Good morning from ZL where the QRN is reducing as winter approaches.

Walter G3JKV mentioned the RF Design article on low power LF propagation.
Nat ZL3VN and myself have regular QSOs using backyard sized antennas and
QRP over a 300km (mostly sea) path on 181.4kHz. We find that 1 watt
transmitter output is sufficient for R5 regular CW most of the time.
Dropping to 0.5 watts output makes readability marginal. However, the
signals are regular CW in a 500 hz bandwidth so there is certainly scope
for extending the distance or reducing the power greatly.