Had a quick look and my plans arent on my work PC... must have moved them to home PC....
Had a quick look on the internet and found...
http://www.iceinspace.com.au/index.p...63,285,0,0,1,0
Low and behold its in our own back yard.....
While it isnt the one I used it is the same desing style, and pulse width modulation technique, where you vary the on/off timing cycle. It seems to also be in kit form so there isnt much of a problem building it (wish I knew at the time). The only thing to watch is that it can drive the correct current as dew zappers are current intensive (this can be easily handled via the resistors used if you know electronics).
An alternative design is....
http://home.comcast.net/~astrophoto/Articles/Dew.htm
Cheers
M