Gerhard Fiedler connectionbrazil.com> writes: > Does this matter a lot for a SAW stabilized oscillator? You can't peak the output if the inductor is off. Iow, use a trimmer cap and keep changing the board until you get maximum out tunable with the cap (not at the end of the tunable domain - there should be two peaks per cap turn). After that you can put in a SMD cap and 'tune' the inductor as Vasile said. The 'inductor' at 433 MHz is a J or U shaped one turn of copper trace. You can calculate it yourself, take 5nH/cm of coil wire length and Thomson's formula. The tuning cap will be mostly the transistor collector plus the trimmer plus stray capacitance on the board, i.e. you can't go below 5 pF probably. So for 433 MHz and 5 nH/cm and 5 pF it works out to about 5 cm length. If you look in a keyfob TX you will see a trace about this long. The width of the trace changes both the 5 nH/cm parameter and self capacitance. So: as I said, take some values, cross your fingers, build it, and see if it works. Then rinse and repeat. 'Calculating' this without concrete data for the board material and what is near the circuit (battery, user's hand etc) is useless. > Also, without being able to actually measure the parameters of this > transmission line, how do I know whether the inductor itself is off or the > capacitor? RF without instruments is like photography without light. You need 'some' experience to get things done, but you can never be sure that your transmission is not mostly on the 3rd harmonic or worse without looking with something. At the very least a Schottky diode detector hooked to a scope, and an absorbtion tuner, but that's fairly lame as 'instruments' go. A ham radio receiver for 432 MHz with working S-meter and a converter (10 MHz xtal + mixer) is an asset. If this is a serious project (more than a one-off), rent a specan or rent hours at a lab that has one. You need a specan that covers the 3rd harmonic at least (better the Ft of the used transistor). Peter P. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist