A few images I use when describing satellite footprints and beams.
A few images I use when describing satellite footprints and beams.
Two images to help provide a gauge of orbital heights compared to the Earth’s size.
Just a few graphics on atmospheric opacity lifted from the internet to help explain why some waves get through the atmosphere while others don’t.
Reprinted from Urgent Communcations at http://urgentcomm.com/disaster-response/when-going-gets-tough-hams-get-going
When the going gets tough, hams get going
A handheld radio, portable antennas, extra batteries and cables, a soldering iron, clean clothes, snack bars and a length of rope.
That’s some of what you’ll find in a “go-bag.” And if you’re one of the many amateur-radio operators who volunteer during local emergencies, you always keep a go-bag packed. When disaster strikes, you grab it and rush to a Red Cross shelter, an emergency operations center (EOC) or some other activity hub to do what you do best — get messages through, despite all sorts of obstacles.
They don’t often get a lot of publicity, but amateur-radio operators — or “hams” — play an important role in emergency response.
“They’re a prime example of a grassroots effort,” said Keith Robertory, manager of disaster response emergency communications at the American Red Cross in Washington, D.C. “They live where the disaster occurs, and they already have the equipment, the knowledge of the location and knowledge of how the disaster would impact that location. So they’re immediately there and can start doing work.”
Hams often swing into action well before a storm or other event causes havoc on the ground. During hurricane season in the Caribbean, for instance, hams in that region keep their eyes on the weather out their windows, said David Sumner, chief executive officer (CEO) of the American Radio Relay League (ARRL) in Newington, Conn. They use their radios to call in observations to the National Hurricane Center in Miami.
As the storm passes, it might knock out power and damage antennas, “so they rig another antenna, start up the generator, and they’re back in business,” Sumner said
When hurricanes, blizzards, ice storms, earthquakes, tornadoes or other forces of nature cause widespread damage, hams get to work wherever they’re needed. In some cases, they transmit messages to take the place of two-way radio or phone systems that have been rendered inoperable in the aftermath of a disaster.
For instance, as Superstorm Sandy overwhelmed parts of the northeastern U.S. last October, some hams assisted regional hospital systems that had lost the ability to communicate among their buildings, Robertory said.
“Somebody would go to them and say, ‘We need this message passed to this building,'” he said. “They would get on the radio, call the amateur-radio operator in that other building, and give them the message.” The second operator then carried the message to the recipient.
Amateur-radio operators also help individuals contact family members, help the Red Cross conduct damage assessments and help get shelters established, Robertory said. For instance, people in a shelter might want to register on the Red Cross’s “Safe and Well” system to let family and friends know that they’re okay, but the shelter might not have power or Internet access at the time.
“An amateur-radio operator can call an amateur-radio operator somewhere else who has Internet access and relay information to put into a missing-persons database,” Robertory said.
Even when other networks are operating, ham operators take some of the load off those communications systems when traffic gets heavy.
In the aftermath of Sandy, volunteers with the Greater Bridgeport Amateur Radio Club in Connecticut handled messages for three evacuation centers housing about 800 local residents.
“They were ready to take calls and dispatch people,” said Dana Borgman, press information officer for Region 2 of Connecticut Amateur Radio Emergency Service (ARES), a volunteer organization. “The messages could be about supplies, logistics — any kind of reports.”
Public-safety communications networks in Bridgeport were operating at the time, Borgman said. Ham radios supplemented those channels. But, if the phone system in a shelter stopped working, hams could step into the void.
“If someone in a shelter needed to make a request, they could call someone at a different point, such as the EOC,” Borgman said. “They’d establish communication and say, ‘I have a request from the shelter manager. We need 200 cots and more fresh water.'” An operator at the other end would relay the request to the appropriate person.
Members of ARRL’s New York City-Long Island section provided similar aid after Sandy. At the time, Jim Mezey — now manager of that section — held the emergency coordinator’s post. Because he lives in Nassau County on Long Island, he focused most of his attention there.
“I did a lot of traveling,” he said. “I was without power for a while, so I used my mobile station to do most of my work. I also moved to the county EOC and worked with the Radio Amateur Civil Emergency Services (RACES)” — another volunteer group. For the most part, however, section members provided services to the Red Cross.
Finding enough manpower during the emergency became a bit tricky, because many of the radio volunteers from Long Island live on the hard-hit South Shore, Mezey said.
“They had their own problems with floods and losing power,” he said. “Their batteries lasted only so long, and that was it. No gasoline, no way to get around.”
Of course, for volunteers whose homes were flooded, taking care of their own families took top priority, he said.
Amateur clubs can swing into action quickly because they maintain ongoing partnerships with myriad emergency-response organizations. The ARRL has developed memoranda of understanding with 13 national organizations, such as the American Red Cross, the Association of Public-Safety Communications Officials (APCO), the Salvation Army and the Federal Emergency Management Agency (FEMA). Many operators also take advantage of training opportunities.
“A lot of the amateur-radio operators are now becoming CERT (Community Emergency Response Team) members,” said Borgman. “Also, we encourage our members to take all of the ICS (Incident Command System) training.”
