Re: [time-nuts] Noise and non-linear behaviour of ferrite transformers
On 24.07.2014 18:00, Ackermann, John R wrote: Just FWIW, the TADD-1 uses transformers to provide DC isolation, but the shield side of the coax goes to ground through a 0.1uF cap. The hope is that this reduces the issue that John's referring to (and which I've seen plenty of times using baluns). For optimum results with respect to high RF frequencies, I'd expect that you would need this cap to be annular, so that the cable can pass through the middle, and the outside connects to the chassis hole all around. This is like a feedthrough capacitor, except that the wire that goes through the center actually is a coaxial cable. While feedthrough caps for single wires are common, I haven't seen any for coaxial cables (rigid or semi-rigid cables come to mind). Do they really not exist, and if so why? Or have I failed to look in the right places? Cheers Stefan ___ 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] Noise and non-linear behaviour of ferrite transformers
On 25.07.2014 20:07, Charles Steinmetz wrote: Stefan wrote: shield side of the coax goes to ground through a 0.1uF cap. For optimum results with respect to high RF frequencies, I'd expect that you would need this cap to be annular, so that the cable can pass through the middle, and the outside connects to the chassis hole all around. The coax itself remains coaxial through the connector -- it is just the point on the shield that is bypassed to chassis that is not annular. The low impedance of the shield makes this non-critical up to frequencies where you should be using a waveguide anyway. It is a well-known and proven technique for bypassing shields to chassis with no galvanic connection. (In some cases, the capacitor is paralleled with a resistor of 10 ohms to 1k ohms -- this provides some DC/LF continuity while limiting the possible ground loop current to levels that [hopefully] don't cause noise problems.) Rarely is the cap as large as 0.1uF -- 0.01uF is most common, and 1nF is also quite common. You want the cap to have low inductance (high first self-resonant frequency), and you need to keep the leads very short. Well, yes, I've seen this done many times. However, when making shield terminations, many would tell you that it is important to terminate the shield 360 degrees to the chassis in order to have the best effect. Surely, that also has to be true for RF frequencies when you choose to raise the near-DC impedance of the shield-to-chassis connection to combat a hum loop? I'm just trying to take this to the logical conclusion, which would be an annular capacitor for the shield connection. Cheers Stefan ___ 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] Noise and non-linear behaviour of ferrite transformers
On 25.07.2014 15:56, Tim Shoppa wrote: General Radio used to have some common values of capacitances available in terminator type configuration and passthru/bulkhead type configuration. These were moderately useful doing some bridge-type measurements. I remember blowing one up once, and taking it apart being pretty impressed the capacitor was a concentric design. I haven't seen examples of these newer than the type 874 hermaphoditic connectors. You probably mean capacitors between center conductor and shield? I swear a couple decades ago I saw BNC terminator-type capacitors in the Pasternack catalogs that filled my mailboxes, but I never saw any of these in the flesh. I do know that DC blocking capacitor series-capacitor BNC's are widely available from Pasternack and others. Yes, I've seen those, too. They actually come in 3 variants: DC-blocking on the center conductor, on the outer conductor, or both. None of these is what I mean, though. I meant DC-blocking between outer conductor and chassis, on a passthru connector that blocks DC on neither the center conductor nor the outer conductor. I've no idea why this is not a common item, just as feedthru capacitors for single wires are. Cheers Stefan ___ 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] Sad news Ulrich Bangert
A great loss and a sad story, indeed. That leaves me wondering what will happen to his software tools, which we have grown accustomed to using. I'm not aware that he disclosed the sources. Has anybody got access to them and can take care of them? Or will all this good work fade away? Cheers Stefan On 24.06.2014 23:17, Didier Juges wrote: Thank you Bruce. Like others, I was saddened to hear of Ulrich's passing. His contributions and the good spirit under which he contributed were notable. He will be missed. Didier KO4BB On June 23, 2014 4:58:24 PM CDT, br...@ko4bb.com br...@ko4bb.com wrote: Sadly Ina was terminally ill and died in May 2012. Ulrich kept this to himself until about six months later in an email explaining why he had been out of touch. In respect for Ulrich's wishes I kept this news off the list. Ulrich's Obituary indicates that one parent, his in-laws and siblings as well as his nieces/nephews survive him. If requested I'll post the URL for his obituary which includes a contact address. Bruce On June 22, 2014 at 1:16 PM ewkeh...@aol.com wrote: It is a shock and a loss not just to time nuts but many others that where touched and benefited from him. Like in the case of Brooks I know what I will do and I urge those of you that knew him through any type of contact make the old fashioned proper thing by sending his wife a letter or card Frau Ina Bangert, Ortholzer Weg 1, 27243 Gross Ippener Germany Bert Kehren In a message dated 6/22/2014 12:36:22 P.M. Eastern Daylight Time, ail...@t-online.de writes: I am shocked to hear that. Urich was a very helpful friend, I've learned a lot from him. I'm so sorry to hear that. Please allow me to say some words in Ulrichs (and my) native language. Die Nachricht vom Tode Urich's hat mich sehr getroffen. Ich habe ihn als einen hilfsbereiten und offenen Menschen kennen gelernt, aber leider nie persönlich kennen lernen können. Bitte, lieber Hartmut, falls Du Kontakt hast, richte der Familie mein herzliches Beileid aus. Thank you very much. Volker - DF9PL Am 20.06.2014 22:52, schrieb Hartmut Paesler: Dear group, unfortunately I have to deliver the sad news that Ulrich Bangert, DF6JB passed away on 11/06, aged 59. Best regards, Hartmut DL1YDD ___ 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. ___ 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. ___ 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] HP 10811 update
paul swed wrote: I can't believe you found the transistor. When I pulled it out last night, its actually a MPSA18!!! I had not had time to look it up but figured it was a ebay leftover hunt. :-) At that price I may order 20 of them. Like the gain. Toshiba used to make a transistor with even higher gain, the 2SC3112/2SC3113/2SC3295/2SC4666 (same chip, different package). They discontinued it recently, however. Cheers Stefan ___ 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] Very stable synthesizer, alternative to PTS(Programmed Test Sources) x10 or 040?
Jim Lux wrote: On 7/10/13 12:29 PM, Didier Juges wrote: Jim said: It's like a HP 8663B (not the modern Agilent E8663).. very low noise, The Agilent E8663 has similar SSB phase noise spec as the older HP 8662A (-144dBc/Hz @ 10 kHz with option UNY, versus -143 for the 8662). You seem to imply they are different. Can you elaborate? Of course, the Agilent has many more features and 0.001Hz resolution, and the 8662 only goes to 990MHz (I think, I should know, I have two thanks to JohnM...), but are they that much different in pure phase noise or ADEV? Didier It's not the phase noise that raised the problems for us. It's that when you program them for a sweep, it goes in steps that aren't phase continuous AND the behavior when you feed a signal into the FM input isn't the same. The HP 8663B was, at the core, a really good phase locked VCO, so when a sweep is programmed, the output is phase continuous as it sweeps. This is a huge problem when you are testing a very narrow band tracking loop (our deep space transponders have a loop bandwidth of a few Hz) I can't remember the details on the FM input, but it too has some behavior that we depended on. We take the output of the 8663B and run it into a x7 to make the 7150 MHz uplink and/or the 8450 MHz downlink frequencies. Part of the reason we do a x7 is so that any leakage from the synthesizer isn't in band for our receiver under test. A typical input level for test is -150 to -160 dBm, so leakage at the wrong frequency can easily be more than the desired signal. Now you're confusing me. As far as I am aware, there was the 8663A which appeared in the early eighties. And much later came the E8663B, and subsequently the E8663D. I've never seen an 8663B from HP. From the context I would guess that you really mean the 8663A, and not the 8663B, right? Cheers Stefan ___ 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] Phase noise measurement with a scope
Azelio Boriani wrote: The problem with sampling 'scopes is that you cannot get a continuos samples stream. I think that the TimePod correlates continuously in time. Does that matter for phase noise measurements? Doesn't that just make the measurement take correspondingly more time? Cheers Stefan ___ 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] Phase noise measurement with a scope
Magnus Danielson wrote: On 06/13/2013 04:26 PM, Stefan Heinzmann wrote: Azelio Boriani wrote: The problem with sampling 'scopes is that you cannot get a continuos samples stream. I think that the TimePod correlates continuously in time. Does that matter for phase noise measurements? Doesn't that just make the measurement take correspondingly more time? It matters a lot, since the length of memory will limit the how close in you can do it. You can naturally make multiple runs, and that's what the TimePod do, but with decimations done in realtime by the firmware. You can do it with high speed ADCs, but it won't bee cost efficient and it will cost you in speed, as you need to do much in software processing to get there. The TimePod is in that context a fairly well balanced design as in bang for the buck. Another aspect I like is that it can do pretty neat long-term measurements. That's of course true when you want to build or buy an instrument just for this job. I don't