Next week I want to try QRSS3 with my earth mode VLF system to extend the range. As in the test this week, Spectran software will be used my PC to filter and decode it. For a stable source I'll use a crystal and divide this down to sub-9kHz. Looking around for a suitable simple circuit I found G4HCL's very simple 1750Hz toneburst circuit which uses a 455kHz ceramic resonator (pulled slightly) and a 4060 IC as a divide by 256. With a crystal instead of the ceramic oscillator this should be perfect if followed by some filtering to produce a decent sine wave output. See M1GUR's page for more details.