ICS training teaches operators about the structure of incident command and how to use standard terminology, rather than terms specific to police, firefighters, radio operators or other specialists.
Beyond delivering messages, hams offer a lot of miscellaneous technical assistance, some of which is quite ingenious, Robertory said.
“They like to ‘MacGyver’ things,” he said. “You’ll hear a lot of amateur-radio people say, ‘Give me a car battery, an antenna and a radio and I can communicate from anywhere.'”
In times of disaster, hams tend to be extremely flexible, Robertory said.
“In the morning, they’ll set up an antenna and start communicating,” he said. “They’ll set up a satellite dish for us, and then they’ll set up a computer. They’ll troubleshoot a printer, and then they’ll teach someone how to use the fax machine.”
Clearly, when the going gets tough, it’s great to have someone on hand with a go-bag, a radio — and the attitude of a ham.
Satellites provide a valuable link during disasters since it requires no local terrestrial infrastructure beyond where you are setting up. Cell phones require cell towers within a few miles to be working and not overloaded. Wireline services require a connection through the disaster to where you are. Satellite systems do require a power source. Depending on the size, it can be a vehicle’s 12 volt power outlet, a portable generator or a vehicle mounted generator.
A satellite is in an orbit around the Earth. There are many different ways to position a satellite in orbit depending on the need. A common orbit for communication satellites is a geostationary orbit 22,236 miles above the Earth. Precision is needed when working with satellites at that distance. One degree off and the satellite will be missed by 388 miles. That is like aiming to land in Washington DC and really ending up in Detroit or Boston.
The antenna used makes a big difference. Let’s start by looking at a two-way radio antenna. Most handheld two-way radios have an omni-directional antenna. That means it doesn’t favor any specific direction so orientation doesn’t matter as much. This gain in flexibility is matched with a loss in “punch” or sending power. Imagine a basic light bulb in a lamp with no shade. It spreads light everywhere. That’s how an omni-directional antenna works.
What if you want that light to be focused to only project sideways? Like an all around white light on a boat. The bulb and the lens are constructed to direct the light in a specific pattern. This is similar to a high gain antenna. The main punch of the radio signal is increased perpendicular to the antenna by reducing the energy projected parallel out the top and bottom of the antenna.
Now you want to project light in a single focused direction such as a spot light or flashlight. The bulb is constructed with reflectors and other features to direct the light. The same is true with radio antenna. A directional antenna is also called a beam or Yagi-Uda antenna. Most of your neighborhood roof mount TV antennas take this form. A series of metal rods direct the radio waves to a higher focus then the use of a single rod.
Wait, a TV antenna? I thought those were receiving only? The neat thing about antennas is that they will receive with the same characteristics as they transmit. A highly directional antenna is more sensitive and will better pick up a signal from its pointed direction then an omni-directional antenna. However, if the same signal came from a different direction then where the directional antenna is pointed, then the omni-directional antenna will receive it better.
So why don’t we always use directional antennas? Think back to two-way radio repeaters. The repeater’s antenna an example of when you want to broadcast the signal widely. Directional antennas are good for communications between two known locations. Onmi-directional antennas are good when you don’t know where the other location is, or it keeps changing and moving the antenna continually is impractical.
Going back to our analogy of light to describe radio waves, now imagine that you need a highly focused light. A laser pointer; it is designed to send out a highly focused beam of light that can be seen for long distances. The radio version of this is the satellite dish. The transmitter bounces the signal off a parabolic reflector which theoretically sends all the energy in the same direction in a narrow beam. These very narrow focus antennas are called “very small aperture terminal” (VSAT).
This series of examples is just discussing the shape of the antenna relative to the direction and focus of the radio waves. It is possible to use practically any frequency with any shape of antenna so long as the antenna is properly tuned. Different radio bands are naturally more efficient for communication modes when combined with certain types of antennas.
The important thing to remember here is just because you can do something doesn’t mean you want to do it. This is where you need to rely on your radio technicians to design the most effective system using the right frequencies and modes to get the message to the final destination.
The simplest radio is the analog radio that transmits and receives on the same frequency. All radios build from this model. Imagine two people standing apart, each with a simple radio and antenna. When one talks, the other listens; and vise versa.
Radio operators wanted to get more distance from their equipment. Repeaters came into service. A repeater can rebroadcast (or repeat) a transmission from a higher tower, at a higher power and over a longer range. The radio operator will transmit on frequency “A” while the repeater listens on frequency “A”. The repeater rebroadcasts the transmission on frequency “B”. Other radio operators will tune to frequency “B” to hear the broadcast. Each radio will transmit on one frequency while receive on a second.
Analog radios transmit the operator’s voice directly by modulating either the frequency or amplitude depending on the mode. Digital radios encode the operator’s voice into a binary pattern. The binary pattern modulates the radio signal. This allows a digital radio to receive the binary pattern and convert it back to voice more clearly than an analog radio. Interference to the digital radio signal is less likely to influence the quality of the signal. Digital radio signals can also carry non-voice information. These include radio handset identification, unit numbers and location information.
