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AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
On Jul 1, 7:24 am, wrote:
radium, I applaud you in your interest generating discussion. if there are no questions there are no answers; dumb or smart! to me your questions came across wonderfully, and generated both responses. as humans we stand on two legs, most of us that is. men get the honor and privilage to stand on three legs from time to time. this is our blessing and our curse! Thanks for your understanding. ps. how would u like to change the cell phone industry? Analog cells phones should stop using FM and should start using AM between frequencies of 40,000 to 285,000 Hz. As I learned recently, 40 KHz is the minimum radio frequency required to coherently transmit/receive audio signals. The highest sound a human can hear is 20 KHz. The radio-frequency used must be at least 2x the intended frequency of the information being transmitted/received. I chose 285 KHz to be the highest radio frequency for cell-phones because it is roughly the highest-frequency categorized as "long wave" radio. and your discussion group of course! You mean the anti-yahoo group? http://groups.google.com/group/yahoo...s?lnk=li&hl=en |
"Radium" [email protected] COMPLETE IDIOT..........
"Radium" wrote in message oups.com... On Jul 1, 7:24 am, wrote: Analog cells phones should stop using FM and should start using AM between frequencies of 40,000 to 285,000 Hz. I chose 285 KHz to be the highest radio frequency for cell-phones because it is roughly the highest-frequency categorized as "long wave" radio. IDIOT!......complete idiot...... |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
On Sun, 01 Jul 2007 12:16:35 -0700, Radium
wrote: On Jul 1, 7:24 am, wrote: radium, I applaud you in your interest generating discussion. if there are no questions there are no answers; dumb or smart! to me your questions came across wonderfully, and generated both responses. as humans we stand on two legs, most of us that is. men get the honor and privilage to stand on three legs from time to time. this is our blessing and our curse! Thanks for your understanding. ps. how would u like to change the cell phone industry? Analog cells phones should stop using FM and should start using AM between frequencies of 40,000 to 285,000 Hz. --- Good idea. The available spectrum between 40kHz and 285kHz is 245kHz wide, so at a little less than 3kHz per channel the maximum number of channels available would be 82. That means that no more than 82 people can be on the air at the same time. Probably all over the world, to boot, what with those frequencies being able to propagate over long distances. That's probably a good thing, because with those 1875 meter long 1/4 wave whips at 40kHz and those 263 meter 1/4 wave whips at 285kHz on the mobiles, any more people on the air than that would certainly create a hazardous situation. -- JF |
AM electromagnetic waves: 20 KHz modulation frequency on anastronomically-low carrier frequency
On 7/1/07 11:53 AM, in article , "John Smith I"
wrote: Don Bowey wrote: [more crap!] Oh, that explains it, your understanding of amplitude modulation is: AM = Black Magic. ROFLOL! JS OK you stupid ****, I'm almost out of patience with your ignorance. I was hoping you might learn something, but I see that is unlikely. AM is a process of frequency multiplication. Now you tell me where you think such multiplication takes place on a phone line, and I'll follow-uo by telling why you're full of crap. SIMECS! |
"Radium" a COMPLETE IDIOT... - More Likely An In-Complete-Want-To-Be [.]
On Jul 1, 12:50 pm, "Porgy Tirebiter" wrote:
"Radium" wrote in message oups.com... On Jul 1, 7:24 am, wrote: Analog cells phones should stop using FM and should start using AM between frequencies of 40,000 to 285,000 Hz. I chose 285 KHz to be the highest radio frequency for cell-phones because it is roughly the highest-frequency categorized as "long wave" radio. - IDIOT!......complete idiot...... PT - Once again why waste your time replying to his posts ? ? ? {Oops Like I Am Doing Too !} Actually "Radium" would appear to be an In-Complete-Want-To-Be driven by the 'urge' to Post these Forever Ponding Questions for others to charge at like Don Quijote's quest to slay Windmills {a fool's errand} http://en.wikipedia.org/wiki/Don_Quixote http://en.wikipedia.org/wiki/Fool%27s_errand FWIW - While many of his Post might fit into the "sci.electronics.basics" NewsGroup; often they would be consider OFF-TOPIC in other NewsGroups like : rec.radio.shortwave, rec.radio.amateur.antenna, alt.cellular.cingular, alt.internet.wireless, etc IMHO - In another life "Radium" would have made a great High School Science Teacher : Who's Students when on to do great things with their lives : Because "Radium" Touched Them With A Thirst For Knowledge And A Quest For Answers. -but- These NewsGroups are NOT a High School Science Class -and- "Radium" is just being 'radium'. http://en.wikipedia.org/wiki/Radium -alas- Our "Radium's" Half-Life of Readable Interest http://en.wikipedia.org/wiki/Half-life is at best about 16.04 Seconds ~ RHF |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
Radium hath wroth:
ps. how would u like to change the cell phone industry? Analog cells phones should stop using FM and should start using AM between frequencies of 40,000 to 285,000 Hz. Analog cell phones are going to be history in the US on Feb 18, 2008. Japan killed off analog around June 1999, Korea in Jan 2000, most of Europe in 1997, etc. 40KHz thru 285Khz? Great idea. Just one minor problem. A 1/4 wave antenna at about 100Khz frequency is 750 meters long. That's going to be a rather large antenna for literally dragging behind you. Maybe a balloon? Maybe a loop like this one? http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=10850 Of course propagation might be a problem, as it will only work at night and you'll have to connect to a cell site on the opposite coast for those frequencies to work. The customers can be ignored when they complain about atmospheric static and noise. Of course, 240KHz of usable bandwidth is much less than the hundreds of MHz currently in use by cellular providers, so there will substantially fewer users. Let's see.... there are 240 million subscribers in the US. Your AM system can handle about 40 users (6KHz channels), so your cell phone bill will only be 6 million times larger than it is currently. Now do you see why the microwave bands are so in demand for cellular. As I learned recently, 40 KHz is the minimum radio frequency required to coherently transmit/receive audio signals. Coherently? I would be worried if you planned to incoherently transmit/receive audio signals. Perhaps if you added 40KHz to your word salad, it would make your blather more coherent. (Hint: Look up the definition of coherent and then use it where appropriate). Actually, you're close. 40KHz is the common frequency used by ultrasonic TV remote controls. I've seen PWM modulation system using a pair of these to act as a crude cordless phone (that doesn't require FCC type certification). You could probably go down to 20KHz, but then intermodulation products (mixes) between the audio and the carrier will begin to be a problem. Congratulations, you got one thing mostly correct. The highest sound a human can hear is 20 KHz. Voice is from 300 to 3000Hz. You could probably get away with 300 to 2400Hz. If you're planning to transmitting AM hi-fi or data, then you might need the 20KHz. The radio-frequency used must be at least 2x the intended frequency of the information being transmitted/received. Ummm... no. You're apparently thinking of the Shannon rule for information bandwidth: http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem If your input audio is perhaps bandwidth limited to 3KHz, a 6KHz carrier will not work. You'll get considerable mixing (aliasing) and audio intermodulation crud. The carrier would need to be somewhat higher in frequency as limited by whatever output RF filtering is used. I chose 285 KHz to be the highest radio frequency for cell-phones because it is roughly the highest-frequency categorized as "long wave" radio. Nope. See details at: http://en.wikipedia.org/wiki/Longwave -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
"Radium" a COMPLETE IDIOT... - More Likely AnIn-Complete-Want-To-Be [.]
