Amateur radio organization ARRL has announced that its online course on Radio Frequency Interference will remain open through Sunday, June 28, 2009. Courses are also offered on Amateur Radio Communications Level I; Antenna Modeling; Antenna Design and Construction; the Ham Radio (Technician) License Course; and Propagation, Analog Electronics, and Digital Electronics. Students register for a particular session that may be 8, 12, or 16 weeks (depending on the course), and they may access the course at any time of day during the course period, completing lessons and activities at convenient times depending on their personal schedules.For registration particulars, visit the ARRL website.