On Fri, 14 Mar 2014 11:11:06 -0500, Frnak McKenney <frnak@far.from.the.madding.crowd.com> wrote:>> Since the essential thing is keeping the noise level down at the >> primary receiver. One idea would be to use a _battery_powered_ >> receiver far from any electric wiring or electronic gadgets feeding >> the extracted signal to a Bluetooth or similar narrow band link with >> perhaps 1 mW of transmitter power and hence long battery life, >> especially if operated only a few minutes each hour. >> >> In the house, use the received Bluetooth signal to amplitude modulate >> a local 60 kHz oscillator radiating a few meters to the receivers. >> >> Of course, you must be careful to avoid any feedback from your >> in-doors transmitter to the primary receiver, since both operate on >> the same frequency. > >Ah. Interesting: LF receiver ==> HF transmitter, then HF receivers >==> LF transmitters. That approach gets me around the problem of >running coax -- and, more importantly, crawling around in my attic -- >but adds a bit of overall cost: last time I checked, 3x Bluetooth >modules would run me about $90US.In fact you could do with any voice grade (0.3 - 3 kHz) radio (Bluetooth, Walkie talkie etc.). The primary receiver could be a direct conversion receiver with a local oscillator running at 59 or 61 kHz. This will create a beat tone at 1 kHz which can then be transferred using the voice grade radio link into the house. In the house, you need an 59 or 61 kHz oscillator and an amplitude modulator. A simple amplitude modulator will produce an additional sideband at 58 or 62 kHz, but this should not harm the indoor clocks. The main question is, is a single sideband receiver needed at the main receiver or is a double sideband receiver sufficient. If the band is sufficient quiet at 56-58 or 62-65 kHz is quiet, even a simple DSB receiver would be enough. If you use a tuned loop, this can be used to attenuate the image response. Take a look at example circuits using the NE602 oscillator/mixer chip, which could be used both as the primary receiver as well as the indoor transmitter (possibly beefed up by a single amplifier stage).
Methods for improving 60kHz RF signal (WWVB)?
Started by ●March 13, 2014
Reply by ●March 14, 20142014-03-14
Reply by ●March 14, 20142014-03-14
On Fri, 14 Mar 2014 21:01:31 +0200, upsidedown@downunder.com wrote:>On Fri, 14 Mar 2014 11:11:06 -0500, Frnak McKenney ><frnak@far.from.the.madding.crowd.com> wrote: > >>> Since the essential thing is keeping the noise level down at the >>> primary receiver. One idea would be to use a _battery_powered_ >>> receiver far from any electric wiring or electronic gadgets feeding >>> the extracted signal to a Bluetooth or similar narrow band link with >>> perhaps 1 mW of transmitter power and hence long battery life, >>> especially if operated only a few minutes each hour. >>> >>> In the house, use the received Bluetooth signal to amplitude modulate >>> a local 60 kHz oscillator radiating a few meters to the receivers. >>> >>> Of course, you must be careful to avoid any feedback from your >>> in-doors transmitter to the primary receiver, since both operate on >>> the same frequency. >> >>Ah. Interesting: LF receiver ==> HF transmitter, then HF receivers >>==> LF transmitters. That approach gets me around the problem of >>running coax -- and, more importantly, crawling around in my attic -- >>but adds a bit of overall cost: last time I checked, 3x Bluetooth >>modules would run me about $90US. > >In fact you could do with any voice grade (0.3 - 3 kHz) radio >(Bluetooth, Walkie talkie etc.). The primary receiver could be a >direct conversion receiver with a local oscillator running at 59 or 61 >kHz. This will create a beat tone at 1 kHz which can then be >transferred using the voice grade radio link into the house. > >In the house, you need an 59 or 61 kHz oscillator and an amplitude >modulator. > >A simple amplitude modulator will produce an additional sideband at 58 >or 62 kHz, but this should not harm the indoor clocks. > >The main question is, is a single sideband receiver needed at the main >receiver or is a double sideband receiver sufficient. If the band is >sufficient quiet at 56-58 or 62-65 kHz is quiet, even a simple DSB >receiver would be enough. If you use a tuned loop, this can be used to >attenuate the image response. > >Take a look at example circuits using the NE602 oscillator/mixer chip, >which could be used both as the primary receiver as well as the indoor >transmitter (possibly beefed up by a single amplifier stage). >The signal is simple pulse amplitude modulation with the information content in the pulse width... <http://www.analog-innovations.com/SED/WWVB-Schematic+Data.pdf> ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●March 14, 20142014-03-14
On Fri, 14 Mar 2014 12:11:39 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Fri, 14 Mar 2014 21:01:31 +0200, upsidedown@downunder.com wrote: > >>On Fri, 14 Mar 2014 11:11:06 -0500, Frnak McKenney >><frnak@far.from.the.madding.crowd.com> wrote: >> >>>> Since the essential thing is keeping the noise level down at the >>>> primary receiver. One idea would be to use a _battery_powered_ >>>> receiver far from any electric wiring or electronic gadgets feeding >>>> the extracted signal to a Bluetooth or similar narrow band link with >>>> perhaps 1 mW of transmitter power and hence long battery life, >>>> especially if operated only a few minutes each hour. >>>> >>>> In the house, use the received Bluetooth signal to amplitude modulate >>>> a local 60 kHz oscillator radiating a few meters to the receivers. >>>> >>>> Of course, you must be careful to avoid any feedback from your >>>> in-doors transmitter to the primary receiver, since both operate on >>>> the same frequency. >>> >>>Ah. Interesting: LF receiver ==> HF transmitter, then HF receivers >>>==> LF transmitters. That approach gets me around the problem of >>>running coax -- and, more importantly, crawling around in my attic -- >>>but adds a bit of overall cost: last time I checked, 3x Bluetooth >>>modules would run me about $90US. >> >>In fact you could do with any voice grade (0.3 - 3 kHz) radio >>(Bluetooth, Walkie talkie etc.). The primary receiver could be a >>direct conversion receiver with a local oscillator running at 59 or 61 >>kHz. This will create a beat tone at 1 kHz which can then be >>transferred using the voice grade radio link into the house. >> >>In the house, you need an 59 or 61 kHz oscillator and an amplitude >>modulator. >> >>A simple amplitude modulator will produce an additional sideband at 58 >>or 62 kHz, but this should not harm the indoor clocks. >> >>The main question is, is a single sideband receiver needed at the main >>receiver or is a double sideband receiver sufficient. If the band is >>sufficient quiet at 56-58 or 62-65 kHz is quiet, even a simple DSB >>receiver would be enough. If you use a tuned loop, this can be used to >>attenuate the image response. >> >>Take a look at example circuits using the NE602 oscillator/mixer chip, >>which could be used both as the primary receiver as well as the indoor >>transmitter (possibly beefed up by a single amplifier stage). >> > >The signal is simple pulse amplitude modulation with the information >content in the pulse width... > > <http://www.analog-innovations.com/SED/WWVB-Schematic+Data.pdf> > > ...Jim ThompsonThe format seems to be similar to Rugby or Mayflingen codes. My main point of using some audio frequency method for the downlink radio was the avoidance of transferring any DC contents on the link. Since apparently the ordinary clock receivers are not very picky about the actual carrier frequency, a slightly detuning between the primary receiver and the indoor transmitter would in fact be a good thing, since this reduces the risk for feedback from the indoor transmitter to the outdoor primary receiver.
Reply by ●March 14, 20142014-03-14
On 2014-03-14, Frnak McKenney <frnak@far.from.the.madding.crowd.com> wrote:>> I used a multi-turn 8" loop antenna encased in 1/2" copper pipe >> (with a fiber joint to avoid a shorted turn. > > Square/rectangular, yes? Or is there some easy way to bend Cu pipe > into a nice, pretty circle? <grin!>anneal it first. (get it red-hot with a propane torch) then when it cools it'll be soft and can be formed by hand. -- Neither the pheasant plucker, nor the pheasant plucker's son. --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
Reply by ●March 15, 20142014-03-15
On Thu, 13 Mar 2014 08:11:58 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>I used a multi-turn 8" loop antenna encased in 1/2" copper pipe (with >a fiber joint to avoid a shorted turn.I have used several hula hoops for various loop antennas. Of course the simplest case was a single turn HF loop with RG-58 coax (with a break in the shield at the top to avoid the short). I also tried an MF loop made of a ribbon cable (offset by one each turn) to make a multiturn loop, but the stray capacitance was far too great for any MF operation, putting the resonance frequency below the MF band, but this might be acceptable for LF or ELF operation.
