[time-nuts] Terrestrial GPS

Peter Reilley suggests a backup to GPS using terrestrial transmitters. This idea has been around since the early days of GPS. The terrestrial transmitters were called "pseudo-satellites", or "pseudolites" for short. The big problem with this idea is that the GPS signal format has a narrow dynamic

[time-nuts] "Super Rubidium" filter mod for PRS-10?

Corby has said more than once that it's not worth doing the "super 5065" optical filter mod to small telecon rubidiums, because they have too many other compromises in their designs. What about the SRS PRS-10? By some indications, it's the best current-production rubidium around. It doesn't have

[time-nuts] eBay GPS antennas

FYI, Antcom and AeroAntenna are two manufacturers of high-quality American-made GPS / GNSS antennas. Antcom's datasheets are confusing to read, and AeroAntenna hides theirs behind a customer-login barrier, so most of eBay doesn't know exactly what they are. This means that good antennas are often

[time-nuts] theoretical Allan Variance question

What's the expected value of ADEV at tau = 1 s for time-interval measurements quantized at 1 ns? This question can probably be answered from pure theory (by someone more mathematical than me), but it arises from a very practical situation. I have several HP5334B counters comparing PPS pulses from

[time-nuts] Timing from Iridium satellites

Some time-nuts had expressed interest in the work I do to obtain timing information from Iridium satellites, as an independent backup to GNSS. A presentation we gave in May is now available at < http://www.atis.org/wsts/docs/2016/5-03_Satelles_Cobb_Test%20Results%20Iridium.pdf > We are scheduled

Re: [time-nuts] PRS10 rubidium lamp module failure

Follow-up: as several time-nuts noted, there was a lot of corrosion on parts of the lamp module. Oddly, there was no corrosion on the rest of the PRS10, or on the TS2500 which it came out of. The resistor lead was severely oxidized and partly melted. It's possible that the inductance of the

[time-nuts] PRS10 rubidium lamp module failure

R901, on the far right, is shown on the schematic as "air heater". It apparently got hot enough to create a localized thermal runaway in its lead wire. There was ample evidence of arcing. A half-melted bit of wire fell away before I could take the picture. Without that heater working, the lamp is

[time-nuts] Convert ADEV specs to MDEV?

TimeLab can show "mask" overlays on various plots. It comes with a set of ADEV masks for cesium clocks, derived from the manufacturer's specifications for those clocks. Those masks don't show up on MDEV plots, because the manufacturers don't provide MDEV specs. For the mathematicians out there:

Re: [time-nuts] 1 PPS 50-ohm driver

Sorry, newer scopes annotate a little better. Settings were 0.5 V/div and 2 ns/div. Trigger level is 1.4 V. Scope is HP 54720D with 54712A plugin (built in 50-ohm termination). The installed bandwidth of the plugin is somewhere between 1.0 and 1.5 GHz. I should have mentioned all that in the

[time-nuts] 1 PPS 50-ohm driver

Here's a scope photo from a PPS driver built exactly to the description in my earlier post. It's a 74ACT04 in a TSSOP package, with five parallel outputs driving five 220-ohm resistors (0402 SMT) to form a 50-ohm output. The photo shows 2 ns rise time for the leading edge of the pulse. The scope

[time-nuts] 50-ohm PPS driver

The "standard cheap" way to make a 1 PPS 50-ohm output is to use a 74ACT04 hex inverter chip powered by 5V. The chip is specified for 24 mA from each output pin. Connect 5 inputs together to your PPS signal. Run each of the 5 outputs through a 220 ohm series resistor, then tie them together as

[time-nuts] HP 5065A flaws and improvements

Bob Camp wrote: > The 5065 has great ADEV numbers. > In “as delivered” condition it has horrid > TC and pressure sensitivity. That's the first I've heard of any drawbacks to the 5065. Can you give more details on this? The "as delivered" implies that there may be improvements available? Any

Re: [time-nuts] Iridium source?

The use of Iridium satellite signals for timing, location, and position-based authentication is being commercialized by a startup called Satelles. The technology is known as Satelles Timing and Location, or STL. Prototype STL timing systems are providing PPS with

Re: [time-nuts] Unique TBolt GPS characteristics

GPS engine with its cm 50Hz solution updates. I wonder how good of frequency resolution/accuracy vs. time it can do? ws Stewart Cobb posted: Every GPS receiver calculates its clock offset (phase error, in time-nut terms) as part of its four-dimensional position

[time-nuts] Unique TBolt GPS characteristics

Every GPS receiver calculates its clock offset (phase error, in time-nut terms) as part of its four-dimensional position fix. It can apply almost the same math to calculate its clock rate (frequency error) as part of a four-dimensional velocity fix. In position hold mode, the Thunderbolt

Re: [time-nuts] Errors on HP 58503A GPS time frequency reference receiver bought from yixunhk.

I have bought several items from this seller and left positive feedback because the items arrived promptly and appeared to work. Problems only became apparent days, weeks, or months later. But by then it was too late to change feedback. This seller admits to changing the firmware on a GPSDO to

Re: [time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812A GPSDO system

A wiring diagram of the Z3809A cable interconnect cable was published earlier on this list. That information appears to be incorrect. The cable is actually wired pin 1 to pin 15, pin 2 to pin 14, etc. Another way to describe it is that for each wire in the cable, the pin numbers on each end of

Re: [time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812A GPSDO system

I have now tested 3 pairs of these units (full Z3810AS system), always in pairs. One Z3811 box was DOA. It drew power at the appropriate level, but the lights did not light up and there was no response on the SatStat port. AECI quickly swapped it for a working unit, and even paid return

[time-nuts] HP 5370, 5371, 5372, 5373

This list has a lot of discussion of HP 5370 time-interval counters, including the BeagleBone CPU upgrade. The usual sources seem to have HP 5371, 5372, and 5373 units available as well. From the profession of model numbers, and the cosmetics of the front panels, one might assume that these are

Re: [time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812...

Message: 7 Date: Tue, 21 Oct 2014 06:59:04 -0400 From: gandal...@aol.com To: time-nuts@febo.com Subject: Re: [time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812... Message-ID: eac2.4de53503.41779...@aol.com Content-Type: text/plain; charset=US-ASCII It seems

[time-nuts] Lucent KS-24361, HP/Symmetricom Z3809A, Z3810A, Z3811A, Z3812A GPSDO system

Fellow time-nuts, This (long) post is a review of the HP/Symmetricom Z3810A (or Z3810AS) GPSDO system built for Lucent circa 2000. I wrote it because I looked for more information before I bought one, and couldn't find much. It's relevant because (as of this writing), you can buy a full system

Re: [time-nuts] Homemade GPS Receiver

Date: Fri, 26 Sep 2014 10:07:56 +0100 From: Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk To: Peter Putnam pe...@ni6e.com, Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Homemade GPS Receiver

[time-nuts] How to open solder-sealed OCXOs?

What's the best way to open an OCXO in the typical solder-sealed tinned steel can? I don't mind destroying the can itself, as long as the innards are not harmed. The goal is to run some experiments with thermal impedance as discussed here last week, and to ovenize parts of the EFC controller for

[time-nuts] Thunderbolt tuning DAC theory of operation

While poking around the Thunderbolt to determine whether -5V could be used in place of -12V, I discovered how the OCXO tuning DAC works. Apologies if this is old news, but I haven't seen it documented before. The 10MHz sine wave from the OCXO is squared up and used to clock the Xilinx 5200 CPLD

[time-nuts] powering Trimble Thunderbolt with -5V rather than -12V

Executive summary: you can power a surplus gold Thunderbolt using a -5V supply in place of a -12V supply, and it will probably work just fine. Details: The manual for Trimble Thunderbolts specifies power supplies of +5V, +12V, and -12V. It turns out that power supplies that provide +5V, +12V,

[time-nuts] Trading stocks faster than light

www.nanex.net/aqck2/4436.html Financial markets in Chicago and New York reacted to news from Washington -- milliseconds faster than the news could have reached them. Includes at the end some discussion of news organizations that aren't so good about synchronizing their master clock ...

[time-nuts] [OT] a different sort of time-nut

http://www.lawoftime.org The 13 Moon / 28-day calendar (synchronometer) is the key that allows us access to the vast realm of the synchronic order ... This is a Galactic timing program that also serves as a master synchronization matrix that any other calendar or numerical system can be plugged

[time-nuts] GPS antenna splitter buyers' guide

(If this shows up twice, I apologize. Gmail seems to have switched me to sending HTML-formatted mail by default, and the time-nuts server doesn't like that. Anyone know how to switch back permanently?) It's possible to use standard microwave power dividers as GPS antenna splitters, but they have

Re: [time-nuts] Austron 2200 Y2K?

The ST2010 GPS receiver chip took 10 MHz and a GPS L1 signal in, and produced a 35.42 MHz second IF to drive a SAW filter. (It also digitized the SAW filter output, but you wouldn't need that part.) These chips were designed by Plessey, which sold the business to Mitel, which sold the business to

[time-nuts] HP 53132A time interval measurement quantized?

Guys, My HP 53132A counter works fine as a frequency counter. When I try to use it to measure time intervals (say, between two PPS pulses), the measurements are quantized in steps of 100ns. For example, if the two PPS are nearly aligned, the measurements will be either 0.0980us or -0.0020us. If

Re: [time-nuts] Z3815A

Your Z3815A may need more cooling than it's getting, especially if you have it resting horizontally as it looks like it should. I bought one of those kits from China about a year and a half ago. Powered it up, waited for it to lock ... and it was dead within a week, with the unmistakable smell

Re: [time-nuts] GPS position survey

A subtle point: The GPS satellite orbits are controlled so that their (nominal) ground tracks precisely repeat every day. To make this work, their day is not a standard 24-hour day but a sidereal day lasting 23 hours, 56 minutes, and about 4 seconds. The satellites actually go around the earth

[time-nuts] Precise positions for GPSDOs

A GPSDO typically makes the assumption that the position of its antenna is fixed and well-known. That removes position uncertainty from the navigation equations, and allows all the information from the satellite measurements to be used to improve the time estimate. Errors in this position create

Re: [time-nuts] FTS-4040A cesium, and STEL-1173 NCO chip

Interesting, I have a problem Datum 4040A as well. I purchased it several years ago and when it fail to work correctly I put it aside. I wonder if mine has the same problem ... You could try powering it up and checking its telemetry with the Monitor3 program available on the Symmetricom website.

[time-nuts] (Datum) FTS-4040A cesium, and STEL-1173 NCO chip

Guys, I'm working on a sick FTS-4040A cesium frequency reference, which is basically a box and power supply wrapped around the FTS-5045 cesium beam module. (Datum bought FTS, then Symmetricom bought Datum, but this 1995 device is too old to appear on the Symmetricom website. This was one of the

[time-nuts] DATUM 9390-52054 Grief again...

I do not recognize the GPS receiver module, but it has the following number on it: TNL 22880-B. I have the schematics for the overall DATUM 9390-25054, but the GPS module is just a block. By the way, the GPS block on the DATUM overall schematic is marked, SV6 / (TANS). I suspect this

Re: [time-nuts] GPS usable for weather forecasting?

I wonder if you cannot do this same work from the ground. Has anyone tried tracking single GPS satellites from the ground using very high gain tracking antenna. Many times. USAF does this each time they launch a new GPS satellite, to check out all the kit in a high-res view before they switch

Re: [time-nuts] Need info on Trimble 4000S GPS Surveyor

The fundamental frequency in the GPS system is 1.023 MHz, chosen so that a 10-bit maximum-length feedback shift register (MLFSR) clocked at that frequency would complete one cycle of 1023 states in precisely one millisecond. The civilian C/A codes or Gold codes are generated by combining two such

[time-nuts] repairing General Technology (Tracor) 304-B rubidium standard

Guys, I'm repairing a 1960's vintage lab-grade rubidium standard, General Technology Corporation model 304-B. Apparently Tracor bought GTC soon after this unit was made, because references to this as a Tracor 304-B seem to be more common. I've made some progress, but now it seems like time to

[time-nuts] Z3805A cooling requirements?

This may be a newbie question, but I'm a newbie, so: Do the HP telecom GPSDOs (Z38xx) require external airflow for cooling? They don't have built-in fans, but they sorta look like they depend on a rack-level cooling fan, which a telecom rack would almost certainly have. I ask because I bought a