Huh, I always had this image of a coil, with help from the ferrite. But now I see the ferrite as a little magnetic dipole flipping around, and the coil tucked in close* to sense the emf (changing B-Field.)
George H.
*(High filling factor in NMR parlance.)
You mean like a FitBit Surge, Garmin Forerunner, TomTom Spark, or probably another dozen "smart watches"?
Pretty much, though I now wear a smart watch to track exercise and my heart rate. Before I got this one, I hadn't worn a watch for thirty years.
How about a link for the wristwatch?
-- Rick
So if you turn on your Verizon phone where it can't see a GPS signal, it can't connect to the network? That's a bit surprising.
-- Rick
Am 18.04.2016 um 06:48 schrieb John Larkin:
The reception of the GPS signal is inside of Buildings often not possible, the short wave signal is much better in that respect.
Jorgen
My watch has a solar cell to keep the battery charged.
Bill
The best for sport being:
Glenn
Den 19/04/2016 kl. 08.19 skrev rickman: ...
Looking for multi time-zone radio controlled receiver wrist watches (24-hour option pay in euro)? - look for world radio support:
Check if summer-time is supported (if needed).
E.g.
Eurochron EFAUS 100 - Radio Controlled Solar-powered Watch:
Casio Releases OCEANUS Watches That Receive Both of GPS Signals and Radio Wave Time-Calibration Signals to Keep Accurate Time Anywhere in the World:
Clock radio:
euro mentioned:
radio controlled clock radios ought to be standard :-) :
Glenn
GPS is NOT required for a cell phone to operate. This can easily be demonstrated on any smartphone, where it is possible to temporarily disable the GPS sub-system in order to save battery power. Only a location request by a PSAP (public safety answering point) will turn it back on. You can also try operating a cell phone in an area where GPS reception is lacking (underground garage, dense forest, subway, tunnel, etc). I think you'll find that your cell phone still works, even though a GPS monitoring program will show no satellites.
Incidentally, having GPS time and network time has some interesting side effects. WWVB does UTC, while GPS does GPS time. At this time, GPS is 17 seconds ahead of UTC. Most GPS receivers compensate for this 17 second offset in order to produce accurate terrestrial time, but some cell phone manufactures didn't quite get it right. Here's a comparison of my PC clock with my cell phone GPS time:
Old Verizon is CDMA, which requires that all its base stations be GPS synchronized. The time is then rebroadcast to the handset. No GPS receiver is required in the handset. There are products that deliver CDMA time: LTE is much the same: but I couldn't find any stand alone time receivers for LTE.
Also, "feature phones" which have a GPS receiver solely for the required 911 location feature, do not have enough horsepower to produce a lat-long or time fix in the handset. All the chip does is deliver the various satellite delays to the cellular network provider. They pass the delay data to a central server, that adds DGPS correction, sector data from the cell tower, time of arrival data, and probably some fudge factors to the mix, calculates a position, and delivers it to the phone, cellular provider, PSAP (public safety answering point), or government spy agency. Somewhere in the package is the exact time.
The best of my knowledge, there are no cell phones that have a 60 KHz WWVB receiver inside. It would not be very practical to obtain a time fix only once per day, which is the way "atomic clock" and wristwatch timing devices operate. After midnight, they wake up, and listen for clean WWVB data. If they get three good transmissions in a row, they set the clock's time, and turn off for the rest of the night. If there's no accurate fix, it turns off, waits a while, and tries again later. Note that each WWVB fix takes 1 minute. That means the receiver needs 3 minutes of error free data every night in order to work.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I was hoping that someone else would explain how it works, mostly because I don't understand exactly how H (magnetic) field signals propagate and a few other LF (low frequency) details. However, that's never stopped me from offering an explanation.
The noise level on 60kHz is very high. Most of the noise is from atmospheric lightning and switching power supplies.
At a wavelength of 5000 meters, and continental path lengths, propagation is essentially ground wave using the H field (magnetic) rather than the E field (electric). While the WWVB transmit antenna is a big horizontal dipole, the H field is vertically polarized. This should drive you nuts trying to determine which way to "aim" the ferrite rod antenna: I did some tinkering and confirmed that it makes a difference: Horizontal loopstick perpendicular to WWVB. That's what a good signal should look like: Horizontal loopstick with the end pointed at WWVB, mostly noise:
On Sun, 17 Apr 2016 21:48:23 -0700, John Larkin Gave us:
The modulation schema is probably also a part of why the baseline noise is not so much of a factor.
You know... PSK, FSK and the like. The manner and level of FEC is likely also involved.
On Mon, 18 Apr 2016 01:23:42 -0400, rickman Gave us:
Not true... We have a GPS antenna chip on our radio that is smaller than 1 inch square by just around an 1/8" thick.
On Mon, 18 Apr 2016 01:23:42 -0400, rickman Gave us:
GPS is one of the tiniest signals received out there. It gets received at just over baseline noise figures.
On Mon, 18 Apr 2016 07:18:25 -0700, John Larkin Gave us:
There's Larkin being an abject idiot... again.
That's a good explanation. I figured the S/N ratio was the biggest concern. A friend of mine has a $500 antenna simulator that displays the radiation patterns of various antennas based on wire elements, lengths, spacing, etc. But I don't know if does ferrite rods. He's always coming up with new designs that occupy half the back yard.
--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@netfront.net ---
How are those new earrings looking?
-- John Larkin Highland Technology, Inc lunatic fringe electronics
This is from the guy who brags about how much he contributes to the group.
-- Rick
But not at 60 kHz. That is the point. The reason for needing a great antenna is to achieve an input signal level significantly above the receiver noise level. At these lower frequencies a great antenna is not needed since the environmental noise received by the antenna will be greater than the receiver noise level for even a marginal antenna.
The only useful feature of an antenna at these frequencies is its directionality. Loop antennas have nulls in the direction the stick points, perpendicular to the loop plane, and receive the signal in all directions in the plane. Not much to be done with it. What exactly would be the point of simulating that? Ferrite loops are well understood.
-- Rick
Thanks. It was a question worth answering.
$500 would probably be a student licence for NEC4 and one of the front end programs: However, it doesn't do ferrite rod antennas. However, it can be modeled as a magnetic loop antenna. "Rickman" and I have independently attempted to model a WWVB magnetic loop antenna using LTspice with uncertain results. The theory is that an antenna is nothing more than a matching transformer between the impedance of free space (377 ohms) and the input impedance of the receiver. If that's true, then almost any antenna can be modeled in the same manner as a transformer including the ferrite core. It won't show an antenna pattern or gain, but all the impedances, losses, and coupling numbers will be there.
This should be useful if you want to design ferrite rod VLF antennas:
On my flat roof, I do much the same as your friend, except I prefer free or shareware tools. Some examples (not all are mine): Note that they're mostly wire antennas on HF/VHF/UHF. VLF antennas at
60KHz are unfamiliar ground for me. I've built some WWVB antennas, which unfortunately fail to correspond to my calculated performance numbers, which is a sure sign that I've screwed up somewhere. Eventually, I'll get it right.This might also be of interest:
"WWVB Time signal @ 60Khz VLF" The receiver was a 10MHz downconverter to one of the numerous SDR-RTL USB dongles. The antenna is a TINY PA0RDT design: which is a good demonstration that as long as you're above the base line RF amp noise level of the receiver, you can hear signal as well as can be done with a much larger antenna. The good news is that it won't occupy the other half of your back yard.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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