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#10
July 16th 07, 01:55 AM
posted to sci.electronics.basics,rec.radio.shortwave,rec.radio.amateur.antenna,alt.cellular.cingular,alt.internet.wireless
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How I would like to change the cell phone industry [was AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency]
In rec.radio.amateur.antenna Jeff Liebermann wrote:
Radium hath wroth: AFAIK, the main issue with AM is that it is much more vulnerable to magnetic disruptions than FM. Wrong. Take a magnet, any magnet. Wave it around your AM or FM radio. Hear anything different? You won't. Therefore, forget about magnetic disturbances. The main issue with AM is susceptibility to pulsed noise, as found in motors, fans, auto engines, and computahs. FM doesn't have as bad a problem because the limiter in the receiver clips everything to the same level, thus reducing the effect. That is why when you are listening to the AM radio at home and someone turns on the microwave-oven, you here those odd sounds on the receiver. No. Microwave ovens operate at 2400Mhz. AM broadcast operates at 1MHz. No way there's going to be any interference there. However, the microwave oven may have a fan or CPU that runs the display, that belches garbage at 1MHz. I just tried mine and there's a tiny bit of buzz coming from the display section when I shove an AM radio right up to the display. If that's what you're hearing, I would test it with a different microwave oven. If only yours has the problem, I suggest you consider a replacement. Also, if there is a solar prominence you can hear the resulting magnetic disruptions on an AM radio receiver. They sound scary and enjoyable at the same time. You can also hear lightning storms. In the US, most of those are in the south east of the country. Nothing like interference from 3000 miles away. Lightning detectors operate in the 25-50KHz region. Incidentally, there are about 8 million lightning hits per day, which is why the noise sounds almost continuous. (chomp...) Sorry, my time is up. Please insert $0.25 for the next 3 minutes. Don't tell him about whistlers. -- Jim Pennino Remove .spam.sux to reply. |
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