[eszed]

Around 1920 my great-grandfather, I am told, built a 1w radio transmitter in his basement in San Francisco, with an aerial running up the outside of the chimney. I've no idea what frequencies he used, but he regularly spoke with fellow enthusiasts in Europe and New Zealand - several of them came to visit, when my grandfather was a child. By 1930 there was enough interference that was no longer possible with such a low-power set.

[wildzzz]

Probably something like 200 or 100m. The higher frequencies don't start opening up until the late 20s.