It's been awhile since the last time I played with WSPR data mode amateur radio software.
Seeing 10metre band is quite I decided to try out my homebrew 5/8th wave ground plane antenna today with WSPR.
Never ceases to amaze on the results produced. First I set the rig up for about 500mW at the antenna (had to do the coax loss calculations I posted previously). After the first couple of overs the results for my call sign popped up on wsprnet.org spot database. My 1/2 watt transmission was being hear in Moscow 2637km away, also in Germany, Spain, Holland and strong (positive SNR) reception in Denmark and Sheltand all on 10metre band!
Later reducing the power into the antenna to less than 200mw I still had several consistent reports from GM4SLV in the Shetland, and couple in Ireland (Cork) and Denmark.

Trying with QRO (1 whole watt) for awhile to see where I popped up and as I suspected it was not really needed... if there is a path then I would be heard on WSPR with mW's and increasing power did nothing other than get better SNR report from the one path that is being reported... Shetland. This band closure ties in with the other Southern UK WSPR beacons on 10metre. Seems like an excellent propagation tool.

update: Today 11th Jun with 5watts 9076km hop into south Africa...
2011-06-11 10:56 28.126083 IO81vh ZS6BIM KG44df