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July 3rd 07, 03:07 AM
posted to sci.electronics.basics,rec.radio.amateur.antenna,alt.cellular.cingular,alt.internet.wireless,sci.physics
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How can such a small device -- a wrist watch -- receive such long-wave radio signals?
On Jul 3, 1:30 pm, Radium wrote:
On Jul 1, 4:34 pm, Jeff Liebermann wrote inhttp://groups.google.com/group/sci.electronics.basics/msg/41b78aad0ad... : Tommy Tootles hath wroth: 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. Yes, but the original derranged rantings required that *AUDIO* be used. This was suppose to be some kind of replacement for cellular. None of the long wave time standards belch audio like the short wave WWV stations. However, these time code transmitters operate at RF frequencies as low as 20KHz (mostly in Russia). See: http://www.npl.co.uk/time/measurement_time/time_trans.html (2002) How do they get that 1250 meter long antenna ( 1/4 wave at 60 kHz) inside that itty bitty wrist watch case? ;-) Touche and good question. Most of the desktop variety have a ferrite rod loaded with lots of fine wire. I have several like this, one with an external rod. However, that's obviously not going to work in a wris****ch unit. I don't have any idea what's inside or how the antenna done, but I can guess(tm). Here's one way: http://www.leapsecond.com/pages/atomic-bill/ The question has been asked befo http://www.eham.net/forums/Elmers/148090 However, no real description of what's inside the wris****ch. Going to the source: http://tf.nist.gov/stations/radioclocks.htm NIST Recommended Practices for WWVB receivers. http://tf.nist.gov/general/pdf/1976.pdf (See section 8A) "We recommend that RCC products should be sensitive enough to successfully synchronize to signals from WWVB with a field strength of 50 uV/m, if the signal to noise ratio exceeds 20 dB. The RF bandwidth of the receiver should be narrow, typically =B110 Hz or less." and: "Wris****ch antennas should not be contained in the band, so that RCC watch bands can be replaced in the same manner as the bands of ordinary watches when they are damaged or worn out." So much for the antenna in the wrist band idea. So, the question is, what type of tiny antenna will work with such a field strength at 60KHz. I dug through the FCC ID web pile looking for an inside photo of Casio watch, but couldn't find anything. I'm gonna have to either break one open, and/or calculate the field strength of a very small ferrite rod antenna (later). -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 Sorry, I am now extremely interested and frustrated about how the wris****ch can be so tiny yet receive so long-wave signals. Just how does such a magical device work? It seems to defy laws of science that such a small device can operate at such long-wavelengths of radio waves. I suspect it's probably something those FBI/CIA *******s are going to keep secret from us. Sick government f---scums. USA citizens should turn against the FBI/ CIA and molest the f---ing s--- out of their colons using bubbas' c-- ks. I want to know how such a tiny device can operate at such a long wavelength. Unfortunately, that info is classified by the FBI/CIA, and then won't let me or any USA citizen find out about it. I am getting so ****ed off right now. I am so interested in this wris****ch question yet I am so angry about it because the FBI/CIA won't let me know about it. F--k the CIA/FBI, may they be raped by big bubbas. No offense but please respond with reasonable answers & keep out the jokes, off-topic nonsense, taunts, insults, and trivializations. I am really interested in this. Normally they can coil the aerial inside the device either as a real coil or on an IC. This takes a lot of space however. |
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