Re: [time-nuts] Boeing 787 GPS reception trouble
On Mon, 2 Jun 2014 20:18:00 +0100 "Bill Woodcock" wrote: > > I'm posting this from inside an Ethiopian 787, on the ground, with > the doors closed. I just completed a fifteen-minute voice call > initiated from inside the plane, with reasonable reception and no > drops, while the doors were open. And I was able to get a new GPS > location in less than two seconds (though that wasn't from cold boot, > so I don't know whether it was able to accelerate the process using > cached data previously received). The phone (an iPhone 5S) is showing > three bars inside the plane, and was varying between three and four > bars outside. Note that the non-linear mapping of signal strength to > "bars" is a matter of intense negotiation between carriers and > vendors, and shouldn't be taken as a literal indicator of anything at > all. Likewise, Ethiopian may have ordered planes with significantly > different options than ANA (no center overhead storage in business, > for example) and used different paint formulation. > > Nevertheless, in this specific case, I'm not seeing anything that > seems out-of-the-ordinary relative to other aircraft. > -Bill You probably know this, but just in case, cell phone GPS is assisted, i.e. AGPS. It uses tower information to assist in lock. [Also data, as many a roamer has found out when billed. On an iphone, the saving grace is it has real problems with APN settings, so often it won't use the assist when roaming.] I recall my GSM phone making some RF burps once when I was using it in the desert where there was no cellular service. But the poster that said the phone would listen before transmitting has a good point, so I need to repeat this experiment sometime. I was using a spectrum analyzer and picked up my phones chirping. Regarding radiation, I've used my Geiger counter at mile high altitudes in Nevada and never got a count per second, even with the gamma shield not used. You can look at the DOE CEMP stations: http://www.cemp.dri.edu/ Some of the radiation monitors are not working, but this one is and it has typical readings of 15uR/hr. > http://www.cemp.dri.edu/cgi-bin/cemp_stations.pl?stn=rach As a crude estimate, 1000CPM = 1mR/hr, or 1CPM = 1uR/hr. So I suspect the 60CPM received in Colorado is use to local radiation rather than cosmic rays. My Ludlum isn't calibrated, but I've compared it to one from the DOE using their source and it matched close enough for government work. ___ 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] Boeing 787 GPS reception trouble
On Mon, Jun 2, 2014 at 10:36 PM, Jim Lux wrote: > On 6/2/14, 7:16 AM, Brian Lloyd wrote: > >> On Mon, Jun 2, 2014 at 8:57 AM, Jim Lux wrote: >> >> O, and since navigation using the ADF and tuning to a AM >>> broadcast station wasn't unusual. >>> >> >> >> Well, it is quite unusual for IFR (instrument flight rules) operation. But >> VFR pilots would sometimes use an AM broadcast station for navigation >> assistance. >> >> > Back in 1980, the examiner asked me how to do it, but didn't make me do it. > He wasn't allowed to. It is not part of the practical test standard for the private pilot certificate. Still, it is useful. I have been flying long enough to experience nearly every form of electronic navigation available in aircraft. I have actually flown an Adcock "A/N" range. I have landed an aircraft in instrument conditions using precision approach radar (PAR or GCA). I have used ADF, VOR, DME, RNAV, LORAN-C, INS, and now GPS. Airplanes haven't changed much but boy the radios sure have! >> I had to learn how to do it when taking flying lessons: it was widely >>> acknowledged ( in 1980) to be nearly useless, >>> >> >> >> Not entirely. I still make sure my planes are equipped with ADF (LF/MF >> direction finding) due to my experience with GPS outages over the >> Caribbean >> and Atlantic. I have experienced outages of over an hour where both my >> panel-mount and hand-held GPS receivers stopped working. ADF was all I >> had. >> I suspect that since I was flying a plane popular with drug-smugglers (a >> Piper Aztec), I was being tracked, followed, and GPS jammed. (I lived in >> the Virgin Islands, traveling to Florida on a regular basis. I would stop >> in the Turks and Caicos or Bahamas to refuel.) >> > > I was referring to the "AM station as beacon", and to be fair, they were > all talking about compared to conventional VOR/DME, and maybe if you had > one of them new fangled RNAV units that mathematically transformed VOR/DME > into lat/lon, etc. > ADF is less accurate than VOR/DME. It is much less accurate than DME/DME. It is archaic. But it works. If the beacon is at the airport itself ADF is amazingly accurate for making an approach. It has a unique characteristic that it is difficult to jam. (LORAN-C was better and I *REALLY* miss LORAN-C as a backup to GPS.) There are large stretches of the Atlantic and Caribbean where the only two navaids that are available are GPS and LF/MF NDBs. Sure I can use pilotage/ded-reconing and hop from island to island. But I have now experienced multiple total GPS outages. It makes me nervous the dependence we are developing on a system that is surprisingly vulnerable to a denial-of-service attack. I do hope that LORAN-C comes back. The original idea of the European Galileo system to use LORAN-C to distribute DGPS data was brilliant. The DGPS datalink was itself a source of high-quality time and position information that is nearly impossible to jam. What a concept! Has anyone considered how a large-area GPS outage would effect us? I *really* don't like having all my eggs in one basket. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ 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] VNA design
Hi, I have an HP 8412B and an HP 8413A, which go with the HP 8410, for $ 30.00 ( maybe less) each plus actual shipping. They look good but I have no way to test then since I have no mainframe. Contact offline if interested. I can email pictures. They will be at the Huntsville Hamfest later this summer. Bill Reed ree...@otelco.net -Original Message- From: Alexander Pummer Sent: Monday, June 02, 2014 5:18 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] VNA design Although I used to work for one of the competitor, I still do have a complete working 8410, Rick is right, it is a very nice teaching tool 73 KJ6UHN On 6/2/2014 2:36 PM, Richard (Rick) Karlquist wrote: On 6/2/2014 12:41 PM, Brooke Clarke wrote: Hi: I started with the HP 8410 and added an external computer. Since it can be used manually I think it's an excellent way to learn about VNAs. http://www.prc68.com/I/MWTE.shtml#NA For my last 8 years at Agilent before retiring in March, I was doing advanced R&D on network analyzers. The newer guys coming up didn't have an intuitive understanding of network analyzer architectures like I did. I started using the 8410 back in 1973 before I even worked for HP. Because of the modular design, it was like a teaching tool that forced you to understand what was going on. When I mentored the young guys, I would explain to them a lot of principles based on the 8410. Modern network analyzers are too "automatic". The 8410 puts modern VNA's into perspective. BTW, I used to sit next to Dick Lee, who was a member of the 8410 design team in 1963 at the dawn of the golden age of microwave instruments based on YIG tuned oscillators and step recovery diode samplers. As you noted, the architecture was built around the YIG tuned oscillator and certain things were done that way they were because of that. Rick Karlquist N6RK ___ 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. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ 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] Boeing 787 GPS reception trouble
On 6/2/14, 7:16 AM, Brian Lloyd wrote: On Mon, Jun 2, 2014 at 8:57 AM, Jim Lux wrote: O, and since navigation using the ADF and tuning to a AM broadcast station wasn't unusual. Well, it is quite unusual for IFR (instrument flight rules) operation. But VFR pilots would sometimes use an AM broadcast station for navigation assistance. Back in 1980, the examiner asked me how to do it, but didn't make me do it. I had to learn how to do it when taking flying lessons: it was widely acknowledged ( in 1980) to be nearly useless, Not entirely. I still make sure my planes are equipped with ADF (LF/MF direction finding) due to my experience with GPS outages over the Caribbean and Atlantic. I have experienced outages of over an hour where both my panel-mount and hand-held GPS receivers stopped working. ADF was all I had. I suspect that since I was flying a plane popular with drug-smugglers (a Piper Aztec), I was being tracked, followed, and GPS jammed. (I lived in the Virgin Islands, traveling to Florida on a regular basis. I would stop in the Turks and Caicos or Bahamas to refuel.) I was referring to the "AM station as beacon", and to be fair, they were all talking about compared to conventional VOR/DME, and maybe if you had one of them new fangled RNAV units that mathematically transformed VOR/DME into lat/lon, etc. Once the rule is in place, it's very, very hard to get it removed, because of the "if we allow X, and a plane has a problem, everyone is going to say "it was because of X" even if it wasn't, so let's just keep things the same." Amen. ___ 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] "Audio" DAC for GPSDO?
Hi The DAC noise is likely “outside the loop” in a GPSDO. It’s not reduced by feedback. You can indeed find some of these parts that are noisy enough to degrade the ADEV or phase noise of an OCXO. Bob On Jun 2, 2014, at 10:13 PM, Bob Stewart wrote: > Hi Bob, > > I decided to look at Mouser for 16-bit DACs, and found the MAX541CCPA for > $12.47. On the one hand, it's an extra $12.47 for the project. On the > other, the dsPIC is a 3.3V device. I'll have to give some thought as to > whether I want to lose that much output range between the DAC and the EFC > divider which will be placed right at the OCXO. Given the flexibility of the > dsPIC33 pin remapping, I may just add it to the board but jumper around it at > first. Hmm, I could just place it right at the OCXO, since I need to > communicate with it with SPI. TBH, I don't think I have the equipment needed > to measure the noise unless it's really bad. I'm already way past my ability > to measure with my TIC daughterboard added to the VE2ZAZ board. > > This is all new territory for me. Should be fun. =) > > Bob > > > > From: Bob Camp > To: Discussion of precise time and frequency measurement > Sent: Monday, June 2, 2014 8:01 PM > Subject: Re: [time-nuts] "Audio" DAC for GPSDO? > > > Hi > > There are several reasons why they don’t recommend the typical MCU DAC for > control applications: > > 1) They are noisy at low frequency (1/f noise corner). That impacts their > hitting their INL and DNL specs. > 2) They have constant current leakage at DC. That makes their “center” value > wander around by more than the spec’s would suggest. > 3) The major steps are trimmed for AC (high sample rate) compensation (the > trim includes capacitance effects). At DC … no capacitance effects. > > Yes it’s all one big mess and the effects slop back and forth between the > categories. Bottom line - they very much do not want you to measure their INL > and DNL numbers on a continuous DC basis and then return the parts as being > out of spec. MCU ADC’s can have some of the same issues. Even some pretty > fancy outboard ADC’s only work well at DC if you put a chopper around them. > > Bob > > On Jun 2, 2014, at 7:22 PM, Bob Stewart wrote: > >> Hi Poul, >> >> I've been reviewing microchips literature and the way I read it is that the >> DAC isn't sensitive to staying at a fixed value. If it's on, the FIFO is >> fed to the DAC. If the FIFO is drained, then the user-settable default >> value is fed to the DAC. When the output amp is turned off, it goes to a >> high impedance output. I also noticed that Finput can vary from 0-45 khz. >> I'm not certain what a 61db SNR would mean at DC values. I see that the >> specifications are for a 15 uA load. I assume that's not hard to meet with >> a typical op-amp. >> >> It's interesting that in one paragraph they call the DAC default register a >> safety feature for industrial control applications, and then a few inches >> later a black box warns that it's not recommended for control type >> applications. >> >> >> Bob >> >> >> >> >> From: Poul-Henning Kamp >> To: Bob Stewart ; Discussion of precise time and frequency >> measurement >> Sent: Monday, June 2, 2014 4:08 PM >> Subject: Re: [time-nuts] "Audio" DAC for GPSDO? >> >> >> In message <1401742940.44103.yahoomail...@web142705.mail.bf1.yahoo.com>, Bob >> Stewart writ >> es: >> >>> Could someone explain to me how such an audio DAC differs from a non >>> -audio DAC and why it's not suitable for this application?=A0 Is this just >> >>> a disclaimer from microchip to avoid liability or is there some practical >>> reason to go with a traditional DAC? >> >> A lot of them have DC protections, so you can't leave them at a particular >> input value for very long before they go into safety mode and clamp the >> output to zero. >> >> Your speakers love them for this, your OCXO not so much. >> >> >> -- >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> p...@freebsd.org | TCP/IP since RFC 956 >> FreeBSD committer | BSD since 4.3-tahoe >> Never attribute to malice what can adequately be explained by incompetence. >> ___ >> 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 --
Re: [time-nuts] "Audio" DAC for GPSDO?
