[time-nuts] Re: GPS failed
Hey Skipp! A couple of thoughts… Why do you need an amplified antenna in a high and open spot, unless the coax run is longer than about 40’? Is it practical to move one of the existing antennas away from the current location as a test to see if it’s a failure vs overload? Assuming it is physically practical to do so, of course. From Tom Holmes, N8ZM > On Jul 11, 2022, at 8:49 AM, skipp Isaham via time-nuts > wrote: > > Hello to the Group, > > I'd like to get some opinions and war stories regarding GPS reliability at > high RF level and elevation locations. > > Background: Three different hill-top GPS receivers, all different types, > using > different antennas mounted on an outside fixiture, plain view of the open > sky, > all stopped working. > > Test antennas were brought in and placed on a fixture well away from the > original antennas, the recevers went back in to capture and lock. > > From what I understand, the original antennas are what I would call straight > preamp with no pre-selection / filtering. > > The ordered and now inbound replacements are said to contain a SAW filter > system. It is the intent of the client to just place these "improved > antennas" in > to service and get on with life. > > I would suspect a GPS antenna (and receiver) could be subject to RF overload > or blocking, however, we're assuming nothing major has changed at the site, > nor > any nearby location. One might think there are more GPS receivers being > pushed > out of reliable operation by the world around them, I'm just not hearing > those stories > from a lot of people using them (GPS receivers). > > Any new install GPS receiver antenna ordered will/should contain some > pre-selection > to potentially avoid a problem, even some years down the road? Seems like > that's > where things are going... no more off the shelf, wide band, (hot) > preamplified GPS antennas > in busy locations? > > Thank you in advance for any related comments and/or opions ... > > cheers, > > skipp > > skipp025 at jah who dot calm > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: Time-nuts at WSTS conference
"scotsh whiskey" Was this intentional to indicate that more than a little bit of imbibing was involved in arriving at the new standards? Tom Holmes, N8ZM -Original Message- From: Lux, Jim Sent: Thursday, May 12, 2022 5:54 PM To: time-nuts@lists.febo.com Subject: [time-nuts] Re: Time-nuts at WSTS conference On 5/12/22 2:48 PM, Gary Woods wrote: > On Thu, 12 May 2022 12:01:48 -0600, you wrote: > >> I've found that corridor discussions have included redefinition of >> SI-second, quantum computers, optical clocks, security on PTP clocks, >> time-scale algorithms, uncertainty of different measures. Oh, and I just >> won a bottle of scotsh whiskey. > Excellent, Magnus! I remember a tech seminar years ago, where the > instructor avowed that 80% of the education took place during the > coffee breaks! > The best international standards start as a discussion the hallway or bar, with scribbles on a paper napkin. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com
[time-nuts] Re: GPSDO - GPS1300-10-1000 by RFX Ltd. UK
John... If you haven't already, look into the Leo Bodnar GPSDO. It is a couple hundred bucks US, and the people I know who have them are pretty happy with them. Not sure off the top of my head if they make a PPS, however. And, he is in the UK. Tom Holmes, N8ZM -Original Message- From: John Moran, Scawby Design Sent: Tuesday, March 01, 2022 5:12 PM To: time-nuts@lists.febo.com Subject: [time-nuts] Re: GPSDO - GPS1300-10-1000 by RFX Ltd. UK Bob, Jim - Thanks for the detailed replies. You have both managed to confirm the difficulties and unknowns involved in being a fledgling TimeNut. I think that is what prompted me to try to avoid as many unknowns as possible by buying one that was at least guaranteed to work, especially in the un-locked mode because I'm not sure what my GPS viewing here will be like until I have a unit to play with. A problem we have over here is that there isn't the huge eBay market for such things, so choice is really limited to Chinese recycled/cloned stuff of unknown provenance. OK, I could buy from a US supplier but, and I will probably be jumped on for saying this, US suppliers seem incapable of finding reasonably priced delivery methods. A recent example was a nice slide rule I was interested in for $36, but carriage was $86 ... I didn't buy. Getting back to GPSDOs - given that, when locked, they are probably all quoted as 'close to Caesium' (British), I will still buy a new one, but more reasonably priced and then try to acquire an SC-cut crystal to start making an OCXO to eventually form the heart of a GPSDO. I like the comments about holdover and recovery from holdover ... one of you keeps talking about rabbit holes, I think I see one looming. John ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: too many two's
Seems appropriate that it falls on a Two's-day. Tom Holmes, N8ZM -Original Message- From: Jeremy Nichols Sent: Monday, February 21, 2022 9:23 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Re: too many two's On Mon, Feb 21, 2022 at 5:24 PM Tom Van Baak wrote: > Get your cameras ready. Coming up in an hour: > > 2022-02-22 02:22:22 UTC = MJD 59632.098866 = time_t 1645496542 > > or second chance, 20 hours later: > > 2022-02-22 22:22:22 UTC = MJD 59632.932199 = time_t 1645568542 > > /tvb > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. > -- Jeremy Nichols Sent from my iPad 6. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: HP Z3801A project update
HI Ed & Ed... Thanks for the plot. The dive towards zero just before the spike s surprising; maybe a funky data point? Anyway, I'm not doubting that the observations are correct, just curious about the timing and source of that power spike. Like maybe the controller decided it wasn't heating fast enough? Tom Holmes, N8ZM -Original Message- From: Ed Palmer Sent: Saturday, January 29, 2022 11:07 AM To: time-nuts@lists.febo.com Subject: [time-nuts] Re: HP Z3801A project update On 2022-01-29 2:30 AM, "Tom Holmes" wrote: > Ed... > > Very good data! > > I am curious about one part of the warmup process. At around 7 minutes, the > power jumps up radically, which you attribute to > the outer oven kicking in. It has often been stated on this list that the > outer oven was intended for use during really cold > starts, which I would expect should cause it to kick on almost immediately > during a very cold start. I am assuming your start > was from room temperature. For a room temp start, I wouldn't expect it to > kick on at all if it's purpose was as reported. Or > do I have the oven functions reversed? > > Tom Holmes, N8ZM I can confirm Ed's tests. Attached is a similar test that I did on my Z3801A. If it matters, mine is the 24V nominal version. My test was done at 27V. The power supply was an HP6622A with GPIB. I wrote a program to query the current being drawn each second. The current value was later converted to power. Ed ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: HP Z3801A project update
Ed... Very good data! I am curious about one part of the warmup process. At around 7 minutes, the power jumps up radically, which you attribute to the outer oven kicking in. It has often been stated on this list that the outer oven was intended for use during really cold starts, which I would expect should cause it to kick on almost immediately during a very cold start. I am assuming your start was from room temperature. For a room temp start, I wouldn't expect it to kick on at all if it's purpose was as reported. Or do I have the oven functions reversed? Tom Holmes, N8ZM -Original Message- From: ed breya Sent: Friday, January 28, 2022 9:50 PM To: time-nuts@lists.febo.com Subject: [time-nuts] Re: HP Z3801A project update I've been doing some more cold start testing, and thought I'd share this info, for any Z3801A owners who may be curious about the behavior. Some aspects are probably well known since long ago. I've seen it all since first starting work on this some 10-12 years ago, so I know approximately what it does. Now I have been able to make some more convenient observations. The setup is simply measuring the external DC input current and voltage while the process goes, to estimate the input power needed, roughly how much, and when. Only the input P is noted. The total gets used up in running the Z3801A, the other circuits, and conversion losses. Almost all the changes in power are due to the Z3801A going through its cold startup process. Here's a summary from a run I did this afternoon. T=0, start, 33 W The running supplies for everything, and the internal oven of the OCXO are turned on first. When the oven is approaching being warmed up enough, the P gradually drops to about 25 W, at about T+7 min. It then rather suddenly jumps to somewhere around 50 W as the outer oven is turned on, then fairly quickly down to 45 W, then gradually declines. The GPS lock indicator came on at about T+10 min, not coincident with any particular oven condition. The power continues to drop off very gradually (there's a lot of mass to heat up), until reaching nearly steady state around T+50 min, at about 25 W. So, figure it takes about ten minutes to achieve lock (this particular setup), but about an hour for everything to fully warm up. Ed ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: in-ground clock room
Which suggests a possible damping mechanism. From Tom Holmes, N8ZM > On Sep 11, 2021, at 10:08 AM, Adrian Godwin wrote: > > Doesn't that depend on the configuration of the fields ? > For instance, a pair of facing like poles will repel and, as you say, make > a good spring. > But a magnet falling down an aluminium tube will go slowly, because of the > generated eddy currents and their subsequent fading due to the lossy > aluminium. > > >> On Sat, Sep 11, 2021 at 2:02 PM Poul-Henning Kamp >> wrote: >> >> >> Gilles Clement writes: >> >>> Magnetic levitation, dampening external vibrations ? >> >> By theselves magnetic fields are just really good springs. >> >> To get any kind of dampening you either need to add a >> dash-pot (=shock-absorber) as a dissipative device or >> you need to modulate the magnitic field to emulate >> the same result. >> >> I'm told the latter is much harder than it sounds. >> >> -- >> 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@lists.febo.com -- To unsubscribe send >> an email to time-nuts-le...@lists.febo.com >> To unsubscribe, go to and follow the instructions there. >> > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: uncertainty/SNR of IQ measurements
Now, re-reading my response and thinking a little longer, I understand your question a little better, maybe. I see where you are coming from if RF and LO are the same frequency, and it's not totally clear to me yet what happens as the phase changes. My quick back of the napkin (yes, I actually used one!) suggested outputs from a single DBM at zero phase difference of 0 * Flo, and the input noise plus the LO noise would seem to me to be additive, not multiplied. Basically a phase detector. But then I recalled that for PN measurements, the LO and test signal have to be maintained at 90 degrees shift for there to be a zero volts DC component to use for steering but the noise sidebands are then what is measured. I guess I really need to go play in the lab a bit. Tom Holmes, N8ZM -Original Message- From: Tom Holmes Sent: Thursday, August 26, 2021 2:27 PM To: 'Discussion of precise time and frequency measurement' Subject: [time-nuts] Re: uncertainty/SNR of IQ measurements HI Jim... >From my admittedly limited understanding of IQ demodulators, the first thing >done is to split the signal power (signal, noise, and all) evenly between two paths, which then ideally feed identical double balanced mixers (I'm thinking of a hardware implementation, obviously) whose only difference is the quadrature phase of the LO. So both paths are seeing the same SNR at that point. So my first guess would be that the relative phase of the LO to the input signal would only affect the phase of the output from each path, but the noise content ( or modulation if there is any) would not be any different between the two paths. I'm not aware that a single DBM used as a downconverting mixer shows any preference to the phase angle of the input to the LO. Tom Holmes, N8ZM -Original Message- From: Lux, Jim Sent: Thursday, August 26, 2021 1:37 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] uncertainty/SNR of IQ measurements This is sort of tangential to measuring time, really more about measuring phase. I'm looking for a simplified treatment of the uncertainty of I/Q measurements. Say you've got some input signal with a given SNR and you run it into a I/Q demodulator - you get a series of I and Q measurements (which might, later, be turned into mag and phase). If the phase of the input happens to be 45 degrees relative to the LO (and at the same frequency), then you get equal I and Q values, with (presumably) equal SNRs. But if the phase is 0 degrees, is the SNR of the I term the same as the input (or perhaps, even, better), but what's the SNR of the Q term (or alternately, the sd or variance) - Does the noise power in the input divide evenly between the branches? Is the contribution of the noise from the LO equally divided? So the I is "input + noise/2" and Q is "zero + noise/2" If one looks at it as an ideal multiplier, you're multiplying some "cos (omega t) + input noise" times "cos (omega t) + LO noise" - so the noise in the output is input noise * LO + LO noise *input and a noise * noise term. I'm looking for a sort of not super quantitative and analytical treatment that I can point folks to. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: uncertainty/SNR of IQ measurements
HI Jim... >From my admittedly limited understanding of IQ demodulators, the first thing >done is to split the signal power (signal, noise, and all) evenly between two >paths, which then ideally feed identical double balanced mixers (I'm thinking >of a hardware implementation, obviously) whose only difference is the >quadrature phase of the LO. So both paths are seeing the same SNR at that >point. So my first guess would be that the relative phase of the LO to the >input signal would only affect the phase of the output from each path, but the >noise content ( or modulation if there is any) would not be any different >between the two paths. I'm not aware that a single DBM used as a >downconverting mixer shows any preference to the phase angle of the input to >the LO. Tom Holmes, N8ZM -Original Message- From: Lux, Jim Sent: Thursday, August 26, 2021 1:37 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] uncertainty/SNR of IQ measurements This is sort of tangential to measuring time, really more about measuring phase. I'm looking for a simplified treatment of the uncertainty of I/Q measurements. Say you've got some input signal with a given SNR and you run it into a I/Q demodulator - you get a series of I and Q measurements (which might, later, be turned into mag and phase). If the phase of the input happens to be 45 degrees relative to the LO (and at the same frequency), then you get equal I and Q values, with (presumably) equal SNRs. But if the phase is 0 degrees, is the SNR of the I term the same as the input (or perhaps, even, better), but what's the SNR of the Q term (or alternately, the sd or variance) - Does the noise power in the input divide evenly between the branches? Is the contribution of the noise from the LO equally divided? So the I is "input + noise/2" and Q is "zero + noise/2" If one looks at it as an ideal multiplier, you're multiplying some "cos (omega t) + input noise" times "cos (omega t) + LO noise" - so the noise in the output is input noise * LO + LO noise *input and a noise * noise term. I'm looking for a sort of not super quantitative and analytical treatment that I can point folks to. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: Testing a GPS mag mount antenna
BTW, Skipp, there is a slim chance that a non-amplified antenna is a DC short, so wise to check that before you try to power it up from a PS or a receiver.. Tom Holmes, N8ZM -Original Message- From: Dana Whitlow Sent: Saturday, August 21, 2021 12:13 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Re: Testing a GPS mag mount antenna I love Dan's idea, with one caveat. The transmission through a powered-down LNA is an unknown, probably even to the manufacturer. Thus comparing output signal levels with power on or off is pretty meaningless. But his test with power on should be a great way to get some clue that the antenna is working, and is clearly simpler to perform than what I was suggesting yesterday. Dana On Sat, Aug 21, 2021 at 9:49 AM Daniel Schultz wrote: > > Should I be able to "see something" on or around the GPS frequency other > > than what I suspect will be something visual looking like a noise/pulse > > source/signal? > > You could try sweeping a harmonic from a signal generator across the > antenna > passband, this would be visible on the spectrum analyzer and might give > you an > idea if the preamp is amplifying or attenuating the signal. Try it with the > preamp power on and off. If your signal generator does not generate > sufficient > harmonics at L band you can feed the signal into an overdriven MMIC > amplifier. > > Dan Schultz N8FGV > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: Thunderbolts ...
Dana... That temperature sensitivity to HVAC systems exists to some degree on most examples of this type of box, and really suggests that more attention needs to be paid to keeping drafts at bay, as well as providing a reasonably stable temperature and humidity environment for the T'bolt. I wouldn't be so fast to blame the box. Tom Holmes, N8ZM -Original Message- From: Dana Whitlow Sent: Tuesday, July 20, 2021 2:23 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Re: Thunderbolts ... My experiences with the T'Bolt have not been entirely satisfactory. If I set the loop lime constant long enough to get a satisfying smoothing of the GPS noise (a few hundred seconds), then the thermal sensitivity of the VCXO on the T'Bolt rears its ugly head and I see a lot of my HVAC system cycling instead. The T'Bolt E supposedly has a double- oven XO, so I'd like to give that a try. But my wallet says "whoa"! According to Bodnar, his units do have some choices in the time constant setting. I've been considering ordering a Bodnar just for frequency agility, but have been holding off out of concern for the complications of dealing with a foreign supplier. Dana On Tue, Jul 20, 2021 at 12:42 PM John Ackermann wrote: > The Bodnar GPSDO is great for what it is, and has the great advantages of > small size, low power consumption, low cost, and frequency agility. But it > doesn't have an OCXO so its short term and holdover performance isn't in > the same league as the T'bolt or Z38whatever boxes. > > John > > On Jul 20, 2021, 1:11 PM, at 1:11 PM, Bob Darlington < > rdarling...@gmail.com> wrote: > >Same. He probably got 250+ requests in short order. I'm curious how > >the > >Leo Bodnar GPSDOs compare. I'm considering one of these over a > >thunderbolt for field use for ham radio EME work. > > > >-Bob N3XKB > > > >On Tue, Jul 20, 2021 at 10:59 AM Wes wrote: > > > >> I wrote Tom, at the address he gave, on Saturday with a query. So > >far, no > >> reply. > >> > >> Wes N7WS > >> > >> On 7/19/2021 4:59 PM, John Miles wrote: > >> > If you're looking for a low cost surplus GPSDO, the ones Tom > >mentioned in > >> > his post on Saturday are the ones you want. Not a Thunderbolt-E, > >and not > >> > something from the China surplus/e-waste market. > >> > > >> > -- john, KE5FX > >> > > >> ___ > >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > >send > >> an email to time-nuts-le...@lists.febo.com > >> To unsubscribe, go to and follow the instructions there. > >___ > >time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > >send an email to time-nuts-le...@lists.febo.com > >To unsubscribe, go to and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: A perfect drink for a time nut (who drinks those kinds of drinks)
Wojciech... Perfect!! Tom Holmes, N8ZM -Original Message- From: Wojciech Owczarek Sent: Wednesday, April 07, 2021 9:52 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] A perfect drink for a time nut (who drinks those kinds of drinks) This list sees reasonably little non-technical or otherwise lightweight content, so I thought I'd share this. Some people drink alcohol, some do not, for various reasons - this must be respected - but for those who do... I recently came into possession of a bottle of spirits, and immediately thought of time-nuts: https://compagniedesindesrum.com/wp-content/uploads/2015/12/Compagnie-des-Indes-Tricorne_2017.jpg I think this just goes to show how much time-nuttery sticks in one's head. Firstly it is rum; given how much seafaring and the need for precise navigation has influenced timekeeping, rum seems a natural fit. But a three-cornered hat? Now that's at least 1.4142 times more like it! Yes, every other label of rum may have a pirate reference, but this time it's in the name, so maybe twice more like it in the end. Regards, Wojciech -- - Wojciech Owczarek ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: The Collapse of Puerto Rico’s Iconic Telescope [April 5th, 2021 New Yorker]
A lot of the gear, such as the MASER, was in buildings on the ground which suffered little or no damage. Tom Holmes, N8ZM -Original Message- From: Bob kb8tq Sent: Tuesday, March 30, 2021 8:40 AM To: ew ; Discussion of precise time and frequency measurement Subject: [time-nuts] Re: The Collapse of Puerto Rico’s Iconic Telescope [April 5th, 2021 New Yorker] Hi Based on what’s known publicly, the gear that was not destroyed is still siting there waiting for a decision about “what’s next”. There are a lot of ideas kicking around. Bob > On Mar 30, 2021, at 7:06 AM, ew via time-nuts > wrote: > > GOOD Morning Tom > >Thank you for the super information Read it over and over. To me > no joy, sadness for Astronomy, Science, Puerto Rico and the US. China is now > the leader with a 500 meter unit! Did follow it since the seventies because > of the low noise receivers. Remember the 417 Triodes? I had some for Ham > use. Any > body knows what happened to its Maser? > Bert > Kehren > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
Re: [time-nuts] Anybody plotted the ADEV of a V8 idle speed?
Idle speed is simply controlled to an rpm value, which thus makes it tied, loosely, to the CPU clock. The phase noise is quite awful, by anyone's standards, mainly because the parameters measured to control fuel and spark timing, are noisy. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Hal Murray Sent: Saturday, February 06, 2021 9:48 PM To: Discussion of precise time and frequency measurement Cc: hmur...@megapathdsl.net Subject: [time-nuts] Anybody plotted the ADEV of a V8 idle speed? w...@triconet.org said: > Although Mr. Wineland's IQ must be at least 50 points higher than mine, we do > have something in common. I too owned a '36 Ford in my youth, about the same > time as he did, although mine was a Cabriolet not a coupe, and I fitted it > with an OHV Studebaker V8, a smaller displacement clone of a Cadillac V8. Speaking of V8s... Just a simple graph of idle speed vs time for the first few minutes after a cold start might be a fun high school science project. Is the idle speed of a modern warm engine locked to the CPU's crystal or is there a feedback loop setting some pollution or mileage parameter? In the old days (pre computer), there was some thermal input to the idle speed. I assume it was a bimetalic element. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_l ists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] "Q for dummies"
I was told that one of the killers of superconductivity is magnetic fields. I guess they 'fixed' that. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Mike Feher Sent: Tuesday, January 26, 2021 1:07 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] "Q for dummies" I recall back in the late 60’s visiting some friends at BNL. One of them took me through the cryogenic lab. In one they had an LC running at near 0 and it could be heard in a receiver. We know for L, Q in its simplest form is Xl/R. At superconductor temperatures R approaches 0 and therefore Q approaches infinity. Consequently the circuit oscillated by itself. I was amazed. Slightly different, but in the same lab they showed me an electromagnet in a superconductor cooled environment. I noticed it was wound with uninsulated wire. I inquired about that and was told that contact resistance is so much higher than the superconductor resistance, and they could get more turns without insulation. Regards – Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 848-245-9115 -Original Message- From: time-nuts On Behalf Of Dana Whitlow Sent: Tuesday, January 26, 2021 9:36 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] "Q for dummies" If anybody can even approach doing justice to the Q concept, including why it matters, in just two sentences, that person will have definitely earned the "Qulitzer prize" in technical journalism. Here's my entry: "A circuit's Q is closely related to its internal energy losses compared to external energy exchanges. A high Q can mean better efficiency, better conformance with expected performance (especially in filter applications), longer ringdown times (wineglass compared to milk glass) and (unfortunately) higher price." Dana ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] x86 CPU Timekeeping and clock generation
Thanks to Chris, Magnus, and Trent for clearing things up. Never would have expected going to the effort of putting in a cheap clock, only to use it very little. Who knows what evil lurks in the minds of engineers? And I am one! Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Trent Piepho Sent: Wednesday, January 06, 2021 6:36 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] x86 CPU Timekeeping and clock generation On Wed, Jan 6, 2021 at 6:26 AM Tom Holmes wrote: > > Am I missing something or maybe I don't understand > the situation , but I am under the impression that > the RTC has it's own battery and crystal unrelated > to the processor clock. Seems like in that case, > the 24 MHz won't have any effect on the > timekeeping drift. It was like that, but the days of external RTC chips, e.g. from Dallas, are largely over. PC now have it integrated into the chipset. Though it still has a power source and 32.768kHz xtal of its own. In the embedded SoC world of phones, Raspberry PIs, and the OP's Tinkerboard, there would virtually always be an RTC available in the SoC with the CPU, or in the PMIC, or in both. This would usually have its own 32.768kHz xtal, but often there is an option to reduce the BoM and use an internal RC oscillator instead of an external xtal or clock signal, at greatly reduced accuracy. The 32k xtal isn't for timekeeping accuracy, but for power savings. In the lowest power modes the main PLLs will be shut down. Certain parts of the SoC will still be able to run using the 32kHz clock domain and a low power output from the PMIC. Linux doesn't use the RTC as the system clock. During boot, the kernel will usually set the system time from the RTC, and then the RTC doesn't get used much, if at all. There is a mode where the system time is periodically copied back into the RTC, which can be enabled with NTP. And software like chrony has the ability to manage the RTC and keep it in sync more intelligently, though I don't think any distro uses this by default. There are a number of sources that Linux can use as the system clock. An on x86 system, it would usually be tsc, hpet, and acpi_pm. On an ARM board, arch_sys_counter. The kernel subsystems for RTCs and for clocksources are totally separate and the RTC, e.g. rtc-cmos, isn't a clocksource. Using adjtimex, it's possible to see what the current kernel parameters are for clock adjustment. The frequency adjustment would need to be zero. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_l ists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] x86 CPU Timekeeping and clock generation
Am I missing something or maybe I don't understand the situation , but I am under the impression that the RTC has it's own battery and crystal unrelated to the processor clock. Seems like in that case, the 24 MHz won't have any effect on the timekeeping drift. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Trent Piepho Sent: Wednesday, January 06, 2021 6:03 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] x86 CPU Timekeeping and clock generation On Tue, Jan 5, 2021 at 9:42 PM Luiz Paulo Damaceno wrote: > The 24 MHz comes from an synthesizer that is locked to an atomic clock, the > clock of NTP server (also 24 MHz, but an embedded board (Tinkerboard)) also > comes from the same Atomic clock that is feeding other synthesizer for > generates 24 MHz to this board. The RK3288 has some PWM generators. These are of course also fed from PLLs derived from the same 24 MHz input. So, why not produce a signal on the PWM that can be compared to your reference? This would tell you if the error is in the clock generation on the SoC or something in software that happens afterward. Or at least as far as the PWM clock tree overlaps the kernel timesource clock tree, which could be the CPU clock but it can be other things too. > The experiment is the following: 1- synchronize the computer's clock to NTP > server then leave it running free (no periodic synchronization), 2 - NTP will set the frequency skew too, so even if it is not doing periodic synchronization, there may still be a programmed frequency skew. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_l ists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] L1/L2 survey antenna $125 new
Wow! I sure got that wrong! The picture definitely shows a female TNC with the normal pin configuration. Guess I need to drink stronger iced tea. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Tom Holmes Sent: Friday, November 13, 2020 4:47 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] L1/L2 survey antenna $125 new Dana, it is a male TNC RP, which means reverse polarity. The center pins are reversed from the normal condition. Very commonly done on WiFi gear in the US due to some FCC paranoia about people hooking up amplifiers, which the aftermarket world immediately addressed. Ain't capitalism grand?! Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Dana Whitlow Sent: Friday, November 13, 2020 3:17 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] L1/L2 survey antenna $125 new Thanks, Bob. I zoomed in on the image that shows the connector without the cover, and it sure looks like a female connector to me (contradicting what the SparkFun description says). I could not determine which handedness applies to the threads, however- not quite enough resolution in the photo. I'm inclined to suspect that this is in fact a standard TNC female connector. What possible motive could an industry have for using a non-standard connector type except for meeting some silly FCC regulation (which clearly does not apply here). Dana On Fri, Nov 13, 2020 at 1:34 PM Robert LaJeunesse wrote: > Just spotted this: https://www.sparkfun.com/products/17382 > > Datasheet: > https://cdn.sparkfun.com/assets/6/e/a/9/2/BT-147_G NSS_Antenna_Datasheet.pdf > > Chokeplate design, 40dB LNA, TNC connector > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_l ists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_l ists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_l ists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] L1/L2 survey antenna $125 new
Dana, it is a male TNC RP, which means reverse polarity. The center pins are reversed from the normal condition. Very commonly done on WiFi gear in the US due to some FCC paranoia about people hooking up amplifiers, which the aftermarket world immediately addressed. Ain't capitalism grand?! Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Dana Whitlow Sent: Friday, November 13, 2020 3:17 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] L1/L2 survey antenna $125 new Thanks, Bob. I zoomed in on the image that shows the connector without the cover, and it sure looks like a female connector to me (contradicting what the SparkFun description says). I could not determine which handedness applies to the threads, however- not quite enough resolution in the photo. I'm inclined to suspect that this is in fact a standard TNC female connector. What possible motive could an industry have for using a non-standard connector type except for meeting some silly FCC regulation (which clearly does not apply here). Dana On Fri, Nov 13, 2020 at 1:34 PM Robert LaJeunesse wrote: > Just spotted this: https://www.sparkfun.com/products/17382 > > Datasheet: > https://cdn.sparkfun.com/assets/6/e/a/9/2/BT-147_G NSS_Antenna_Datasheet.pdf > > Chokeplate design, 40dB LNA, TNC connector > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_l ists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_l ists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Impedance question
Belinda... In general you want to have the impedances matched in order to keep the waveforms clean. What that implies is that you have to know the source impedance as well as the load impedance. Not all sources are 50 ohms, it seems, so some homework is in order to be successful. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of SimBeej Sent: Monday, September 07, 2020 8:04 PM To: time-nuts@lists.febo.com Subject: [time-nuts] Impedance question Dear fellow Time-Nuts, I have a question about impedance matching (and I apologise in advance for my blatant ignorance on this matter, but I don't have a background in electronics and hardware, so am having to learn along the way). When using frequency counters (in my case a 53230A and SR620) for making frequency or time interval measurements, should I be choosing 50 ohm for 1 mega ohm as the input impedance (where the input to the counter might be either a 10 MHz signal or two 1 pps signals from a variety of oscillators, depending on whether I am doing frequency or time interval measurements)? Initially I thought it would be best to match the impedances (in which case I should be using 50 ohm), but now I am not so sure. When I tried to read up on it, I found there is a lot of conflicting information out there. I trust the Agilent Application Note 200 (Fundamentals of Electronic Counters) and it says "for frequencies up to 10 MHz an input of 1 mega ohm is usually preferred". However, the same document also states that "the higher the impedance the more susceptible to noise and false counts the counter becomes". And could there possibly be a problem with reflections if the impedances aren't matched? If anyone out there has a good handle on this sort of stuff and can provide me with some advice, it would be greatly appreciated. Thanks. Belinda ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Problems with Lady Heather and Asus Aspire A515-55 laptop with an HP 58503A GPS receiver
