SCOTTS CRYSTAL RADIOS - Headphones, crystal radios, instructional/technical information and more.
BORDEN RADIO COMPANY- Antique Radio Schematics and more, Kits & Parts. Articles by Lance Borden WB5REX on crystal sets, the Armstrong Regenerative, and a restoration article for the All American Five tube tabletop radios.
RF Cafe - Extensive resource for science and engineering.
National Radio Club–World’s oldest and largest medium wave DX club.