Hi Bob, I decided to look at Mouser for 16-bit DACs, and found the MAX541CCPA for $12.47. On the one hand, it's an extra $12.47 for the project. On the other, the dsPIC is a 3.3V device. I'll have to give some thought as to whether I want to lose that much output range between the DAC and the EFC divider which will be placed right at the OCXO. Given the flexibility of the dsPIC33 pin remapping, I may just add it to the board but jumper around it at first. Hmm, I could just place it right at the OCXO, since I need to communicate with it with SPI. TBH, I don't think I have the equipment needed to measure the noise unless it's really bad. I'm already way past my ability to measure with my TIC daughterboard added to the VE2ZAZ board. This is all new territory for me. Should be fun. =) Bob From: Bob Camp To: Discussion of precise time and frequency measurement Sent: Monday, June 2, 2014 8:01 PM Subject: Re: [time-nuts] "Audio" DAC for GPSDO? Hi There are several reasons why they don’t recommend the typical MCU DAC for control applications: 1) They are noisy at low frequency (1/f noise corner). That impacts their hitting their INL and DNL specs. 2) They have constant current leakage at DC. That makes their “center” value wander around by more than the spec’s would suggest. 3) The major steps are trimmed for AC (high sample rate) compensation (the trim includes capacitance effects). At DC … no capacitance effects. Yes it’s all one big mess and the effects slop back and forth between the categories. Bottom line - they very much do not want you to measure their INL and DNL numbers on a continuous DC basis and then return the parts as being out of spec. MCU ADC’s can have some of the same issues. Even some pretty fancy outboard ADC’s only work well at DC if you put a chopper around them. Bob On Jun 2, 2014, at 7:22 PM, Bob Stewart wrote: > Hi Poul, > > I've been reviewing microchips literature and the way I read it is that the > DAC isn't sensitive to staying at a fixed value. If it's on, the FIFO is fed > to the DAC. If the FIFO is drained, then the user-settable default value is > fed to the DAC. When the output amp is turned off, it goes to a high > impedance output. I also noticed that Finput can vary from 0-45 khz. I'm > not certain what a 61db SNR would mean at DC values. I see that the > specifications are for a 15 uA load. I assume that's not hard to meet with a > typical op-amp. > > It's interesting that in one paragraph they call the DAC default register a > safety feature for industrial control applications, and then a few inches > later a black box warns that it's not recommended for control type > applications. > > > Bob > > > > > From: Poul-Henning Kamp > To: Bob Stewart ; Discussion of precise time and frequency > measurement > Sent: Monday, June 2, 2014 4:08 PM > Subject: Re: [time-nuts] "Audio" DAC for GPSDO? > > > In message <1401742940.44103.yahoomail...@web142705.mail.bf1.yahoo.com>, Bob > Stewart writ > es: > >> Could someone explain to me how such an audio DAC differs from a non >> -audio DAC and why it's not suitable for this application?=A0 Is this just > >> a disclaimer from microchip to avoid liability or is there some practical >> reason to go with a traditional DAC? > > A lot of them have DC protections, so you can't leave them at a particular > input value for very long before they go into safety mode and clamp the > output to zero. > > Your speakers love them for this, your OCXO not so much. > > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > ___ > 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] "Audio" DAC for GPSDO?
Hi There are several reasons why they don’t recommend the typical MCU DAC for control applications: 1) They are noisy at low frequency (1/f noise corner). That impacts their hitting their INL and DNL specs. 2) They have constant current leakage at DC. That makes their “center” value wander around by more than the spec’s would suggest. 3) The major steps are trimmed for AC (high sample rate) compensation (the trim includes capacitance effects). At DC … no capacitance effects. Yes it’s all one big mess and the effects slop back and forth between the categories. Bottom line - they very much do not want you to measure their INL and DNL numbers on a continuous DC basis and then return the parts as being out of spec. MCU ADC’s can have some of the same issues. Even some pretty fancy outboard ADC’s only work well at DC if you put a chopper around them. Bob On Jun 2, 2014, at 7:22 PM, Bob Stewart wrote: > Hi Poul, > > I've been reviewing microchips literature and the way I read it is that the > DAC isn't sensitive to staying at a fixed value. If it's on, the FIFO is fed > to the DAC. If the FIFO is drained, then the user-settable default value is > fed to the DAC. When the output amp is turned off, it goes to a high > impedance output. I also noticed that Finput can vary from 0-45 khz. I'm > not certain what a 61db SNR would mean at DC values. I see that the > specifications are for a 15 uA load. I assume that's not hard to meet with a > typical op-amp. > > It's interesting that in one paragraph they call the DAC default register a > safety feature for industrial control applications, and then a few inches > later a black box warns that it's not recommended for control type > applications. > > > Bob > > > > > From: Poul-Henning Kamp > To: Bob Stewart ; Discussion of precise time and frequency > measurement > Sent: Monday, June 2, 2014 4:08 PM > Subject: Re: [time-nuts] "Audio" DAC for GPSDO? > > > In message <1401742940.44103.yahoomail...@web142705.mail.bf1.yahoo.com>, Bob > Stewart writ > es: > >> Could someone explain to me how such an audio DAC differs from a non >> -audio DAC and why it's not suitable for this application?=A0 Is this just > >> a disclaimer from microchip to avoid liability or is there some practical >> reason to go with a traditional DAC? > > A lot of them have DC protections, so you can't leave them at a particular > input value for very long before they go into safety mode and clamp the > output to zero. > > Your speakers love them for this, your OCXO not so much. > > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > ___ > 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] Note on early VNA's
Jeff: Was really great to see you yesterday at BreezeShooters! Hope to see you again soon, maybe better yet, chat on the air! 73, Jim wb4...@amsat.org On 6/2/2014 6:11 PM, k...@aol.com wrote: To the learned audience: I agree that the 8410 is an excellent place to start to learn about VNA architecture and issues. I, as well, learned the HP 8410, first as manual system, then we did the automation ourselves (Westinghouse was too cheap to buy a "bundled" system) using a 9825 desktop calculator, from the HP app note of "Semi-automated Network Analysis". My education in this regard was superb! My industrious Vietnamese grad student is learning the issues from my 8410 books and he is building a more modern version. However, a slight clarification about the early VNA's: They were not YIG based, that came later. The classic HP8542A system was a BWO based system with the 8690 Sweeper and a bunch of plug-in drawers that worked with a Signal Multiplexer to yield a 1-18 GHz system. A 5100 based synthesizer was used to lock the harmonic converter to eliminate harmonic "skip" cal errors (Brooke alluded to this) and the whole mess was driven by an HP 1000 mini-computer and had a reel to reel tape drive for mass storage! It was huge ( a three bay rack) and cost $250K in 1968 money (a lot today, $1.5 M ??). I had one of these systems and still have parts of it! I automated my own newer 8410 system in 1986 when I started my consulting company and used the 12 term error model software pak (HP11863??) in RM Basic on a 9826 computer (big step up!). While I do not recommend this approach for anyone today, the old literature provides great insight into the issues, where the errors come from and so on, as HP had figured all this stuff out. It is a shame that shipping to Europe is so high, as a lot of these systems and components are still around (I have six 8410 systems still !). A mainframe is under $50.00 and I bought a working 8411A converter for $20.00 at Dayton this year (dont ask why, I guess it was too cheap). I had just about every variant of this stuff, VLF through 40 GHz. Man, HP engineering was tops in those days! Still, I think a very dedicated homebrewer could build his own design for a < 3GHz VNA from adapted "wireless" parts, but I am too lazy for that. I much prefer hacking some proven hardware into what I need. 73 Jeff Kruth In a message dated 6/2/2014 5:47:17 P.M. Eastern Daylight Time, time-nuts-requ...@febo.com writes: Message: 7 Date: Mon, 02 Jun 2014 14:36:09 -0700 From: "Richard (Rick) Karlquist" To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] VNA design Message-ID: <538cee49.6000...@karlquist.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed On 6/2/2014 12:41 PM, Brooke Clarke wrote: Hi: I started with the HP 8410 and added an external computer. Since it can be used manually I think it's an excellent way to learn about VNAs. http://www.prc68.com/I/MWTE.shtml#NA For my last 8 years at Agilent before retiring in March, I was doing advanced R&D on network analyzers. The newer guys coming up didn't have an intuitive understanding of network analyzer architectures like I did. I started using the 8410 back in 1973 before I even worked for HP. Because of the modular design, it was like a teaching tool that forced you to understand what was going on. When I mentored the young guys, I would explain to them a lot of principles based on the 8410. Modern network analyzers are too "automatic". The 8410 puts modern VNA's into perspective. BTW, I used to sit next to Dick Lee, who was a member of the 8410 design team in 1963 at the dawn of the golden age of microwave instruments based on YIG tuned oscillators and step recovery diode samplers. As you noted, the architecture was built around the YIG tuned oscillator and certain things were done that way they were because of that. Rick Karlquist N6RK ___ 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. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ___ 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] "Audio" DAC for GPSDO?
I think these kinds of DACs are meant to be clocked out at some fixed sample rate, like 44.1KHz and your software has to stuff a FIFO so there is some milliseconds of delay in the queue. Before you use these write some pseudo-code and see if you can make it work. One idea is to never write to the FIFO and change the "default" value that gets written when the FIFO is empty, that way you never mess with filling a FIFO thousands of times per second. My Arduino's PWM outputs are working well. The GPSDO has been running now for months. It's proof that you can do this with no external active components. I'm sure there must be some version of a PIC that has analog outputs that can directly drive a XO's EFC pin.If you need even one external IC, you'd be best off getting a different uP. On Mon, Jun 2, 2014 at 2:02 PM, Bob Stewart wrote: > Now that my TIC is working with Bert's board, I'm considering taking the next > step of designing a GPSDO from scratch. There are several projects I'd like > to do with a dsPIC33, so that was a natural choice. But I now understand > that it has an "audio" DAC and is not recommended for process control. Could > someone explain to me how such an audio DAC differs from a non-audio DAC and > why it's not suitable for this application? Is this just a disclaimer from > microchip to avoid liability or is there some practical reason to go with a > traditional DAC? > > On reading through the various datasheets, it appears to me that the concern > might be that the input data to the DAC might be interrupted, thus causing it > to go to some programmable "safe" output voltage. My initial thought was > just to control the value of the safe voltage and not bother to feed the DAC, > though I haven't really explored the idea. > > Bob - AE6RV > ___ > 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. -- Chris Albertson Redondo Beach, California ___ 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] "Audio" DAC for GPSDO?
