## Sources of link degradation (cont. 2)

### Interference #### Interference arises owing to contamination of the channel by extraneous signals, for example, from power lines, machinery, ignition systems, other channel users, and so on. If the characteristics are known, then interference can often be suppressed by filtering or subtraction, for example, car suppressers). Interference is often impulse-like in nature and we know from our knowledge of the Fourier transform and Fourier series expansion that an impulse contains energy over a very wide bandwidth. In the case of ignition noise, the ignition system may be firing at only 4000 Hz, (1000 rpm), yet significant high frequency energy will exist at frequencies of several MHz. |