http://ww1.microchip.com/downloads/en/DeviceDoc/70093a.pdf You don't want a copper pour under the antenna. Check out pages 27 and 28 of the doc above. Steven Bible did the rfPIC sessions at the 2002 and 2003 MASTERs. Search on his name at the Microchip web site and you'll find a half dozen white papers on RF stuff. (http://tinyurl.com/3b2zl) http://ww1.microchip.com/downloads/en/DeviceDoc/prt5.pdf This whitepaper has plenty o' math to make my head spin. Might help you. -----Original Message----- From: Jim Tellier Sent: Jun 23, 2004 3:30 PM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE:] Circuit Board Loop Antenna? Harold Hallikainen wrote: > I'm working on an RFID project and need to make a 208uH loop antenna. I'd > like to try to do it as a rectangular spiral trace on a circuit board. Can > anyone suggest a resource on calculating the inductance of such an > inductor? Harold, Are you by any chance doing something with an RFPIC device? They have an appnote (AN831 = Matching Small Loop Antennas to RFPIC devices", or similar title); I've not read it (yet), but it may contain something useful. I'm also starting a project of that type with a RFPIC12F675, and thought about doing the pcb trace thing as well. In uChip's device sheet for the '675, they illustrate a schematic using a "loop antenna" but they don't spec its inductance :^( I thought that was kind of lame; I can't imagine it's not critical at ~480MHz! I'm still working on a Eagle layout for my project (which is both my first RFPIC project AND first surface-mount pcb... woo-hoo!), and was planning on using a full copper pour ground plane on side 2. I wonder how that will affect the idea of a spiral loop ant on side 1? I imagine it would result in a hugely directional emitter, wouldn't you think? I'll look forward to moving ahead with this as soon as I too get some questions answered! Jim > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body