Something different...
 

For those of you whose radars and RTF freqs get significantly affected by Tropo Ducting, you may want to have a look at this website

http://www.iprimus.ca/~hepburnw/tropo_nwe.html

It will give you an idea of where to expect the worst primary clutter and the areas in which you may get unexpected improved RTF coverage or interference from distant stations.