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Radio controlled clock question
I figure many guys in this group must have one of those "atomic clocks" set
by the Boulder radio broadcast. Have any of you had problems with bogus signals -- someone intentionally setting clocks wrong? I live in La Mesa (near San Diego) and periodically find my clock to be incorrect -- usually by exactly one minute or hour. I've even caught it setting itself at times of the day it has no business resetting itself. SOMEbody's messing, as far as I can tell -- and they've been doing it for several years. Is that a common problem with these things? (I see that NIST actually PUBLISHES the time signal format on their site, which should make it very easy for radio-geeks to tamper.) --cleve |
#2
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Hi Cleve:
The NIST correction signal for digital clocks is transmitted on a very low frequency (far below the AM broadcast band). Although it's theoretically possible for somebody to transmit a VLF signal to spoof your clock, putting together a VLF transmitter and antenna and then putting out a signal of any appreciable power would be very, very difficult. As a rule of thumb, the lower you go in frequency, the greater the natual and manmade radio noise. Modern electrical and electronic equipment puts out a LOT of radio crud in the VLF portion of the spectrum. This interference goes long distances over power lines and electrical wiring. Worse, power lines and wiring work as antennas and radiate this manmade crud. My advice would be to try moving your clock to a different location in an attempt to get it away from any interference. If you really want to get serious, you can get a portable AM radio, tune it to an empty frequency, and walk around the house and listen to the noise to determine where the interference is minimal. When you find a quieter place, put your clock there. In addition to manmade interference is the problem of getting good reception of the actual NIST correction signal. Houses in southern California typically use metal foil-backed insulation in the walls and metal screen to hold the stucco. The foil and screen really block radio signals. If your clock uses a length of wire to receive the correction signal, try the following: - Make sure the wire is fully stretched out to its full length - Once you've found a fairly interference free part of your home, drill a tiny diameter (1/8 inch) hole through the wall insert a small diameter brass tube from a hobby shop through the wall, and then put your wire antenna through the wall. Then string up the wire in a straight line. I hope that helps. Regards, Brian Webb, KD6NRP Southern California "cleve" wrote in message news:kDaDc.1358$6r1.499@fed1read06... I figure many guys in this group must have one of those "atomic clocks" set by the Boulder radio broadcast. Have any of you had problems with bogus signals -- someone intentionally setting clocks wrong? I live in La Mesa (near San Diego) and periodically find my clock to be incorrect -- usually by exactly one minute or hour. I've even caught it setting itself at times of the day it has no business resetting itself. SOMEbody's messing, as far as I can tell -- and they've been doing it for several years. Is that a common problem with these things? (I see that NIST actually PUBLISHES the time signal format on their site, which should make it very easy for radio-geeks to tamper.) --cleve |
#3
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On Sat, 04 Sep 2004 23:32:41 GMT, "Brian Webb"
wrote: Hi Cleve: The NIST correction signal for digital clocks is transmitted on a very low frequency (far below the AM broadcast band). Although it's theoretically possible for somebody to transmit a VLF signal to spoof your clock, putting together a VLF transmitter and antenna and then putting out a signal of any appreciable power would be very, very difficult. As a rule of thumb, the lower you go in frequency, the greater the natual and manmade radio noise. Modern electrical and electronic equipment puts out a LOT of radio crud in the VLF portion of the spectrum. This interference goes long distances over power lines and electrical wiring. Worse, power lines and wiring work as antennas and radiate this manmade crud. My advice would be to try moving your clock to a different location in an attempt to get it away from any interference. If you really want to get serious, you can get a portable AM radio, tune it to an empty frequency, and walk around the house and listen to the noise to determine where the interference is minimal. When you find a quieter place, put your clock there. You might also try hooking up a suction cup pickup (used for recording off a phone handset) to a cheap (~$13) Radio Shack portable hand-sized amplifier. Amazing noises, especially in the vicinity of dimmer switches. Also fun on electric commuter trains. In addition to manmade interference is the problem of getting good reception of the actual NIST correction signal. Houses in southern California typically use metal foil-backed insulation in the walls and metal screen to hold the stucco. The foil and screen really block radio signals. If your clock uses a length of wire to receive the correction signal, try the following: - Make sure the wire is fully stretched out to its full length - Once you've found a fairly interference free part of your home, drill a tiny diameter (1/8 inch) hole through the wall insert a small diameter brass tube from a hobby shop through the wall, and then put your wire antenna through the wall. Then string up the wire in a straight line. I hope that helps. Regards, Brian Webb, KD6NRP Southern California "cleve" wrote in message news:kDaDc.1358$6r1.499@fed1read06... I figure many guys in this group must have one of those "atomic clocks" set by the Boulder radio broadcast. Have any of you had problems with bogus signals -- someone intentionally setting clocks wrong? I live in La Mesa (near San Diego) and periodically find my clock to be incorrect -- usually by exactly one minute or hour. I've even caught it setting itself at times of the day it has no business resetting itself. SOMEbody's messing, as far as I can tell -- and they've been doing it for several years. Is that a common problem with these things? (I see that NIST actually PUBLISHES the time signal format on their site, which should make it very easy for radio-geeks to tamper.) --cleve |
#4
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Thanks for the suggestions, guys.
