PS: DL0AO is now running a series of one-hour recordings with 137.5 kHz dial and 480 Hz samplerate, i.e. 137.50 to 137.74 kHz band. At 100x speed, each one will be good for 36 seconds of speech. To avoid interference to WSPR and FW stations, longer tests should preferrably take place above 137.6 kHz.
73, Markus