Think of the wavelength. An inch movement is huge in terms of relative pha= se at 2GHz. At 457kHz the wavelength is about 656m and an inch gives you n= o measurable phase difference. There's a new ham band nearby, where I thi= nk they've already set the biggest distance record you can without leaving = earth. Many more things are reflectors and absorbers up high. Down in the 100's o= f kHz, reflectors are usually microscopic in terms of wavelength, and almos= t nothing attenuates the signal. Ferrite absorbing blocks as used in EMI c= hambers do almost nothing. Copper mesh works pretty well. What frequency were you thinking of using? -- David VanHorn Lead Hardware Engineer Backcountry Access, Inc. 2820 Wilderness Pl, Unit H Boulder, CO =A080301 USA phone:=A0303-417-1345 =A0x110 email:=A0david.vanhorn@backcountryaccess.com=A0 -----Original Message----- From: piclist-bounces@mit.edu On Behalf Of Neil Sent: Monday, October 7, 2019 12:42 PM To: Microcontroller discussion list - Public. Subject: Re: [EE] Locating object position by radio --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .