Robert Thanks, looks like the hassle factor is greater than the fun factor on this one :( Guess I'll have to start a search for an HP58532A, VIC-100, Vaisala or similar. I don't think a cheapy £4 patch antenna will give the same performance. regards Grant > Hi Grant, > Keep the Palisade as it is. It's got a useful 1 PPS output. Also it's almost impossible to open the case without destroying it. The two halves are epoxyed together with a very good joint geometry! There is no obvious way to get to the antenna output. If you want to hack something, have a look for one of the Vaisalla GPS radiosondes. They have a nice Bi-Helix antenna, LNA and filter. But even a simple patch on a ground plane will do. > > Robert G8RPI. > > >