Mark,
I see some LEA-6T units and some NEO-M8N units. Has anyone done any timing
tests on these since they came up last time on time-nuts? The prices just seem
to be way on the low side.
Bob
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Hi Rami,
I am very interested in your 5370 power conversion. Can you give us any more
information as to the model number of the buck regulators you used and where
you got them. Did you run into any problems? Did you make any notes or
drawings?
Bob
Hi Nick,
Let's use the example of a Ublox timing receiver. In the TIM-TP data package,
there is a qErr value, which is the quantization error of the *next* PPS pulse
output by the receiver. At the next PPS, you would subtract that from the
unwrapped phase measurement your GPSDO makes and that
Interestingly enough, the Ublox LEA series of timing receivers has a USB port
which you can connect directly to a USB cable. Of course you want to use an
ESD device, etc.
Bob
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The LEA-6T is a good receiver, but it does have a sawtooth bug. From time to
time, when the sawtooth is approximately 10,299 (or is it 10,399?) ps, the sign
of the sawtooth is wrong. It's an easy fix: Just check whether the sawtooth
makes "this" corrected measurement worse than the previous c
M
Subject: Re: [time-nuts] Allan Deviation recipe?
Yo All!
With help from Tom Van Baak and Bob Stewart, I have 6 weeks worth of
GPS Serial and PPS timing data in a nice ADEV chart. I think.
Check it out:
https://rellim.com/graphs/adev.png
That is for a SiRF III (MR-350P) with a bad sky
For my next GPSDO board revision, I would like to include one of Tom's PICDiv
devices to give a much better 1PPS out than the Ublox receivers are capable of.
This means that it has to be started (or slewed to be) exactly on time. So I
was wondering if anyone had experimented in controlling the
But would it really solve your problems, Jim? The problem is essentially that
periodically, there are two different clock times that represent the same
moment in time. For telescopes, stock markets, spread spectrum, time-based
encryption, etc that's a big problem. Would it not be better to se
In timing mode, you care very much about the quantization error messages.
Bob
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From: Gary E. Miller
To: Mark Sims
Cc: "time-nuts@febo.com"
Sent: Satu
Hi Brooke,
Thanks for that info. I've got the important bits (PRS and GPSDOs) now hooked
up to an APC Smart-UPS 700. What will happen when it goes to battery power, I
don't know. I've been doing qualification testing on a new batch of GPSDOs, so
I haven't had time to do any testing of power f
I let an older, well-aged GPSDO warm up overnight and then I ran a test with
the UPS. Attached were the PRS*, the GPSDO, and the 5370A. I didn't notice
anything when I removed power. I did notice about a 450ps phase spike when I
plugged the UPS back in some 640 seconds later. But that was it
Charles, I can't speak for Brooke, but I have to point out that each of us has
different needs when it comes to powering our lab. For myself, if I lose
power, that's OK. I'm retired selling a few GPSDOs here and there and working
on some other stuff, so I don't need a 24/7 operation. What I'd
Hi Jerome,
This may or may not be of any help, but have you considered using several
RTL-SDR devices running at the same time? You'd need to use a common clock,
and probably a number of other enhancements. But, if you could pull it off,
you'd have a wideband RDF type of device. You'd probably
I liked the Adafruit too when I was using it a couple of years ago, but it did
have a bad habit of going walkabout. Yeah, a lot of that was my antenna, but
it's still worth mentioning.
Bob -
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Hi Bill,
A lot of us are hams. The ARRL handbook has a section on grounds, including
the need for bonding additional grounds to the power line ground. A loop of
heavy gauge wire around the house that has periodic 8' ground rods is seen as a
good thing as long as it's bonded to the power line g
Earlier this year, with some help, I pulled the dish off of an old DishTV
antenna on the roof and put a 5V bullet antenna on the mast. I also pulled a
new cable through by attaching it to the old one. The problem is that I was
not able to measure the new cable. So, the question is, without go
ethod of getting a 1PPS should probably be in a new
thread. I'd be happy to link to a schematic if wanted.
Bob
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From: Bob Camp
To: Bob Stewa
/GFS-GPSDOs/info
From: Bob Albert
To: Bob Stewart ; Discussion of Precise Time and Frequency
Measurement ; Discussion of precise time and frequency
measurement
Sent: Monday, August 8, 2016 2:18 PM
Subject: Re: [time-nuts] Safely getting the electrical length of a connected
antenna feed
A number of posts have appeared about Zynq SDRs on the "Shera revisited"
thread. So, I'd like to ask the more general question: Are there any low cost
SDRs that are suitable for measuring phase noise when coupled with a DMTD? I
believe what I'm looking for is something with enough bits to work
Hi Bob,
You want to get something along the lines of ebay item 272331719376 or
262202931320. The boom is pretty important, otherwise how do you get your
boards under the microscope if they're not very small? Some time ago, I got a
Bausch & Lomb Stereo 3 with 10X oculars and a 0.5 barlow. The
Why is velocity factor an issue? Aren't we only interested in the electrical
time from one end of the coax to the other?
Bob
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From: Didier Juges
To: Bo
Hi Brooke,
It looks like I've asked a question poorly, yet again. So, let me try again.
I have this idea of combining a DMTD with an SDR. So, said that way, it looks
like what I really need is a 2-channel audio SDR. And having said that, maybe
what I'm looking for is an external USB sound ca
0 Hz range.
Is that correct or are you looking for something to use instead of a DMTD?
Bob
> On Aug 11, 2016, at 3:29 PM, Bob Stewart wrote:
>
> Hi Brooke,
> It looks like I've asked a question poorly, yet again. So, let me try again.
> I have this idea of combining a
: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Thursday, August 11, 2016 5:12 PM
Subject: Re: [time-nuts] Low cost SDR suitable for phase noise measurement?
On Thu, 11 Aug 2016 19:29:08 + (UTC)
Bob Stewart wrote:
> It looks like I've asked a questio
surement?
>
> Hi
>
> Just to clarify:
>
> You are looking for a way to digitize the output(s) of the mixer(s) in a
> DMTD. The
> “target signal” is in the 1 to 10 Hz range.
>
> Is that correct or are you looking for something to use instead of a DMTD?
>
>
It's been pointed out to me that I didn't understand the function of the 1PPS
of a time standard. I confess that somehow I had confused the term to be
timing standard; which would be an entirely different thing. But, this is
time-nuts, so I should have realized...
Anyway, is there a standard,
d
standard for this, or is this something that everyone (except the newbie) knows
so well that it's not worth discussing?
Bob
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From: Attila
th how my
unit works as a frequency standard.
Bob
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From: Attila Kinali
To: Bob Stewart
Cc: Discussion of Precise Time and Frequency Measurement
Sent:
: mag...@rubidium.se
Sent: Tuesday, August 16, 2016 6:49 PM
Subject: Re: [time-nuts] Holdover
Bob,
On 08/16/2016 11:31 PM, Bob Stewart wrote:
> Hi Attila,
> In my unit, which is a frequency standard, I chose to tell the receiver to
> stop sending 1PPS pulses when it loses sync to the sats.
V.com
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From: Magnus Danielson
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Cc: mag...@rubidium.se
Sent: Wednesday, August 17, 2016 1:05 AM
Subject: Re: [time-nuts] Holdover
Bob,
That is what seem to
Thanks Chris. Those are more considerations that I hadn't thought of. I begin
to see why there's no "standard".
Bob
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From: Chris
The stuff I use is Chipquik SMD291AX. The first syringe of it I bought was
from Mouser and was 15 grams. That was back in 2014. The second syringe I got
was SMD291AX10, which is 35 grams. It's dated 3/15/16, so you can see how long
solder paste will last if you take reasonable car of it. I
Hi Tim,
If I understand your post correctly, you're using a frequency counter to
measure the accuracy of your GPSDO. Assuming there's nothing wrong with the
GPSDO, what you're actually doing is measuring the frequency accuracy of your
counters. Unless you have something that is known to be mor
OTOH, how many time-nuts have any interest in paying for a power supply that's
up to time-nuts standards? It's really not easy to bring a small product to
market at a small price. Even if you completely discount the personal effort
of design, construction, and marketing, there's the issue of p
Charles,
said: "So the answer is to bring crap to market because nobody will pay for
something that actually does the job?"
I don't mean to cause offense, but is everything you don't like crap? The
reality is that whatever the market will bear is what determines what comes to
market. If you ca
Nick said:
"Jim Miller's 10 kHz GPSDO that’s been referenced here has either solved this
problem, or the 10 kHz output of the Jupiter is substantially better than the
Venus’ 10 MHz output, or the design doesn’t give the results time-nuts expect
from a GPSDO. Which of those applies?"
Hi Nick,
You
I've been spending a small amount of my time looking into making a sort of
hybrid DMTD with a pair of DBMs up front feeding the stereo input to a sound
card. So, I got the 100KHz LPF back from Oshpark and hooked it up to my scope
for verification - an obvious step. Then I hooked it up to my 34
I'm running a holdover/recovery test
on the code and hardware changes to get a reliable 1PPS from my GPSDO, so there
is some very slow movement over the range of 0 to 100ns.
Bob
From: Bob Camp
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Saturda
From: Bob Camp
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Saturday, October 1, 2016 6:24 PM
Subject: Re: [time-nuts] Measuring phase with an HP 3456A?
HI
DMTD = Dual Mixer Time Difference
Single Mixer = what is commonly used for most things.
re, and this will
need software in any case.
Bob
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From: Bob Albert
To: Discussion of precise time and frequency measurement ;
Bob Stewart
Sent: Saturday, October 1, 2016 6:46 PM
Subject: Re: [time-nuts]
: [time-nuts] Measuring phase with an HP 3456A?
On 10/1/2016 5:13 PM, Bob Stewart wrote:
> Hi Bob Albert,
>
> Completely eliminate the use of the term "DMTD". I didn't post that.
Actually you did in your first post.
"I've been spending a small amount of my
For my GPSDO, I need to calculate the OCXO aging for holdover projection
purposes as well as get some figure of merit for the recent past of the OCXO
stability. The latter is so that I can determine that the PLL has (or soon
will have) a good lock. I'm developing on a dfPIC33FJ128MC802, and I'
d once every 5 minutes will give me something for aging rate.
Bob -
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From: Jim Harman
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Hi Nick,
Are you applying sawtooth correction to your phase measurement? If not, are
you merely seeing a hanging bridge that dissolves into at a normal sort of
tick-tock movement?
Bob
From: Nick Sayer via time-nuts
To: Discussion of precise time and frequency measurement
Sent: Wednes
voting algorithm?
> On Oct 5, 2016, at 4:52 PM, Bob Stewart wrote:
>
> Hi Nick,
>
> Are you applying sawtooth correction to your phase measurement?
Yes, these are post-correction observations. I have some confidence that my
corrections are scaled appropriately for the ADC va
Bob -
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From: Jim Harman
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Wednesday, October 5, 2016 9:14 PM
Subject: Re: [time
said: "The somewhat amazing holdover estimates on the HP units are one example
of this problem. It does not take much testing to quickly realize that they are
far more often wrong than right on a unit that has been on power for less than
a few weeks."
Thank you Bob. These two sentences clear it
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From: Tim Shoppa
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Thursday, October 6, 2016 12:37 PM
Subject: Re: [time-nuts] Measure GPSDO
Hi Randal,
I've got a bad cold, so I can only hope this response is rational.
To begin with, you need some sort of Time Interval Counter (TIC), as well as
some way to get the measurements from it into your computer. Once you get
that, then you get a free copy of John Miles' indispensable Timelab
ing for in order to really use the
Timelab software.
Thanks again for the help, all you time-nuts, as I seem to be ready to take the
next step...
-Randal R.
(at CubeCentral)
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Stewart
Sent: Frida
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Stewart
Sent: Friday, 07 October, 2016 12:43
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Inexpensive Alternative to a 5120A
Here's the one I recommend: http://prologix.biz/gpib-ethern
if more
than that is really useful, but a multiple of 24 may bias it toward
environmental conditions at startup, so perhaps 64 hours would b
e better.
Bob
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The problem with two counters is that they will never read exactly the same.
What would be better is if the TICs were able to steer the first incoming
signal to start and the next to stop, and then apply a sign based on where the
first pulse came from. Of course, then you have the problem of d
Don't forget the possibility of saving the data to a file and pre-processing
the file before sending it to Timelab.
Bob
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From: Magnus Danielson
To: time
Hi Bob,
Is it actually possible to address two devices on one GPIB adapter with
Timelab? I admit to not reading the documentation carefully, but I've not been
able to do this directly. The only way I could think of doing it was to use
some software to send the data to a file and then use Timel
--
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From: Bob Camp
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Sunday, October 9, 2016 11:50 AM
Subject: Re: [time-nuts] TimeLab
Hi
> On Oct 9, 2016, at 12:27 PM, Bob
I've actually got 10 or 12 of those sitting in a box. I got them because of
the "grounded" power header. The units I got used the 3-pin header but only
had a 2-wire plug. So, something seemed wrong and I opened it up. I noticed
the same thing: that the non-soldered ground pin went nowhere.
