Here is the patent you'd be infringing. Given that you're in ZA?? you _may_ get away with infringing it for a short while. (I seem to recall that US patents are now good for 20 years instead of 17) It never ceases to amaze me what 'prior art' the patent office will grant patents for. I KNOW I saw this technique used in some RF test equipment from the late 60's, so why was a patent granted? http://www.delphion.com/details?pn=US04494100__ Inventors: Stengel; Robert E. , Pompano Beach, FL Nejdl; Charles W. , Ft. Lauderdale, FL Applicant(s): Motorola, Inc., Schaumburg, IL Issued/Filed: Jan 15, 1985/ July 12, 1982 A planar inductance element includes a generally flat substrate of electrically insulating material. First and second substantially flat spiral coils, having respective inner and outer ends, are disposed on opposite sides of the substrate. The coils are spiraled in the same direction as viewed from one side of the substrate with one coil spiraling out and one spiraling in. The inner ends of the coils are joined through the substrate to couple the coils in series. The outer ends of the coils provide terminals for the inductor. The means/methods are disclosed for discretely and progressively trimming the inductor. Werner Soekoe wrote: > > Mark, > > You have totally confused me now. I don't have the feintest idea what the > ohms/mm is all about. But lets put it this way. I will be using the > oscillator circuits in transmitters and receivers. The one will transmit at > +- 100MHz (FM Band) and the other at approxiamately 280 MHz. > > What can you tell me about this? > > Thanx > Werner > WernerS@fsl.gov.za > > ----- Original Message ----- > From: "Mark Hull" > To: > Sent: Thursday, November 30, 2000 12:37 PM > Subject: [EE]: Coil Imprinted on PCB > > Hi Werner > > What frequency are you working at? > Most PCB coil calculations work in impedance terms as in ohms / mm when at > RF frequencies. > You then just have to zigzag the track to fit into the space you're using. > > Below RF you have to use conventional components. > > Cheers > Mark > ------------------------------------------------------------------- > Mark Hull > Engineering/Technical > EMS (Africa) (Pty) Ltd > PO Box 1026, Melville, 2109, South Africa > Ph +27 11 482 4470 Fax +27 11 726 2552 > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.