Muriel, you wrote: - In a room, I have turned on a compact fluorescent lamp driven by a ballast (electromagnetic). The lamp power is 9W.
- In another room (next room) I have turned on a TV. In channel 2 (VHF) I could see two horizontal lines, about 17cm apart from each other. They keep circulating at the TV screen in a low (subjective) velocity. Question: Is there a relation/pattern in: * the distance (between the lines) * orientation of the lines (horizontal, vertical, diagonal) * velocity of the lines in the screen (slow, steady, fast) Dave: I assume you are in France and the TV standard is SECAM, or elsewhere in Europe with PAL. They have the same horizontal line frequency of 15.625 kHz with 50 frames per second. This will sync up nicely with 50 Hz AC line power. The rate at which the lines roll through the TV screen is the beat frequency between the frame rate and the AC line frequency. If it rolls through every 5 seconds there is a 0.2 Hz difference. The double line is due to the AC source creating noise twice per cycle, which is 100 times per second. Note that the frame rate of TV is derived from a 4.433618 MHz source. TV stations usually hold this within 1 Hz and you can rely on this being a better short-term frequency standard than is the AC line frequency (which is good over very long periods). In the US the TV standard is NTSC. This has a horizontal rate of 15.734 KHz with a frame rate of 59.94 Hz. This causes a 0.06 Hz beat frequency with the 60 Hz line power. Dave Cuthbert Micron Technology This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