In the past, public safety departments would acquire many different frequencies to cover all their projected needs. They may set aside frequencies for major incident coordination, training, and secondary activities. Unfortunately, these were also seldom events that occurred only a few times a year. This lead to a waste of resources to maintain the frequencies and the additional equipment. A trunked radio system separates the concept of a radio channel from a specific frequency. One frequency is designated as the control channel while all the other frequencies are open. All radios monitor the control frequency to get digital control signals from the central coordinating system. A user would never listen to this frequency as it is all digital control signals for the radio to use. A user may dial a channel called “dispatch”. The radio checks to see which frequency is currently assigned to the dispatch channel, and then tunes that frequency for the radio operator. Meanwhile, the radio will monitor the control channel in the event the dispatch channel changes frequency. If a radio is set to a channel that has no traffic, there will not be a frequency assigned. A trunked radio system may have only 20 radio frequencies to serve 100 channels. The radio of frequencies to channels really depends on how often each channel is expected to be used.
The frequency spectrum is divided into many bands, or areas of use. Frequency ranges can be assigned to any number of uses, such as: maritime, aeronautical, amateur, broadcast, fixed or mobile stations, land mobile, satellite, public safety and private/business. The NTIA frequency allocation chart shows all of these bands color coded. Some bands have multiple uses yet they’re always very similar, such as mobile satellite and fixed satellite.
The two way radio bands most used in emergency management are private land mobile (which includes public safety and business), amateur and to a lesser extent FRS, GMRS, and CB.
Satellite is another form of radio with a highly focused antenna. We’ll talk more about satellite frequencies in that section.
There is a lot more in common between radios and cell phones then most people expect. It can be hard to see similarities when the user interfaces are designed so differently. Fundamentally, they both have a power source that drives the device to generate a signal across an antenna. In turn, the antenna generates radio waves that run through the atmosphere until they hit another antenna attached to a receiver.
If you could see radio waves, they’d appear as if we had hundreds of lights turned on all around us. We’d see the waves coming off our cell phones, wifi-enabled devices, blue-tooth devices, wireless phones, cellular-enabled tablets and hot spots. Also visible is the radio waves from your neighbors’ equipment coming right through your walls as if the walls weren’t even there. The wireless baby monitor would probably appear just as annoying as the tantruming child. Larger sources of radio waves would emanate from cell towers. Way off in the distance, AM and FM towers would glow like a sun. Even the fast food drive through isn’t immune due to the wireless headsets and speakers. Look to the sky and you’ll see the satellites sending their signal to the earth. Right above the equator, the concentration of transmitting satellites would resemble the Milky Way. Add in all the natural sources and unintended sources from poorly designed electrical systems to really complete the image. No lie. Radio waves are everywhere.
In the US, the National Telecommunications and Information Administration will set the broad allocation of the spectrum and how it can be used. They publish the US Frequency Allocations: The Radio Spectrum chart. It is very finely divided down, yet you’ll still see major sections allocated to broadcasting. Spectrum is a finite resource. We cannot create any more and all of it is allocated to something. That is why spectrum management is so important. Broadcasting has had to make better and more efficient use of the spectrum to keep it. Hence the evolution of HD radio; which by the way is hybrid digital not high definition. It also led to the use of Digital TV to include more information and resolution in the TV station’s broadcast.
At the bottom of this chart is the full spectrum. Near the left end is the audible wave lengths; the middle contains a very narrow band of the visible spectrum; and the far right is cosmic rays. The continuous range of frequencies (and then some) is called “DC to daylight”. DC refers to direct current or 0 Hertz. Daylight refers to the band of visible light, starting about 405 THz. Thz is Terahertz or 1012 Hertz. If you’re used to the metric system, Tera comes after Giga. Looking for a radio that does “DC to daylight” isn’t a literal radio. It is referring to a radio that will continuously cover all possible radio bands. Keep in mind that the more bands (frequency ranges) a radio will cover; the less impressively it can master a single band. Think of it this way: a Swiss army knife provides a lot of tools which are better than nothing, but far less handy then having the actual tool needed.
National Telecommications and Information Administration. (2003). U.S. Frequency Allocation Chart. Retrieved from http://www.ntia.doc.gov/osmhome/allochrt.html
The International Association of Emergency Managers (IAEM) conference in November 2011 has put out a call for speakers. The deadline of February 25 is fast approaching. I decided to pitch a 1 hour breakout session loosely based on the course I teach at GWU. Below is what I sent in. Let me know your thought and make suggestions. Continue reading IAEM 2011 Conference Speaker Submittal
The future of amateur radio is going to be good one … so long as diehards don’t pigeon hole amateur radio into particular frequency, mode or way of operating. As I headed up to Dayon for Hamvention, I wondered just how long amateur radio was going to be around. I suspected that in ten to twenty years, it will not look much like it does now and could be gone. Thankfully, there were folks up in Dayton that helped to shift my mindset. Now I think that amateur communications will still be here and it will not look like it does now. Looking around Dayton, it is easily taken that amateur radio is technology for white haired men – and it is easily perceived as older white men. True, there are women, young people, and people of different origins that enjoy it but not to the extent of older white men. An injection of younger and more diverse people is badly needed. A failure of recruitment will signal the death of amateur radio.