Hi Poul, I've been reviewing microchips literature and the way I read it is that the DAC isn't sensitive to staying at a fixed value. If it's on, the FIFO is fed to the DAC. If the FIFO is drained, then the user-settable default value is fed to the DAC. When the output amp is turned off, it goes to a high impedance output. I also noticed that Finput can vary from 0-45 khz. I'm not certain what a 61db SNR would mean at DC values. I see that the specifications are for a 15 uA load. I assume that's not hard to meet with a typical op-amp. It's interesting that in one paragraph they call the DAC default register a safety feature for industrial control applications, and then a few inches later a black box warns that it's not recommended for control type applications. Bob From: Poul-Henning Kamp To: Bob Stewart ; Discussion of precise time and frequency measurement Sent: Monday, June 2, 2014 4:08 PM Subject: Re: [time-nuts] "Audio" DAC for GPSDO? In message <1401742940.44103.yahoomail...@web142705.mail.bf1.yahoo.com>, Bob Stewart writ es: >Could someone explain to me how such an audio DAC differs from a non >-audio DAC and why it's not suitable for this application?=A0 Is this just >a disclaimer from microchip to avoid liability or is there some practical >reason to go with a traditional DAC? A lot of them have DC protections, so you can't leave them at a particular input value for very long before they go into safety mode and clamp the output to zero. Your speakers love them for this, your OCXO not so much. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] VNA design
Although I used to work for one of the competitor, I still do have a complete working 8410, Rick is right, it is a very nice teaching tool 73 KJ6UHN On 6/2/2014 2:36 PM, Richard (Rick) Karlquist wrote: On 6/2/2014 12:41 PM, Brooke Clarke wrote: Hi: I started with the HP 8410 and added an external computer. Since it can be used manually I think it's an excellent way to learn about VNAs. http://www.prc68.com/I/MWTE.shtml#NA For my last 8 years at Agilent before retiring in March, I was doing advanced R&D on network analyzers. The newer guys coming up didn't have an intuitive understanding of network analyzer architectures like I did. I started using the 8410 back in 1973 before I even worked for HP. Because of the modular design, it was like a teaching tool that forced you to understand what was going on. When I mentored the young guys, I would explain to them a lot of principles based on the 8410. Modern network analyzers are too "automatic". The 8410 puts modern VNA's into perspective. BTW, I used to sit next to Dick Lee, who was a member of the 8410 design team in 1963 at the dawn of the golden age of microwave instruments based on YIG tuned oscillators and step recovery diode samplers. As you noted, the architecture was built around the YIG tuned oscillator and certain things were done that way they were because of that. Rick Karlquist N6RK ___ 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] Note on early VNA's
To the learned audience: I agree that the 8410 is an excellent place to start to learn about VNA architecture and issues. I, as well, learned the HP 8410, first as manual system, then we did the automation ourselves (Westinghouse was too cheap to buy a "bundled" system) using a 9825 desktop calculator, from the HP app note of "Semi-automated Network Analysis". My education in this regard was superb! My industrious Vietnamese grad student is learning the issues from my 8410 books and he is building a more modern version. However, a slight clarification about the early VNA's: They were not YIG based, that came later. The classic HP8542A system was a BWO based system with the 8690 Sweeper and a bunch of plug-in drawers that worked with a Signal Multiplexer to yield a 1-18 GHz system. A 5100 based synthesizer was used to lock the harmonic converter to eliminate harmonic "skip" cal errors (Brooke alluded to this) and the whole mess was driven by an HP 1000 mini-computer and had a reel to reel tape drive for mass storage! It was huge ( a three bay rack) and cost $250K in 1968 money (a lot today, $1.5 M ??). I had one of these systems and still have parts of it! I automated my own newer 8410 system in 1986 when I started my consulting company and used the 12 term error model software pak (HP11863??) in RM Basic on a 9826 computer (big step up!). While I do not recommend this approach for anyone today, the old literature provides great insight into the issues, where the errors come from and so on, as HP had figured all this stuff out. It is a shame that shipping to Europe is so high, as a lot of these systems and components are still around (I have six 8410 systems still !). A mainframe is under $50.00 and I bought a working 8411A converter for $20.00 at Dayton this year (dont ask why, I guess it was too cheap). I had just about every variant of this stuff, VLF through 40 GHz. Man, HP engineering was tops in those days! Still, I think a very dedicated homebrewer could build his own design for a < 3GHz VNA from adapted "wireless" parts, but I am too lazy for that. I much prefer hacking some proven hardware into what I need. 73 Jeff Kruth In a message dated 6/2/2014 5:47:17 P.M. Eastern Daylight Time, time-nuts-requ...@febo.com writes: Message: 7 Date: Mon, 02 Jun 2014 14:36:09 -0700 From: "Richard (Rick) Karlquist" To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] VNA design Message-ID: <538cee49.6000...@karlquist.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed On 6/2/2014 12:41 PM, Brooke Clarke wrote: > Hi: > > I started with the HP 8410 and added an external computer. > Since it can be used manually I think it's an excellent way to learn > about VNAs. > http://www.prc68.com/I/MWTE.shtml#NA > For my last 8 years at Agilent before retiring in March, I was doing advanced R&D on network analyzers. The newer guys coming up didn't have an intuitive understanding of network analyzer architectures like I did. I started using the 8410 back in 1973 before I even worked for HP. Because of the modular design, it was like a teaching tool that forced you to understand what was going on. When I mentored the young guys, I would explain to them a lot of principles based on the 8410. Modern network analyzers are too "automatic". The 8410 puts modern VNA's into perspective. BTW, I used to sit next to Dick Lee, who was a member of the 8410 design team in 1963 at the dawn of the golden age of microwave instruments based on YIG tuned oscillators and step recovery diode samplers. As you noted, the architecture was built around the YIG tuned oscillator and certain things were done that way they were because of that. Rick Karlquist N6RK ___ 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] Is it Hz or MHz ?
On 06/02/2014 10:51 AM, Tom Van Baak wrote: The value of 5E^-11 refers to the resolution that the precision can be relied upon after taking into account all the factors that influence it. It means that there is an error that can be as much as +/-5 parts per e^-11. No, it can be way more. A 5e-11 spec value is likely just RMS, or 1-sigma. Actual measurements will show significantly larger 2-sigma, 3-sigma, etc. value. Your "as much as" wording sounds more like a 6-sigma, or peak-to-peak spec. One must be very careful to match the measurement used to make the spec with how the device is intended to be used. For example, Magnus will likely tell us about MTIE, which is a perfect-storm, worst-case time error spec. It's very different from rough 1-sigma specs we usually talk about. Indeed. ADEV measurements give RMS-ish values, 1-sigma values, and is intended for random noiseforms. When listing the frequency stability of an oscillator you usually specify the 3-sigma value. However, doing that for ADEV measures the usual way would give you a false sense of what the confidence intervals is, since you need to look at chi-square distribution instead for similar limits. Then, systematic deviations exists also while being locked in. Those will dominate as you slip out of lock. For systematics, the MTIE may be a better measure to consider. Cheers, Magnus ___ 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] VNA design
On 6/2/2014 12:41 PM, Brooke Clarke wrote: Hi: I started with the HP 8410 and added an external computer. Since it can be used manually I think it's an excellent way to learn about VNAs. http://www.prc68.com/I/MWTE.shtml#NA For my last 8 years at Agilent before retiring in March, I was doing advanced R&D on network analyzers. The newer guys coming up didn't have an intuitive understanding of network analyzer architectures like I did. I started using the 8410 back in 1973 before I even worked for HP. Because of the modular design, it was like a teaching tool that forced you to understand what was going on. When I mentored the young guys, I would explain to them a lot of principles based on the 8410. Modern network analyzers are too "automatic". The 8410 puts modern VNA's into perspective. BTW, I used to sit next to Dick Lee, who was a member of the 8410 design team in 1963 at the dawn of the golden age of microwave instruments based on YIG tuned oscillators and step recovery diode samplers. As you noted, the architecture was built around the YIG tuned oscillator and certain things were done that way they were because of that. Rick Karlquist N6RK ___ 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] "Audio" DAC for GPSDO?
In message <1401742940.44103.yahoomail...@web142705.mail.bf1.yahoo.com>, Bob Stewart writ es: >Could someone explain to me how such an audio DAC differs from a non >-audio DAC and why it's not suitable for this application?=A0 Is this just >a disclaimer from microchip to avoid liability or is there some practical >reason to go with a traditional DAC? A lot of them have DC protections, so you can't leave them at a particular input value for very long before they go into safety mode and clamp the output to zero. Your speakers love them for this, your OCXO not so much. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] "Audio" DAC for GPSDO?
Now that my TIC is working with Bert's board, I'm considering taking the next step of designing a GPSDO from scratch. There are several projects I'd like to do with a dsPIC33, so that was a natural choice. But I now understand that it has an "audio" DAC and is not recommended for process control. Could someone explain to me how such an audio DAC differs from a non-audio DAC and why it's not suitable for this application? Is this just a disclaimer from microchip to avoid liability or is there some practical reason to go with a traditional DAC? On reading through the various datasheets, it appears to me that the concern might be that the input data to the DAC might be interrupted, thus causing it to go to some programmable "safe" output voltage. My initial thought was just to control the value of the safe voltage and not bother to feed the DAC, though I haven't really explored the idea. Bob - AE6RV ___ 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] VNA design
On 2 Jun 2014 19:07, "Alexander Pummer" wrote: > > I do not wanted to discourage any body, but building the hardware of a network analyzer is not a simple task, and requires substantial instrumentation, software could solve hardware problems to certain limit only > 73 > KJ6UHN VERY TRUE The larger the hardware errors, the larger the errors that need to removed so the accuracy of measurements suffer with the slightest change in temperature. Adapters with a poor return loss BEFORE the calibration plane can still cause problems with stability of measurements. Despite error correction, it is not uncommon to do things like improve the match at test ports with attenuators. I think it would be unwise to embark on designing a VNA unless one has at least used one first. I don't think designing a VNA is the best way to get one. Perhaps after buying one (8510 or 8753 is probably best) then designing one is likely to be more productive. Dave. ___ 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] VNA design
Hi: I started with the HP 8410 and added an external computer. Since it can be used manually I think it's an excellent way to learn about VNAs. http://www.prc68.com/I/MWTE.shtml#NA It turns out that when automating a VNA the same frequency is measured many times during cal and device testing. If the frequency is not exactly the same errors are introduced. The early systems used sweep generators and harmonic locking which might lock to different harmonic numbers thus causing errors. Later systems used EIP frequency counters to phase lock the sweepers to minimize that problem and the newest systems use frequency synthesizers with good reference oscillators (Time Nuts content). Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html ___ 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] Boeing 787 GPS reception trouble
I'm posting this from inside an Ethiopian 787, on the ground, with the doors closed. I just completed a fifteen-minute voice call initiated from inside the plane, with reasonable reception and no drops, while the doors were open. And I was able to get a new GPS location in less than two seconds (though that wasn't from cold boot, so I don't know whether it was able to accelerate the process using cached data previously received). The phone (an iPhone 5S) is showing three bars inside the plane, and was varying between three and four bars outside. Note that the non-linear mapping of signal strength to "bars" is a matter of intense negotiation between carriers and vendors, and shouldn't be taken as a literal indicator of anything at all. Likewise, Ethiopian may have ordered planes with significantly different options than ANA (no center overhead storage in business, for example) and used different paint formulation. Nevertheless, in this specific case, I'm not seeing anything that seems out-of-the-ordinary relative to other aircraft. -Bill > On Jun 2, 2014, at 10:03, "Tom Van Baak" wrote: > > 1) When I fly I often use my iPhone while on the ground, before take-off or > after landing. > > 2) I sometimes carry a GPS receiver. When permitted (varies by airline), it's > fun to log NMEA data for a flight and later plot the flight path and duration > with UTC accuracy. > > 3) On occasion I also bring a logging Geiger counter. It's amazing how much > background radiation there is up at flight altitude compared to down at > ground level. You can go from 10 or 20 CPM (counts per minute) at home to, > say, 500! CPM at 40k feet. Those of you who live in mile-high Colorado enjoy > higher background levels. I know, because my Geiger counter was wonderfully > close to 60 CPM (= 1 CPS) in a hotel near NIST. Yes, I have the 1PPS ADEV > plot for this and, yes, background radiation makes the world's worst "atomic" > clock. > > Anyway, over the years I've collected some nice GPS > latitude/longitude/altitude data sets as well as background radiation as a > function of altitude. Just to be clear, I do turn off these devices according > to airline regulations. > > Now I have never had a problem with reception in the terminal, walkway, or > even while seated inside a plane. I figured the aluminum frame of the plane > was thin enough that photons at cell, GPS, and gamma frequencies easily pass > through the outer shell or the windows. > > But last week I flew the new composite Boeing 787 Dreamliner and noticed > something quite different. From the second I entered the plane, I lost both > cell and GPS reception. It didn't matter how close I was to a window or not. > I know the word "composite" sounds inert, but carbon fiber must be somewhat > conductive, yes? And there must be serious lightning suppression layers too, > maybe? Furthermore, the B787 windows are exotic; like giant oval LCD screens > which electronically dim from near transparent to very opaque. Does all this > make the new 787 a record-holding RF-tight flying Faraday cage? > > Is this the first airplane in history where a time-nut can't receive GPS? At > least gamma rays make it though, so I got RAD data. But no GPS data. Not a > single SV fix the entire time I was inside the plane. > > Has anyone else noticed this? Or know about this? Please respond only if you > have real information. I can speculate as well as anyone; so it's solid > technical, RF, EMF, or composite carbon fiber engineering info I'm looking > for. > > Thanks, > /tvb > > ___ > 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] VNA design
I do not wanted to discourage any body, but building the hardware of a network analyzer is not a simple task, and requires substantial instrumentation, software could solve hardware problems to certain limit only 73 KJ6UHN On 6/2/2014 10:38 AM, Dr. David Kirkby wrote: On 2 Jun 2014 17:33, "Ed Palmer" wrote: There's a DIY project to build a spectrum analyzer at http://scottyspectrumanalyzer.com . Since it's modular, one version of the project is to add a couple of modules that change it into a network analyzer. But I think a VNA is an order of magnitude more complex than a SA - pun intended! The software is probably where the biggest work is. A modular design for a VNA would be interesting, as different sources, couplers etc could be used depending on frequency range. Dave. ___ 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] VNA Project
Hello! Most of the time I do not anything of significance to contribute, but VNA's are near & dear to me. I currently have a grad student working on a poor mans VNA that will go to 2700 MHz. The issue is phase measurement over that range, which, even though there are a bunch of chips that purport to do this, not really. So a synthesized tracking dual channel super het system is needed to measure phase over 0-360 degrees, where the phase component of the vector is measured at a fixed frequency, comparing the reference to the test channel. A good starting place for understanding is the manual for the HP8410A/B/C VNA from the '80's, available online at Agilent. It will explain many of the issue and provide a block diagram that you can modify with modern components. Two synthesizers (or a dual with IF offset on one) are probably the best way for the stimulus & receiver LO. 73 Jeff Kruth WA3ZKR In a message dated 6/2/2014 12:00:28 P.M. Eastern Daylight Time, time-nuts-requ...@febo.com writes: Message: 1 Date: Mon, 2 Jun 2014 16:43:12 +0200 From: Attila Kinali To: time-nuts@febo.com Subject: [time-nuts] VNA design Message-ID: <20140602164312.66b92049910fcab6c8aa8...@kinali.ch> Content-Type: text/plain; charset=US-ASCII Hi, I know this is not exactly a time-nut question, but i guess this is the best place i know to ask about this stuff. I recently got introduced into the usefullness of a VNA. But these things are horribly expensive for home use, even if bought from ebay (before you say anything, remember i live in europe, where every boat anchor hast to travel a long way). But given that most of the designs that are on ebay are from the 80s and early 90s, i thought that with todays ICs it should be easy to come up with a design that does the same thing but can be build on a kitchen table. Well, my problem now is, that i don't know how to build a VNA. Yes, i understand the basic principle. I can come up with a design that should work. But i have no clue about any problems or difficulties in building these devices. Ie it's very likely that i fall into a dozen traps when i try to build one. I tried to get information on how to build a VNA, or what kind of trouble people had operating one, but beside the VNA book[1] Rick mentioned a couple of months ago and ko4bb's site (thanks man! your manual collection is a gold mine!), my searches came out blank. As i'm quite sure that there is information of that kind out there, i would like to ask whether someone could point me to some documents, webpages, books, papers, etc that would show me the detailed design of VNA, the problems people had with some designs or anything else that would be of interest in such an endavor. Also, any good resource on how to build a directional coupler that does 10-3000MHz without going to exotic materials would be much appreciated. All papers i found deal mostly with stuff above 5GHz. Seems like "low frequency" couplers are considered "a solved problem". Attila Kinali [1] Handbook of Microwave Component Measurements: with Advanced VNA Techniques by Dunsmore, 2012 ___ 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] VNA design
Also, a convenient signal source with built-in attenuator: http://www.rf-consultant.com/calibrated-signal-generator/ Don Dr. David Kirkby > On 2 Jun 2014 15:50, "Attila Kinali" wrote: >> >> I recently got introduced into the usefullness of a VNA. But these >> things are horribly expensive for home use, even if bought from ebay >> (before you say anything, remember i live in europe, where every >> boat anchor hast to travel a long way). But given that most of the >> designs that are on ebay are from the 80s and early 90s, i thought that >> with todays ICs it should be easy to come up with a design that does >> the same thing but can be build on a kitchen table. > > There are a few designs around. The early version of the VNWA was > described in QEX. There is the N2PK design too. The latter has a limited > frequency range, but a high dynamic range. > > All modern professional systems with two ports use 4 receivers. Earlier > designs use 3 receivers which is not good for TRL calibration. > > I think it would be a huge task. I think that the main issue would be the > software. > I have been considering adding the "unknown thru" calibration method to my > HP 8720D. That in itself would be quite a task, but writing all the > software for a VNA would be a huge task. > > I thought TAPR had a similar project but I don't recall it producing > anything close to workable. > > BTW the software options for the HP 8753's are now easily available, so if > you do buy an 8753 (probably the best choice), don't worry about what > software options it has. > > I would really like to see an open hardware and software VNA, but it would > be a lot of work. > > If you do it, think about having 3 or 4 ports with independent sources for > optimal balanced measurements. > > I don't think that there's much point producing a design with just a TR > test set. > > Dave. > ___ > 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. > > -- "The power of accurate observation is commonly called cynicism by those who have not got it." -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road Huson, MT, 59846 mail: POBox 404 Frenchtown MT 59834-0404 VOX 406-626-4304 Skype: buffler2 www.lightningforensics.com www.sixmilesystems.com ___ 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] VNA design
Those interested might look at RedPitaya.com for a new piece of hardware that might be used. Less than $500 without a "box" Don Dr. David Kirkby > On 2 Jun 2014 15:50, "Attila Kinali" wrote: >> >> I recently got introduced into the usefullness of a VNA. But these >> things are horribly expensive for home use, even if bought from ebay >> (before you say anything, remember i live in europe, where every >> boat anchor hast to travel a long way). But given that most of the >> designs that are on ebay are from the 80s and early 90s, i thought that >> with todays ICs it should be easy to come up with a design that does >> the same thing but can be build on a kitchen table. > > There are a few designs around. The early version of the VNWA was > described in QEX. There is the N2PK design too. The latter has a limited > frequency range, but a high dynamic range. > > All modern professional systems with two ports use 4 receivers. Earlier > designs use 3 receivers which is not good for TRL calibration. > > I think it would be a huge task. I think that the main issue would be the > software. > I have been considering adding the "unknown thru" calibration method to my > HP 8720D. That in itself would be quite a task, but writing all the > software for a VNA would be a huge task. > > I thought TAPR had a similar project but I don't recall it producing > anything close to workable. > > BTW the software options for the HP 8753's are now easily available, so if > you do buy an 8753 (probably the best choice), don't worry about what > software options it has. > > I would really like to see an open hardware and software VNA, but it would > be a lot of work. > > If you do it, think about having 3 or 4 ports with independent sources for > optimal balanced measurements. > > I don't think that there's much point producing a design with just a TR > test set. > > Dave. > ___ > 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. > > -- "The power of accurate observation is commonly called cynicism by those who have not got it." -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road Huson, MT, 59846 mail: POBox 404 Frenchtown MT 59834-0404 VOX 406-626-4304 Skype: buffler2 www.lightningforensics.com www.sixmilesystems.com ___ 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] VNA design
One which is, IMHO, good value for money is this one. I've been very pleased with mine. http://sdr-kits.net/VNWA3_Description.html Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] VNA design