I'm working on the Aging and Thermal Correction algorithms in my GPSDO. At
this point, it's pretty simple: For aging, every X seconds I either increment
or decrement the DAC value by 1 as determined by the unit's performance
history. For thermal, every X seconds (user settable) I check to see
Hi John,
Have you looked into walk-in humidors to see if there are any ideas there that
you could use? Yeah, those use high levels of humidity, but there might be
something in common with your needs.
Bob
-
AE6RV.com
GFS GPSDO lis
Bob
From: Attila Kinali
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Wednesday, October 26, 2016 1:28 PM
Subject: Re: [time-nuts] Aging and Thermal Correction in Holdover
On Wed, 26 Oct 2016 17:01:17 + (UTC)
Bob Stewart wrote:
> I'm
From: Attila Kinali
To: Discussion of precise time and frequency measurement
Sent: Thursday, October 27, 2016 1:45 PM
Subject: Re: [time-nuts] Aging and Thermal Correction in Holdover
On Thu, 27 Oct 2016 16:13:06 + (UTC)
Bob Stewart wrote:
> Since I want to keep this
Hi Bob,
Can't the OCXOs be characterized pretty closely by someone with the right tools
and staff? I don't have a big sample to speak from, but the Trimbles I use
only have a couple of ceramic coated pieces, and those can be exposed down to
the die by hand and then characterized, can't they? G
>From experience, I can tell you that you can't always depend on the seller
>when it comes to how to feed your new OCXO. For instance, the seller of the
>Trimble 65256 insisted that it took 12V. So, that's what I used, and all the
>magic smoke came tumbling out.
Bob
From: Peter Reille
Perfect? I can't tell you that. But I can tell you that the 1s ADEV that I
can measure is limited to the stability of the reference oscillator, and to the
resolution and stability of the measuring device. For example, I have an HP
5370A TIC. It's good to about +/- 20ps. So, that's the lower
Hi Michael,
I've got a dumb question about the need for a really good flywheel oscillator
for the 12.6Ghz Yb clock: What is the signal that is locking that oscillator?
Is it a 1PPS, or is it something in the RF domain, such as 10MHz or higher?
I still hope to make a modern version of the old wa
12.6 GHz hyperfine transition
> in Yb is not continuous. There's a measurement sequence of state
> preparation etc that means you only get an error measurement every 10 to
> 100 s. so you need a good flywheel in between.
>
> Cheers
> Michael
>
> On Thursday, 3 Nove
In the general case, is the impact of changing the ambient temperature around
an OCXO from, say, 40C to 41C the same as changing it from 41C to 40C all else
being equal? IOW, if I somehow have the same temperature ramp over the same
time period in both directions, will I wind up with the same f
OK, never mind. I see the obvious. Phase changes faster at a higher frequency
than it does at a lower frequency.
Bob
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From: Bob Stewart
To
fore I can get there.
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From: Scott Stobbe
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Saturday, November 5, 2016 1
Bob -
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From: Bob Camp
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Saturday, November 5, 2016 11:54 AM
Subject: Re: [time
an plot.
Anyway, does any of this answer your question? If not, let me know what's
missing.
Bob -
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From: Hal Murray
To: Bob Stewart ;
Oh dear. I attached the wrong file. Here's the correct one.
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___
time-nuts mailing list -- time-nuts@febo.com
T
Hi Tom,
Personally, I wouldn't touch this without a hot air gun. I don't know what
your budget is. What I consider reasonable may be an order of magnitude
smaller than for you. So, I use a generically labeled 852D+ rework combo. It
has both solder pencil and hot air gun. There are better ho
Hi John,
I've never used the hot tweezers. I'm going to have to look into them.
Normally, for desoldering, I use a narrower nozzle with an elevated temperature
- usually between 280C and 350C. That blows the part completely off the pads
just as soon as the solder flows, with little impact on
-
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From: Hal Murray
To: Bob Stewart
Cc: Hal Murray
Sent: Saturday, November 5, 2016 6:23 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
> The OCXO has been hot for a number of months.
Then I don'
that DAC and an HP3458...
On Sun, Nov 6, 2016 at 12:39 AM, Bob Stewart wrote:
> Hi Hal,
>
> With a 20 bit DAC, even a small aging rate is going to show up. I'll let the
> one GPSDO cook for a month or so and see what it shows then. I'll also pull
> the data from the log
and “ground” from grabbing the OCXO is
harder
to measure, but also pretty typical. It sums right into the EFC line.
It’s not a rabbit hole so much as the details of the design at the level you
have chosen
to look at.
