DSC Tech Library
This section of our technical library presents information and documentation relating to Emergency Broadcasting Systems and Disaster Recovery Applications.
Should an emergency arise in your community, our 911 broadcast service can deliver large volumes of calls quickly using thousands of phone lines simultaneously. In the event of a blizzard, wild fire or devastating flood, your community can be notified quickly given specific instructions if an evacuation is required using our emergency broadcasting service. If a dangerous chemical spill occurs in your community, you can target specific areas to call. If a severe snow storm hits your area, your community can be notified of school closings or event cancellations.
The following article relates to emergency broadcasting and how it is used in various communities today. This information was obtained from the internet with attribution to the author and/or community.
Alternatives to cellular communications in emergencies
National Terror Alert, www.nationalterroralert.com
When the power is off, phones go out and the internet is down, when police, fire, and hospital services are overwhelmed, amateur radio operators are there to take up the slack as emergency communcations volunteers. They have, in fact, been there in virtually all disasters in recent memory .. Hurricanes, fires, ice storms, earthquakes, floods and so on.
With a little forethought and a few bucks, you can prepare yourself for similar events in the future and avoid being incommunicado when you need it the most.
Here are some criteria for setting up an emergency communications system:
There are at least five communications systems that more or less meet these criteria. Some have big drawbacks, others minor ones. In making your choice, you should examine your own needs and match them with the appropriate system.
- 1) It should be easy to operate
- 2) have effective range
- 3) have a modest amount of protection against interference
- 4) be inexpensive (i.e. low initial cost, low maintenance and no monthly fees)
- 5) be readily available
- 6) be able to operate "off the grid"
In the late '50s, the FCC took a set of frequencies from the Amateur Radio service and designated it as the Citizen's Band. The rules were simple: a rubber stamp license, low power, ease of operation and channelized tuning. But the service was a relative sleeper 'til the '70s when movies like "Smokey and the Bandit" and popular tunes like "Convoy," with their "rachet jawin'," truck drivin' cowboys, captured the American imagination. That sent a stampede of otherwise respectable Americans onto the airwaves and the Interstate and overwhelmed the sluggish FCC which promptly abandoned the band to the mayhem that ensued. The Commission's only response to the millions of yahoos yelling at each other over CB was to expand the band to 40 channels.
If you haven't used a CB in the last 20 years, a few things may surprise you: 1) The units themselves are virtually unchanged (which leads one to wonder if they're still selling off excess inventory from the initial craze). 2) Prices for complete systems are cheap. 3) In many areas, the CB channels are relatively quiet. Advantages of using CB radios for emergency communications are considerable. Aside from the low price tag, lack of licensing and fees, they are operated on your car's 12v. electrical system and can be easily operated from home using a small, cheap motorcycle battery. Their range, depending on antenna type and placement, can be anywhere from one to fifteen miles.
Disadvantages of CB's are few, but persistent. Antennas tend to be large (4' to 8' on vehicles and larger for "base" or home stations). While much smaller antennas are sold, their effective range is drastically reduced. Transmissions tend to "leak" into all kinds of other electronic devices. In the home, CBers will often be heard on TV speakers, corded telephones, electronic keyboard speakers, etc. This was an aspect the FCC came to regret as the Commission was faced with hundreds of thousands of complaints from frustrated neighbors. Another problem is that sometimes, during favorable atmospheric propagation, range can be as great as several thousand miles. Thousands of people all hitting their mike buttons at the same time sets up an unearthly squeal and nobody gets through.
Prices for CB radios range from US$50 to $150 for full-sized mobile-mount radios to $230 for handheld portable units with AM/Single Side Band (SSB) capabilities. I recommend units with built-in Weather Radio receivers. Antennas are sold separately and range from $28 to $75 and usually have attached cables and connectors to simply plug into the back of the unit.
49MHz Personal Communicators
After the CB fiasco and before the Family Radio Service was established, manufacturers took advantage of FCC rules regarding transmissions in the 49MHz band. They built small, lightweight, self-contained, low power systems which featured a single headset with boom mike attached to the transmitter/controller which could be clipped onto the user's belt or pants pocket. Usually single channel operation only, some models are sold with as many as five frequency channels. All feature PTT (push-to-talk) mikes as well as VOX (voice operated) transmitters. The VOX feature makes them ideal "hands free" systems for cyclists, joggers or motorcyclists. Without speakers, the audio is heard only through the earphone. Early cordless phones, baby monitors and a few other devices share this band.
The advantage of this system is the extremely low power drain. Most sets are powered by only 2 or 3 AA batteries and can be in service for months. Their size makes them perfect for traveling lightand taking up very little space. The big disadvantage is limited range. Expect under a quarter mile coverage with these systems. This can be seen as an advantage when you don't want to battle hundreds of other people on your frequency.
