Lessons Learned About Frequency Sharing in the Amateur Radio Service Gregory D. Lapin, PhD, PE American Radio Relay League

July 28, 2005Lapin - Lessons Learned from Amateur Radio2 For Most Communications, The Paradigm is Shifting From… Each communicator/broadcaster is assigned fixed frequency channels. No one else uses an assigned channel except the licensee. Channels are reassigned geographically based on expected propagation.

July 28, 2005Lapin - Lessons Learned from Amateur Radio3 …Toward the Paradigm Upon Which The Amateur Radio Service Is Based The Amateur Radio Service is assigned relatively small bands of frequencies scattered throughout the spectrum to experiment with propagation. Groups of frequencies are specified for different communications modes. Licensees are given the right can use any assigned frequency as long as they do not interfere with other licensees.

July 28, 2005Lapin - Lessons Learned from Amateur Radio4 The Amateur Radio Paradigm All licensees have an equal right to use all frequencies. No frequencies are permanently assigned by regulation for anyone or for any purpose. Some frequencies have permanent assignment by agreement (via a frequency coordinator). Emergency communications always have priority. Hams have nearly 100 years of experience in refining this type of operating.

July 28, 2005Lapin - Lessons Learned from Amateur Radio5 In the beginning… There was Spark Gap – the original UWB No crystals, no filters – just raw RF power Circa 1910

July 28, 2005Lapin - Lessons Learned from Amateur Radio6 Frequency Sharing Was a Challenge King Spark ! Grown now to full maturity, Glorious old sparks! Night after night they boomed and echoed down the air lanes. Night after night the mighty chorus swelled, by ones, by twos, by dozens, until the crescendo thunder of their Stentor bellows shook and jarred the very Universe! A thousand voices clamored for attention. Nervous, impatient sparks, purring petulantly. Clean-cut business-like sparks batting steadily along at a thirty-word clip. Survival of the fittest. Higher and higher powers were the order of the day. The race was on, and devil take the hindmost. Interference. Lord, what interference! Bedlam! Well, it could not be Utopia. -Arthur Lyle Budlong excerpted from The Story of the American Radio Relay League

July 28, 2005Lapin - Lessons Learned from Amateur Radio7 The Solution In the 1920s, trans-Atlantic experiments with narrowband CW transmissions showed that they could coexist in the same frequency band without interference. 50 CW signals could occupy the same frequency space as one spark gap signal. A 5-watt CW signal could be heard over a greater distance than a 500-watt spark gap signal. By 1924 spark gap had virtually disappeared.

July 28, 2005Lapin - Lessons Learned from Amateur Radio8 Amateur Frequency Allocations

July 28, 2005Lapin - Lessons Learned from Amateur Radio9 Lessons to Avoid Interference When Sharing Frequencies 1.Listen before transmitting. 2.Ask if the apparently unused frequency is actually in use. 3.Keep transmissions short. 4.Use minimum power necessary. 5.Different stations trying to use the same frequency should be able to understand each other. 6.Coordinate frequency use by other means (such as a common control channel or the Internet to schedule a frequency and time to communicate).

July 28, 2005Lapin - Lessons Learned from Amateur Radio10 Why Listening to a Frequency Isn’t Enough A B C C is talking to B A listens but does not hear C A starts transmitting and interferes with B trying to hear C

July 28, 2005Lapin - Lessons Learned from Amateur Radio11 Regulations and Agreements Regulations specify which frequencies can be used and which modulation modes can be used on them. Band Plans are agreements that set aside specific sub-bands of frequencies for specific modes.

July 28, 2005Lapin - Lessons Learned from Amateur Radio12 Limitations of Regulations Regulations allow different modulation modes to be on the same set of frequencies. How can one ask if a frequency is being used if everyone doesn’t understand the question? Solutions to this include agreeing on Band Plans and Frequency Coordination.

July 28, 2005Lapin - Lessons Learned from Amateur Radio13 Some Modulation Modes That Band Plans Specify Digital Modes CW QRP CW SSB, SSTV and other Wideband Modes SSB QRP Experimental Beacons AM RTTY DX Window Packet Satellite Downlinks Satellite Uplinks FM Repeater Inputs FM Repeater Outputs Auxiliary Links FM Simplex Radio Remote Control Amateur TV Earth-Moon-Earth Experimental Spread Spectrum

July 28, 2005Lapin - Lessons Learned from Amateur Radio14 A Modern Amateur Radio Experiment in Frequency Sharing WiFi (IEEE b) format and technology is leveraged to provide High Speed Multimedia networking on Amateur Radio frequencies. Off-the-shelf hardware is connected to innovative antenna designs with higher power as permitted under Amateur Radio regulations. Details at

July 28, 2005Lapin - Lessons Learned from Amateur Radio15 My Favorite Story of Cooperatively Sharing a Frequency