Don... What email client do you use? It did not work like that for me in Outlook. Usually I can see the poster's email in the From line, and if need be copy it manually. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Don Lewis Sent: Sunday, June 07, 2020 6:27 PM To: Discussion of precise time and frequency measurement ; Bob kb8tq Subject: Re: [time-nuts] Problems with Lady Heather and Asus Aspire A515-55 laptop with an HP 58503A GPS receiver Ctrl-R will 'reply' only to the sender. Don N5CID = On 6/7/2020 5:12 PM, Bob kb8tq wrote: > Hi > > Having done *exactly* the same thing a while back: > > Be very careful about what the “to” address is when you try to do a private > message. The headers > get populated with the TimeNuts email address. It’s not as easy to do an off > list reply as it seems …. > > Bob > >> On Jun 7, 2020, at 5:48 PM, Alberto di Bene wrote: >> >> On 2020-06-07 18:11, W7SLS wrote: >> >>> So as not to consume group bandwidth on a “USB-Serial Adapter thread”, >>> sending privately >> After all, it wasn't actually a private message 8-) >> >> Alberto >> >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] ThunderBolt question
As the chip is a message, not a time hack per se, all the delay can do is make it more difficult to decode the message. That's how these COFDM-type schemes work. It's why your digital TV signal (which in the US is not a COFDM signal, but still behaves similarly) falls off a cliff when things get bad rather than fade away into noise like analog does. With analog, you get ghosts, but in digital, you just get garbage which may or may not be decode-able into a picture and sound. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Dana Whitlow Sent: Saturday, June 06, 2020 9:54 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ThunderBolt question I wish I could give some numbers. Sadly, I don't know how to calculate them nor do I have the equipment to do empirical measurements of that level of accuracy. But I could do an arm-waving estimate. Suppose that the delayed signal component is in phase with the direct signal, but 20 dB down, and is delayed by 100 nsec. Then I could see how the apparent centroid of a given chip could be displaced by about 10 nsec, which would be enough to cause complaint from many time-nuts. Personally I'm not into time keeping of that order of magnitude, but I'd like my GPS- disciplined oscillator to be phase stable to within 10's of ps over about a 1 minute time frame. At present I cannot seem to do this well unless I let my Rb free-run. Dana On Sat, Jun 6, 2020 at 8:43 AM Tom Holmes wrote: > No caveats required. > > Give some numbers on how loud that MP signal has to be to cause a problem. > My original example of line losses for a relatively short cable still > suggests to me that it is a minimal problem. If the S/N of a satellite is > poor, the receiver algorithm is likely to not use it if there are better > choices, and there often will be. > > Tom Holmes, N8ZM > > -Original Message- > From: time-nuts On Behalf Of Dana > Whitlow > Sent: Saturday, June 06, 2020 8:52 AM > To: Discussion of precise time and frequency measurement < > time-nuts@lists.febo.com> > Subject: Re: [time-nuts] ThunderBolt question > > Basically true, Tom, but with some caveats: > > The GPS system was originally designed, as you say, to provide > positions and velocity > information to military users in the field. Errors of a few meters were of > little consequence. > > But now, we have the time-nuts, surveyors, etc, who are decidedly pushing > the envelope > of GPS accuracy. Some users want sub-nanosecond timing accuracy, surveyors > want > mm-level position accuracy, etc, and doing these things indeed requires > extreme attention > to detail. > > As I understand it, multipath components that are delayed by about a few > chips or more > basically appear as a wee bit of added noise and have negligible > consequence unless > they are comparable to the direct signal in power. However, MP components > whose > delay is less than about a chip time have the effect of tugging the > apparent temporal > location of the direct signal to some new value. Note that this is in the > range of practical > round trip cable delays in at least some installations. At Arecibo, for > example, the one-way > cable lengths from GPS antennas on the roof to their respective receivers > was about > 200 ft. Round trip was thus 400 ft physical, hence up to about 600 ft > depending on > what the cables were using for the dielectric. That's about 0.6 chip > length for the C/A > code GPS signal. > > Another factor which will influence the error introduced will be the RF > phase relationship > between the direct and delayed signal component. > > Gee, this stuff gets complicated ... > > Dana > > > On Sat, Jun 6, 2020 at 7:30 AM Tom Holmes wrote: > > > Dana... > > The question that comes to mind is just how much effect a weak a long > > delayed reflection will have on overall system performance since it will > > only matter to SV’s with poor S/N. The modulation scene which allows all > > the SV's to transmit on the same frequency has to be pretty robust in the > > face of both widely varying signal strengths and multiple signals > arriving > > at different times. It’s a similar scheme to CDMA cell phones, which > > operate in a much more difficult environment with regard to signal > > strengths, multi-path, and number of on channel signals. And those work > > amazingly well. > > > > Further, I am led to believe that once you have enough SV’s in view to > > get a good set of ‘readings’, ionospheric effects are the limiting factor > > until you go to a multi-band receiver. > > > > Yes, to wring the last ounce of performance out of GPS takes a
Re: [time-nuts] ThunderBolt question
No caveats required. Give some numbers on how loud that MP signal has to be to cause a problem. My original example of line losses for a relatively short cable still suggests to me that it is a minimal problem. If the S/N of a satellite is poor, the receiver algorithm is likely to not use it if there are better choices, and there often will be. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Dana Whitlow Sent: Saturday, June 06, 2020 8:52 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ThunderBolt question Basically true, Tom, but with some caveats: The GPS system was originally designed, as you say, to provide positions and velocity information to military users in the field. Errors of a few meters were of little consequence. But now, we have the time-nuts, surveyors, etc, who are decidedly pushing the envelope of GPS accuracy. Some users want sub-nanosecond timing accuracy, surveyors want mm-level position accuracy, etc, and doing these things indeed requires extreme attention to detail. As I understand it, multipath components that are delayed by about a few chips or more basically appear as a wee bit of added noise and have negligible consequence unless they are comparable to the direct signal in power. However, MP components whose delay is less than about a chip time have the effect of tugging the apparent temporal location of the direct signal to some new value. Note that this is in the range of practical round trip cable delays in at least some installations. At Arecibo, for example, the one-way cable lengths from GPS antennas on the roof to their respective receivers was about 200 ft. Round trip was thus 400 ft physical, hence up to about 600 ft depending on what the cables were using for the dielectric. That's about 0.6 chip length for the C/A code GPS signal. Another factor which will influence the error introduced will be the RF phase relationship between the direct and delayed signal component. Gee, this stuff gets complicated ... Dana On Sat, Jun 6, 2020 at 7:30 AM Tom Holmes wrote: > Dana... > The question that comes to mind is just how much effect a weak a long > delayed reflection will have on overall system performance since it will > only matter to SV’s with poor S/N. The modulation scene which allows all > the SV's to transmit on the same frequency has to be pretty robust in the > face of both widely varying signal strengths and