Prices for 49MHz Personal Communicators range from $30 to $50 each.
Family Radio Service
Once again, the FCC has tried to give the average citizen a chance to use the airwaves with a new scheme they call the "Family Radio Service" (FRS). Here the Commission sought to re-dress the problems of the first citizen's band. They assigned the band frequencies in the UHF region (around 462MHz) which limits the propagation-induced range. They also limited the output to one-half watt and transmissions use Frequency Modulation (FM). All are small, battery-powered "handi-talkies" which can easily fit into a pocket. The Commission has again chosen channelized operation and this time has allowed 14 channels for use.
Advantages of FRS units are that they are very compact (typically 4" h x 2.5" w x 1.5" d) and weighing 6-10 ounces. The UHF frequency means they have very short antennas (typically only a few inches). Some units also have such useful features as optional headset/boom mikes for VOX operation, audible low battery alert and transmit LED. Some units feature 38 "interference eliminator codes" which are subaudible tones which let your unit respond only to other units transmitting a designated tone. Other notable features include a programmable scan feature and automatic "power off" (shuts down if not used after a certain period of time). The main disadvantage of these units is the relatively short range. While manufacturers claim up to two miles, don't expect more than a mile.
Expect to pay $50 each for basic FRS models, $90-$190 for higher-end models with additional features.
General Mobile Radio Service
The General Mobile Radio Service (GMRS) is like the FRS in that it operates in the 460MHz region, uses small handi-talkies and is intended to be used by individuals to communicate with immediate family members. The big differences are that GMRS requires an FCC license with a fee and users must be 18 years or older. In addition, the output of these units is considerably greater (1 to 5 watts), allowing a range of coverage from 5 to 25 miles, depending on terrain and antenna position.
There are 23 GMRS channels used on an unassigned basis and dependent on the cooperation of all users. The channels are split up for base, mobile relay and fixed station or mobile station use. Each license is assigned one or two of eight possible channels or pairs as requested by the license applicants. In order to avoid interference or conflicts in use, the FCC recommends monitoring existing frequencies in your area before making your application and requesting your channels.
The advantage of the GMRS is that this is the most useful of the previously listed services, but brings with it disadvantages of government oversight and stringent frequency assignment. GMRS radios are bigger than FRS units and have more features. Higher power means more batteries (as many as 6 AAs) and a higher price. Expect to pay $200 for handheld 2 watt units and considerably more for 5 watt base station transceiver.
The great grandpappy of the two way radio scene is the Amateur Radio service whose operators are known as Hams and who have pioneered radio communications since the first decade of this century. AR is also the most regulated of the non-commercial services, it can end up being the most expensive, but it can also be the most versatile and powerful.
All hams and their stations must be licensed by the FCC, and in order to receive a license, you must pass a written exam. Any license above the entry level also requires a proficiency in Morse Code. There's no fee for the license (which is good for ten years), no age requirement and operators are allowed to use any frequency for which their license qualifies them.
A nationwide system of repeaters on the 144MHz and 440MHz bands allows nearly seamless communications as hams travel around the country. These repeaters are built, installed and maintained by active and well-populated local amateur radio clubs. Traditional amateur frequencies in the shortwave bands provide excellent coverage for local, regional, national, and even international, communications. Unfortunately, there's not one radio for all of these capabilities which is why hams typically have three or four separate radios and antennas.
The easiest way into ham radio is via the "Technician" class license which requires a written test based on a text available through many sources. This class allows the user to operate(among others) in the 2 meter band (144MHz). Small handi-talkies for 2 meters are relatively cheap and give a range of 20-50 miles depending on terrain, power and whether or not you're using a repeater. Many repeaters provide access to 911 services through the handi-talkie.
Expect to pay $200-$500 for 2 meter transceivers depending on features. If you're planning to use Amateur Radio for your family, each member needs a Technician license and their own handi-talkie.
The FCC has made it illegal to modify any of these radios to operate in any band other than the one for which they were intended or to make it possible to place telephone calls from the radios.
Despite what sales people might tell you, or manufacturers' claims, none of these services offer privacy. Anyone with a similar unit or a scanner can tune into your conversations. You don't need to buy any of these transceivers to find out what's happening in your area in an emergency. Any scanner capable of tuning the VHF or UHF bands can tune in. Any shortwave radio capable of tuning as high as 27MHz can monitor the Citizen's Band. This is particularly useful in winter when you need to know about road conditions in your immediate area. Frequencies for these services can be found at the FCC sources listed below.
Additional Communication Devices
- Solar/Wind-up Radio