I once measured a 250 mV RMS signal (+1 dBm) at my receiver input when
using a vertical antenna, from KGEI, a religious shortwave broadcasting
station near San Francisco, about 600 miles from here. It was at night,
and KGEI was just above the 40 meter band, 7335 kHz as I recall. They
were broadcasting in Russian, so their pattern was probably pretty much
in my direction.

I'm quite sure the folks in Europe routinely see signals larger than
this from SW broadcast stations.

Roy Lewallen, W7EL

K7ITM wrote:
We expect the local down the block may overload our receiver when he
keys up his kilowatt 40kHz from the frequency we're listening to, but
what are the largest signals received via skip in the HF bands? What
are the chances you'd ever see anything as large, say, as 0dBm into
your receiver via skip? (0dBm = 73dB above s9, given that s9 = 50uV
into 50 ohms.) This could potentially include SW broadcast stations
running fairly high power.

Cheers,
Tom