On 2 Jun 2014 18:14, "Thomas S. Knutsen" wrote: > > The design of an VNA is an interesting thing. It requires quite high focus > on good RF practices and screening. > > In the range 0-3GHz there is no low cost devices avaible, not counting the > copper mountain tech boxes ( http://www.coppermountaintech.com/ ). Up to > 1.3GHz there is the DG8SAQ VNWA avaible from sdrkits, these can also be > used with mixers to extend the max frequency. The VNWA is an 2 detector VNA > that needs an S-parameter testset in order to get all the 4 S-parameters. > > An homebrew alternative would be fun to do, but its a lot of work, both in > getting reproduceable data from the hardware and in programming. Building > somthing that is connected to the PC simplifies things a lot. > Couplers and detectors are not the hardest thing to make, some small SMD > resistors, an balanced amplifier - detector and things should work to 6GHz > or higher with some care in the layout. > Signal generation is perhaps the hardest part, there is AFAIK no single > solution working from LF to high UHF, one cool alternative is to build an > generator with an YIG and mixing down, but that requires a lot of work to > get stable over the range 0-3GHz. In addition you need to keep the signal > from the generator out of the detector in order to keep the dynamic range > high. > If you are building your own VNA, I would build it with 4 detectors and the > posibility to re-configure those. It opens for several of the more advanced > calibration methods and eliminates some of the errors in the VNA. > > If I were to build something, I think I would base it on the N2PK design, > as there is documentation and programs avaible that makes for some part of > the work. > > There are some IC's avaible that do the detection of the power levels, > AD8302 comes to mind, the common denominator for these are that they don't > solve for the phase sign, and thereby are not true vector. In addition, > those I have tested don't behave to well with > > As an alternative, the HP8410 series are avaible here in the EU, sometimes > quite cheap I assume you mean 8510. > The accuracy of the VNA is determined by the calkit used to calibrate it. > There is no way around obtaining an good calkit, learning how to use it > without destroying it, and do repeatable calibrations. The calkit is the > single most important part of the VNA. Do use an calkit for the connectors > you are going to measure, don't add adaptors or worse, coaxial cable after > the calibration plane. I had at one point an HP 8753A (3 GHz) VNA with a full S-parameter test set. It cost me about 50% of what my HP 85054B 18 GHz N calibration kit cost me and I think I got the 85054B cheap at about $3800. I do sell low cost calibration kits for N, SMA and X-band waveguide. Dave ___ 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] Boeing 787 GPS reception trouble
I've flown on 787s three times before, and am about to do so again later today. The prior times I used my cell phone as normal and didn't give it any thought. This time I'll pay particular attention and report back. Twice for me have been Ethiopian Air, once London-Addis, once Dulles-Addis. The third time was ANA Osaka-San Francisco. Today will be London-Addis again, but a different actual plane, since the previous one is one of the ones that burned. -Bill > On Jun 2, 2014, at 10:03, "Tom Van Baak" wrote: > > 1) When I fly I often use my iPhone while on the ground, before take-off or > after landing. > > 2) I sometimes carry a GPS receiver. When permitted (varies by airline), it's > fun to log NMEA data for a flight and later plot the flight path and duration > with UTC accuracy. > > 3) On occasion I also bring a logging Geiger counter. It's amazing how much > background radiation there is up at flight altitude compared to down at > ground level. You can go from 10 or 20 CPM (counts per minute) at home to, > say, 500! CPM at 40k feet. Those of you who live in mile-high Colorado enjoy > higher background levels. I know, because my Geiger counter was wonderfully > close to 60 CPM (= 1 CPS) in a hotel near NIST. Yes, I have the 1PPS ADEV > plot for this and, yes, background radiation makes the world's worst "atomic" > clock. > > Anyway, over the years I've collected some nice GPS > latitude/longitude/altitude data sets as well as background radiation as a > function of altitude. Just to be clear, I do turn off these devices according > to airline regulations. > > Now I have never had a problem with reception in the terminal, walkway, or > even while seated inside a plane. I figured the aluminum frame of the plane > was thin enough that photons at cell, GPS, and gamma frequencies easily pass > through the outer shell or the windows. > > But last week I flew the new composite Boeing 787 Dreamliner and noticed > something quite different. From the second I entered the plane, I lost both > cell and GPS reception. It didn't matter how close I was to a window or not. > I know the word "composite" sounds inert, but carbon fiber must be somewhat > conductive, yes? And there must be serious lightning suppression layers too, > maybe? Furthermore, the B787 windows are exotic; like giant oval LCD screens > which electronically dim from near transparent to very opaque. Does all this > make the new 787 a record-holding RF-tight flying Faraday cage? > > Is this the first airplane in history where a time-nut can't receive GPS? At > least gamma rays make it though, so I got RAD data. But no GPS data. Not a > single SV fix the entire time I was inside the plane. > > Has anyone else noticed this? Or know about this? Please respond only if you > have real information. I can speculate as well as anyone; so it's solid > technical, RF, EMF, or composite carbon fiber engineering info I'm looking > for. > > Thanks, > /tvb > > ___ > 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] VNA design
On 2 Jun 2014 17:33, "Ed Palmer" wrote: > > There's a DIY project to build a spectrum analyzer at http://scottyspectrumanalyzer.com . Since it's modular, one version of the project is to add a couple of modules that change it into a network analyzer. But I think a VNA is an order of magnitude more complex than a SA - pun intended! The software is probably where the biggest work is. A modular design for a VNA would be interesting, as different sources, couplers etc could be used depending on frequency range. Dave. ___ 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] VNA design
On Mon, 02 Jun 2014 09:35:41 -0700 "Richard (Rick) Karlquist" wrote: > Julius said that he designed it before > the era of cheap calibration. Now that everyone has calibration, > you don't need a good directional coupler. You can get away > with a MiniCircuits coupler. How about impedance matching issues? Can those be calibrated away? > But in fact it is > even easier to just use a resistive bridge. Four ordinary > resistors will easily go to 3 GHz. Use a differential amplifier > at the output. Lots of info on this in the literature. I somewhat fear that the parasitics of resistors will give me garbage when going to >1GHz. Maybe i should look into those and calculate how much performance they would cost. > Another way to make in effect a directional coupler is to use > a 180 degree hybrid. My understanding is, that those are rather narrow band. Those i've seen were at most one octave in range. > Don't even think about trying this at home. You mention that for both Podell's and Botkas design. May i ask what the reason is? Why do you think it cannot be done at home? Also, i quickly tried to search for both Botka and Podell. While Podell gives a couple of matches on ieeexplore, Botka comes back almost empty. Any hints to for finding references to their work? > BTW, you didn't mention software, but that's a big part of > the job. Because i have not had a look into that yet. My guess is that phase detection of a known frequency (i ignore multi-tone detection due to harmonics for the moment) is known and should be easy. So the big part of the softare is getting thins into the PC and doing a good job of presenting the data, ie GUI stuff. And GUI is, once you have a graphical design, just implementation work. Please correct me if i'm mistaken. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] VNA design
On 2 Jun 2014 15:50, "Attila Kinali" wrote: > > I recently got introduced into the usefullness of a VNA. But these > things are horribly expensive for home use, even if bought from ebay > (before you say anything, remember i live in europe, where every > boat anchor hast to travel a long way). But given that most of the > designs that are on ebay are from the 80s and early 90s, i thought that > with todays ICs it should be easy to come up with a design that does > the same thing but can be build on a kitchen table. There are a few designs around. The early version of the VNWA was described in QEX. There is the N2PK design too. The latter has a limited frequency range, but a high dynamic range. All modern professional systems with two ports use 4 receivers. Earlier designs use 3 receivers which is not good for TRL calibration. I think it would be a huge task. I think that the main issue would be the software. I have been considering adding the "unknown thru" calibration method to my HP 8720D. That in itself would be quite a task, but writing all the software for a VNA would be a huge task. I thought TAPR had a similar project but I don't recall it producing anything close to workable. BTW the software options for the HP 8753's are now easily available, so if you do buy an 8753 (probably the best choice), don't worry about what software options it has. I would really like to see an open hardware and software VNA, but it would be a lot of work. If you do it, think about having 3 or 4 ports with independent sources for optimal balanced measurements. I don't think that there's much point producing a design with just a TR test set. Dave. ___ 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] VNA design
On Mon, 2 Jun 2014 09:01:37 -0700 Chris Albertson wrote: > Today you can do most of the processing in software. All you need is A/D > and D/A converters that can handle the required bandwidth and get the raw > numbers into the computer. Look up "SDR" type radios and search on the > combination of SDR and VNA and you'll find a few. Then with the same > hardware you have a VNA, spectrum analyzer, oscilloscope, low power > transceiver and so on. This idea is somewhat easy through HF. That's actually the base idea. Get some wide range synthesizer (eg like HMC832LP6GE or LTC6946) for the test signal and one for the detection part. Mix down the received signal and use some ADC to move into digital domain. There preprocess the data in an FPGA (data reduction) and do all difficult stuff in the PC. Yes, it all sounds so easy. But i'm sure there must be some trap in there, which i cannot see yet. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] VNA design
On Mon, 02 Jun 2014 09:46:38 -0600 Ed Palmer wrote: > There's a DIY project to build a spectrum analyzer at > http://scottyspectrumanalyzer.com . Since it's modular, one version of > the project is to add a couple of modules that change it into a network > analyzer. That looks very interesting. Thanks for the link! > If you search ebay for directional couplers, I can almost guarantee that > you will find what you want at a reasonable price. Yes. But if i ever build something, it should be reproducible for others as well. Thus i don't want to rely on stuff from ebay which can suddenly disapear. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] VNA design
The design of an VNA is an interesting thing. It requires quite high focus on good RF practices and screening. In the range 0-3GHz there is no low cost devices avaible, not counting the copper mountain tech boxes ( http://www.coppermountaintech.com/ ). Up to 1.3GHz there is the DG8SAQ VNWA avaible from sdrkits, these can also be used with mixers to extend the max frequency. The VNWA is an 2 detector VNA that needs an S-parameter testset in order to get all the 4 S-parameters. An homebrew alternative would be fun to do, but its a lot of work, both in getting reproduceable data from the hardware and in programming. Building somthing that is connected to the PC simplifies things a lot. Couplers and detectors are not the hardest thing to make, some small SMD resistors, an balanced amplifier - detector and things should work to 6GHz or higher with some care in the layout. Signal generation is perhaps the hardest part, there is AFAIK no single solution working from LF to high UHF, one cool alternative is to build an generator with an YIG and mixing down, but that requires a lot of work to get stable over the range 0-3GHz. In addition you need to keep the signal from the generator out of the detector in order to keep the dynamic range high. If you are building your own VNA, I would build it with 4 detectors and the posibility to re-configure those. It opens for several of the more advanced calibration methods and eliminates some of the errors in the VNA. If I were to build something, I think I would base it on the N2PK design, as there is documentation and programs avaible that makes for some part of the work. There are some IC's avaible that do the detection of the power levels, AD8302 comes to mind, the common denominator for these are that they don't solve for the phase sign, and thereby are not true vector. In addition, those I have tested don't behave to well with As an alternative, the HP8410 series are avaible here in the EU, sometimes quite cheap, if you can wait a bit. Mine is mostly used at microwaves, with some external mixers and testsets. If you are low on cash, this may be the best approach, but it requires some work. The accuracy of the VNA is determined by the calkit used to calibrate it. There is no way around obtaining an good calkit, learning how to use it without destroying it, and do repeatable calibrations. The calkit is the single most important part of the VNA. Do use an calkit for the connectors you are going to measure, don't add adaptors or worse, coaxial cable after the calibration plane. The book by Joel Dunsmore is excelent, highly reccomended if you are doing or interested in VNA measurments. BR. Thomas. 2014-06-02 16:43 GMT+02:00 Attila Kinali : > Hi, > > I know this is not exactly a time-nut question, but i guess this is > the best place i know to ask about this stuff. > > I recently got introduced into the usefullness of a VNA. But these > things are horribly expensive for home use, even if bought from ebay > (before you say anything, remember i live in europe, where every > boat anchor hast to travel a long way). But given that most of the > designs that are on ebay are from the 80s and early 90s, i thought that > with todays ICs it should be easy to come up with a design that does > the same thing but can be build on a kitchen table. > > Well, my problem now is, that i don't know how to build a VNA. > Yes, i understand the basic principle. I can come up with a design > that should work. But i have no clue about any problems or difficulties > in building these devices. Ie it's very likely that i fall into a dozen > traps when i try to build one. > > I tried to get information on how to build a VNA, or what kind of trouble > people had operating one, but beside the VNA book[1] Rick mentioned a > couple > of months ago and ko4bb's site (thanks man! your manual collection is a > gold > mine!), my searches came out blank. As i'm quite sure that there is > information of that kind out there, i would like to ask whether someone > could point me to some documents, webpages, books, papers, etc that would > show me the detailed design of VNA, the problems people had with some > designs or anything else that would be of interest in such an endavor. > > > Also, any good resource on how to build a directional coupler that > does 10-3000MHz without going to exotic materials would be much > appreciated. All papers i found deal mostly with stuff above 5GHz. > Seems like "low frequency" couplers are considered "a solved problem". > > > Attila Kinali > > [1] Handbook of Microwave Component Measurements: with Advanced VNA > Techniques > by Dunsmore, 2012 > > -- > The trouble with you, Shev, is you don't say anything until you've saved > up a whole truckload of damned heavy brick arguments and then you dump > them all out and never look at the bleeding body mangled beneath the heap > -- Tirin, The Dispossessed, U. Le Guin > _
