| ??? 04/05/07 12:47 Read: times Msg Score: +1 +1 Informative |
#136678 - Everything is a source of noise... Responding to: ???'s previous message |
You're running an unshielded board. Every trace is a source of noise. Everytime a signal switches state, your board emits RF energy. This RF energy will have harmonics too. It's not just the xtal, it's the xtal frequency, it's harmonics, and all derivitives of that clock and their harmonics generated by the uC which is in turn dependent on the code it's running. Curtailing this noise is an entire area of specialty in and of itself. This is why Kai is always promoting ground planes and multi-layer PCB's. Pick the wrong xtal, say one that has a harmonic on your local airport's glide slope equipment, and unpleasant people with guns and badges will show up at your house. Rob |
| Topic | Author | Date |
| my board creates white noise. | 01/01/70 00:00 | |
| Everything is a source of noise... | 01/01/70 00:00 | |
| Me too. | 01/01/70 00:00 | |
| It is normal | 01/01/70 00:00 | |
| Don't add resistors to the crystal | 01/01/70 00:00 | |
| RF-emission spectrum was discussed earlier... | 01/01/70 00:00 | |
| It's not the crystal | 01/01/70 00:00 | |
| what other lines? | 01/01/70 00:00 | |
| any | 01/01/70 00:00 | |
| AM carriers | 01/01/70 00:00 | |
| All other lines | 01/01/70 00:00 | |
one of the reasons for internal memory | 01/01/70 00:00 |