Reply by ●March 15, 20142014-03-15
On a sunny day (Fri, 14 Mar 2014 10:16:45 -0500) it happened Frnak McKenney <frnak@far.from.the.madding.crowd.com> wrote in <S-adnYMsl6fAgL7OnZ2dnUVZ_rGdnZ2d@earthlink.com>:> >Wouldn't solve my WWVB problem, but it might be nice anyway. <grin!>It is Ferry Simple to build a good GPS clock. I just did that :-) one dealextreme GPS module one PIC 18F14K22 1 OLED module Ant Jou Neet Power Too (5V 70 mA) You could think about re-transmitting the time frame (modulating it), Jim already showed the format, its simple. I get UTC time and date, but that shoot not be that Diffy Cult to change to local time based on position. Personally I have Ferry Goot LF reception here, even with bad wall warts.
Reply by ●March 15, 20142014-03-15
On Thu, 13 Mar 2014 09:51:15 -0500, Frnak McKenney <frnak@far.from.the.madding.crowd.com> wrote:>I have two "atomic clocks": one is a La Crosse LCD unit, the other an >"analog" wall clock whose hands are driven by a WWVB-sync 1xAA-powered >mechanism. Following the recent "let's screw with everybody's clocks" >cycle neither of my "atomic clocks" caught it, and I was reminded that >I was Going To Fix This Problem last time. And the time before... ><grin!>That was in late 2012 that WWVB added phase modulation and broke many WWVB receivers. If that's your problem, there are a few fixes, but I suspect they're only useful for higher end receivers. <http://www.maxmcarter.com/rubidium/2012_mod/>>After some years I've discovered that, if I place my clocks near the >west-most window and leave them for a few days, they will usually >re-sync with the current WWVB time; if I don't do this it may be weeks >or months before they pick up a strong enough signal to reset.Sounds like interference. I have the same problem at both my house and my office. I have about 6 assorted WWVB receivers, all of which do not like being near any switching power supply, CCFL lamp, some LED lamps, solar inverters, etc. I built a 60KHz sniffer out of a loopstick cannibalized from one of my cheap receivers that didn't make it through the 2012 transition. I got lazy and just attached it to portable oscilloscope and retuned it to 60KHz to compensate for the scope probe capacitance. Wandering around the house, I identified some of the major noise source. I later did the same test with a larger 60 KHz loop antenna. Don't try this with a shielded loop as I was looking for the magnetic component of the signal, not the electric.>Is there some simple way of strengthening the WWVB signal so my clocks >will reset themselves automatically, preferably one that doesn't >involve stringing wires to each device?The article provided by Neon John: <http://www.ka7oei.com/wwvb_antenna.html> is the best I've seen. However, methinks some explanation of what's happening might be useful. You probably have noticed that 60 KHz antennas come in various sizes. There are tiny solenoid wound loopsticks that fit inside wristwatches. There are typically 8-10mm diameter ferrite rods and coils in various lengths. There are large unshielded loops and there are large shielded loops. However, if you test these devices in an area free from EMI interference, you'll probably find that they all have approximately the same field strength sensitivity when operating a given receiver. I've only compared a large home-made loop with a ferrite loopstick rod antenna, and they were (as far as I could tell) the same. So, what's the difference? Well, the unloaded Q of the various antennas are different. My guess(tm) is about: wristwatch antenna 50 loopstick rod 100 shielded loop 200 Loaded Q is less, and often as low as 1/2 of the unloaded Q. In this case, the Q determines how much extraneous noise the receiver has to deal with. Higher Q picks up less noise, is generally better, but can have a problem with temperature drift. Use only the best capacitors. Too much Q is also a problem if you want to receive other time stations without retuning the antenna. Somewhere between 50 and 100 seems about right. <http://www.c-max-time.com/tech/antenna.php> <http://www.tinaja.com/glib/WWVBexps.pdf> Most better receivers use shielded loops. However, the noise reduction is not just from the increased Q of the loop. It's also because such large loops are usually mounted outside, away from the switching power supplies. They're also magnetically shielded and thus are immune to direct (transformer) coupling from inductors and xformers. In short, if you want to get rid of the interference problem, get a better antenna and/or move the antenna away from the interference sources. As you note, propagation varies with the time of day. In general, the best signals are when both the transmitter and receiver are at night. <http://tf.nist.gov/tf-cgi/wwvbmonitor_e.cgi> <http://www.nist.gov/pml/div688/grp40/vb-coverage.cfm> (A working Java is required). What the graphs mean is that it's not going to update at some times of the day, no matter how good a location or hardware you are using. Interestingly, you'll find that 60 KHz propagation does not exhibit short term fades and dropouts that are so common on the higher shortwave frequencies with WWV.>And, if I have to build it, what would be a good unidirectional LF >antenna type?Bidirectional is usually good enough. Loop yagi style constructs are impractical because the element spacing will need to be about 1/4 wavelength apart, which at 60 KHz is about 1,250 meters. Some kind of phasing contraption using two loops and null out a single direction if you're dealing with a difficult noise source, such as an arcing power line insulator also won't work. Getting the loops far enough apart might be difficult. Too close, and they hear the same signals and cancel everything.>I have two neighbors to my SW and NW, and I really don't >want to mess up their equipment. <grin!>Build a 60 KHz sniffer and see if they really are a problem. My bet is that if you have interference problems, it's local. Incidentally, there's a small chance you'll run into something like these solar micro-inverters: <http://www.solarvoltpower.net/resources/KD-WVC-260W%20Owners%20Manual.pdf> They switch at 50 KHz, but communicate low speed data to a computah with a 60 KHz carrier. I haven't seen one yet, but I'm told that they do cause WWVB problems. Good luck. -- 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
Reply by ●March 15, 20142014-03-15
On Sat, 15 Mar 2014 10:45:47 -0700, Jeff Liebermann <jeffl@cruzio.com> wrote:>On Thu, 13 Mar 2014 09:51:15 -0500, Frnak McKenney ><frnak@far.from.the.madding.crowd.com> wrote: > >>I have two "atomic clocks": one is a La Crosse LCD unit, the other an >>"analog" wall clock whose hands are driven by a WWVB-sync 1xAA-powered >>mechanism. Following the recent "let's screw with everybody's clocks" >>cycle neither of my "atomic clocks" caught it, and I was reminded that >>I was Going To Fix This Problem last time. And the time before... >><grin!> > >That was in late 2012 that WWVB added phase modulation and broke many >WWVB receivers. If that's your problem, there are a few fixes, but I >suspect they're only useful for higher end receivers. ><http://www.maxmcarter.com/rubidium/2012_mod/> >[snip] Aha! I didn't know about that phase modulation addition. Reading here.... <http://www.nist.gov/pml/div688/grp40/wwvb.cfm> the way they did it will raise havoc with the synchronous AGC AM detection schemes used in most old clocks, and in my old chip design... <http://www.analog-innovations.com/SED/WWVB-Schematic+Data.pdf> I'll have to muse over that and see if there's a solution. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●March 15, 20142014-03-15
On Fri, 14 Mar 2014 21:01:31 +0200, upsidedown@downunder.com wrote:>On Fri, 14 Mar 2014 11:11:06 -0500, Frnak McKenney ><frnak@far.from.the.madding.crowd.com> wrote: > >>> Since the essential thing is keeping the noise level down at the >>> primary receiver.Exactly.>>> One idea would be to use a _battery_powered_ >>> receiver far from any electric wiring or electronic gadgets feeding >>> the extracted signal to a Bluetooth or similar narrow band link with >>> perhaps 1 mW of transmitter power and hence long battery life, >>> especially if operated only a few minutes each hour.I don't think battery operation will help much. At the low power requirements for a WWVB front end, a simple analog power supply should be adequate. If you're worried about conducted emissions from the power lines, then there are various power line filters and ferrite beads that should help.>>> In the house, use the received Bluetooth signal to amplitude modulate >>> a local 60 kHz oscillator radiating a few meters to the receivers.Ummm... Bluegoof has an end to end latency of about 150 msec. I've measured end to end audio latency at up to about 300 msec with various BT devices. With such an arrangement, your clock will be about 1/4 second behind. However, you can use an AptX codec, which reduces the end to end latency to a claimed 32 msec. <http://en.wikipedia.org/wiki/AptX> However, if you don't need this level of precision, you can probably ignore the added latency.