multiple signals arriving > at different times. It’s a similar scheme to CDMA cell phones, which > operate in a much more difficult environment with regard to signal > strengths, multi-path, and number of on channel signals. And those work > amazingly well. > > Further, I am led to believe that once you have enough SV’s in view to > get a good set of ‘readings’, ionospheric effects are the limiting factor > until you go to a multi-band receiver. > > Yes, to wring the last ounce of performance out of GPS takes attention to > the details, but don’t lose sight of how it was designed to work for users > in less than optimum (military field operations) in the first place. > From Tom Holmes, N8ZM > > > On Jun 6, 2020, at 7:14 AM, Dana Whitlow wrote: > > > > It's one thing to maintain lock in a multipath environment, quite > another > > thing > > to get "full" accuracy of GPS measurements of PVT. > > > > An interesting difference between my scenario of poorly matched > impedances > > and "ordinary" multipath is this: In the poor matching scenario, all the > > received > > signals will be impaired identically, while in the ordinary multipath > > scenario, > > signals from different satellites will suffer different (and > time-varying) > > multipath > > impairments. I'm not at all sure what effect this difference will have > on > > final > > outcome, but my gut feel is that the case where all signals are impaired > > identically > > could lead to worse effects. > > > > Dana > > > > > >> On Fri, Jun 5, 2020 at 8:43 PM Tom Holmes wrote: > >> > >> Dana... > >> > >> I think that you are neglecting two important mitigating factors. > >> > >> 1. the cable loss at 1575MHz, even for a 25' run of RG-6, reduces those > >> reflections quite a lot from one end to the other. It amounts to 2 > - 3 > >> dB in 25', depending on cable quality. > >> > >> 2. a 1.5:1 SWR is not a very big reflection to begin with, on the order > of > >> 20% of the incident power, about 7 dB. I am rounding a lot here just to > >> keep the math easy...for me. > >> > >> By the time a reflection has made the round trip from the receiver back > to &g
Re: [time-nuts] ThunderBolt question
Dana... The question that comes to mind is just how much effect a weak a long delayed reflection will have on overall system performance since it will only matter to SV’s with poor S/N. The modulation scene which allows all the SV's to transmit on the same frequency has to be pretty robust in the face of both widely varying signal strengths and multiple signals arriving at different times. It’s a similar scheme to CDMA cell phones, which operate in a much more difficult environment with regard to signal strengths, multi-path, and number of on channel signals. And those work amazingly well. Further, I am led to believe that once you have enough SV’s in view to get a good set of ‘readings’, ionospheric effects are the limiting factor until you go to a multi-band receiver. Yes, to wring the last ounce of performance out of GPS takes attention to the details, but don’t lose sight of how it was designed to work for users in less than optimum (military field operations) in the first place. From Tom Holmes, N8ZM > On Jun 6, 2020, at 7:14 AM, Dana Whitlow wrote: > > It's one thing to maintain lock in a multipath environment, quite another > thing > to get "full" accuracy of GPS measurements of PVT. > > An interesting difference between my scenario of poorly matched impedances > and "ordinary" multipath is this: In the poor matching scenario, all the > received > signals will be impaired identically, while in the ordinary multipath > scenario, > signals from different satellites will suffer different (and time-varying) > multipath > impairments. I'm not at all sure what effect this difference will have on > final > outcome, but my gut feel is that the case where all signals are impaired > identically > could lead to worse effects. > > Dana > > >> On Fri, Jun 5, 2020 at 8:43 PM Tom Holmes wrote: >> >> Dana... >> >> I think that you are neglecting two important mitigating factors. >> >> 1. the cable loss at 1575MHz, even for a 25' run of RG-6, reduces those >> reflections quite a lot from one end to the other. It amounts to 2 - 3 >> dB in 25', depending on cable quality. >> >> 2. a 1.5:1 SWR is not a very big reflection to begin with, on the order of >> 20% of the incident power, about 7 dB. I am rounding a lot here just to >> keep the math easy...for me. >> >> By the time a reflection has made the round trip from the receiver back to >> the antenna and them back to the receiver, which is how the delay would >> have >> to manifest itself, it will be down at least 15 dB from its original self, >> and probably more. Given the coding of GPS signals which allows several >> satellites to share a common frequency band, that is not going to be much >> of >> a problem. And if only one end of the path actually is 75 ohms, then there >> won't be a delayed signal. >> >> Tom Holmes, N8ZM >> >> -Original Message- >> From: time-nuts On Behalf Of Dana >> Whitlow >> Sent: Friday, June 05, 2020 9:01 PM >> To: Taka Kamiya ; Discussion of precise time and >> frequency measurement >> Subject: Re: [time-nuts] ThunderBolt question >> >> I'd like to point out that mismatches at the ends of an antenna cable *can* >> cause trouble. When both ends are mismatched, each bit of detail in the >> signal >> gets partially reflected back and forth, each time delayed by the round >> trip propagation >> delay in the cable, and so you have something like multipath going on. >> Fortunately the >> successive reflections get weaker with time, generally quite rapidly. >> Since many >> GPS users seem very concerned about multipath resulting from poor antenna >> placement, >> I think this factor should be considered as well and not just get swept >> under the rug. >> >> The amplitude of the "multipath" resulting from cable mismatches depends on >> the product >> of the voltage reflection coefficients at the two ends of the cable. If >> either end is perfectly >> matched, then the quality of the match at the other end is not significant >> vis-a-vis apparent >> multipath problems and only affects transmission loss. >> >> But when there is a mismatch on both ends, then the length of the cable >> comes into play >> as well. A longer cable means more delay between successive reflections, >> which is just >> like multipath involving longer delays between the direct and the reflected >> signals. >> >> Cheers, >> >> Dana (K8YUM) >> >> On Fri, Jun 5, 2020 at 7:13 PM Taka Kamiya via time-nuts < >&g
Re: [time-nuts] ThunderBolt question
Dana... I think that you are neglecting two important mitigating factors. 1. the cable loss at 1575MHz, even for a 25' run of RG-6, reduces those reflections quite a lot from one end to the other. It amounts to 2 - 3 dB in 25', depending on cable quality. 2. a 1.5:1 SWR is not a very big reflection to begin with, on the order of 20% of the incident power, about 7 dB. I am rounding a lot here just to keep the math easy...for me. By the time a reflection has made the round trip from the receiver back to the antenna and them back to the receiver, which is how the delay would have to manifest itself, it will be down at least 15 dB from its original self, and probably more. Given the coding of GPS signals which allows several satellites to share a common frequency band, that is not going to be much of a problem. And if only one end of the path actually is 75 ohms, then there won't be a delayed signal. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Dana Whitlow Sent: Friday, June 05, 2020 9:01 PM To: Taka Kamiya ; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ThunderBolt question I'd like to point out that mismatches at the ends of an antenna cable *can* cause trouble. When both ends are mismatched, each bit of detail in the signal gets partially reflected back and forth, each time delayed by the round trip propagation delay in the cable, and so you have something like multipath going on. Fortunately the successive reflections get weaker with time, generally quite rapidly. Since many GPS users seem very concerned about multipath resulting from poor antenna placement, I think this factor should be considered as well and not just get swept under the rug. The amplitude of the "multipath" resulting from cable mismatches depends on the product of the voltage reflection coefficients at the two ends of the cable. If either end is perfectly matched, then the quality of the match at the other end is not significant vis-a-vis apparent multipath problems and only affects transmission loss. But when there is a mismatch on both ends, then the length of the cable comes into play as well. A longer cable means more delay between successive reflections, which is just like multipath involving longer delays between the direct and the reflected signals. Cheers, Dana (K8YUM) On Fri, Jun 5, 2020 at 7:13 PM Taka Kamiya via time-nuts < time-nuts@lists.febo.com> wrote: > 50 ohm / 75 ohm question is really irrelevant in this kind of thing. > Trmble itself says in manual, not to be concerned with this apparent > mismatch. > In my particular case, I have a home lab standard and existing system. I > have an antenna and network of distribution amplifiers. They are all 50 > ohms and N connectors. Some ports have BNC adapters attached. I have > pretty much standardized everything to SMA, N, or BNC. > > I boxed a power supply, T-bolt, and buffer amp in a metal case. I bought > a short cable (RG58) that goes from F to BNC. On back of the case, I have > BNC to N adapter. I also have a few adapters that goes from F to BNC for > the test bench. It really doesn't matter what you use, as long as it makes > a solid connection. > > Advantage of F connectors and RG6 are, cheap, abundant, and low loss for > the size. Advantage of having house standard is, less adapters and less > headache. > > --- > (Mr.) Taka Kamiya > KB4EMF / ex JF2DKG > > > On Friday, June 5, 2020, 7:22:33 PM EDT, Robert DiRosario < > ka3...@comcast.net> wrote: > > I have a Trimble ThunderBolt GPSDO that I just received. It has an F > connector for the antenna input, and BNC connectors for the 1 pps and 10 > MHz outputs. Is the receiver input impedance really 75 Ohms, or is it 50 > Ohms and they just used the F connector to distinguish it from the > others? What do people do, just use a 50 Ohm antenna? > > Thanks > > Robert DiRosario > > KA3ZYX > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] TAPR TICC and TADD-2 Minis
Frank... What is interesting is that all of your traces appear to be identical except for the vertical scale factor, which suggests that the ringing you are seeing, which is much improved from your earlier plots, is still a little bit of a problem. I am going to guess that , as Bob pointed out, is probably due to a reflection problem in the input side of the attenuator. Could be the attenuator input impedance is not a good match to the source, or could be a cable impedance issue. I hope that suggests some things you could try experimentally and educationally to sort it out. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Frank O'Donnell Sent: Tuesday, June 02, 2020 1:19 PM To: time-nuts@lists.febo.com Subject: Re: [time-nuts] TAPR TICC and TADD-2 Minis On 6/1/20 9:11 AM, Bob kb8tq wrote: > Scope basics: Thanks for the comments. Very helpful as background beyond this immediate project. > A 10 db pad ahead of the feed through is another way to deal with this. It > should at > lest get you into the 20 db return loss range. I have a nice JFW variable attenuator, and inserted it between the TADD-2 Mini and the scope to capture the Thunderbolt's 10 MHz signal converted to square wave with 0, 3, 6, 10 and 20 dB attenuation. Screen shots are attached (very small, but there are five of them). > One of the reasons there are compensated scope probes is to get around this > issue. There are a variety of them out there with a range of capabilities. > Yes, the > fancy fet probes cost more than something simple ……. Currently the only probes I have is the stock pair that came with the Siglent digital scope (an SDS1202?X-e). I also recently bought a vintage Tektronix T922 analog scope, but it didn't include probes. Thus I might be in the market for a good set of probes. If there are suggestions for any that aren't more expensive than, say, a T922 or a used Thunderbolt, I'd be very interested. Thanks again, Frank ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] The 10811 double oven mystery
Then what was the purpose of the inner oven? Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Jarl Risum Sent: Wednesday, April 08, 2020 3:53 PM To: time-nuts@lists.febo.com Subject: [time-nuts] The 10811 double oven mystery I have been puzzled by a mistake which has been published recently on this list and elsewhere as well. It concerns the operation of the HP 10811 double oven TCXO used in the HP Z3801 GPSDO. It is claimed that the outer oven is only in use during start up or during extremely low ambient temperatures and is not operating during normal conditions. This is not correct. The 10811 outer oven circuit in the HP Z3801 is designed to maintainin a stable temperature around the 10811-60158 OCXO somewhere in the interval between 60 and 65 deg. C in order to reduce the 10811-60158 OCXO's sensitivity to temperature changes which – without the outer oven - is specified as 4,5 x 10 e-9 from 0 to 71 deg. C. The HP Z3801 was made as a GPS disciplined timebase for synchronization of CDMA Cellular Wireless Land Network base stations and was required to maintain system syncronization for up to 24 hours in situations with failure of GPS reception. In order to satisfy this requirement, the HP Z3801's internal processor keep track of the gradual ageing of the 10811 during normal GPS-disciplined operation and applies a calculated, predicted correction voltage to keep the OCXO on frequency during periods with no GPS signal (HP's Smart Clock technology). A diagram and detailed description of the 10811 outer oven circuit can be found at KO4BB's manual collection under http://www.ko4bb.com/getsimple/index.php?id=manuals=02_GPS_Timing/Z3801. Pictures of the outer oven can be found at www.realhamradio.com/GPS_Frequency_Standard.htm. In 2013 Warren Sarkison published an improved 10811 Outer Oven Controller with improved temperature regulation. Description and numerous references to his design can be found by Googling ”Warren S. Design 10811 Outer Oven Controller”. This circuit - or something similar - is much to be recommended if optimum operation of the dual oven 10811 outside of the HP Z3801 is considered. Jarl ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] HP 5335A and using the HPIB for control
Perrier... When you say programming is impossible, is that for lack of software or some other reason? I know of a utility from Keysight, called IOLibs, which would very manually let you send the appropriate commands to the counter, 1 or 2 at a time. Seems to me that it would only take a few commands to achieve what you need. Warning: It is very large, like several tens of megabytes, but it offers some debugging tools as well, and lots of other features. It is really intended to serve as a go-between for software apps to facilitate talking to instruments, but I've found the ability to simply issue one line commands to instruments is very helpful for software development. Others may tell you that the National Instruments version is better, and in some respects it may be, but you can get this from Keysight for free. Last I heard, NI wanted $ for their version. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Perry Sandeen via time-nuts Sent: Wednesday, March 04, 2020 3:29 PM To: time-nuts@lists.febo.com Cc: Perry Sandeen Subject: [time-nuts] HP 5335A and using the HPIB for control Learned Gentlemen, While my TN stuff is packed for moving, I took a look at the HP 5335 spec sheet. It appears that the gate time can be extended up to 10^7 seconds which would be very useful. Talking with Bob Camp off list he said that any HPIB controls would involve some programming which is impossible to do. There is a labview home program for about $100 but that would also require some programing. I could make extended gate times by making a 1PPS from my 10MHz reference and using it for the external gate start and counting it to get my desired stop time or perhaps there is the possibility of doing an internal mod to the counter which if it wouldn't be fairly simple, I'd rather not try. Does anyone know of or have a program that I could put on a laptop (windoz) to control the gate time function? For several reasons at this time buying something newer like a HP53131 or equivalent to accomplish this is not feasible. Thoughts? Regards, Perrier ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] multimeter
HI Jim... I guess the obvious questions are what are you replacing, and what do you need it to do? Is this a bench unit or handheld? Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Jim Palfreyman Sent: Saturday, March 23, 2019 8:06 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] multimeter Hi all, I think I'm in the market for a new digital multimeter. Could I have some recommendations? Jim ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] PPS clock module