I got a similar answer in alt.astronomy back in June. The guy who replied also indicated that Japan broadcasts a similar but incompatable time signal on the same frequency, and that might interfere here in CA. I've relocated/reoriented the clock and I haven't had any problems for awhile. The oddest was shortly after I bought it a couple of years ago. Something progressively "tested" the ability to set it during the course of one day: first it was exactly one hour off; later, 10 minutes; then 1 minute; then 10 seconds. It seemed to be a systematic "test" -- not at all random -- as if someone was testing their ability to set these clocks. Ever since then, I've been highly suspicious whenever I find that clock to be in disagreement with my standard clocks. Thanks for your replies. I very much appreciate it. --cleve wrote in message ... On Sat, 04 Sep 2004 23:32:41 GMT, "Brian Webb" wrote: Hi Cleve: The NIST correction signal for digital clocks is transmitted on a very low frequency (far below the AM broadcast band). Although it's theoretically possible for somebody to transmit a VLF signal to spoof your clock, putting together a VLF transmitter and antenna and then putting out a signal of any appreciable power would be very, very difficult. As a rule of thumb, the lower you go in frequency, the greater the natual and manmade radio noise. Modern electrical and electronic equipment puts out a LOT of radio crud in the VLF portion of the spectrum. This interference goes long distances over power lines and electrical wiring. Worse, power lines and wiring work as antennas and radiate this manmade crud. My advice would be to try moving your clock to a different location in an attempt to get it away from any interference. If you really want to get serious, you can get a portable AM radio, tune it to an empty frequency, and walk around the house and listen to the noise to determine where the interference is minimal. When you find a quieter place, put your clock there. You might also try hooking up a suction cup pickup (used for recording off a phone handset) to a cheap (~$13) Radio Shack portable hand-sized amplifier. Amazing noises, especially in the vicinity of dimmer switches. Also fun on electric commuter trains. In addition to manmade interference is the problem of getting good reception of the actual NIST correction signal. Houses in southern California typically use metal foil-backed insulation in the walls and metal screen to hold the stucco. The foil and screen really block radio signals. If your clock uses a length of wire to receive the correction signal, try the following: - Make sure the wire is fully stretched out to its full length - Once you've found a fairly interference free part of your home, drill a tiny diameter (1/8 inch) hole through the wall insert a small diameter brass tube from a hobby shop through the wall, and then put your wire antenna through the wall. Then string up the wire in a straight line. I hope that helps. Regards, Brian Webb, KD6NRP Southern California "cleve" wrote in message news:kDaDc.1358$6r1.499@fed1read06... I figure many guys in this group must have one of those "atomic clocks" set by the Boulder radio broadcast. Have any of you had problems with bogus signals -- someone intentionally setting clocks wrong? I live in La Mesa (near San Diego) and periodically find my clock to be incorrect -- usually by exactly one minute or hour. I've even caught it setting itself at times of the day it has no business resetting itself. SOMEbody's messing, as far as I can tell -- and they've been doing it for several years. Is that a common problem with these things? (I see that NIST actually PUBLISHES the time signal format on their site, which should make it very easy for radio-geeks to tamper.) --cleve |
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