I recently made my annual pilgrimage to Dayton, Ohio, to attend the Dayton Hamvention. In May each year, approximately 25,000 amateur radio operators, or hams, and other electronics enthusiasts descend upon Dayton to renew old friendships, check out the latest radio technology, browse through the huge electronics flea market or attend educational forums. "Amateur" has nothing to do with their technical or operational expertise--it simply means they have no financial interest in pursuit of their hobby.
The motto of the American Radio Relay League--the National Association of Amateur Radio, "When All Else Fails," was definitely in play during one Apollo mission. When the primary recovery ship, USS Hornet, lost radio contact with NASA Mission Control in Houston, the ship's ham station contacted a ham in my hometown of Lafayette, La. The local ham connected the Hornet with Houston via a telephone patch until the military radio system was operational again.
Hams have been at the forefront of wireless communications from the beginning. During both World Wars and subsequently, hams provided a large base of trained military radio operators and electronics technicians. In 1961 hams designed the Orbiting Satellite Carrying Amateur Radio (OSCAR) just four years after the Soviets launched Sputnik. In the `70s hams developed VHF repeater stations and, in the early `80s, packet radio networks. These achievements predated widespread public acceptance of cell phone technology and digital communications protocols. Finally, many hams donated their time, resources and expertise for public service communications during Hurricanes Katrina and Rita.
Which brings me to the topic at hand: software defined radios (SDRs). In the past few years the Department of Defense (DoD) and the SDR Forum, among others, have been developing the software communications architecture (SCA). SCA is the foundation of the Joint Tactical Radio System (JTRS), a software programmable, wideband, multiwaveform radio system designed meet a wide range of demanding tactical communications requirements. JTRS will provide connectivity to DoD's Global Information Grid (GIG) as well as interoperable communications with civilian first responders.
SDRs are definitely the future of radio communications. Hams have rapidly evolved several generations of SDRs, and the growing acceptance of SDRs has been spurred on by the advent of low-cost digital signal processors (DSPs) and field programmable gate arrays (FPGAs). Extensive use of open source software encourages experimentation and customization by end users. Developers issue frequent software updates incorporating the latest improvements and ensure that fielded SDRs never go obsolete. Hams have established discussion groups to facilitate exchange of SDR designs, operational information and ad hoc standards for modular hardware and software.
I was taken back by the realization that these ham activities looked like desirable characteristics of a broad, consensus-based military/aeronautical (MILAERO) radio development program. Obviously there are some differences between the MILAERO and amateur radio domains, such as high reliability (the USS Hornet incident not withstanding!), certification, packaging, security and waveform complexity. The DoD/industry collaboration through the SDR Forum is a good start. However, International Traffic in Arms Regulations (ITAR) prohibit the broadest dissemination of key JTRS documentation outside of the traditional military radio development community. To effectively leverage the vast intellectual and economic engine of the marketplace, DoD would do well to further open up dialogue with the entire radio community by working to mitigate ITAR issues and turn over ownership of the underlying architecture documents to an industry standards organization.
The SDR genie is very much out of the bottle. It just makes good sense to acknowledge this and use it to provide our combat forces and first responders the most cost-effective, mission-capable communications systems possible. The aviation industry would also be well served by dramatic cost reductions in equipping aircraft with SDR voice and data links in the future.
Glen Logan is a senior systems engineer, supporting the Office of the Undersecretary of Defense, and an associate fellow of the American Institute of Aeronautics and Astronautics. He has been a licensed amateur radio operator (call sign WA5UHF) since 1968.