Re: [time-nuts] VNA design
On Mon, 2 Jun 2014 11:09:55 -0400 Scott McGrath wrote: > You might want to look at the N2PK and DG8SAQ vector network analyzer > projects there are also some commercial USB based 'personal' network > analyzers out there starting about 6K I've seen both and looked at their implementation. Especially DG8SAQ is conceptually quite interesting IMHO (using the harmonics of an DDS chip). But i'd like to get at least to 1.6GHz (think GPS) Otherwise i would have ordered one of them already. (Side note: i am not sure whether i will get to building a VNA. I am currently just playing with the idea and try to learn about their function as much as possible) > > As for directional couplers. I would suggest buying vs building Mini > Circuits has a line of high quality inexpensive couplers in both coaxial > and surface mount at price points affordable for individuals these really > are a solved problem. Yes. But their SMD are only 3 port, ie the isolated port is internally terminated. Which in turn means, i'd need to put two of those in to get both transmitted and reflected wave. > > You could of course build waveguide based Couplers at lower frequencies they > would be physically large but easy to construct if you have access to > machine tools I think all the Minicircuit ones are build using transformers. I cannot think of any other way to get such a large bandwith in these small dimensions otherwise. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] Boeing 787 GPS reception trouble
Said Jackson wrote: > Wonderful. It also means cell phones will crank up their power > searching for a signal [...] At least with GSM, a mobile station needs to receive a base station signal before it transmits anything at all. If no cell network signals are received at all, the mobile should not be transmitting anything at all either, as without a base station signal it has no idea what frequency channel it should be transmitting on, etc. I would think that the same principle would hold for all other widely deployed cell- phone technologies.. > Thankfully there are alternative ways to fly. Such as? SF ___ 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] Boeing 787 GPS reception trouble
On 2 Jun 2014 10:03, "Tom Van Baak" wrote: > Now I have never had a problem with reception in the terminal, walkway, or even while seated inside a plane. I figured the aluminum frame of the plane was thin enough that photons at cell, GPS, and gamma frequencies easily pass through the outer shell or the windows. I do have quite a bit of data on that, having measured the attenuation both in flight tests and on the ground. (I don't trust the latter anyway.) I can't share it unfortunately. But you should be aware of of how the systems in aircraft that allow one to use a phone work. The cellular operators were keen that one could not cause interference on the ground by a phone connecting to many base stations. For this reason the planes incorporate a noise generator that raises the background noise so that the phone cant hear any cell sites on the ground. I would not expect that to be enabled below about 3000 m, but it is quite possible that the noise generator was on. I would not expect it to jam GPS frequencies, but certainly those used by mobile phones. Dave ___ 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] VNA design
On 6/2/2014 7:43 AM, Attila Kinali wrote: Also, any good resource on how to build a directional coupler that does 10-3000MHz without going to exotic materials would be much I once had the opportunity to discuss directional couplers with Julius Botka, then with HP/Agilent. Specifically, a true directional coupler he designed that approached the range of 10-3000 MHz. IMHO, Botka was one of the greatest experts of all time in this area. It took extreme attention to detail to get it to work. It didn't so much involve exotic materials, but rather expertise. Don't try this at home kids. Julius said that he designed it before the era of cheap calibration. Now that everyone has calibration, you don't need a good directional coupler. You can get away with a MiniCircuits coupler. But in fact it is even easier to just use a resistive bridge. Four ordinary resistors will easily go to 3 GHz. Use a differential amplifier at the output. Lots of info on this in the literature. Another way to make in effect a directional coupler is to use a 180 degree hybrid. I also had the opportunity to study Alan Podell's amazing designs and even have discussions with him. I dissected one of his 10-3000 MHz hybrids. (Originally made by Anzac, now available from Macom Technology for about 5 Benjamins). Don't even think about trying this at home. BTW, you didn't mention software, but that's a big part of the job. Rick Karlquist N6RK ___ 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] Boeing 787 GPS reception trouble
Wonderful. It also means cell phones will crank up their power searching for a signal, and the passengers are sitting inside a microwave oven since the RF energy can't escape. Thankfully there are alternative ways to fly. Bye, Said Sent From iPhone On Jun 2, 2014, at 8:45, Chris Albertson wrote: > On Mon, Jun 2, 2014 at 1:55 AM, Tom Van Baak wrote: > >> >> But last week I flew the new composite Boeing 787 Dreamliner and noticed >> something quite different. From the second I entered the plane, I lost both >> cell and GPS reception. It didn't matter how close I was to a window or >> not. > > > I bet this is nothing to do with carbon fiber vs. aluminum skin. Both > would have to be conductive. I bet it's the metal film on the windows. > The metal skin of the older planes would have been a perfect shield but > the windows let the signals in. But on the new plane the windows have a > conductive metal film. So I bet the difference is entirely because of the > change in window design. > > Even in buildings some "energy saving" windows have coatings that are > conductive and don't allow GPS to pass. > -- > > Chris Albertson > Redondo Beach, California > ___ > 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] VNA design
There's a DIY project to build a spectrum analyzer at http://scottyspectrumanalyzer.com . Since it's modular, one version of the project is to add a couple of modules that change it into a network analyzer. If you search ebay for directional couplers, I can almost guarantee that you will find what you want at a reasonable price. Ed On 6/2/2014 8:43 AM, Attila Kinali wrote: Hi, I know this is not exactly a time-nut question, but i guess this is the best place i know to ask about this stuff. I recently got introduced into the usefullness of a VNA. But these things are horribly expensive for home use, even if bought from ebay (before you say anything, remember i live in europe, where every boat anchor hast to travel a long way). But given that most of the designs that are on ebay are from the 80s and early 90s, i thought that with todays ICs it should be easy to come up with a design that does the same thing but can be build on a kitchen table. Well, my problem now is, that i don't know how to build a VNA. Yes, i understand the basic principle. I can come up with a design that should work. But i have no clue about any problems or difficulties in building these devices. Ie it's very likely that i fall into a dozen traps when i try to build one. I tried to get information on how to build a VNA, or what kind of trouble people had operating one, but beside the VNA book[1] Rick mentioned a couple of months ago and ko4bb's site (thanks man! your manual collection is a gold mine!), my searches came out blank. As i'm quite sure that there is information of that kind out there, i would like to ask whether someone could point me to some documents, webpages, books, papers, etc that would show me the detailed design of VNA, the problems people had with some designs or anything else that would be of interest in such an endavor. Also, any good resource on how to build a directional coupler that does 10-3000MHz without going to exotic materials would be much appreciated. All papers i found deal mostly with stuff above 5GHz. Seems like "low frequency" couplers are considered "a solved problem". Attila Kinali [1] Handbook of Microwave Component Measurements: with Advanced VNA Techniques by Dunsmore, 2012 ___ 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] Boeing 787 GPS reception trouble
In message <538c82b8.5020...@earthlink.net>, Jim Lux writes: >The reason for "radio receiver ban" originally [...] Actually, there was a very specific incident where somebody brought a television on a plane in order to see something important. We're talking 1950-1960 timeframe and and a tube-television. Apparently this disturbed something in the cockpit, but there is no evidence to indicate that it was actually a problem in the cockpit, only that they spotted some kind of noise. And that's when and why the FAA introduced the ban. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Boeing 787 GPS reception trouble
On Mon, Jun 2, 2014 at 1:55 AM, Tom Van Baak wrote: > > But last week I flew the new composite Boeing 787 Dreamliner and noticed > something quite different. From the second I entered the plane, I lost both > cell and GPS reception. It didn't matter how close I was to a window or > not. I bet this is nothing to do with carbon fiber vs. aluminum skin. Both would have to be conductive. I bet it's the metal film on the windows. The metal skin of the older planes would have been a perfect shield but the windows let the signals in. But on the new plane the windows have a conductive metal film. So I bet the difference is entirely because of the change in window design. Even in buildings some "energy saving" windows have coatings that are conductive and don't allow GPS to pass. -- Chris Albertson Redondo Beach, California ___ 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] VNA design
Today you can do most of the processing in software. All you need is A/D and D/A converters that can handle the required bandwidth and get the raw numbers into the computer. Look up "SDR" type radios and search on the combination of SDR and VNA and you'll find a few. Then with the same hardware you have a VNA, spectrum analyzer, oscilloscope, low power transceiver and so on. This idea is somewhat easy through HF. On Mon, Jun 2, 2014 at 7:43 AM, Attila Kinali wrote: > Hi, > > I know this is not exactly a time-nut question, but i guess this is > the best place i know to ask about this stuff. > > I recently got introduced into the usefullness of a VNA. But these > things are horribly expensive for home use, even if bought from ebay > (before you say anything, remember i live in europe, where every > boat anchor hast to travel a long way). But given that most of the > designs that are on ebay are from the 80s and early 90s, i thought that > with todays ICs it should be easy to come up with a design that does > the same thing but can be build on a kitchen table. -- Chris Albertson Redondo Beach, California ___ 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] Boeing 787 GPS reception trouble
I build and fly large model rockets. Many use carbon fiber in their construction. I can tell you that carbon fiber does conduct electricity... not quite as well as pure metals, but pretty darn good... and the conduction is anisotropic (better conduction along the fibers than across their diameter... and the same for thermal conductivity). And that it makes a GREAT RF shield. Most of my rockets have tracking transmitters in them... most at around 220 Mhz A single layer of 5 oz carbon cloth around a phenolic body tube can almost totally block the tracking signal of a transmitter that has a 20+ mile open-air range. Once inside the carbon wrapped airframe, it has a range of a couple hundred feet. You get the tracking signal only when the rocket separates and the tracking transmitter is extracted from the airframe. An interesting observation is that putting the transmitter in an aluminum airframe has little effect on its range.It seems that that the "semi-condcutive" properties of the carbon fiber is responsible for its RF properties. ___ 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] VNA design
Attila You might want to look at the N2PK and DG8SAQ vector network analyzer projects there are also some commercial USB based 'personal' network analyzers out there starting about 6K As for directional couplers. I would suggest buying vs building Mini Circuits has a line of high quality inexpensive couplers in both coaxial and surface mount at price points affordable for individuals these really are a solved problem. You could of course build waveguide based Couplers at lower frequencies they would be physically large but easy to construct if you have access to machine tools Most commercial VNAs are still in the boat anchor class for size and weight at the office we have a R&S 40 Ghz 4 port VNA and it's still huge and heavy along with a fleet of agilents Sent from my iPad > On Jun 2, 2014, at 10:43 AM, Attila Kinali wrote: > > Hi, > > I know this is not exactly a time-nut question, but i guess this is > the best place i know to ask about this stuff. > > I recently got introduced into the usefullness of a VNA. But these > things are horribly expensive for home use, even if bought from ebay > (before you say anything, remember i live in europe, where every > boat anchor hast to travel a long way). But given that most of the > designs that are on ebay are from the 80s and early 90s, i thought that > with todays ICs it should be easy to come up with a design that does > the same thing but can be build on a kitchen table. > > Well, my problem now is, that i don't know how to build a VNA. > Yes, i understand the basic principle. I can come up with a design > that should work. But i have no clue about any problems or difficulties > in building these devices. Ie it's very likely that i fall into a dozen > traps when i try to build one. > > I tried to get information on how to build a VNA, or what kind of trouble > people had operating one, but beside the VNA book[1] Rick mentioned a couple > of months ago and ko4bb's site (thanks man! your manual collection is a gold > mine!), my searches came out blank. As i'm quite sure that there is > information of that kind out there, i would like to ask whether someone > could point me to some documents, webpages, books, papers, etc that would > show me the detailed design of VNA, the problems people had with some > designs or anything else that would be of interest in such an endavor. > > > Also, any good resource on how to build a directional coupler that > does 10-3000MHz without going to exotic materials would be much > appreciated. All papers i found deal mostly with stuff above 5GHz. > Seems like "low frequency" couplers are considered "a solved problem". > > >Attila Kinali > > [1] Handbook of Microwave Component Measurements: with Advanced VNA Techniques > by Dunsmore, 2012 > > -- > The trouble with you, Shev, is you don't say anything until you've saved > up a whole truckload of damned heavy brick arguments and then you dump > them all out and never look at the bleeding body mangled beneath the heap >-- Tirin, The Dispossessed, U. Le Guin > ___ > 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] VNA design
