I hold a 137 Khz special permit valid until 2005 and it says
135.7 to 137.8 Khz with a max ERP of 1 Watt.
Yes, you read it well 1 WATT only.
We all have the 1 Watt ERP limit, it is implemented in the CEPT
recommendation that allows ham operation on 137kHz.
But keep in mind that antenna efficiency is extemely low on LF, most likely
0.1% or less. So you probably need more than 1kW TX power to get 1 Watt ERP.
I guess that my ERP is about 30 to 50 mW, running 350 Watt RF power. Best
DX is CW is OH1TN (about 1700km), so you can do a lot with just a few mW ERP.
73, Rik ON7YD