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source for 60 kHz loopstick antenna
I'm trying to get a radio clock to sync up with WWVB (60 kHz out of
Colorado). In the place that I want to place the clock, I can not get it to sync, even at night when the signal is stronger. Inside the clock is a small ferrite-core loopstick antenna. I figured out which way the gain pattern pointed on the thing (i.e. not along the axis of the ferrite rod) and tried positioning the clock for maximum signal, but no luck. So now I'd like to try a better antenna. I won't have the time to make one myself, and I'd probably do it badly anyway. It seems that I should be able to buy an antenna for this fairly cheaply (thank you to my capitalist exploiter overlords!), but I can't find one. Ideally, one designed for WWVB's 60 kHz would be great, but I'll settle for anything really, as long as it claims to have some decent gain at 60 kHz. This clock is going inside a building, inside two layers of cinder block / concrete walls, so it's possible that I just won't be able to get a signal in there no matter what I use. The external-antenna-and-a-wire-run concept is the next step, but I'd rather not to that unless I have to. We're moving out of that facility in a few months so that would be wasted labor. What are some sources for loopstick antennas? On another note, in searching this forum, someone said: An LF loopstick antenna wound on a 1/2 inch diameter rod is *much* less efficient than a 1-meter square air loop Assuming I have the space, am I better off trying this with a few big loops of wire instead of a small ferrite loopstick? What are the rules of thumb for comparing the two types of loop antennas? Thanks! |
Hi Chris,
try to make a rectangular coil, about 1 ft x 1 ft, some 30 turns wound by a fairly thin magnet wire (#25 to #30). Bring it into resonance at 60 kHz by a capacitor, some 8000 - 10000 pF. Place the coil vertically, aiming to the transmitter, and place the clock to its center. You do not need any mods of the clock. The signal should be significantly stronger. BR from Ivan (Chris Campbell) wrote in message om... I'm trying to get a radio clock to sync up with WWVB (60 kHz out of Colorado). In the place that I want to place the clock, I can not get it to sync, even at night when the signal is stronger. Inside the clock is a small ferrite-core loopstick antenna. I figured out which way the gain pattern pointed on the thing (i.e. not along the axis of the ferrite rod) and tried positioning the clock for maximum signal, but no luck. ... |
To design small, VLF to HF, multi-turn loop antennas, download program
RJELOOP3 in a few seconds and run immediately. Sides of square, number of turns, spacing between turns, value of tuning capacitor, and other data. ---- .................................................. .......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp |
Where are you? I'm in Illinois and just got one of the clocks. I know it
helps you not not a bit for me to say mine sync'ed up quickly, but everybody says that kinda' stuff (:-).. Don't think there is anything to buy... Make is the only way. The instructions for mine say that it only listens at certain times and can take a few _DAYS_ to sync up. That seems strange to me...oh well. Ivan's passive loop is a VERY good idea - easy. I don't think cinder block walls will matter. Search for "lowfer". I wanted to actually hear WWVB and do a little SWLing for NDBs (300-500KHz) w/ my new IC 706 and did some snooping. A good loop takes a little bit of work. -- Steve N, K,9;d, c. i My email has no u's. "Chris Campbell" wrote in message m... I'm trying to get a radio clock to sync up with WWVB (60 kHz out of Colorado). In the place that I want to place the clock, I can not get it to sync, even at night when the signal is stronger. Inside the clock is a small ferrite-core loopstick antenna. I figured out which way the gain pattern pointed on the thing (i.e. not along the axis of the ferrite rod) and tried positioning the clock for maximum signal, but no luck. So now I'd like to try a better antenna. I won't have the time to make one myself, and I'd probably do it badly anyway. It seems that I should be able to buy an antenna for this fairly cheaply (thank you to my capitalist exploiter overlords!), but I can't find one. Ideally, one designed for WWVB's 60 kHz would be great, but I'll settle for anything really, as long as it claims to have some decent gain at 60 kHz. This clock is going inside a building, inside two layers of cinder block / concrete walls, so it's possible that I just won't be able to get a signal in there no matter what I use. The external-antenna-and-a-wire-run concept is the next step, but I'd rather not to that unless I have to. We're moving out of that facility in a few months so that would be wasted labor. What are some sources for loopstick antennas? On another note, in searching this forum, someone said: An LF loopstick antenna wound on a 1/2 inch diameter rod is *much* less efficient than a 1-meter square air loop Assuming I have the space, am I better off trying this with a few big loops of wire instead of a small ferrite loopstick? What are the rules of thumb for comparing the two types of loop antennas? Thanks! |
Steve Nosko wrote:
Where are you? I'm in Illinois and just got one of the clocks. I know it helps you not not a bit for me to say mine sync'ed up quickly, but everybody says that kinda' stuff (:-).. Don't think there is anything to buy... Make is the only way. The instructions for mine say that it only listens at certain times and can take a few _DAYS_ to sync up. That seems strange to me...oh well. Ivan's passive loop is a VERY good idea - easy. I don't think cinder block walls will matter. Search for "lowfer". I wanted to actually hear WWVB and do a little SWLing for NDBs (300-500KHz) w/ my new IC 706 and did some snooping. A good loop takes a little bit of work. All you will hear is nothing, unless your detector and audio amp goes down to DC. The modulation rate is one bit per second, by reducing the carrier level by 10 dB. There is no audio modulation, because the signal is also a frequency standard. The only way you would hear it would be to mix a signal to beat against WWVB to produce a heterodyne in the radio's pass band. -- We now return you to our normally scheduled programming. Take a look at this little cutie! ;-) http://home.earthlink.net/~mike.terrell/photos.html Michael A. Terrell Central Florida |
"Michael A. Terrell" wrote: Steve Nosko wrote: Where are you? I'm in Illinois and just got one of the clocks. I know it helps you not not a bit for me to say mine sync'ed up quickly, but everybody says that kinda' stuff (:-).. Don't think there is anything to buy... Make is the only way. The instructions for mine say that it only listens at certain times and can take a few _DAYS_ to sync up. That seems strange to me...oh well. Ivan's passive loop is a VERY good idea - easy. I don't think cinder block walls will matter. Search for "lowfer". I wanted to actually hear WWVB and do a little SWLing for NDBs (300-500KHz) w/ my new IC 706 and did some snooping. A good loop takes a little bit of work. All you will hear is nothing, unless your detector and audio amp goes down to DC. The modulation rate is one bit per second, by reducing the carrier level by 10 dB. There is no audio modulation, because the signal is also a frequency standard. The only way you would hear it would be to mix a signal to beat against WWVB to produce a heterodyne in the radio's pass band. -- We now return you to our normally scheduled programming. Take a look at this little cutie! ;-) http://home.earthlink.net/~mike.terrell/photos.html Michael A. Terrell Central Florida I hear it fine with several different receivers provided I use either CW or SSB. But! I CANNOT hear it on my IC-706; it does not seem to come alive until somewhere between 200 and 300kHz. Dave |
Dave Holford wrote:
I hear it fine with several different receivers provided I use either CW or SSB. But! I CANNOT hear it on my IC-706; it does not seem to come alive until somewhere between 200 and 300kHz. Dave Try using a HP312 series Frequency Selective Voltmeter for the receiver. Build a 60 KHz tuned loop and look at it with a scope. You can see the modulation, because it is so slow. It is a CW signal with a 10 dB gain reduction modulation with a maximum level change of twice per second. (Normal and -10 dB) I built a three foot square copper loop with an insulator where it was mounted on a cast aluminum electrical box, and wound 20 turns of wire inside the 3/4" copper pipe after it was soldered together. I used an op amp to give some gain,. and I could watch the modulation. The big problem was a neighbor about a half mile away left a TV set on 24/7 and the horizontal oscillator drifted after the station went off, and the harmonics would drift right through 60 KHz. I wanted to use it for a frequency standard, but I couldn't do it there. I will try it again, some day, now that I have a couple miles of woods between me and Colorado. I have enough gain to get around 12V P-P at the power inserter. I used 75 ohm cable and "F" fittings because they were handy, but I would use Mini Circuits MMICs and 50 Ohm cable if I built another outdoor 60 KHz antenna. -- We now return you to our normally scheduled programming. Take a look at this little cutie! ;-) http://home.earthlink.net/~mike.terrell/photos.html Michael A. Terrell Central Florida |
"Michael A. Terrell" wrote: Dave Holford wrote: I hear it fine with several different receivers provided I use either CW or SSB. But! I CANNOT hear it on my IC-706; it does not seem to come alive until somewhere between 200 and 300kHz. Dave Try using a HP312 series Frequency Selective Voltmeter for the receiver. Build a 60 KHz tuned loop and look at it with a scope. You can see the modulation, because it is so slow. It is a CW signal with a 10 dB gain reduction modulation with a maximum level change of twice per second. (Normal and -10 dB) I built a three foot square copper loop with an insulator where it was mounted on a cast aluminum electrical box, and wound 20 turns of wire inside the 3/4" copper pipe after it was soldered together. I used an op amp to give some gain,. and I could watch the modulation. The big problem was a neighbor about a half mile away left a TV set on 24/7 and the horizontal oscillator drifted after the station went off, and the harmonics would drift right through 60 KHz. I wanted to use it for a frequency standard, but I couldn't do it there. I will try it again, some day, now that I have a couple miles of woods between me and Colorado. I have enough gain to get around 12V P-P at the power inserter. I used 75 ohm cable and "F" fittings because they were handy, but I would use Mini Circuits MMICs and 50 Ohm cable if I built another outdoor 60 KHz antenna. -- We now return you to our normally scheduled programming. Take a look at this little cutie! ;-) http://home.earthlink.net/~mike.terrell/photos.html Michael A. Terrell Central Florida I have no problem receiving it on a number of different Ham and General Coverage receivers using random wires or simple vertical whips. I also hear it well with an active antenna. I have not noticed any real QRM problems on 60kHz although there are some really strong noise sources at other frequencies nearby. Dave 45N 75W |
Dave Holford wrote:
"Michael A. Terrell" wrote: Dave Holford wrote: I hear it fine with several different receivers provided I use either CW or SSB. But! I CANNOT hear it on my IC-706; it does not seem to come alive until somewhere between 200 and 300kHz. Dave Look at the design of the front end. If it is capacitor coupled, the capacitive reactance is so high that it blocks anything below 200 KHz. In this case you can add another cap in parallel to improve the lower frequencies. Multiply the original by 100 or higher, and add it in parallel to reduce the capacitive reactance, and the attenuation. I built a broadband DC block for my bench at Microdyne that had five caps in parallel. It was flat to less that a half dB from 50 KHz to 450 MHz, and had a VSWR of less than 1.05 across the entire range. It was built to maintain a 50 ohm impedance end to end. If it has a transformer, the losses are too high at low frequencies. In that case I would build a low pass filter and pre amp, and couple it to the input of the mixer to see how it performs. You would have to shut it off to use other bands, though. Try using a HP312 series Frequency Selective Voltmeter for the receiver. Build a 60 KHz tuned loop and look at it with a scope. You can see the modulation, because it is so slow. It is a CW signal with a 10 dB gain reduction modulation with a maximum level change of twice per second. (Normal and -10 dB) I built a three foot square copper loop with an insulator where it was mounted on a cast aluminum electrical box, and wound 20 turns of wire inside the 3/4" copper pipe after it was soldered together. I used an op amp to give some gain,. and I could watch the modulation. The big problem was a neighbor about a half mile away left a TV set on 24/7 and the horizontal oscillator drifted after the station went off, and the harmonics would drift right through 60 KHz. I wanted to use it for a frequency standard, but I couldn't do it there. I will try it again, some day, now that I have a couple miles of woods between me and Colorado. I have enough gain to get around 12V P-P at the power inserter. I used 75 ohm cable and "F" fittings because they were handy, but I would use Mini Circuits MMICs and 50 Ohm cable if I built another outdoor 60 KHz antenna. -- We now return you to our normally scheduled programming. Take a look at this little cutie! ;-) http://home.earthlink.net/~mike.terrell/photos.html Michael A. Terrell Central Florida I have no problem receiving it on a number of different Ham and General Coverage receivers using random wires or simple vertical whips. I also hear it well with an active antenna. I have not noticed any real QRM problems on 60kHz although there are some really strong noise sources at other frequencies nearby. Dave 45N 75W They only signals I saw were WWVB, and that damned TV's harmonics drifting through 60 KHz after the station went off the air. The guy was only there a couple days a month, and left the TV on to make people think he was home. -- We now return you to our normally scheduled programming. Michael A. Terrell Central Florida |
Ivan wrote:
try to make a rectangular coil, about 1 ft x 1 ft, some 30 turns wound by a fairly thin magnet wire (#25 to #30). Bring it into resonance at 60 kHz by a capacitor, some 8000 - 10000 pF. Place the coil vertically, aiming to the transmitter, and place the clock to its center. You do not need any mods of the clock. The signal should be significantly stronger. Now, just so I understand you correctly, you're saying I don't actually connect this loop antenna to the clock? I just place the clock in the center of it, and the loop antenna (I guess) induces a stronger signal in the clock's internal antenna? Wow, I'd love that. As for the loop ends, I just connect them together across the cap? And when you say "vertically, aiming to the transmitter", you mean that the plane of the loop intersects with the transmitting station, right? That is, I don't point the *face* of the loop at the transmitter, I point the edge towards it. Right? So, anyway, I'm making an antenna. Alright :) I downloaded and played with Reg's program and have a configuration that might work well. Can I stack wire turns, and if not, why not? It seems that all the designs have the wire turns lined up next to each other like: ***** and never ***** ***** ***** Is there something about keeping each loop *exactly* the same circumferential length (not even 0.2% difference) that dramatically affects loop antenna performance? Or some other affect? I'd like to fill a 5mm x 5mm cross section with wire turns, which means stacking them. |
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Richard Clark wrote:
The ultimate explanation is that if you read the instructions carefully, you may find they state to try on one wall, or move to another and try again (pretty much the same advice as that above, less all the wire and capacitors). The "synchronization" does not always happen all at once (again, this is undoubtedly discussed in the instructions - or used to be). You may spend up to a week discovering the sweet spot where the receiver responds. We have fielded many such questions as yours in the past, and I cannot recall anyone coming back after having given up (and I don't recall one needing an external antenna). Oh, I'm sure lots of folks ask questions here about these clocks :) Believe me, I tried and I was very patient. I tried the clock set up in five different locations, which included several orthogonal directions, and I left it in each position for at least 24 hours, and probably a lot longer. I spent a month on this and I'm not exaggerating. It was months ago (I *did* give up :) and my memory is fuzzy but I know I left it up at least overnight in each position, and for a week or more in some locations (i.e. on the bench, pointing in different directions). I never got a sync indoors. It's just that now I'm trying again, after having given up. Thanks for your help and I'll try the surrounding-loop solution. Makes me wish I'd taken that antenna design course in EE school. |
Chris Campbell wrote: I'm trying to get a radio clock to sync up with WWVB (60 kHz out of Colorado). ... From experience there are also differences in the performance of WWVB clock receivers of the same brand and model from opening the box and later from differences in aging. Several years ago I ordered a wris****ch and two travel clocks from one of then and still prominent "atomic" clock outfits. One of the travel clocks locked up soon (overnight? - brain cells fade) and the second shortly afterwards. The wris****ch just would not lock up - very small antenna, so I wasn't surprised that it would take longer. I tried leaving it overnight in parts of the away from PC, TV, radio, ... and orienting it in various ways to point it to Colorado. After about two weeks, when I had given up and was ready and call the company, I went on a trip from northern NJ to California. Somewhere, sometime during the trip it locked up. Then after returning home... nothing. Making a very long story short, the company _finally_ sent me a replacement wris****ch. The new one locked up nearly every night for the next 2 years and then, after any guarantee was gone, it quit. It still runs, just has long since drifted off time. Nothing since in the last 3 years, despite the deal of trying to find a 60-kHz quiet place, reorienting it... In the meantime, the travel clocks were doing fine, no matter where they were left or what part of the country I was in. Then about 2 years ago, one of them quit. Again - try finding that sweet, magic spot, leaving it side by side with its brother, oriented in the same direction. Always the same result - one fine, one deaf. I have thought about building a loop antenna like as has been disussed here to see if I could get at least the deaf travel clock locking. Tek makes tunable AM Loop antennas where the AM radio sits next to the loop and they do work out here in rural New Jersey. This discussion may yet spur me to physical wire and solder, not just typing, action. Somewhere I did have the URL of web page where a fellow built a shielded loop with an amplifier and all. The passive design, using Reg's program as a start, is simpler. I have several of the Sam's Club US$23 atomic wall clocks that lock up just fine, mounted on walls facing every which way. The outside temperature reading 433MHz receiver seems to be a flaky, marginal design, but that's a different story. Cheers, 73 Ron McConnell N 40º 46' 57.9" W 74º 41' 21.9" FN20ps77GV75 per w2iol or FN20ps77GU46 per K2RIW http://home.earthlink.net/~rcmcc |
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Chris Campbell wrote:
"I am trying to get a radio clock to sync up with WWVB (60 KHz out of Colorado). A course in antennas is nice but loop antennas are covered in the "ARRL Antenna Book". In my 19th edition, loop antennas are covered starting on pages 5-1 and 14-2. See Fig 3 on page 14-3. At 60 KHz, any practical loop is physically small in terms of wavelength. The far field pattern of a small circular loop is the same as that of a small square loop of the same enclosed area (Kraus edition 3, page 197). Area equals the square`s side length squared, and that is equal to pi times the radius squared for the circular loop. Current is all in the same direction in the small loop, so there`s a null perpendicular to the plane of the loop and radiation is in the plane of the loop. If the loop is placed in the vertical position, radiation is vertically polarized as required for all ground wave propagation. Far field strength associated with a small loop is directly proportional to the enclosed area in terms of wavelength (Formula 8 on page 199 of Kraus). Every receiving antenna is also a transmitting antenna. The most power that may be tapped from the antenna is 50%, and a matched load is required to extract 50%. Any mismatch increases the % of re-radiation. At a 100% mismatch, i.e., a shorted dipole or an untapped resonant loop, 100% of the energy captured must be re-radiated. So, set up a large resonant loop to capture all the 60 KHz energy you can. Position the 60 KHz receiver (clock) to couple the most desired energy and the least undesired energy possible into the receiver. A high-Q loop, except for radiation resistance, is desirable. Litz` wire uses copper better than solid wire does at 60 KHz. Best regards, Richard Harrison, KB5WZI |
Ron McConnell wrote:
I have thought about building a loop antenna like as has been disussed here to see if I could get at least the deaf travel clock locking. Tek makes tunable AM Loop antennas where the AM radio sits next to the loop and they do work out here in rural New Jersey. This discussion may yet spur me to physical wire and solder, not just typing, action. Somewhere I did have the URL of web page where a fellow built a shielded loop with an amplifier and all. The passive design, using Reg's program as a start, is simpler. I have several of the Sam's Club US$23 atomic wall clocks that lock up just fine, mounted on walls facing every which way. The outside temperature reading 433MHz receiver seems to be a flaky, marginal design, but that's a different story. Cheers, 73 Ron McConnell I built a Sheilded, amplified loop for my tests, and got a decent signal a few miles north of Orlando, years before they built the new towers, and transmitter. As far as the oudoor thermometer, Some cordless phones on the same band search for an open frequency, and wipe out the sync between the sensor and the clock. I need a cordless phone, more than the outdoor temperature, so I don't worry about it. -- We now return you to our normally scheduled programming. Michael A. Terrell Central Florida |
Steve and group:
I tuned my IC706 down there, and apparently the front end filters block anything that low. My Kenwood R-5000 hears the signal fine with a 100' random wire. The radio I would really like to try, the RCA AR-88LF, only goes down to 74 KHz, and I sold the old RAK? RAL? Navy monster which covers that range, so I have to believe the R-5000 on this one. The signal is a little weak mid-day, but strong the remainder of the time. I bought one of the cheap "atomic" wris****ches last month, and have been experimenting with orientation for sync. It has an indicator which shows if it has locked up in the last 24 hours, and the manual says it tries at 3 AM in whatever time zone it is set to. The wall clocks also have a lock indicator, and their manual says they try several times in the wee hours if the first try doesn't result in synchronization. But BEWARE, I have now observed two different instances, once each with two different clocks, that while indicating that resynchronization had occurred the previous evening, the clock indicated the time which was exactly 1 minute off, apparently due to a thunderstorm during the night. The orientation where the wris****ch synchronizes reliably is face down, BTW. -- Crazy George Remove N O and S P A M imbedded in return address |
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Chris:
I thought someone else would answer, but here it is: For highest Q you want the minimum capacitance between start and end, so what you suggest will work, but try to actually make the layers carefully so the outside layers don't collapse down to the first. -- Crazy George Remove N O and S P A M imbedded in return address "Chris Campbell" wrote in message om... (OK1SIP) wrote: try to make a rectangular coil, about 1 ft x 1 ft, some 30 turns wound by a fairly thin magnet wire (#25 to #30). Bring it into resonance at 60 kHz by a capacitor, some 8000 - 10000 pF. Place the coil vertically, aiming to the transmitter, and place the clock to its center. You do not need any mods of the clock. The signal should be significantly stronger. [I asked this a couple days ago but it was at the tail end of a longer message so maybe that's why nobody replied.] Can I stack wire turns, and if not, why not? It seems that all the designs have the wire turns lined up next to each other like: ***** and never ***** ***** ***** Is there something about keeping each loop *exactly* the same circumferential length (not even 0.2% difference) that dramatically affects loop antenna performance? Or some other affect? I'd like to fill a 5mm x 5mm cross section around the perimeter of the clock with wire turns, which means stacking them. |
Michael A. Terrell wrote: Ron McConnell wrote: I have several of the Sam's Club US$23 atomic wall clocks that lock up just fine, mounted on walls facing every which way. The outside temperature reading 433MHz receiver seems to be a flaky, marginal design, As far as the oudoor thermometer, Some cordless phones on the same band search for an open frequency, and wipe out the sync between the sensor and the clock. I need a cordless phone, more than the outdoor temperature, so I don't worry about it. My cordless phones work on 2.4GHz and the remote thermometers are on 433MHz - a frequency which is shared among many types of gadgets. I should add that there seemed to have been a redesign of the Sam's Club clock about a year ago. The remote temperature receiver seems better in new ones. I have 3 different brands of atomic-clocks-with-remote-thermometers working from one remote Sam's Club remote thermometer transmitter. Back to ham antennas... :) Cheers, 73 Ron McConnell N 40º 46' 57.9" W 74º 41' 21.9" FN20ps77GV75 per w2iol FN20ps77GU46 per K2RIW Magnetic declination 13ºW in early 2004 http://home.earthlink.net/~rcmcc |
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