Ten milliwatts is really not much output power. It is just one hundredth of 1Watt ! Yet under the right circumstances, a 10mW HF signal can be heard and decoded many kilometers away.
But don't take my word for it. You need to try it to believe it :-)
See http://www.genesisradio.com.au/VK2DX/10mw.html
73 Nick VK2DX/QRPP
