Have noticed an odd occurance with relays

When I built a test version of my clocking and counting circuitry, I noticed that whenever my TV was on channel 42 (Notice this bit of oddness right here, with reference to Douglas Adams greatest work) and a specific light was on, large amounts of interference would appear on the tv screen. This happened only under these conditions. I have since fixed it, but the cause was that the line to the light in question would pick up rf interference from the relays and it would transmit thwence to the tv. Very odd. The source was that the clocking would cause chater in a defunct relay that would do the same for the rest. My solution: Capacitors. Every once in a while I have a 0.01uF capacitor, with a really large one across the power supply. No more TV interference. Now just have to figure out why the radio station keeps calling... :wink:

Look at the dimensions of the wiring. You might have a resonant loop at the television frequency.

Many years ago in Canada when television first was used, some room lights would jam it. What was happening was the shape of the lamp filaments formed a magnetron. The magnetic field from the filament would interact with the electrons leaving the filament and the voltage drop across the vacuum between two points on the filament.

Having replace the bad relay and anding the capacitors, which I was going to do anyway to reduce the problems of having contact chatter basically cause pulses to the coils of other relays, thus heating them. This is a problem with my old relays, not the new ones as much (some of the relay I am using are in their 50s!)