>>> Of course, you must be careful to avoid any feedback from your >>> in-doors transmitter to the primary receiver, since both operate on >>> the same frequency.Good luck. Self interference will certainly be a problem.>>Ah. Interesting: LF receiver ==> HF transmitter, then HF receivers >>==> LF transmitters. That approach gets me around the problem of >>running coax -- and, more importantly, crawling around in my attic -- >>but adds a bit of overall cost: last time I checked, 3x Bluetooth >>modules would run me about $90US.>In fact you could do with any voice grade (0.3 - 3 kHz) radio >(Bluetooth, Walkie talkie etc.). The primary receiver could be a >direct conversion receiver with a local oscillator running at 59 or 61 >kHz. This will create a beat tone at 1 kHz which can then be >transferred using the voice grade radio link into the house. > >In the house, you need an 59 or 61 kHz oscillator and an amplitude >modulator. > >A simple amplitude modulator will produce an additional sideband at 58 >or 62 kHz, but this should not harm the indoor clocks. > >The main question is, is a single sideband receiver needed at the main >receiver or is a double sideband receiver sufficient. If the band is >sufficient quiet at 56-58 or 62-65 kHz is quiet, even a simple DSB >receiver would be enough. If you use a tuned loop, this can be used to >attenuate the image response. > >Take a look at example circuits using the NE602 oscillator/mixer chip, >which could be used both as the primary receiver as well as the indoor >transmitter (possibly beefed up by a single amplifier stage).The occupied bandwidth of WWVB is about 5 Hz (shortest pulse width is about 200 msec). The LW (long wave) frequencies are really noisy from EMI and atmospheric noise (mostly lightning crashes). This noise and interference are the major limitation to decent reception. Retransmitting on a nearby frequency isn't going to work well. Besides, it would be classified as an intentional radiator (FCC Part 19.something) which restricts the transmit power and operating frequencies. The possibility of interference to itself and other time receivers doesn't make this a very attractive idea. Instead, mix and upconvert the WWVH signal to some other much higher frequency. Pick something in the HF ham bands for testing. Power line communications for telephone extensions works well enough at HF frequencies. A single antenna and TRF (tuned RF) receiver, with the 60Khz amplifier signal fed to an upconverter (mixer), could feed the entire house. Install downconverters (mixers) that feed various clocks and devices, or just decode the WWVB data directly at the higher HF frequency. The waveform will be exactly the same as what the receiver produces. Big advantage is that since this secheme does not decode and re-modulate, there's very little added time delay. You can also isolate the receiver from the displays with optical fiber. No need for anything elaborate. Just an IR LED and photo detector that will operate at 60 KHz. Amplify, maybe add some AGC (automatic gain control), and feed the LED emitter directly. If you don't like fiber, then do it with infrared "free space" communications and some optics. -- 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
Reply by ●March 15, 20142014-03-15
On Sat, 15 Mar 2014 12:05:27 -0700, Jeff Liebermann <jeffl@cruzio.com> wrote:>I don't think battery operation will help much. At the low power >requirements for a WWVB front end, a simple analog power supply should >be adequate. If you're worried about conducted emissions from the >power lines, then there are various power line filters and ferrite >beads that should help.A bit more on power line emissions and WWVB: <http://www.prc68.com/I/LF-Ant.shtml> The whip antenna is tunable and run from an AC power supply. However, the conducted junk from the power line made 60 KHz reception rather problematic, until the author added additional RF filtering and bypassing. Some performance reports with a Spectracom 8206 antenna, which is a shielded ferrite rod type: <http://www.febo.com/time-freq/wwvb/sig-strength/wwvb-spectracom.html> Note that at some times of the day, the SNR is near zero making AM demodulation impossible. -- 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
