In September 2006, the FCC’s Office of Engineering and Technology granted a Part 5 experimental license -- WD2XSH -- to the ARRL on behalf of a group of radio amateurs who were interested in investigating spectrum in the vicinity of 500 kHz. Called the ARRL 500 kHz Experiment, this group of hams -- led by Fritz Raab, W1FR -- received permission to experiment and do research between 505-510 kHz using narrowband modes at power levels of up to 20 W effective radiated power (ERP), using CW and PSK31.

The original 500 kHz license called for 23 discrete fixed sites across the US: at Raab’s QTH in Vermont, as well as at sites in Arkansas, California, Colorado, Illinois, Louisiana, Massachusetts, Minnesota, Mississippi, New Hampshire, New Jersey, New York, North Carolina, Oregon, Rhode Island, Tennessee, Texas and Virginia. In 2008, the FCC expanded the scope of the experimental license, allowing for more frequencies, more stations and portable operations: The group could now operate between 495-510 kHz, the number of stations increased from 23 to 42, and participants could now operate within 50 km of their designated stations.

“Operators had to overcome numerous challenges to put transmitters and antennas on the air on these frequencies,” Raab told the ARRL. “Their work has shown that ordinary amateurs can indeed make use of these frequencies. The total of more than 100,000 hours logged by the participants demonstrates that amateurs can use the band without causing harmful interference to other services. Tests of ground-wave communication show that the band can be used for reliable, regional emergency communication.”

At the 2012 World Radiocommunication Conference (WRC-2012), delegates approved an amateur secondary MF allocation between 472-479 kHz. The ARRL would like to acknowledge the contributions of the participants in the ARRL 500 kHz Experiment to the recent approval of this new allocation, and to thank them for their efforts.

The 31 US amateurs who have put stations on the air on 500 kHz are:

W1NZR         WD2XSH/1    Brown Beezer
W5TVW        WD2XSH/2    Sandy Blaize
KW1I             WD2XSH/5    Dale Gagnon
W5THT          WD2XSH/6    Pat Hammel
W5JGV         WD2XSH/7    Ralph Hartwell

W2ILA           WD2XSH/9    Tom Mackie
W4DEX          WD2XSH/10  Dex McIntyre
WS4S            WD2XSH/11  Connard Murray
AI8Z              WD2XSH/12  Mike Mussler
K0JO              WD2XSH/13  John Oehlenschlager (SK)

W1FR             WD2XSH/14  Fritz Raab
W5OR             WD2XSH/15  Don Reaves
WE0H             WD2XSH/16  Mike Reid
AA1A             WD2XSH/17  Dave Riley
N1EA              WD2XSH/18  David Ring

K9EUI             WD2XSH/19  Bob Roehrig
N6LF              WD2XSH/20  Rudy Severns
W0RW            WD2XSH/21  Paul Sigornelli
K2ORS           WD2XSH/23  Warren Ziegler
KL7Q              WD2XSH/28  Roger Brown

KN8AZN        WD2XSH/29  Fred Temple
WA1ZMS       WD2XSH/31  Brian Justin
W0RPK          WD2XSH/34  Ralph Wallio
K0HW            WD2XSH/35  Jim Wennblom
W5GHZ          WD2XSH/36  Harold Deitz

W1XP             WD2XSH/37  Bob Reif
KN1H             WD2XSH/38  John Collins
W1HK            WD2XSH/41  Marshall Cross
K2LRE           WD2XSH/42  Mike Shaw
AC6QV          WD2XSH/44  Bill Isakson
KL7UW          WD2XSH/45  Edward Cole

Stations in 14 countries, including the United States, have been granted 500 kHz experimental privileges: Sweden, Germany, the Czech Republic, the United Kingdom, Belgium, Canada, Norway, Romania, Denmark, Ireland, the Netherlands, Iceland and New Zealand.