On 7/1/07 2:11 PM, in article
, "RHF" wrote: On Jul 1, 12:50 pm, "Porgy Tirebiter" wrote: "Radium" wrote in message oups.com... On Jul 1, 7:24 am, wrote: Analog cells phones should stop using FM and should start using AM between frequencies of 40,000 to 285,000 Hz. I chose 285 KHz to be the highest radio frequency for cell-phones because it is roughly the highest-frequency categorized as "long wave" radio. - IDIOT!......complete idiot...... PT - Once again why waste your time replying to his posts ? ? ? {Oops Like I Am Doing Too !} Actually "Radium" would appear to be an In-Complete-Want-To-Be driven by the 'urge' to Post these Forever Ponding Questions for others to charge at like Don Quijote's quest to slay Windmills {a fool's errand} http://en.wikipedia.org/wiki/Don_Quixote http://en.wikipedia.org/wiki/Fool%27s_errand FWIW - While many of his Post might fit into the "sci.electronics.basics" NewsGroup; often they would be consider OFF-TOPIC in other NewsGroups like : rec.radio.shortwave, rec.radio.amateur.antenna, alt.cellular.cingular, alt.internet.wireless, etc IMHO - In another life "Radium" would have made a great High School Science Teacher : Who's Students when on to do great things with their lives : Because "Radium" Touched Them With A Thirst For Knowledge And A Quest For Answers. But a teacher MUST be rational. You rate Radium with more potential than I can. This most recent post is really off the wall. -but- These NewsGroups are NOT a High School Science Class -and- "Radium" is just being 'radium'. http://en.wikipedia.org/wiki/Radium -alas- Our "Radium's" Half-Life of Readable Interest http://en.wikipedia.org/wiki/Half-life is at best about 16.04 Seconds ~ RHF . . . . |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-low carrier frequency
"Ian Jackson" wrote in message ... In message , cledus writes snip The fundamental answer is no, it is not possible to generate AM where the baseband signal is a pure 20 kHz sinewave and Fc20kHz. The reason is that the modulated waveform consists of the sum of a sinewave at Fc, a sinewave at Fc+20kHz, and a sinewave at Fc-20kHz. If Fc20kHz then one of the components becomes a "negative" frequency. So the carrier must be greater than the baseband signal to prevent this. I'm afraid that this is not correct. The 'laws of physics' don't suddenly stop working if the carrier is lower than the modulating frequency. However, there's no need to get into complicated mathematics to illustrate this. Here is a simple example: (a) If you modulate a 10MHz carrier with a 1MHz signal, you will produce two new signals (the sidebands) at the difference frequency of 10 minus 1 = 9MHz, and the sum frequency of 10 plus 1 = 11MHz. So you have the original carrier at 10MHz, and sideband signals at 9 and 11MHz (with a balanced modulator - no carrier - only 9 and 11MHz). (b) If you modulate a 1MHz carrier with a 10MHz signal, you will produce two new signals (the sidebands) at the difference frequency of 1 minus 10 = minus 9MHz, and the sum frequency of 1 plus 10 = 11MHz. The implication of the negative 'minus 9' MHz signal is that the phase of the 9MHz signal is inverted, ie 180 degrees out-of-phase from 9MHz Actually there would be no phase flip. cos(-a) = cos(a) produced in (a). So you have the original carrier at 1MHz, and sidebands at 9 and 11MHz (again, with a balanced modulator - no carrier - only 9 and 11MHz). The waveforms of the full composite AM signals of (a) and (b) will look quite different. The carriers are at different frequencies, and the phase of the 9MHz signal is inverted. However, with a double-balanced modulator, you will only have the 9 and 11MHz signal so, surprisingly, the resulting signals of (a) and (b) will look the same. A double-balanced mixer is a multiplier. A * B = B * A [Note that, in practice, many double-balanced modulators/mixers put loads of unwanted signals - mainly due the effects of harmonic mixing. However, the basic 'laws of physics' still apply.] Finally, although I have spoken with great authority, when I get a chance I WILL be doing at test with a tobacco-tin double-balanced mixer, What's a tobacco-tin double-balanced mixer? a couple of signal generators and a spectrum analyser - just to make sure that I'm not talking rubbish. In the meantime, I'm sure that some will correct me if I'm wrong. You did pretty good. Ian. -- -- rb |
AM electromagnetic waves: 20 KHz modulation frequency on an astronomically-lowcarrier frequency
Jeff Liebermann wrote:
40KHz thru 285Khz? Great idea. Just one minor problem. A 1/4 wave antenna at about 100Khz frequency is 750 meters long. That's going to be a rather large antenna for literally dragging behind you. Well, your math is correct. However, the so-called "atomic" wrist watches receive their time signal from WWVB which transmits at 60kHz. How do they get that 1250 meter long antenna ( 1/4 wave at 60 kHz) inside that itty bitty wrist watch case? ;-) |
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