There is a popular DIY VNA designed by N2PK, boards are available from a fellow in Ontario Canada, a quick google search should find the information for you. Also, Sam Wettlerlin has published much on his web site with respect to Scotty's Spectrum Analyzer project, VNA, return loss bridges, etc. http://www.wetterlin.org/sam/ Also, there is an interesting project called the Poor Hams Scalar Network Analyzer (PHSNA) which may be of interest. There is an active Yahoo group. All that is missing is a phase detector to make it a simple VNA. Based on Arduino and the inexpensive AD9850/AD9851 DDS boards from Asia. I'd like a VNA too but I am starting small with the PHSNA and will build from there. My needs are not that great, just as a learning tool and to support my ham radio tinkering. Cheers, Graham ve3gtc -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Attila Kinali Sent: June-02-14 10:43 AM To: time-nuts@febo.com Subject: [time-nuts] VNA design Hi, I know this is not exactly a time-nut question, but i guess this is the best place i know to ask about this stuff. I recently got introduced into the usefullness of a VNA. But these things are horribly expensive for home use, even if bought from ebay (before you say anything, remember i live in europe, where every boat anchor hast to travel a long way). But given that most of the designs that are on ebay are from the 80s and early 90s, i thought that with todays ICs it should be easy to come up with a design that does the same thing but can be build on a kitchen table. Well, my problem now is, that i don't know how to build a VNA. Yes, i understand the basic principle. I can come up with a design that should work. But i have no clue about any problems or difficulties in building these devices. Ie it's very likely that i fall into a dozen traps when i try to build one. I tried to get information on how to build a VNA, or what kind of trouble people had operating one, but beside the VNA book[1] Rick mentioned a couple of months ago and ko4bb's site (thanks man! your manual collection is a gold mine!), my searches came out blank. As i'm quite sure that there is information of that kind out there, i would like to ask whether someone could point me to some documents, webpages, books, papers, etc that would show me the detailed design of VNA, the problems people had with some designs or anything else that would be of interest in such an endavor. Also, any good resource on how to build a directional coupler that does 10-3000MHz without going to exotic materials would be much appreciated. All papers i found deal mostly with stuff above 5GHz. Seems like "low frequency" couplers are considered "a solved problem". Attila Kinali [1] Handbook of Microwave Component Measurements: with Advanced VNA Techniques by Dunsmore, 2012 -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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. This electronic message, as well as any transmitted files included in the electronic message, may contain privileged or confidential information and is intended solely for the use of the individual(s) or entity to which it is addressed. If you have received this electronic message in error please notify the sender immediately and delete the electronic message. Any unauthorized copying, disclosure or distribution of the electronic message is strictly forbidden. NAV CANADA accepts no liability for any damage caused by any virus and/or other malicious code transmitted by this electronic communication. Le présent message électronique et tout fichier qui peut y être joint peuvent contenir des renseignements privilégiés ou confidentiels destinés à l’usage exclusif des personnes ou des organismes à qui ils s’adressent. Si vous avez reçu ce message électronique par erreur, veuillez en informer l’expéditeur immédiatement et supprimez le. Toute reproduction, divulgation ou distribution du présent message électronique est strictement interdite. NAV CANADA n’assume aucune responsabilité en cas de dommage causé par tout virus ou autre programme malveillant transmis par ce message électronique. ___ 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] VNA design
Hi, I know this is not exactly a time-nut question, but i guess this is the best place i know to ask about this stuff. I recently got introduced into the usefullness of a VNA. But these things are horribly expensive for home use, even if bought from ebay (before you say anything, remember i live in europe, where every boat anchor hast to travel a long way). But given that most of the designs that are on ebay are from the 80s and early 90s, i thought that with todays ICs it should be easy to come up with a design that does the same thing but can be build on a kitchen table. Well, my problem now is, that i don't know how to build a VNA. Yes, i understand the basic principle. I can come up with a design that should work. But i have no clue about any problems or difficulties in building these devices. Ie it's very likely that i fall into a dozen traps when i try to build one. I tried to get information on how to build a VNA, or what kind of trouble people had operating one, but beside the VNA book[1] Rick mentioned a couple of months ago and ko4bb's site (thanks man! your manual collection is a gold mine!), my searches came out blank. As i'm quite sure that there is information of that kind out there, i would like to ask whether someone could point me to some documents, webpages, books, papers, etc that would show me the detailed design of VNA, the problems people had with some designs or anything else that would be of interest in such an endavor. Also, any good resource on how to build a directional coupler that does 10-3000MHz without going to exotic materials would be much appreciated. All papers i found deal mostly with stuff above 5GHz. Seems like "low frequency" couplers are considered "a solved problem". Attila Kinali [1] Handbook of Microwave Component Measurements: with Advanced VNA Techniques by Dunsmore, 2012 -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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] Boeing 787 GPS reception trouble
On Mon, Jun 2, 2014 at 8:57 AM, Jim Lux wrote: > On 6/2/14, 2:27 AM, Poul-Henning Kamp wrote: > > >> It would be trivial to add a passive GPS repeater to the plane, but >> the airtraffic industry has never been happy about people being >> able to receive navigation signals inside planes, worrying that >> somebody might try to blow up the plane at some specific place >> (or non-place), so that ain't gonna happen. >> >> >> > I don't know that it's that reasoning. It's more about the innate > conservatism of people who make things that fly. > > The reason for "radio receiver ban" originally was fear that Local > Oscillator leakage would adversely affect cockpit instrumentation: > particularly things like low frequency beacon receivers, which were none > too selective, and since navigation using the ADF and tuning to a AM > broadcast station wasn't unusual. Well, it is quite unusual for IFR (instrument flight rules) operation. But VFR pilots would sometimes use an AM broadcast station for navigation assistance. > I had to learn how to do it when taking flying lessons: it was widely > acknowledged ( in 1980) to be nearly useless, Not entirely. I still make sure my planes are equipped with ADF (LF/MF direction finding) due to my experience with GPS outages over the Caribbean and Atlantic. I have experienced outages of over an hour where both my panel-mount and hand-held GPS receivers stopped working. ADF was all I had. I suspect that since I was flying a plane popular with drug-smugglers (a Piper Aztec), I was being tracked, followed, and GPS jammed. (I lived in the Virgin Islands, traveling to Florida on a regular basis. I would stop in the Turks and Caicos or Bahamas to refuel.) > but, hey, if all the other radios fail, any port in a storm, etc. About > the only older radio nav technology is A-N ranges (if you believe > Wikipedia, they were gone by 1980 "mostly disappearing by the 1970s") > > Birdies in a consumer radio in your living room or car aren't a big > problem. Birdies in a navigation instrument are a potentially big problem. > They could be and they are. Interestingly enough, the only radios that ever interfered with my VHF nav receivers were my own VHF comm and nav receivers. LO leakage from one radio would show up on one of the others. I have never experienced that problem with any consumer device. Even in the 1980s, there were a lot of planes flying with fairly archaic > radios, although I suspect no commercial jet was using a VFO tuned radio: > they'd be using "banks of crystals" or PLL tuning. In general aviation, > the first non VFO radios were from King in the 60s, and I think > synthesizers came in around 1970 (King KX 170 and 175). I was astounded at > the number of crystals in one of my Narco radios when I took it out of the > plane to fix it (a 1973-74 vintage radio). Half that box was basically a > big rotary switch and dozens of crystals. > A "crystalplexer" radio that was dual-conversion with both LOs using switched crystals. CB radios used the same thing back in the late 1960s and early 1970s. PLL LOs came later. Typical spurious responses in a COM or NAV receiver would be something like > -60dB down, but a few milliwatts leaking from some guy's FM radio on board > would easily be bigger than than that, since the receiver threshold is > about 1 microvolt into 50 ohms (-110 dBm). > That may be true but I have never experienced it, even when I tried. The only time I have ever experienced interference with my comm or nav radios it was from another comm or nav radio in the plane. Most use a 10.7MHz IF which means, for the spectrum from 108MHz-138MHz, you are very likely to have a lot of overlap between LO and desired receive frequency. Once the rule is in place, it's very, very hard to get it removed, because > of the "if we allow X, and a plane has a problem, everyone is going to say > "it was because of X" even if it wasn't, so let's just keep things the > same." Amen. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ 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] Boeing 787 GPS reception trouble
On 6/2/14, 2:27 AM, Poul-Henning Kamp wrote: It would be trivial to add a passive GPS repeater to the plane, but the airtraffic industry has never been happy about people being able to receive navigation signals inside planes, worrying that somebody might try to blow up the plane at some specific place (or non-place), so that ain't gonna happen. I don't know that it's that reasoning. It's more about the innate conservatism of people who make things that fly. The reason for "radio receiver ban" originally was fear that Local Oscillator leakage would adversely affect cockpit instrumentation: particularly things like low frequency beacon receivers, which were none too selective, and since navigation using the ADF and tuning to a AM broadcast station wasn't unusual. I had to learn how to do it when taking flying lessons: it was widely acknowledged ( in 1980) to be nearly useless, but, hey, if all the other radios fail, any port in a storm, etc. About the only older radio nav technology is A-N ranges (if you believe Wikipedia, they were gone by 1980 "mostly disappearing by the 1970s") Birdies in a consumer radio in your living room or car aren't a big problem. Birdies in a navigation instrument are a potentially big problem. Even in the 1980s, there were a lot of planes flying with fairly archaic radios, although I suspect no commercial jet was using a VFO tuned radio: they'd be using "banks of crystals" or PLL tuning. In general aviation, the first non VFO radios were from King in the 60s, and I think synthesizers came in around 1970 (King KX 170 and 175). I was astounded at the number of crystals in one of my Narco radios when I took it out of the plane to fix it (a 1973-74 vintage radio). Half that box was basically a big rotary switch and dozens of crystals. Typical spurious responses in a COM or NAV receiver would be something like -60dB down, but a few milliwatts leaking from some guy's FM radio on board would easily be bigger than than that, since the receiver threshold is about 1 microvolt into 50 ohms (-110 dBm). Once the rule is in place, it's very, very hard to get it removed, because of the "if we allow X, and a plane has a problem, everyone is going to say "it was because of X" even if it wasn't, so let's just keep things the same." ___ 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] Is it Hz or MHz ?
Hi Tom, My experience is the manufacturer's, of hp or fluke quality, reported error band (their spec sheet) is the worst case (or at least 3 sigma) provided that the device is operated according to the recommended environment, etc. Nonetheless, my statement you quoted is still accurate as to the purpose of the specification. Although I probably should have qualified a bit more. It goes without saying that one should be careful when it comes to specmanship no matter who it is. BillWB6BNQ Tom Van Baak wrote: The value of 5E^-11 refers to the resolution that the precision can be relied upon after taking into account all the factors that influence it. It means that there is an error that can be as much as +/-5 parts per e^-11. No, it can be way more. A 5e-11 spec value is likely just RMS, or 1-sigma. Actual measurements will show significantly larger 2-sigma, 3-sigma, etc. value. Your "as much as" wording sounds more like a 6-sigma, or peak-to-peak spec. One must be very careful to match the measurement used to make the spec with how the device is intended to be used. For example, Magnus will likely tell us about MTIE, which is a perfect-storm, worst-case time error spec. It's very different from rough 1-sigma specs we usually talk about. /tvb ___ 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] Boeing 787 GPS reception trouble
On 6/2/14, 1:55 AM, Tom Van Baak wrote: Has anyone else noticed this? Or know about this? Please respond only if you have real information. I can speculate as well as anyone; so it's solid technical, RF, EMF, or composite carbon fiber engineering info I'm looking for. I haven't noticed it myself, but when Beechcraft was making their pusher twin with carbon fiber, there was a whole raft of stuff they did to make sure it could take a lightning strike, including adding a conductive layer to the skin. It doesn't have to be all that thick, since it's not structural. This is a very real concern for carbon fiber components. And, as you note, since the windows have electric shutters, there's probably an Indium Tin Oxide or similar coating on them, which would make an effective shield. (http://gizmodo.com/5829395/how-boeings-magical-787-dreamliner-windows-work) The basic rule on shielding is that holes where the perimeter is >1/2 wavelength will pass some amount of RF, and when the perimeter is >1 wavelength (e.g. a slot half wavelength long) will pass virtually all of it. So your speculation about the windows in the plane being the pathway through which cell/gps/etc signals pass is a good one. See also http://www.boeing.com/assets/pdf/commercial/airports/acaps/787.pdf ___ 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] Is it Hz or MHz ?
