re "mains hum"
and finally, after any mains powered equipment has been checked for malfunction, ground loops have been eliminated, and any sensitive conductors screened, there are filters.
Filters are typically only used if you have an ariel. such as a radio or TV ariel, that is being swamped by a local powerful transmitter. If you live near a fire station, police station, hospital, etc the transmitted radio waves can swamp your tuning circuits. In this case a combination of capacitors, inductors and resistors is used to filter out a specific frequency.
Even though I might know how to sort such a problem out myself, I would usually just call a local installer about the problem. From experience, working with customers in your area, he/she would know exactly if there are any troublesome transmitter sources and the best selection of components to be used to attenuate the unwanted signals received. If they know what they are doing its usually just a few minutes work. They would have the problem fixed before I could find out what it was. |
