Re: [time-nuts] What are these towers?
Looks like it's an AM broadcast directional array; http://wireless2.fcc.gov/UlsApp/AsrSearch/asrRegistration.jsp?regKey=603263 On 5/20/2011 4:54 PM, Jason Rabel wrote: I was just browsing around on Google Earth and came across this cluster of transmission towers... Anyone care to take a guess what they are for? Television, radio, navigation... or something else? Looks like 11 towers... 29° 59' 34N, 95° 28' 24W -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] ZAPD-3DB-1675-3
I am considering using the ZAPD-3DB for GPS distribution. Any information available before I do something stupid? Thanks Bert Kehren ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] ZAPD-3DB-1675-3
Is that the ZAPD-3DB-1675-3 or ZAPD-3DB-1575-3? From: ewkeh...@aol.com ewkeh...@aol.com To: time-nuts@febo.com Sent: Thursday, May 26, 2011 4:45 PM Subject: [time-nuts] ZAPD-3DB-1675-3 I am considering using the ZAPD-3DB for GPS distribution. Any information available before I do something stupid? Thanks Bert Kehren ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] ZAPD-3DB-1675-3
On 5/26/2011 7:45 AM, ewkeh...@aol.com wrote: I am considering using the ZAPD-3DB for GPS distribution. Any information available before I do something stupid? Thanks Bert Kehren It's hard to say Bert, since MCL do not list anything under that number. I have used one of the ZAPD series for feeding two GPS receivers, but you need to add a blocking cap in one branch, and if the Receiver connected to that one needs to see a load also add a series choke and R combination to make it look like an antenna is connected. With a good well sited antenna the extra 3dB loss will not matter. Dan ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Correction it is a ZAPD-3DB-1575-3
Getting my glasses out it is a 1575-3 Thanks for the correction. Bert Kehren ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IEEE Spectrum Magazine interviews one of our own...
That is the solution: http://xkcd.com/162/ - Henry -- ehydra.dyndns.info Tom Van Baak schrieb: Hi Christopher, Thanks for those interesting links. Note PHK's original ACM article is: http://queue.acm.org/detail.cfm?id=1967009 The recent IEEE mention is: http://spectrum.ieee.org/podcast/at-work/innovation/does-anybody-really-know-what-time-it-is With audio: http://www.ieee.org/netstorage/spectrum/radio/mp3/IEEESpectrum_2011.05.13_LeapSeconds.mp3 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Voltage standards
Hello all, I was reading some old posts about voltage standards from Dr. Kirby, and some others, and one that was mentioned was the older Fluke standards. I did some research on this, going back to the Fluke 730A transfer standard, which I have one of, and found out what the voltage reference and the differential amplifier was from an old Motorola parts book dating from 1968. The voltage reference in the Fluke 730A was most likely the Motorola part number: MCA1914N or the MCA1924N in a can package. Both are rated at 6.8 Vdc, but there is a difference in the maximum voltage change between the two. The MCA1914N is the tightest, with a change of only 0.005 volts from 0 to 75 deg C. The MCA1924N is made for a broader temperature, with a change of only 0.010 volts from -55 to 100 deg C. These are not an oven zener, but a voltage reference. Motorola first produced these using two diodes and a transistor sealed in a can, literally. They used a temperature compensated zener diode, consisting of a zener, and a regular diode, turned with their cathodes facing, and connected together. These were placed inside the can, along with a transistor across from them, then sealed. They used this same reference transistor on up through several transfer standards, including the 732A. The Fluke 730A did not use an op-amp after the reference, but used a dual transistor in a can, and created their own comparator amp. Motorola made several of these along with Fairchild. There are two possibilities here in the parts. I think they used a MD918A or MD918B, which are dual NPN silicon annular transistors, with a Vceo of 15 Vdc, and an Ic of 50 mA. The MD918 series was to be used for differential amplifier applications requiring a matched pair of transistors with a high degree of parameter uniformity under varying environmental conditions. The other possibility on the dual transistor was a 2N2914, which was a dual npn silicon annular transistor, especially designed for low-level, low noise, differential amplifier applications, featuring very high Beta, guaranteed from 10 uAdc to 1 mAdc, and excellent noise characteristics. Next, the Fluke 731B used the same voltage reference, but it did not use the dual transistor amp. Fluke changed this to an op-amp, which turns out to be a LM308. This op-amp was then used in the newer models after the 731B. Also, this op amp used a few of the same resistor values, and circuitry, as the two transistor amp. Now, a word about voltage transfer standards. They