Build a LC tank circuit optimized to oscillate at the desired frequency. Then, to keep it locked exactly where you want it input carefully timed (read PIC output) capacitively couple input pulses to keep it "ringing". If the actual resonant frequency of the LC tank is close enough to where you want to be, and it has a high enough Q and you input the drive pulses fast enough it would probably work quite well. Bob Ammerman RAm Systems ----- Original Message ----- From: "Vasile Surducan" To: "Microcontroller discussion list - Public." Sent: Wednesday, August 30, 2006 1:00 AM Subject: Re: [EE]: Source for 13.56MHz oscs, or some way of generating it? >A good hand, one 14MHz crystal and a file ? > > Vasile > > On 8/30/06, Philip Pemberton wrote: >> Hi, >> I don't know if anyone else has noticed this, but there's a full design >> for >> an RFID reader in the current issue of Elektor (September 2005). Only >> problem >> is, it needs a 13.56MHz fundamental-mode crystal - as far as I can tell, >> 13.56MHz is not a standard frequency. Does anyone know where I might be >> able >> to get one of these crystals, or a 27.12MHz fundamental-mode crystal? TTL >> oscillators would also be fine... >> >> Failing that, can anyone suggest a way to generate a stable 13.56MHz >> square >> wave? Bonus points for cheapness and "junkbox buildability" (i.e. if it >> can be >> built out of stuff commonly found in a hobbyist's junk box)... >> >> The design in question is the "Experimental RFID Reader" by Martin >> Ossmann, >> Elektor September 2006, p.34-38. >> >> Thanks. >> -- >> Phil. | Kitsune: Acorn RiscPC SA202 64M+6G >> ViewFinder >> philpem@dsl.pipex.com | Cheetah: Athlon64 3200+ A8VDeluxeV2 >> 512M+100G >> http://www.philpem.me.uk/ | Tiger: Toshiba SatPro4600 Celeron700 >> 256M+40G >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist