Re: [time-nuts] Weather/units question for European members
On May 23, 2014, at 11:12 PM, Mark Sims wrote: > The nice thing about measuring temperature via sonic measurements is that the > measurements are unaffected by solar heating of the apparatus... it does not > need to be in the shade. I stumbled on this paper a while back when I was investigating a similar idea: Wen-Yuan Tsai et al, "An ultrasonic air temperature measurement system with self-correction function for humidity", 2005 Meas. Sci. Technol. 16 548 http://iopscience.iop.org/0957-0233/16/2/030 It uses both time of flight and phase measurements. Since this is for rocketry, note that RockSim (a commercial package for simulating the trajectory of a model rocket flight) lets you choose a variety of units for windspeed and barometric pressure. I've used meters per second and hectoPascals with the kids I mentor on rocketry. One funny thing about weather measurements is that the data that NOAA reports is not what it would seem. The standard ASOS data (which is what NOAA reports in its local current conditions) includes barometric pressure in inches of mercury and in hectoPascals. It turns out that neither is the actual barometric pressure. First, both are compensated to sea level, so they are not reporting the station pressure. Next, the in.Hg measurement is actually "altimeter setting", which is the value which, if set in the Kollsman window of a standard aviation mechanical altimeter located at the ASOS site, will cause the altimeter to indicate the height above sea level of the ASOS site. So it's really not related to sea-level barometric pressure in any direct way; it's not compensated for temperature nor for humidity, etc. It's just based on the standard atmospheric model as used by the standard aviation altimeter. There is a straightforward way to derive station pressure from the altimeter setting, so it's not entirely useless if you are not an aviator. Finally, if you try to compare the reported in.Hg barometric pressure versus the reported hPa barometric pressure, you will often find that the two values are not related by the standard conversion factor from in.Hg to hPa. That is because the ASOS hPa value is actually the average of the current station pressure, corrected to sea level (I don't know what factors are included in that correction), and the sea level corrected station pressure from 12 hours previous. This averaging is to correct for the diurnal variation in station pressure resulting from solar heating. Without this correction, the weather fronts would oscillate back and forth on the weather map with a 24 hour period. So unless you are drawing weather maps, the ASOS hPa value is useless. So, when RockSim asks the user to input "barometric pressure", exactly which one does it mean? Note that it also asks for the height above sea level of the launch site. Does it take altimeter setting and assume that it is measured at the height above sea level of the launch site, derive the station pressure from that, and then apply a temperature and humidity compensated version of the standard atmospheric model to calculate the air density profile for the simulated rocket flight? What if the station height above sea level isn't the same as the launch site above sea level? Does it even take any of these complications into account, and just assume that the number you enter for "barometric pressure" is the station pressure at the launch site? If so, note that most folks just enter the barometric pressure number reported by the local weather forecast. This is one of the dangers of relying on closed-source programs for science and engineering; you can't tell what it's really calculating. It seems like "what is the barometric pressure" should be a simple question, but it turns out to be quite subtle. Best regards, -Steve -- Steve Byan Littleton, MA 01460 -- Steve Byan Littleton, MA 01460 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 4193A 4815A probe compatibility?
On Oct 17, 2013, at 3:38 PM, Richard Karlquist wrote: > If you are below 80 MHz, Linear Technologies makes a thermal power meter > on a chip. Alas, the LT1088 is no longer made. http://www.linear.com/product/LT1088 Best regards, -Steve -- Steve Byan Littleton, MA 01460 ___ 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] Chinese Scopes
On Apr 16, 2012, at 10:23 PM, J. Forster wrote: > To bring this full circle, a friend bought a very clean, working 465 for > $50 at MIT. I passed on a clean 454 for $35; I was sorely tempted, but other items had priority in my budget. Didn't see any 7000-series scopes, and not too much in the way of counters. A bunch of Racal Dana something-or-others from one of the test equipment dealers, but that was about it, other than a non-working HP 5223L. Best regards, -Steve -- Steve Byan Littleton, MA 01460 ___ 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] LORAN-C at MIT
On Apr 15, 2012, at 6:09 PM, J. Forster wrote: > Six. I know someone who has been to almost as many of them as I have is on > this list. However he rarely posts. Another, which makes seven, has not > been seen lately. Eight, I suppose, though I'm by no means a full-fledged time-nut. I did score a Julie Research Labs VDR-106 at the MITflea, so I guess I at least qualify as a volt-nut. I did spot the fellow with the leap-second T-shirt. Best regards, -Steve -- Steve Byan Littleton, MA 01460 ___ 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] Schematic capture, anyone?