are not meant to be as stable as a true primary voltage standard, as they are meant to be used to transfer a voltage from a known source to other equipment being calibrated. The transfer standard is made to be recalibrated in one year increments or closer. Tight tolerances in the short term, in one year or less, are all that is needed. The Fluke 730A, 731B, and 732A and B are all transfer units. The small voltage transfer standard boards, now sold on ebay, are meant for calibration every six months, and are not meant to be a long term primary standard. They should be calibrated from another transfer standard, which has been calibrated from a primary voltage standard, such as a Josephson type, by Fluke, or the NIST. The ones calibrated by using a DMM, no matter who made it, are not calibrated correctly. To calibrate a board correctly requires the use of a voltage transfer standard, that was calibrated by a primary voltage standard, and a very sensitive null meter-detector such as a Fluke 845A, etc. Hope this helps the ones who had a few questions. Will ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Voltage standards
Hello Will, I think you meant to post this on the Volt-Nuts list ? The reference parts used in the Fluke 731/732 are not off the shelf parts, they are selected. While they are referred to as transfer devices, if working correctly, they exceeded their specs versus time on the 10 volt port. I base this on the history of over 50 units that were tracked by Navy's Primary Lab, as these were used to feed the second level labs in the Navy's system. BillWB6BNQ Will Matney wrote: Hello all, I was reading some old posts about voltage standards from Dr. Kirby, and some others, and one that was mentioned was the older Fluke standards. I did some research on this, going back to the Fluke 730A transfer standard, which I have one of, and found out what the voltage reference and the differential amplifier was from an old Motorola parts book dating from 1968. The voltage reference in the Fluke 730A was most likely the Motorola part number: MCA1914N or the MCA1924N in a can package. Both are rated at 6.8 Vdc, but there is a difference in the maximum voltage change between the two. The MCA1914N is the tightest, with a change of only 0.005 volts from 0 to 75 deg C. The MCA1924N is made for a broader temperature, with a change of only 0.010 volts from -55 to 100 deg C. These are not an oven zener, but a voltage reference. Motorola first produced these using two diodes and a transistor sealed in a can, literally. They used a temperature compensated zener diode, consisting of a zener, and a regular diode, turned with their cathodes facing, and connected together. These were placed inside the can, along with a transistor across from them, then sealed. They used this same reference transistor on up through several transfer standards, including the 732A. The Fluke 730A did not use an op-amp after the reference, but used a dual transistor in a can, and created their own comparator amp. Motorola made several of these along with Fairchild. There are two possibilities here in the parts. I think they used a MD918A or MD918B, which are dual NPN silicon annular transistors, with a Vceo of 15 Vdc, and an Ic of 50 mA. The MD918 series was to be used for differential amplifier applications requiring a matched pair of transistors with a high degree of parameter uniformity under varying environmental conditions. The other possibility on the dual transistor was a 2N2914, which was a dual npn silicon annular transistor, especially designed for low-level, low noise, differential amplifier applications, featuring very high Beta, guaranteed from 10 uAdc to 1 mAdc, and excellent noise characteristics. Next, the Fluke 731B used the same voltage reference, but it did not use the dual transistor amp. Fluke changed this to an op-amp, which turns out to be a LM308. This op-amp was then used in the newer models after the 731B. Also, this op amp used a few of the same resistor values, and circuitry, as the two transistor amp. Now, a word about voltage transfer standards. They are not meant to be as stable as a true primary voltage standard, as they are meant to be used to transfer a voltage from a known source to other equipment being calibrated. The transfer standard is made to be recalibrated in one year increments or closer. Tight tolerances in the short term, in one year or less, are all that is needed. The Fluke 730A, 731B, and 732A and B are all transfer units. The small voltage transfer standard boards, now sold on ebay, are meant for calibration every six months, and are not meant to be a long term primary standard. They should be calibrated from another transfer standard, which has been calibrated from a primary voltage standard, such as a Josephson type, by Fluke, or the NIST. The ones calibrated by using a DMM, no matter who made it, are not calibrated correctly. To calibrate a board correctly requires the use of a voltage transfer standard, that was calibrated by a primary voltage standard, and a very sensitive null meter-detector such as a Fluke 845A, etc. Hope this helps the ones who had a few questions. Will ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Voltage standards
Bill, Yes, Fluke did cherry pick on what they bought, or paid to have Motorola to do it. HP does the same when purchasing voltage references, but they both do burn them in themselves after they receive them. The duds are used in less tolerant meters, etc. That is what Fluke wrote about doing in an app note of theirs. Also, the military gets the pick of them all, and is the reason I try to buy military surplus that's in good shape. My Fluke 730A is ex-Navy. Actually, back in 2008, this subject was discussed here on Time Nuts, and was the reason why I made this post. At the time, nobody had crossed the Motorola part numbers, and just called them the part from Motorola. It took digging out an old Motorola manual from 1968 to find them. I am hoping it will help others if they have an older Fluke transfer standard they need to repair, as there are parts still available by a few dealers. However, to get any kind of accuracy, the parts will have to be burned in at least around, or over, a three month period. I also wanted to note that the small transfer boards being offered, by several, should be looked at by the way they are calibrated, if they are to have any sort of precision. Best, Will *** REPLY SEPARATOR *** On 5/26/2011 at 4:18 PM WB6BNQ wrote: Hello Will, I think you meant to post this on the Volt-Nuts list ? The reference parts used in the Fluke 731/732 are not off the shelf parts, they are selected. While they are referred to as transfer devices, if working correctly, they exceeded their specs versus time on the 10 volt port. I base this on the history of over 50 units that were tracked by Navy's Primary Lab, as these were used to feed the second level labs in the Navy's system. BillWB6BNQ Will Matney wrote: Hello all, I was reading some old posts about voltage standards from Dr. Kirby, and some others, and one that was mentioned was the older Fluke standards. I did some research on this, going back to the Fluke 730A transfer standard, which I have one of, and found out what the voltage reference and the differential amplifier was from an old Motorola parts book dating from 1968. The voltage reference in the Fluke 730A was most likely the Motorola part number: MCA1914N or the MCA1924N in a can package. Both are rated at 6.8 Vdc, but there is a difference in the maximum voltage change between the two. The MCA1914N is the tightest, with a change of only 0.005 volts from 0 to 75 deg C. The MCA1924N is made for a broader temperature, with a change of only 0.010 volts from -55 to 100 deg C. These are not an oven zener, but a voltage reference. Motorola first produced these using two diodes and a transistor sealed in a can, literally. They used a temperature compensated zener diode, consisting of a zener, and a regular diode, turned with their cathodes facing, and connected together. These were placed inside the can, along with a transistor across from them, then sealed. They used this same reference transistor on up through several transfer standards, including the 732A. The Fluke 730A did not use an op-amp after the reference, but used a dual transistor in a can, and created their own comparator amp. Motorola made several of these along with Fairchild. There are two possibilities here in the parts. I think they used a MD918A or MD918B, which are dual NPN silicon annular transistors, with a Vceo of 15 Vdc, and an Ic of 50 mA. The MD918 series was to be used for differential amplifier applications requiring a matched pair of transistors with a high degree of parameter uniformity under varying environmental conditions. The other possibility on the dual transistor was a 2N2914, which was a dual npn silicon annular transistor, especially designed for low-level, low noise, differential amplifier applications, featuring very high Beta, guaranteed from 10 uAdc to 1 mAdc, and excellent noise characteristics. Next, the Fluke 731B used the same voltage reference, but it did not use the dual transistor amp. Fluke changed this to an op-amp, which turns out to be a LM308. This op-amp was then used in the newer models after the 731B. Also, this op amp used a few of the same resistor values, and circuitry, as the two transistor amp. Now, a word about voltage transfer standards. They are not meant to be as stable as a true primary voltage standard, as they are meant to be used to transfer a voltage from a known source to other equipment being calibrated. The transfer standard is made to be recalibrated in one year increments or closer. Tight tolerances in the short term, in one year or less, are all that is needed. The Fluke 730A, 731B, and 732A and B are all transfer units. The small voltage transfer standard boards, now sold on ebay, are meant for calibration every six months, and are not meant to be a long term primary standard. They should be calibrated from another transfer standard, which has been calibrated from a primary
Re: [time-nuts] Voltage standards
Will, I beg to differ with you on the military statement. The Navy's Primary LAB received 100 of the 731's that specifically were not hand picked, as you suggest. Out of that 100 a number of them were used for a vast array of testing including destructive testing. A few units had problems right at the start, but the majority held up very well. The purpose being to define the value of the item regarding the Navy's mission and support there of. I know all this because a close friend of mine was the LAB person who did the project. His responsibility, at the LAB was maintaining the Navy's primary voltage reference. From this large test base came a number of improvements my friend suggested to Fluke that were incorporated in later production units. I guess it would be way more accurate to say Fluke used (wisely) the LAB as a beta tester of their product which was brand new at the time. Gaining the Navy's acceptance was a big deal in the scheme of things in those days. The quality of the Fluke equipment was outstanding and, no, the military did not hand pick. The same went for the HP equipment and Tektronix. Simpson was another cornerstone with their 260 VOM as the Navy had a ton of those. So was Triplett who had some very good VOM's in the day. A very good instrument to grab when they show up is the HP 6920 Meter calibrator. Yes it is old but it was specifically built to do VOM's like the simpson and individual meter movements as well. It outputs DC and AC voltage (60 Hz) (zero to 1000) and current (zero to 5A) and is quite handy to have. As for the small transfer boards you refer to, I completely understand what you mean. While they may serve a purpose for the masses, their advertising is a bit misleading to put it kindly. BillWB6BNQ Will Matney wrote: Bill, Yes, Fluke did cherry pick on what they bought, or paid to have Motorola to do it. HP does the same when purchasing voltage references, but they both do burn them in themselves after they receive them. The duds are used in less tolerant meters, etc. That is what Fluke wrote about doing in an app note of theirs. Also, the military gets the pick of them all, and is the reason I try to buy military surplus that's in good shape. My Fluke 730A is ex-Navy. Actually, back in 2008, this subject was discussed here on Time Nuts, and was the reason why I made this post. At the time, nobody had crossed the Motorola part numbers, and just called them the part from Motorola. It took digging out an old Motorola manual from 1968 to find them. I am hoping it will help others if they have an older Fluke transfer standard they need to repair, as there are parts still available by a few dealers. However, to get any kind of accuracy, the parts will have to be burned in at least around, or over, a three month period. I also wanted to note that the small transfer boards being offered, by several, should be looked at by the way they are calibrated, if they are to have any sort of precision. Best, Will *** REPLY SEPARATOR *** On 5/26/2011 at 4:18 PM WB6BNQ wrote: Hello Will, I think you meant to post this on the Volt-Nuts list ? The reference parts used in the Fluke 731/732 are not off the shelf parts, they are selected. While they are referred to as transfer devices, if working correctly, they exceeded their specs versus time on the 10 volt port. I base this on the history of over 50 units that were tracked by Navy's Primary Lab, as these were used to feed the second level labs in the Navy's system. BillWB6BNQ Will Matney wrote: Hello all, I was reading some old posts about voltage standards from Dr. Kirby, and some others, and one that was mentioned was the older Fluke standards. I did some research on this, going back to the Fluke 730A transfer standard, which I have one of, and found out what the voltage reference and the differential amplifier was from an old Motorola parts book dating from 1968. The voltage reference in the Fluke 730A was most likely the Motorola part number: MCA1914N or the MCA1924N in a can package. Both are rated at 6.8 Vdc, but there is a difference in the maximum voltage change between the two. The MCA1914N is the tightest, with a change of only 0.005 volts from 0 to 75 deg C. The MCA1924N is made for a broader temperature, with a change of only 0.010 volts from -55 to 100 deg C. These are not an oven zener, but a voltage reference. Motorola first produced these using two diodes and a transistor sealed in a can, literally. They used a temperature compensated zener diode, consisting of a zener, and a regular diode, turned with their cathodes facing, and connected together. These were placed inside the can, along with a transistor across from them, then sealed. They used this same reference transistor on up through several transfer standards, including the 732A. The Fluke 730A did not use
Re: [time-nuts] Voltage standards
Bill, What I was getting at, on the military equipment, was that generally this equipment has more testing done on it than for the normal industrial consumer. I would assume that Fluke was working with the military here to make the equipment pass the rigorous tests of the military, and as you stated, the Navy helped in furthering the designs. From my understanding, and from reviewing military bids, they wanted testing done on everything to the point it would cost an kings ransom to make. That's why I never did fool with bidding on government contracts. Generally, when a contract is won, the manufacturer will build a certain lot of the equipment to the specs of that order. I know of one company who was building differential voltmeters, who lost to Fluke over not being able to meet the government specs. They tried for an appeal, saying the government was biased, but they lost over something to do with the filtering on the front end, if I remember correctly. In your case, I would say that the Navy's calibration program was wanting to work with Fluke to better the products for the future. You mentioned the HP 6920, but there is another for the analog and 3-1/2 digit meters, well to 4-1/2 digits really, and that was the Fluke 760A, if you didn't mind lugging around all the weight of the unit. I have one of these also, and it is ex-Navy. The HP 6920 turns up on eBay more than the Fluke now, as about all of the 760A's were ex-military units a few years back, and they were gobbled up. The one I bought was freshly calibrated at the time. However, anymore, I use artifact standards for most of my calibration, especially on resistance, and use a round-robin transfer on voltage. Current calibration is done easily, by setting the load resistor tolernace with an artifact standard, and applying an accurate voltage. For frequency, I am using a GPS controlled DOCXO standard and a rubidium, like most of us now. I never did invest in a cesium standard. On the boards that are available, I prefer the Geller. Use them as soon as you buy them, or soon after you build the board, and have him calibrate it. If you build one up, make sure to use a battery system so that the thing will run powered up from the time you ship it for calibration, and then back to you. I could see using one to calibrate my Fluke, and then using its stability for long term precision. The Geller unit would make a good transfer unit to a traceable standard at Fluke. Best, Will *** REPLY SEPARATOR *** On 5/26/2011 at 5:33 PM WB6BNQ wrote: Will, I beg to differ with you on the military statement. The Navy's Primary LAB received 100 of the 731's that specifically were not hand picked, as you suggest. Out of that 100 a number of them were used for a vast array of testing including destructive testing. A few units had problems right at the start, but the majority held up very well. The purpose being to define the value of the item regarding the Navy's mission and support there of. I know all this because a close friend of mine was the LAB person who did the project. His responsibility, at the LAB was maintaining the Navy's primary voltage reference. From this large test base came a number of improvements my friend suggested to Fluke that were incorporated in later production units. I guess it would be way more accurate to say Fluke used (wisely) the LAB as a beta tester of their product which was brand new at the time. Gaining the Navy's acceptance was a big deal in the scheme of things in those days. The quality of the Fluke equipment was outstanding and, no, the military did not hand pick. The same went for the HP equipment and Tektronix. Simpson was another cornerstone with their 260 VOM as the Navy had a ton of those. So was Triplett who had some very good VOM's in the day. A very good instrument to grab when they show up is the HP 6920 Meter calibrator. Yes it is old but it was specifically built to do VOM's like the simpson and individual meter movements as well. It outputs DC and AC voltage (60 Hz) (zero to 1000) and current (zero to 5A) and is quite handy to have. As for the small transfer boards you refer to, I completely understand what you mean. While they may serve a purpose for the masses, their advertising is a bit misleading to put it kindly. BillWB6BNQ Will Matney wrote: Bill, Yes, Fluke did cherry pick on what they bought, or paid to have Motorola to do it. HP does the same when purchasing voltage references, but they both do burn them in themselves after they receive them. The duds are used in less tolerant meters, etc. That is what Fluke wrote about doing in an app note of theirs. Also, the military gets the pick of them all, and is the reason I try to buy military surplus that's in good shape. My Fluke 730A is ex-Navy. Actually, back in 2008, this subject was discussed here on Time Nuts, and was the reason why I made this post. At the time, nobody had crossed the Motorola part
