Low Frequency Radio and Single-Wire Phone Links
- NSS communications & Electronics Section
- Dave Gibsons Radiolocation page
- Paul Jorgensons Cave Radios including HF Thru-The-Earth
- The Nicola-3 earth-current voice cave radio
- Cave radio and Electronics Group of the BCRA
- Natural VLF Radio
- Long Wave Club of America
- SAQ operational high power 17.2kHz mechanical CW transmitter
- All about the new 2200 and 630meter ham bands
- National Speleological Society