question the Timepod, on the contrary I think it is a very good instrument. My aim was rather to find another use for a scope that's already there (it isn't in my case yet, but will be). The RS RTO seems to have a few unusual capabilities for a scope, which might help here. It does seem to do decimation and a number of other math functions in hardware and in real-time. Looking at their description of the I/Q option reminded me of the Timepod manual, specifically the block diagram in there, and brought me to the question I'm asking here. Have a look if you're interested: http://www.rohde-schwarz.de/file/1TD01_0e_RTO_IQ_Software_Interface.pdf While the scope may not be able to continuously acquire and cross-correlate, with no dead time, I would think it capable of taking fairly long shots by storing only the decimated data. There's a chance of it being suitable for phase noise down to 10 Hz from the carrier, I think. Perhaps closer than that. That would already be quite useful, I'd say. Cheers Stefan ___ 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] Phase noise measurement with a scope
Hi all, given that digital scopes have a multichannel ADC for acquisition, which is similar to what a cross-correlating phase noise measurement instrument has, it occurred to me that phase noise measurement might also be possible with a standard digital scope and some post-processing software. The scope usually will have only 8 bits of resolution, but it will have a rather high sampling rate. With oversampling math, one may be able to trade one for the other, at least if the scope's analog frontend is not too bad. Has anyone investigated or tried this? Is it a silly idea to start with? Cheers Stefan Heinzmann attachment: stefan_heinzmann.vcf___ 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] Phase noise measurement with a scope
Marek Peca wrote: Hello, given that digital scopes have a multichannel ADC for acquisition, which is similar to what a cross-correlating phase noise measurement instrument has, it occurred to me that phase noise measurement might also be possible with a standard digital scope and some post-processing software. The scope usually will have only 8 bits of resolution, but it will have a rather high sampling rate. With oversampling math, one may be able to trade one for the other, at least if the scope's analog frontend is not too bad. Has anyone investigated or tried this? Is it a silly idea to start with? yes, did it last week. I think it may have a sense with 1Gsps scope with good quality guts (should check with LC584AL at work). I have tried it with a very cheap one, Rigol 2-channel, originally 50MHz, reflashed to 100MHz. 2 signals, refmeasured, into Ch1, Ch2. Waveforms (2x500Msps) acquired, sinc() interpolated. Results: short-term single-shot jitter around 100ps RMS. Long-term was of no interest for my purpose now, so no observations here. Therefore, it is almost of no use at all for higher precision needs. I was thinking about using a 4-channel scope with cross-spectrum averaging. Look at the Timepod by John Miles for an example of the method. I'm trying to guesstimate if the RS RTO scope, perhaps with the aid of the I/Q option, is capable of doing such measurements, and with what kind of performance. Cheers Stefan attachment: stefan_heinzmann.vcf___ 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] Phase noise measurement with a scope
Marek Peca wrote: (..) I have tried it with a very cheap one, Rigol 2-channel, originally 50MHz, reflashed to 100MHz. 2 signals, refmeasured, into Ch1, Ch2. Waveforms (2x500Msps) acquired, sinc() interpolated. Results: short-term single-shot jitter around 100ps RMS. Long-term was of no interest for my purpose now, so no observations here. Therefore, it is almost of no use at all for higher precision needs. I was thinking about using a 4-channel scope with cross-spectrum averaging. Look at the Timepod by John Miles for an example of the method. I'm trying to guesstimate if the RS RTO scope, perhaps with the aid of the I/Q option, is capable of doing such measurements, and with what kind of performance. My point was, that DSO is basically an ADC. Therefore, there is some amount of noise, nonlinearity and drift, limiting the jitter measurement. Do you think any method can dig more information from given data than sinc() interpolation and zero-crossing computation? The cross-spectrum averaging does indeed do just that, relying on two ADCs to produce uncorrelated noise, which can be averaged out. Or am I misunderstanding your point? Cheers Stefan attachment: stefan_heinzmann.vcf___ 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] question for expert time guys
Can the base stations be interconnected via cable? In that case, wouldn't it suffice to have the mobile device send an unmodulated carrier of low enough frequency, and compare the phase between the receiving base stations, taking the (known) cable delays into account? Cheers Stefan Rick Harold wrote: To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it inexpensive is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. ___ 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.
