Saturday, September 2, 2017

The Role Of HF Amateur Radio in Disaster Communications

Does HF still have a legitimate role in disaster communications?
High frequency, also known as shortwave, is the portion of radio frequency spectrum from 3 MHz to 30 MHz; or to describe it another way, between medium wave (including the AM broadcast band) and VHF (which includes the FM broadcast band).

HF is characterized by ionospheric skip propagation (1), where signals bounce off ionized particles in the upper atmosphere. It is this characteristic that makes HF important, and is the reason that we can tune in shortwave broadcasts from around the world. Without getting too heavily into the science behind ionospheric skip propagation, radiation from the sun ionizes particles in the F layer of the ionosphere, between approximately 100 miles and 300 miles above the earth's surface. The ionization is greatest during daylight hours at any given point. The season is also a factor, as is the 11-year sunspot cycle (2),(3).

In practice, an HF operator or frequency coordinator can choose an operating frequency based upon distance to the receiving station. The lower bands within the HF spectrum work best within a radius of zero to 200-300 miles, while the upper HF bands are better for worldwide communications. If the operator chooses the correct frequency, very little power is required to make contact. Amateur radio operators who are into QRP (low power, often simple equipment) regularly communicate thousands of miles using less than 5 watts and often even less than 1 watt of output power. The author has communicated over 1000 miles using 1 watt or less, and once carried on a two-way contact over approximately 15 miles using 50 microwatts. That's one, twenty-thousandth of a watt!

Back to the subject at hand: the majority of public service and other utility communications has moved away from HF frequencies and into trunked systems and microwave backbone links that connect local radio communication systems with others across the state and even across the country. These new systems have much greater bandwidth and can carry more information, for a greater number of users, at a faster rate than the older technology. To the end user, the new systems are easier to operate and more user-friendly, all the while providing more secure communications.

To be sure, the new systems provide greatly enhanced communications capabilities in day-to-day use. But what about during a disaster? These networks are infrastructure-intensive and cost billions of dollars to install. They're not immune to breakdowns, either. Tornadoes, hurricanes, earthquakes and other natural disasters can bring down these systems just as readily as they can bring down an HF radio antenna. And while the trunked systems can bypass damaged nodes and continue operating at a reduced capacity, such events create greatly increased communication needs. Even if the network does not suffer damage, disasters often overload the capacity of the system to maintain the flow of communications. Have you ever noticed how your Internet service slows down during times of peak usage? The same phenomenon is at work with trunked radio systems.

Consider for example, Hurricane Katrina. Here is what the Armed Forces Communications and Electronics Association had to say after Katrina: " On September 14, 2005, the 9/11 Public Discourse Project issued a report asserting that the response to Hurricane Katrina was a classic failure in command and control. It found no unity of command—or more specifically, no one in charge and no unified incident reporting system to coordinate efforts of local, state and federal agencies. Fixed communications systems failed with no ready means for their restoration. This was not surprising, given that there exists no incentive for the intensely competitive information systems industry to finance ruggedness, redundancy or rapid restoration." (4)

Here is where amateur radio comes in, with HF as well as VHF and UHF communications. From, again using Katrina as an example: "
During Hurricane Katrina, amateur radio provided volunteer operators to support
many served agencies such as Emergency Management,
National Weather Service,
Hurricane Watch and the American Red Cross. This is business as usual for many radio operators in the Amateur Radio Emergency Service, or ARES, nationwide.
After Katrina, amateur radio provided many more volunteer operators to support
an even larger host of served agencies that requested our services. The ARRL
coordinated hundreds of amateur radio operators who
traveled to the devastated
area and provided critical communications capabilities. This work continued for
many weeks. 
The sufficiency and effectiveness of amateur radio
to re-establish communications
systems with equipment they brought in, much of it
owned by these volunteers and
quickly building complete systems from scratch, was
tremendous. Amateur radio
operators themselves were part of the solution, providing experienced communications operators to replace and supplement
local public service
communications personnel in the devastated area. These systems of equipment and operators were very effective, not only for amateur purposes but in support of Emergency Management, Red Cross, Southern Baptist,
Salvation Army and many other organizations.
In each town we set up a High Frequency (HF) amateur radio station to communicate out of the area to Montgomery and the outside world. We also set up
a communications network connecting every Red Cross
facility in a town on a local
short range radio frequency. Our network included
fixed and mobile disaster
vehicle stations."(5)
Of course ham radio antennas can fail during disaster events too, and amateurs suffer power outages as well. But hams who participate in disaster relief efforts have the skills, know-how and equipment to put their stations on the air under all kinds of conditions, including portable field operations. In fact probably the most well-known amateur radio event is Field Day, in which thousands of amateurs all over the USA take to the field with their portable stations for a 24 hour emergency communications exercise.

1 comment:

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