
Voter
Central Transmitter
Link (microwave, phone line, etc.)
RX Only Site
Users do not need to change channel depending on location. System (voter) automatically picks best receive tower site.
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27. Simulcasting
Both repeaters transmit on the same frequency at the same time
Link (microwave, phone line, etc.)
Transmitters must be carefully synchronized to prevent interference in overlap areas
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28. Caller: “The radio system is down.” You: “What kind of system?”
VHF
UHF
700
800
Analog
Conventional Simplex 
Conventional Repeater*
Trunking Repeater
very rare
rare for PS
Digital
Conventional Repeater
The tower is “down”. Does that mean the tower collapsed and is a twisted mass of scrap metal on the ground? Or does that mean the tower site is not providing service because the equipment at the site is damaged or without power?
* Single site? Voted receive sites? Linked repeaters? Simulcast?
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29. Possible Points of Failure
User Radio
Untrained user
Trying to use beyond coverage area, or shielded by terrain
Loss of power (base station) or dead battery (hand-held)
Repeater
Loss of commercial power, backup battery or generator fuel exhausted
Antenna failure (wind or ice damage)
Catastrophic site loss (tornado, fire, explosion)
Link (T1 line, microwave link, etc.)
Loss of power
Antenna failure
Telco circuit outage (phone line, internet)
There’s no point sending an antenna installer if a generator technician is needed. With a few questions from you to the caller, you may be able to compartmentalize the problem.
Interference is a possibility at any location, under normal or disaster circumstances.
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30. Network Status
In a telco or cellular telephone network there is a Network Operations Center (NOC) that knows the status of the network
In Land Mobile Radio (LMR) there is no “the network”
Each radio system is independent
A statewide system or a trunked system may monitor the status of some components of just that system
No one place to go to learn status of all LMR systems
Commercial Mobile Radio Service (CMRS) networks may have a NOC; most public safety radio systems not CMRS customers, they are government-owned LMR
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31. Limitations of the Technology
Radios, without infrastructure, have a short effective range – line-of-sight
Repeaters extend range, but require power
Repeater systems and networks extend the coverage area, but increase complexity
Trunked radio systems increase capacity, but are much more complicated and are not easily transportable
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32. Regulatory & Operational Limitations
Users can not program radios – must be done by a technician (FCC Part 90; not so for NTIA). Some agencies’ radios are password protected - if their technician is not a first responder (and won’t share the password) field programming not possible
Rules are ambiguous and arcane; written for day-to-day operability and interoperability, not catastrophic disaster response
All radio frequencies used by responders should be coordinated with Disaster Emergency Communications (DEC) Group Frequency Manager before use
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33. Programming Limitations
Programming in the field, while under stress , is more likely to lead to errors
Front-panel programming takes a lot of time
Programming by computer takes time to setup the first time, then fast to program multiple radios with the same channels; model-specific hardware and software
Cloning to program multiple radios is fast, but requires model-specific cloning cable and radio passwords
Trunked radio system key needed to program radios, but seldom shared – system tech too busy to program key and freqs into visiting responders’ radios
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34. Problems You May Handle (1 of 3)
Call from state/local (other than simple question) didn’t come through state ESF #2
Refer caller to state ESF #2
Call about radio/telephone/Internet in Joint Field Office (JFO)
Transfer call to JFO Logistics Section, Comm. Unit
Question about radio frequencies/channels
Transfer to your Spectrum Manager
(continued)
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35. Problems You May Handle (2 of 3)
You didn’t deploy your Spectrum Manager?
Shame on you!
Spectrum Manager needs to be among the first boots on the ground – once behind, can never catch up
Fed/state/local or Private Voluntary Organizations (PVO)/Non-Governmental Organization (NGO) needs radios, needs help programming radios, needs help repairing/installing/acquiring antenna, needs temporary tower, needs WiFi, needs internet backhaul, satellite communications, repeaters, remote base stations, trunked radio system…
Get specifics, then task to DEC Group of ESF #2
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36. Problems You May Handle (3 of 3)
Before you start taking calls, work out with DEC Group whether they want to handle generator issues at communications sites, or whether those calls go to ESF #12 (Energy)
Offer to donate radios or comm-specific supplies, services, technicians
Track or transfer in accordance with JFO donations policy
Broadcast station needs help (including generator)
Refer call to your FCC liaison
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37. Making Friends
If FEMA installs equipment or an entire radio system for the locals, can the locals keep it?
No. Non-consumable items purchased with Stafford Act funds will be recovered, refurbished, and re-used on a future disaster; or disposed of through normal US Government excess property procedures
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38. Summary This radio stuff is complicated
Get the right information on the first call
FEMA can get it, whatever it is (if justifiable)
Spectrum Managers – don’t leave home without one
Some of the material in this presentation was adapted from
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