That's the difference between the aerials .I.e. Directional (Horn or dish
etc) or omnidirectional (Dipole).
The aerial depends on the amount of gain  needed to cover the distances you
require with the power available.

----- Original Message -----
From: Matthew Ballinger <MattBeck@AOL.COM>
Sent: 14 July 1999 21:51
Subject: Re: OT: Looking for small 2.4 GHz TX RX pair


> In a message dated 7/14/99 7:50:02 AM Eastern Daylight Time,
> paulb@MIDCOAST.COM.AU writes:
>
> > Jim Ruxton wrote:
> >
> >  > Hi ,I'm looking for a small 2.4 GHz TX - RX pair for a PIC based
> >  > project I'm working on. The RX should be small enough to strap onto a
> >  > PDA without it becoming to obtrusive.
> >
> >    I think you've got a conceptual problem here.  (Low-power) 2.4 GHz
> >  equipment is portable, not mobile.  It works by sitting the unit on
some
> >  furniture and aiming receiver at transmitter and vice versa.
> >
> >    You may not have to aim too accurately, but it is not the sort of
> >  thing you walk around with.  Even less so if it's one-way because you
> >  depend on acknowledgements and retransmission ("packet" protocols) to
> >  get the data through if the link is anything other than fixed.
> >  --
> >    Cheers,
> >          Paul B.
> >
> How do the newer 2.4GHz cordless phones work then?!  Do you have to talk
in
> the same room as the reciever and stand in a certain posistion? I think
not.
> Matt
>