Quoting Olin Lathrop : > David wrote: >> 300m is mighty impressive, but if that is completely directional from >> the board edge then perhaps less useful. > > I thought you said some directionality is OK. You were after all saying = a > dipole would be fine if it wasn't so large. > > What pattern are you looking for? In the plane of the board? Perpendicu= lar > to the board? Something else? OK, so this stems from my lack of understanding of RF in general. The =20 plastic enclosure I have chosen will be mounted vertically, that is =20 the board will be at 90 degrees with respect to the "floor". My assumptions after reading a few theory papers are that: Perpendicular to the ground plane, radiation for antenna such as a =20 whip or helical will be away from the ground plane. This would mean =20 that orientation for short distances such as 20m would not be =20 critical, as long as the front side of the board was facing the =20 receiver. Parallel to the ground plane, radiation will be away from the board =20 edge and quite directional. My assumption is that the whole board =20 must therefore be oriented at least approximately in the correct =20 direction. i.e. if the helical or Splatch antenna mentioned in this =20 thread are mounted on the right edge of the PCB, that edge must be =20 facing the other end of the radio link. If my reading of the propagation diagrams is correct there will be =20 absolutely no transmission in the opposite direction, i.e. a receiver =20 located to the left hand side of the board would be useless. There is not room to mount even a small helical antenna vertically on =20 the board (perpendicular to the plane), as the case is less than an =20 inch thick. This is why the Splatch or helical mounted flat to the =20 board were attractive. I realise I could just dangle a piece of wire through the case and be =20 done with it, but I'd quite like to understand properly how this =20 works. Also, a built-in antenna would be quite cool. David --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .