[time-nuts] ATT RFG-M-RB
I have a ATT RFG-M-RB not Lucent made around 1997. It is different because it does not have the usual Rubidium oscillator in it. It actually has two stacked boards and the lower one is the Rubidium Oscillator. The only thing in the can which snaps off is the physics package. I finally tracked down the frequency adjustment pot which is located on the lower board but there is a access hole in the upper board to access it. The hole in the metal can is not for frequency adjustment but it is a capacitor connected to the RF excitation coil for the lamp. It is very interesting and I would like to have data on it. The Rubidium oscillator is a Efratom 102100-003, this number is on the metal can and also the part number on the printed circuit board. The pin out on the top of the metal can matches the 14 single row pins that connect between the upper board and the Rubidium oscillator board. All thru hole parts . no SMT, including inside the rectangle metal can. 73 Bill wa4lav ___ 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] 510 doubler
Ok, lets get real here. Temperature variations, could cause a phase shift but a very very slow one, the degree would depend on the Q of the filter, temperature coefficient of the crystal, and capacitor and how well it is isolated from turbulent air. I am not new to the game of making sensitive measurements using high Q filters. I would be more concerned with the phase changes due to the fractional Hz 1/f noise of the input threshold voltages of the FET's also any trigger circuit that may follow used to feed counters etc in instruments preceding and following the doubler. I am surprised that you aren't complaining about the sideband noise produced by the Brownian motion of nitrogen molecules inside the crystal case. In this case it is a 2 pole filter and once the phasing capacitor is adjusted the only the mechanical vibrational resonance of the crystal really counts. If you are interested in High Q resonators, phase shift, etc. you might want to take a look at Review of Scientific Instruments 60, 3035 (1989), Use of a helical resonator as a capacitive transducer in vibrating reed measurements where a helical resonator is used to measure the vibrations of small crystals with an sensitivity of 10e-7 Angstroms per square root Hertz bandwith. Also, take a look at citations in other papers and patents referencing this design. I just tried to describe a simple very pure sine wave doubler for your readers. ___ 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] time-nuts Digest, Vol 127, Issue 5
OOPS. what was I thinking, I was trying to minimize the number of transformers and slipped up. The inputs should be in opposite phase and output in parallel with a bifiler wound toroid transformer to provide balanced outputs, one to the crystal and one to the neutralizing (phasing) capacitor. The advantage of the crystal filter is that it provides much higher Q and to some degree, depending on it's selectivity reduces sideband noise. The crystals are cheap and if you like you can add more stages. No tuning required except for the phasing capacitor. If you happen to have a source of precisely cut series resonant 10MHz crystals you could easily go to 100Hz bandpass or even less by using a small value loading resistor. A ladder filter could be used but there is still coupling far off resonance thru a capacitive ladder network consisting of the crystal holders' capacitances and discrete capacitors. An complex LC filter could be constructed but it requires a number of stages along with careful selection of components. 73 Bill wa4lav Message: 4 Date: Wed, 04 Feb 2015 06:57:48 -0500 From: Charles Steinmetz csteinm...@yandex.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] 510 doubler Message-ID: 20150204145756.vsamc...@smtp2m.mail.yandex.net Content-Type: text/plain; charset=utf-8; Format=flowed Bill wrote: Push-Push Jfet amplifier with parallel inputs and a Toroid output transformer, no secondary along with a simple filter using a 10 MHz series resonate crystal connected to one drain and an adjustable capacitor connected to the other would work fine. You connect the other ends of the two together and a loading resistor to ground. The capacitor is used to neutralize or null out the shunt capacitance of the crystal so that a capacitive path for the other frequencies , 5, 15, 20, etc is eliminated. I concur with what Bruce said regarding crystal filters (or any narrow bandpass filter) at the output frequency. More fundamentally, I'm not sure I understand your description of the circuit. You say it is a pair of FETs with parallel input and a transformer (autoformer) output. To me, that suggests the circuit pictured below (one feeds the sources in parallel, the other feeds the gates in parallel -- it doesn't make any difference in how the circuit operates). The usual push-push doubler feeds the FETs differentially, and takes the common-mode output. The diagrammed circuit reverses this -- it feeds the FETs in parallel (common-mode) and takes the 10MHz output differentially. As drawn, the circuit would have essentially no output at the input frequency or any of its harmonics (only that due to the mismatch between the FETs). The only signals it would amplify are uncorrelated signals -- i.e., the FETs' input noise voltages. A quick simulation confirmed no significant output at the input frequency or its harmonics for matched FETs. Simulating mismatched FETs produced a 5MHz signal rich in harmonics, but at a very low level and with no suppression of the 5MHz and its odd harmonics. I assume I misinterpreted your description and that you had a different circuit in mind, or that if you did have this circuit in mind I'm missing something about its operation. Can you please describe again what you had in mind, and how it generates 10MHz? Best regards, Charles -- next part -- A non-text attachment was scrubbed... Name: Fuqua_doubler_sm.gif Type: image/gif Size: 17911 bytes Desc: not available URL: http://www.febo.com/pipermail/time-nuts/attachments/20150204/ed4fa496/attachment.gif -- Subject: Digest Footer ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts -- End of time-nuts Digest, Vol 127, Issue 5 * ___ 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] 510 doubler
Push-Push Jfet amplifier with parallel inputs and a Toroid output transformer, no secondary along with a simple filter using a 10 MHz series resonate crystal connected to one drain and an adjustable capacitor connected to the other would work fine. You connect the other ends of the two together and a loading resistor to ground. The capacitor is used to neutralize or null out the shunt capacitance of the crystal so that a capacitive path for the other frequencies , 5, 15, 20, etc is eliminated. Then follow up with your linear class A amplifier. The loading on the output of the crystal filter will determine it's Q and is not real critical, but should be perhaps around 10-100 times the series resistance of the crystal. Since most readily available crystals are not exactly on frequency a lower Q, higher R would be desired, but that will not greatly affect the 5 MHz or undesired harmonic attenuation. Perhaps one or two kHz bandpass would be just about right. Just don't overdrive the crystal. Also, for the price of $1 or less you may get 10 or so for further experimentation. This combination of doubler and crystal filter should provide a very nice sinewave output 73 Bill wa4lav ___ 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] Correcting jitter on the 1 PPS signalfrom a GPS receiver.
A lot of devices have a low output impedance so that the signal can be split using a TEE adapter with little loss or need for a distribution amplifier. However, the cables must be impedance matched at far end, scope input, to prevent reflections which are the source of the ringing. You can match the impedance at the source and you will get a reflection which will then be absorbed by the source resistance. One way to do this is to get a small 15 turn pot about 100 Ohms put it, in series with the input source and adjust it until the ringing is gone or you can put it at the far end ,input of the scope, to ground and do the same. But the best solution is to get a good feed thru 50 Ohm terminator and put it on the input of the scope. Bill -- Message: 1 Date: Sun, 14 Sep 2014 09:58:54 -0700 From: Said Jackson saidj...@aol.com Peter, That depends. To use 1M Ohms input impedance, you need a 50 Ohms series impedance at the driver chip. Most sources such as the 58503A and Thunderbolt violate that requirement by having only a couple of Ohms output impedance, and are thus not suitable and do need the 50 Ohms termination at the scope least you get horrible ringing as shown in Tom's plots from yesterday. From: time-nuts [time-nuts-boun...@febo.com] on behalf of time-nuts-requ...@febo.com [time-nuts-requ...@febo.com] Sent: Sunday, September 14, 2014 1:11 PM To: time-nuts@febo.com Subject: time-nuts Digest, Vol 122, Issue 42 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@febo.com When replying, please edit your Subject line so it is more specific than Re: Contents of time-nuts digest... Today's Topics: 1. Re: Correcting jitter on the 1 PPSsignalfromaGPSreceiver. (Said Jackson) 2. Re: Correcting jitter on the 1 PPSsignalfromaGPSreceiver. (Peter Reilley) 3. Re: Correcting jitter on the 1 PPSsignalfromaGPSreceiver. (Said Jackson) 4. Fwd: Correcting jitter on the 1 PPS signalfromaGPSreceiver. (Said Jackson) -- Message: 1 Date: Sun, 14 Sep 2014 09:58:54 -0700 From: Said Jackson saidj...@aol.com To: Peter Reilley pe...@reilley.com Cc: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Correcting jitter on the 1 PPS signalfromaGPSreceiver. Message-ID: a77b8502-096e-4d03-864e-4a63af3a9...@aol.com Content-Type: text/plain; charset=us-ascii Peter, That depends. To use 1M Ohms input impedance, you need a 50 Ohms series impedance at the driver chip. Most sources such as the 58503A and Thunderbolt violate that requirement by having only a couple of Ohms output impedance, and are thus not suitable and do need the 50 Ohms termination at the scope least you get horrible ringing as shown in Tom's plots from yesterday. However that means you are pumping up to 100mA through your coax, and scope termination. That makes your coax ground jump many 10's of millivolts (depending on cable length and quality). This IR induced ground jump now also shows up on your 10MHz coax and messes with that signal, as the 1PPS return current partially goes through the 10MHz coax shield and generates a voltage rise on the shield. It's a cluster You can take a multimeter and actually measure the voltage drop on your coax cable shield from one connector to the other. On units with longer 1PPS pulse you see the multimeter twitch once per second (Symmetricom XLI for example) even on a short 1m cable. But if you look at Tom's plots you see that there is some high frequency ringing on the 58503A 1PPS when terminated into 1M, I am not sure thats coming from cable reflections. For those high frequency rings a 1G scope may be better to see what's really going on in the driver. Think about it this way: why would you want to drive a 50 Ohms coax with a 5 Ohms output impedance? That's an absolutely horrible impedance mismatch. But that is what the Trimble Thunderbolt does, and likely also the Resolution-T.. Resulting in ringing up to 10V on your cable. Bye, Said Sent from my iPad On Sep 14, 2014, at 9:04, Peter Reilley pe...@reilley.com wrote: I tried removing the termination and got a little better than 4 nS risetime. Isn't the ringing frequency simply a function of the length of the coax? Isn't it the price you pay for mismatched impedances? Pete. -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Said Jackson via time-nuts Sent: Sunday,
Re: [time-nuts] GPS Spoofing
The idea behind GPS spoofing is that one or several surface antennas and sources could be set up in such a way that they would produce believable position data that would take a vessel off course. The problem with this concept is that the person in charge of the GPS spoofing hardware has to know exactly where the vessel is at all times to start with and other vessels some distance away, and not very far from the target vessel would get contradicting signals from the virtual satellites. Software could be used to detect changes in position data that is inconsistent with present course and recent data. And in most cases there would be a period of very inconsistent signals from satellites and more obvious, signal strengths. Another way to limit spoofing is to use directional antennas that prevent reception from near horizon signals. Or detect low angle signals and sound the alarm or implement a means of ignoring those sources. The problem very high tech systems are often defeated by low tech solutions. Successful GPS spoofing would be very high tech. Many high tech systems that the government had developed in the past have been defeated by low tech methods. An example is the microwave system that is intended to turn back rioters by inducing burning pain. It was defeated by using thick wooden shields which absorbed the RF energy. Human resourcefulness and determination often defeats technology in low tech ways. And the more complex a system is the easier it is to defeat. “The more they overtake the plumbing the easier it is to stop up the drain.” Most discussions have been about wireless spoofing. However, the most reliable way to do it would be an “inside job” where a device would be put on board and patched in the antenna lead. The correct GPS data would be received by the device and then it would produce a virtual constellation of satellites that would direct the vessel off course. However, the programmer would have to know the course that the pilot intended to take in the first place if his goal is to take the vessel to a different destination. 73 Bill wa4lav ___ 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] WWVB BPSK Receiver Project?
You are correct, however, I suppose you are using a loop antenna with a relatively high Q. The antenna gain is related to the Q when you have an antenna with a diameter much less than a wavelength. With a Q of 100 you would have a bandwidth of .6 kHz, If you go to say 20.kHz you would not need that high of a Q. Now, why do you need 1200 Hz bandwidth? Is it sending over 1kbaud data rate? I have not looked at the details. Just recall the data rate was 1 bit/second for time. 1200Hz at 60 kHz would represent a very low Q antenna only 5 or so. If you use CMOS switches you will still get aliasing at odd harmonics. So you would still need a front end filter. If you want a closer sampling frequency just make a simple frequency multiplier and you still can use the sound card output. The real point is where does SDR begin. As I said with CMOS switches you are effectively multiplying or mixing the incomming signal with square waves which have odd harmonics and you still get aliasing. 73 Bill wa4lav PS Just retired Friday. Maybe I will have some time to catch up with these discussions. Many A/D converter systems use a sample and hold before the A/D converter. If you do the same before your sound card (your A/D converter) and drive the SH with an audio output from your sound card, say at 6.1 kHz you would get a 1 kHz signal into your sound card to process. You can call it under sampling aliasing or whatever. Yes, this would work, but instantaneous sampling would tend to alias in many harmonics, requiring good prefiltering at RF (if you can call 60 kHz RF). Just as easy would be a mixer from CMOS switches, driven say at 50 kHz to get 10 kHz into the sound card. The WWVB signal apparently has a double-sided bandwidth of about 1200 Hz (not clear from the paper if that means 3 dB bandwidth or something else). To get all of the signal something like 2 or 3 kHz might be safest, requiring an IF of several kHz at least. Cheers, Peter ___ 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] WWVB BPSK Receiver Project?
I know I am not one of the good-ole-boys here but I'd say go 100% SDR with your PC without an external A/D converter. Ok, how would you do this? You use under sampling. Many A/D converter systems use a sample and hold before the A/D converter. If you do the same before your sound card (your A/D converter) and drive the SH with an audio output from your sound card, say at 6.1 kHz you would get a 1 kHz signal into your sound card to process. You can call it under sampling aliasing or whatever. By the way Ten Tec patented an under sampling scheme many years ago when they started into the SDR business. ___ 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] Norman Ramsey
Just a month ago I found out that Norman Ramsey had died. I met and talked with him about 20 some odd years ago before he recieved the Nobel Prize for Physics. He talked about the first Magentron that he ever saw which was a secret weapon brought to the US to be tested and worked with to make high resolution radar. He was at MIT at the time. He was an interesting fellow to talk to. One of our faculty at the University of Kentucky was one of his graduate students when he was working on the atomic frequency standard. When he received the check, many years after he developed the atomic clock he gave about half to his graduate students that had worked with him. He worked out a deal to purchase a number of computers, and each of these guys got one. The one Dr. McAdam got was an ATT 16 bit system. Fairly fancy at the time. I have a couple of Rubidium sources and think about my short discussion with him at the time. His graduate student was a ham but Dr. Ramsey never was. Dr. McAdam did a great deal of research in atomic physics at UofK before he retired a couple of years ago. 73 Bill wa4lav ___ 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.
