The other consideration with giving S-meter readings on LF is that there is
often a reasonably steady 'noise floor' punctuated by static crashes which
may be pinning the meter for a fair bit of the time. I think we all get
quite good at watching for the noise floor between the crashes and judging
how far the signal lifts the meter above that. One or two people always
give an RST report followed by a "dB out of the noise" figure.
Because of the very slow QSB and predictable groundwave signals these
techniques prove very useful. In fact because of the small number of LF
stations in ZL it is usually possible to guess a station's identity just
from the signal strength!
Thanks Steve and Rick for the VLF info. I turned on an ancient CR300 the
other night, inspired by the mention on the reflector of old Marconi
receivers, and heard VTX3 going strong.