On Feb 23, 2012, at 7:38 PM, Jim Hickstein wrote: > What do people use these days for schematic capture (and just possibly PCB > layout), for low-budget homebrew stuff? [snip] > I'm a Mac shop, but can of course run Windows if need be. Basically there are only two reasonable choices for schematic capture on the Mac: Capilano's DesignWorks: <http://www.capilano.com/dwm_features>. Available only from the Mac App Store. VAMP's McCAD: <http://www.mccad.com/> Years ago, DesignWorks fit my budget much better than McCAD, but today I think they both offer free versions that can handle small hobby projects. For PCB layout on the Mac: Osmond PCB <http://www.osmondpcb.com/> Again, the Osmond free trial handles small hobby-sized boards. The price for the full version is quite reasonable. For spice, see <http://www.macspice.com/> There are some open-source apps using cross-platform GUI frameworks that compile on the Mac: KiCad: <http://kicad.sourceforge.net/wiki/Main_Page> If you can stomach Xwindows applications, then there are many open-source applications such as the Chipmunk system: <http://www.cs.berkeley.edu/~lazzaro/chipmunk/index.html> Best regards, -Steve -- Steve Byan Littleton, MA 01460 ___ 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] looking for data on time code display
On Dec 11, 2011, at 6:18 PM, Jim Palfreyman wrote: > Any chance of a photo? <http://www.gull.us/misc/nixie/dlf-front.jpg> It's not mine, but it looks the same except that the yellow sticker is on the side of mine rather than the front. Best regards, -Steve -- Steve Byan Littleton, MA 01460 ___ 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] looking for data on time code display
On Dec 11, 2011, at 5:25 PM, J. Forster wrote: > I think I've seen IRIG Time Code SW for the PC that uses a sound card, but > I forget where. <http://www.dolben.org/IRIG.php> Best regards, -Steve -- Steve Byan Littleton, MA 01460 ___ 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] looking for data on time code display
On Dec 11, 2011, at 4:12 PM, Bill Hawkins wrote: > Fascinating. I also have one of these with slight differences, but it > does have a Fort Meade tag. Bought it from a guy on the BoatAnchors > list in Atlanta in the dim past. > > The HTID number is H9823180065821, NSN 664500DISPLAY, User ID STWA104 > > The rotary switch adds a 160 KHz position. The two switches are marked > CODE POLARITY and POWER ON. The rear panel has a 4 pin circular jack > labeled AUX and a 24 pin rectangular connector marked PARALLEL. Yeah, mine has those connectors also. Fair also had some with LED displays. > A partly torn tag taped to the top says Made by TRAK, Model ?? 2234/U, > SN 517. A plastic envelope contained a DD Form 1348-1A release/receipt > document from the Defense Reutilization Marketing Office at Meade. It > released 5 of these units worth $1500 each, dated 1-29-98, ship from > H98231 (in HTID number above) to SX1213 (marketing office?). > > Somewhere I'd heard that these units were for locating times on tape > recordings of intercepts. The different filter frequencies are for > different tape speeds, from high speed search to fine positioning. > The code might be IRIG but it could just as easily be something the > NSA invented for the purpose. Maybe part of Project Boresight? <http://jproc.ca/rrp/boresight.html> > I bought it because I'd visited the NSA museum at Fort Meade and seen > the code breaking machines. I didn't find them intimidating at all. > The gift shop would sell me a jacket with NSA logos, but I didn't > know where I would wear it. There is a certain cachet to having a > box that was used by top secret agents to decode radio intercepts. > > Bill Hawkins > > P.S. I'd recommend doing some signal tracing from the Input connector. > We have no idea what signal levels were used, if it wasn't IRIG. I > never found time to do that. Yeah, that'll be on my to-do list. I had hoped the frequencies listed on the controls might trigger some association in someone who's knowledgable about time-codes. 250 Hz doesn't seem to be a legal IRIG time-code frequency, although 1 kHz is. Best regards, Steve -- Steve Byan Littleton, MA 01460 ___ 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] looking for data on time code display
A while back I picked up a couple of what Fair Radio was calling "data line filters". They have a six-digit Nixie time display (hours, minutes, seconds) and apparently decode and display some kind of analog time code (IRIG, maybe?). It was made sometime in the early 70's; it's wire-wrapped with some op-amp filtering and a bunch of TTL for the decoding. The front panel controls are: rotary switch marked "input filter" with positions: 250 Hz, 1000 Hz, 20 kHz, 40 kHz, 80 kHz. toggle switch marked "1000 Hz" and "250 Hz" toggle switch marked "reverse code control" The rear panel has BNC connectors marked "input" and "output". A yellow sticker on the side says: Ft. Meade DTID: H9823190045862 NSN 6625003684180 User ID: HI90159 I bought them with the intention of scavenging them for parts, then later considered making a Nixie clock out of them. But if I can get a clue as to the time-code they understand, I'd now like to restore them to operating condition. Anyone have any info or even speculation on these ? Best regards, -Steve -- Steve Byan Littleton, MA 01460 ___ 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] The future of UTC
On Jul 18, 2011, at 3:02 PM, Tom Holmes wrote: > Someone somewhere is making some money off of this [DST] scam. >From an NPR interview with Michael Downing, author of "Spring Forward: The >Annual Madness of Daylight Saving Time" <http://www.npr.org/templates/story/story.php?storyId=7779869> > Mr. DOWNING: Well, because when we have an hour of sunlight after work, > Americans tend to go shopping. The first and most persistent lobby for > Daylight Saving in this country was the Chamber of Commerce, because they > understood that if their department stores were lit up, people would be > tempted by them. > > In 1986, Congress gave us an extra month of Daylight Saving Time. That's when > we went from six to seven months, which is the period we've been living with > recently. In that congressional hearings, the golf industry alone - these are > the industry estimates - told Congress one additional month of daylight > saving was worth $200 million in additional sales of golf clubs and greens > fees. The barbecue industry said it was worth $100 million in additional > sales of grills and charcoal briquettes. > > BLOCK: This may be kind of an urban legend, but I thought I had heard that > one of the backers behind extending Daylight Saving Time into the beginning > of November was the candy industry, and it all had to do with Halloween. > > Mr. DOWNING: This is no kind of legend. This is the truth. For 25 years, > candy-makers have wanted to get trick-or-treat covered by Daylight Saving, > figuring that if children have an extra hour of daylight, they'll collect > more candy. In fact, they went so far during the 1985 hearings on Daylight > Saving as to put candy pumpkins on the seat of every senator, hoping to win a > little favor. Best regards, -Steve -- Steve Byan Littleton, MA 01460 ___ 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.