John... I have a nixie tube clock that I purchased at Hamvention about 10 years ago that had an optional chip which worked with a 1 PPS input. It was built around a PIC. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Bob kb8tq Sent: Sunday, January 27, 2019 4:34 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] PPS clock module Hi I don’t think anybody runs a clock off of a PPS :) That would be nutty …. The closest I have seen is to womp up a “pulse 60 times” gizmo. Drive that off of the PPS. Feed the output into something designed for use in a bedside clock. I’d guess an 8 pin PIC and a few (dozen) lines of code is the quick way to do it. The obvious problem is that if the PPS is correct, the clock is not going to roll over on the PPS edge (unless the module accepts the 60 pulses at a very fast rate ….. who knows …. ) Bob > On Jan 27, 2019, at 3:48 PM, John Ackermann N8UR wrote: > > I'm putting together a portable Rb standard and thought it would be nice to > include a clock on the panel. I probably haven't hit the magic search words, > but I haven't found what I'm looking: a module (no enclosure) that is driven > by an external PPS and shows at least HH:MM:SS in 24 hour format on a small > LED or LCD display. > > I can whip something together with an Arduino, but rather than reinvent the > wheel I thought I'd ask if anyone knows of something that's ready to go. > > Thanks, > John > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWV Doppler Shift
So if the SI second is specified at sea level, and we know from Einstein and TVB's work that going up a mountain changes a clock's period, how would the second be affected at the center of the Earth ( ignore thermal problems, this is a conceptual discussion) where the net gravity vector might conceivably zero? Or for that matter, at a Lagrange point in space? We do have some data from those locations I would think. A second question (no pun intended) is that given the Earth's elliptical orbit around the Sun, has there been observed an effect of the change in its gravity on atomic clocks? Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Tom Van Baak Sent: Tuesday, November 20, 2018 6:31 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] WWV Doppler Shift > That was the first time that I had seen an xy plot of WWV versus a > stable crystal oscillator. It is even worse than I thought. I had to > look up FRK to see that it is a rubidium standard. I talked to Jim > Maxton the chief engineer of WWVB many times around 1995. An xy cycle of WWV is just 200 ns, about 80x shorter than the 16667 ns cycle of WWVB. So, yes the xy plot in the video seems to jump around a lot, but if that were WWVB it would be 80x less, barely a wiggle. Does someone have a strip chart version of that video? Or, better yet, a raw data set of WWV (or WWVB) phase over a day or week? How hard would it be to use a hands-off SDR to produce a 5 MHz WWV phase data point every second? > Ft Collins is at 5,003 ft and clocks there run fast by 1.663·10^-13. > (g/c^2)/meter) compared to sea level. Yes, an out-of-the-box cesium clock will be relatively fast by that amount. But NIST (and everyone else) uses UTC, which is based on the SI second, which is defined at sea level (and several other footnotes). Which is to say that a national clock or radio transmitter (such as NIST, WWV, WWVB, or DCF77, or GPS for that matter) are adjusted in frequency so they tick SI seconds, and adjusted in phase so they align with UTC. /tvb ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] 10 MHz -> 16 MHz
Hi Pete... TAPR doesn't really discontinue things until we've sold out the quantity we've built. Sometimes that is 100pieces, sometimes 500. It all depends on how many we think we can sell when the kit comes out. If we sell out and still see a lot of interest, we may do a second build. The Clock-Block has been around for a few years and took a couple of years to sell out. >From Tom Holmes, N8ZM > On Oct 9, 2018, at 1:25 PM, Pete Lancashire wrote: > > I just wish the tapr would not discontinue things so fast it seems once you > see it mentioned it's discontinued > >> On Sun, Sep 30, 2018, 1:08 PM Bob kb8tq wrote: >> >> Hi >> >> If (as originally specified) noise and jitter are not a big deal - there >> are a lot >> of chips out there like the ICS570. They are designed to do weird ratio >> frequency >> conversions so 10 to 12 or 10 to 16 are trivial for them. The Clockblock >> board was >> one way to get it all put together. >> >> Bob >> >>> On Sep 30, 2018, at 12:05 PM, Gerhard Hoffmann wrote: >>> >>> >>>> Am 30.09.2018 um 16:49 schrieb Attila Kinali: >>>> >>>> The simplest way I can think of is the following: >>>> Use a 74LV8154 to divide the 10MHz down to 152.587890625Hz. >>>> Use the capture timer unit of the uC to measure the phase of the >>>> pulse. Use any kind of DAC (internal, external, PWM,...) to steer >>>> the 16MHz VCO. Depending on how fast the timer unit runs, this >>>> will give you something in the order of 10-200ns dead-band. >>>> By choosing the right frequency for the timer unit, one can >>>> get it to "dither" a bit and then use averaging. >>>> >>>> For lower jitter, use one half of a Nutt interpolator >>>> to get the timing difference between the 152Hz signal >>>> and the 16MHz (ie similar to what the SRS FS740 does). >>>> Use something akin Nick Sayer's time-to-amplitude converter >>>> for the fine measurement. >>>> >>>> Same works equally well for 12MHz. >>>> >>>> >>> >>> Wow. That's truly a Rube Goldberg design. >>> >>> There is a simpler way. IDT ICS570. Digikey 800-1073-5-ND >>> >>> Solder time less than 10 minutes. >>> I had the 3V3-Version in the parts drawers, officially it takes the 5V >>> version to generate the 160 MHz, but the 3V3 version happened to work, >> too. >>> The difference between 120 and 160 MHz is just a GND wire on pin 6 (vs. >> open) >>> >>> Divide by 10 is left as an exercise. >>> >>> regards, >>> Gerhard >>> >>> (But then, some like to build and tune multiplier chains and mixers.) >>> >>> >> ___ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] WWV and legal issues
Uh, folks...Would the apparently still on hiatus TVB approve of this on-going Urinary Olympiad? Just asking. And hoping post this won’t start another one. Tom Holmes, N8ZM -Original Message- From: time-nuts On Behalf Of Bob kb8tq Sent: Friday, August 31, 2018 11:16 AM To: Martin VE3OAT ; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] WWV and legal issues Hi That works fine if you are doing things manual to check a local standard. If you are trying to disipline a few thousand cell towers 24 hours a day … not so much. It also works for checking frequency. What modern systems need is time. That gets you into a whole world of resolving and identifying individual edges. The WWVB signal really was never set up for this. Loran-C is an example of a signal that was designed to identify a specific edge. Bob > On Aug 31, 2018, at 10:30 AM, Martin VE3OAT wrote: > > But the diurnal phase shifts at VLF are predictable and largely repeatable. > Ignore the phase at night and use only the phase records during the day when > an all-daylight propagation path exists. You might have to "correct" the > absolute phase reading by some multiple of the RF period, but with a low rate > of local standard oscillator drift, this is a simple matter of arithmetic. > Back in the day, I managed Sulzer crystal oscillators at 5 field sites from > my office and could maintain phase continuity for weeks at a time, until we > had to diddle the dial on one or several of them to correct for crystal > aging. Then it was just more arithmetic again. Several of the oscillators > had such low drift rates that all I needed was one daily phase reading from > the VLF phase tracking receiver (Tracor 599Js) at those sites to know the > frequency of the Sulzers there. > > ... Martin VE3OAT > > On Thu, 30 Aug 2018 12:27:12 -0400 > Bob kb8tq wrote: > >> WWVB as transmitted ( = right at the input to the antenna) is a wonderfully >> stable signal. As soon as >> that signal hits the real world things start to degrade. Propagation between >> transmit and receive sites >> is a big deal, even at 60 KHz. On top of that, there is a*lot* of manmade >> noise at 60 KHz. The receive >> signal to noise will never be as good as you might like it to be ?. > > > I don't know about WWVB, but for DCF77 it's known that sunrise/sunset >> causes a phase shift of several 100?s at even moderate distances >> (like ~500km). Unfortunately I don't have any measurements at hand. >> Attila Kinali > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