Hi Kit, For convenience, accuracy is often given as a relative, unit-less value. Think of values like 1%, or 20 ppm, or 5e-11. These are all are unit-less numbers. To translate to absolute units just multiply: 50 Hz times 1% is 0.5 Hz. 1 meter times 20 ppm is 20 microns. 10 MHz times 5e-11 is 500 uHz. 5 MHz times 5e-11 is 250 uHz. 1 MHz times 5e-11 is 50 uHz. 1PPS times 5e-11 is 50 ps. Two issues arise with GPSDO specs: 1) When you talk about frequency, you have to specify the averaging interval(s). Performance can vary considerably depending on interval. It sounds your data sheet does this correctly. 2a) When you talk about time, there are often two meanings. One is relative time, as in pulse to pulse interval accuracy or stability. This is almost always the spec used in the commodity GPS receivers we play with. It's the only spec that matters if the receiver is used for a GPSDO. 2b) The other meaning is absolute time, as in conformance with UTC(k), where k is your local National Measurement Institute (NMI). This is a much more difficult problem, since it requires independent antenna + cable + receiver + TIC calibration against some portable "gold" standard, and likely re-calibrations every year. /tvb - Original Message - From: "Kit Scally" To: Sent: Monday, June 02, 2014 12:28 AM Subject: [time-nuts] Is it Hz or MHz ? > Team Nutters, > > > GPSDO's are often specified for stability as so many parts per x. Using a > Symmetricom 8040C as an example, this has a quoted accuracy of typically > 5E^-11 at shipment. Ageing (monthly and yearly) and ADEV stability rates > for 1, 10 & 100 seconds are also given. This particular device as 1, 5 and > 10 MHz outputs. > > The question - is this "accuracy" with respect to 1Hz - or 10MHz ? If the > latter, then the accuracy figures quoted needs to be modified by 10^6 (Hz to > MHz) to get a feel for the actual frequency changes at 10MHz. > > Glossies of many GPSDO manufacturers seem deathly silent on this point, so > clearly, "something is assumed". I have seen an oscillator comparison chart > by Meinberg (a German company) that in their comparison chart, the accuracy > references need scaling to relate to 1Hz. > > Appreciate some advice and/or direction on this before madness overtakes me > ! > > > Kit > Canberra > Australia ___ 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] Boeing 787 GPS reception trouble
In message , "Tom Van Baak" writes: >I know, because my Geiger counter was wonderfully close to 60 CPM >(= 1 CPS) in a hotel near NIST. Yes, I have the 1PPS ADEV plot for >this and, yes, background radiation makes the world's worst "atomic" >clock. Only for short tau. It should be pretty good at tau > 1e3 years or so ? >But last week I flew the new composite Boeing 787 Dreamliner and >noticed something quite different. From the second I entered the >plane, I lost both cell and GPS reception. This is by design, so the plane can contain its own in-flight wireless services. WLAN in planes is no problem, there is a subset of channels which are almost globally safe to use. However, the next big cash-cow is supposed to be inflight mobile phone + data, and bringing a Mobile Femtocell into any country you might happen to fly over is a regulatory violation and paperwork nightmare. Originally the GSM spec had a sort of "RFC1918" facility, were one specific frequency would be "local space", for exactly this kind of application on marine vehicles. Your phone would never automatically roam to such a net, you'd have to explicitly select that a 'local space' base-station, and you'd be stuck to it, until you manually released it. However, given governments gold-hunt in spectrum allocations, that feature died in the crib, and has not subsequently been revived. Therefore airlines and cruise boats have to use regulated frequencies if they want to offer cell-service. Cruise-boats use a loophole in the international maritime treaties, even when in harbour, they're under their national flag, and since most of them are Bahamas or similar, getting a mobile license and frequency allocation is cheap. (Usually they crank up the power when in harbour and milk any unsuspecting land-locked tourists with exorbitant roaming-charges.) Planes are not similarly "nationalized" and apart from the aeronautical spectrum, they cannot emit any radiation for which they are not licensed by the country they overfly. And so they've started to build the planes as farady-cages. It would be trivial to add a passive GPS repeater to the plane, but the airtraffic industry has never been happy about people being able to receive navigation signals inside planes, worrying that somebody might try to blow up the plane at some specific place (or non-place), so that ain't gonna happen. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Boeing 787 GPS reception trouble
Did they make any announcements regarding this? Most people aren't going to care about GPS, but many people are used to using their cell phones while waiting for the door to close and/or as soon as the wheels touch the ground when landing. If this doesn't work in a 787 I would think that they would make a PA announcement to that effect, rather than having to continuously answer questions regarding the problem. Regards, John On 6/2/2014 2:55 AM, Tom Van Baak wrote: But last week I flew the new composite Boeing 787 Dreamliner and noticed something quite different. From the second I entered the plane, I lost both cell and GPS reception. It didn't matter how close I was to a window or not. I know the word "composite" sounds inert, but carbon fiber must be somewhat conductive, yes? And there must be serious lightning suppression layers too, maybe? Furthermore, the B787 windows are exotic; like giant oval LCD screens which electronically dim from near transparent to very opaque. Does all this make the new 787 a record-holding RF-tight flying Faraday cage? Is this the first airplane in history where a time-nut can't receive GPS? At least gamma rays make it though, so I got RAD data. But no GPS data. Not a single SV fix the entire time I was inside the plane. Has anyone else noticed this? Or know about this? Please respond only if you have real information. I can speculate as well as anyone; so it's solid technical, RF, EMF, or composite carbon fiber engineering info I'm looking for. Thanks, /tvb ___ 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] Boeing 787 GPS reception trouble
1) When I fly I often use my iPhone while on the ground, before take-off or after landing. 2) I sometimes carry a GPS receiver. When permitted (varies by airline), it's fun to log NMEA data for a flight and later plot the flight path and duration with UTC accuracy. 3) On occasion I also bring a logging Geiger counter. It's amazing how much background radiation there is up at flight altitude compared to down at ground level. You can go from 10 or 20 CPM (counts per minute) at home to, say, 500! CPM at 40k feet. Those of you who live in mile-high Colorado enjoy higher background levels. I know, because my Geiger counter was wonderfully close to 60 CPM (= 1 CPS) in a hotel near NIST. Yes, I have the 1PPS ADEV plot for this and, yes, background radiation makes the world's worst "atomic" clock. Anyway, over the years I've collected some nice GPS latitude/longitude/altitude data sets as well as background radiation as a function of altitude. Just to be clear, I do turn off these devices according to airline regulations. Now I have never had a problem with reception in the terminal, walkway, or even while seated inside a plane. I figured the aluminum frame of the plane was thin enough that photons at cell, GPS, and gamma frequencies easily pass through the outer shell or the windows. But last week I flew the new composite Boeing 787 Dreamliner and noticed something quite different. From the second I entered the plane, I lost both cell and GPS reception. It didn't matter how close I was to a window or not. I know the word "composite" sounds inert, but carbon fiber must be somewhat conductive, yes? And there must be serious lightning suppression layers too, maybe? Furthermore, the B787 windows are exotic; like giant oval LCD screens which electronically dim from near transparent to very opaque. Does all this make the new 787 a record-holding RF-tight flying Faraday cage? Is this the first airplane in history where a time-nut can't receive GPS? At least gamma rays make it though, so I got RAD data. But no GPS data. Not a single SV fix the entire time I was inside the plane. Has anyone else noticed this? Or know about this? Please respond only if you have real information. I can speculate as well as anyone; so it's solid technical, RF, EMF, or composite carbon fiber engineering info I'm looking for. Thanks, /tvb ___ 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] Is it Hz or MHz ?
> The value of 5E^-11 refers to the resolution that the precision can be > relied upon after taking into account all the factors that influence > it. It means that there is an error that can be as much as +/-5 parts > per e^-11. No, it can be way more. A 5e-11 spec value is likely just RMS, or 1-sigma. Actual measurements will show significantly larger 2-sigma, 3-sigma, etc. value. Your "as much as" wording sounds more like a 6-sigma, or peak-to-peak spec. One must be very careful to match the measurement used to make the spec with how the device is intended to be used. For example, Magnus will likely tell us about MTIE, which is a perfect-storm, worst-case time error spec. It's very different from rough 1-sigma specs we usually talk about. /tvb ___ 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] Is it Hz or MHz ?
Hi Kit, The value of 5E^-11 refers to the resolution that the precision can be relied upon after taking into account all the factors that influence it. It means that there is an error that can be as much as +/-5 parts per e^-11. At 10 MHz that is +/- 0.0005 Hertz error. At 5 MHz that is +/-0.00025 Hertz error. At 1 MHz it is +/-0.5 Hertz error. And, finally, at 1 Hertz it is +/-0.005 Hertz error. BillWB6BNQ Kit Scally wrote: Team Nutters, GPSDO's are often specified for stability as so many parts per x. Using a Symmetricom 8040C as an example, this has a quoted accuracy of typically 5E^-11 at shipment. Ageing (monthly and yearly) and ADEV stability rates for 1, 10 & 100 seconds are also given. This particular device as 1, 5 and 10 MHz outputs. The question - is this "accuracy" with respect to 1Hz - or 10MHz ? If the latter, then the accuracy figures quoted needs to be modified by 10^6 (Hz to MHz) to get a feel for the actual frequency changes at 10MHz. Glossies of many GPSDO manufacturers seem deathly silent on this point, so clearly, "something is assumed". I have seen an oscillator comparison chart by Meinberg (a German company) that in their comparison chart, the accuracy references need scaling to relate to 1Hz. Appreciate some advice and/or direction on this before madness overtakes me ! Kit Canberra Australia ___ 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] Is it Hz or MHz ?
In message <595D85DC050442D88D7AC80A4476610B@dd09>, "Kit Scally" writes: >The question - is this "accuracy" with respect to 1Hz - or 10MHz ? Both, because it's a relative measure: Your 1Hz will be between 0.999 and 1.001 Hz Your 10MHz will be 999. and 1000.0001 Hz. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Is it Hz or MHz ?
Team Nutters, GPSDO's are often specified for stability as so many parts per x. Using a Symmetricom 8040C as an example, this has a quoted accuracy of typically 5E^-11 at shipment. Ageing (monthly and yearly) and ADEV stability rates for 1, 10 & 100 seconds are also given. This particular device as 1, 5 and 10 MHz outputs. The question - is this "accuracy" with respect to 1Hz - or 10MHz ? If the latter, then the accuracy figures quoted needs to be modified by 10^6 (Hz to MHz) to get a feel for the actual frequency changes at 10MHz. Glossies of many GPSDO manufacturers seem deathly silent on this point, so clearly, "something is assumed". I have seen an oscillator comparison chart by Meinberg (a German company) that in their comparison chart, the accuracy references need scaling to relate to 1Hz. Appreciate some advice and/or direction on this before madness overtakes me ! Kit Canberra Australia ___ 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.