Bob
> On Nov 5, 2016, at 8:10 PM, Bob Stewart wrote:
>
> This see
PSDOs/info
From: Scott Stobbe
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Saturday, November 5, 2016 8:38 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
I think that's a nice plot, it looks like you have stepped 160 LSB over 7 days
or roughly
/neo/groups/GFS-GPSDOs/info
From: Bob Camp
To: Bob Stewart
Sent: Saturday, November 5, 2016 8:46 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
Hi
My experience is that the aging on these oscillators is so far below a number
of issues
that you will not be able to see it in under a
DO list:
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From: Scott Stobbe
To: Bob Stewart
Cc: Discussion of Precise Time and Frequency Measurement
Sent: Saturday, November 5, 2016 9:19 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
If your DAC spans the full EFC range than 1LSB is 1
m the OCXO or the voltage divider; which is a 15K/16K
divider.
Bob
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From: Bob Camp
To: Bob Stewart
Cc: Discussion of Precise Time and Frequency Mea
Hi guys,
First of all, thanks for the additional responses. I was a bit angry and rude
yesterday, and I figured this thread was over. Thanks for staying with me.
I haven't had time to look over the data etc in your responses. I'll do that
and get back to the list if appropriate.
I spoke to At
SDO list:
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From: Scott Stobbe
To: Bob Camp
Cc: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Monday, November 7, 2016 9:34 AM
Subject: Re: [time-nuts] Thermal impact on OCXO
Here is a sample data point taken from
h
st 3 or so days of data collection to project
the near-term behavior; where near-term is less than 3 days into the future.
Bob -
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From: Bob Camp
From: Bob Camp
To: Bob Stewart
Cc: Discussion of Precise Time and Frequency Measurement
Sent: Monday, November 7, 2016 11:54 AM
Subject: Re: [time-nuts] Thermal impact on OCXO
Hi
I would suggest you read the papers on the subject. They are out there. Even
over a few days
OCXO a
le
out. And for sure when I added the test lead to the EFC (breaking a trace in
the process) there was enough off time to thoroughly insult the OCXO.
Bob -
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F
.com/neo/groups/GFS-GPSDOs/info
From: Scott Stobbe
To: Bob Stewart ; Discussion of precise time and frequency
measurement
Sent: Monday, November 7, 2016 2:48 PM
Subject: Re: [time-nuts] Thermal impact on OCXO
Another nice plot! It looks like after 2am you see temperature swings of 1.
I'd like to comment on the idea of measuring the width of the pulse. My
experience with creating the 1PPS from an interrupt is that it's fairly
straightforward how to do the set interrupt: The interrupt happens, you
execute one, maybe two instructions to raise the output pin, and you leave the
h are perfect, down to picoseconds. The talk about "other
stuff" and "priority" and "number of compares" and "ambiguity" is worrisome. It
sounds like a design or coding flaw to me, like what happens when people try to
do precise time with a high level language.
/
all your doing, then, yes, it's an easy job to
make the pulsewidth very stable at whatever value you choose.
Bob
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From: Adrian Godwin
To: Bob Ste
So, are you measuring OCXO stability or EFC stability?
Bob
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From: Tom Van Baak
To: Discussion of precise time and frequency measurement
Sent: Saturday
Just a short comment on getting a PIC up and running. Microchip have come out
with a number of tools, especially their "Configurator" software that will get
you started pretty quickly. And there is a long list of example programs on
microchip's website for simple programs that do things like r
Hi Bob,
said: "Most (> 99%) OCXO’s are made to custom specs for large OEM’s. The sort
consists of “ship these” and “send these to the crusher”. Needless to say,
the emphasis is on a process that throws out as few as possible. "
We've seen a serious improvement in manufacturing yields at close to
I can't help but notice that there is an impact on the measured phase error
every time the TDOP reported by the LEA-6T changes. What I don't know is how
to characterize the impact. Is the impact more of a change in the error band,
rather than a bias in one direction or the other? Would a vari
To me, these devices look like they may have a quartz crystal at the bottom,
and spring and screw adjuster on the top.
Bob - AE6RV
From: Paul Berger
To: Discussion of precise time and frequency measurement
Sent: Saturday, November 26, 2016 10:47 AM
Subject: Re: [time-nuts] Vintage Qua
I built my first set of boards with ExpressPCB, but they get expensive quickly
if you want to make something that's not in their special form factor. I use
KICAD and OshPark.com to make my boards (there are other board makers). I just
ordered some boards that are .7" x .63" that cost $8.40 for
Hi Jim,
A couple of years ago, I asked the group if there was a standard UI that I
should use for the GPSDO that I was developing. Everyone said no, just do what
works. I don't think it occurred to anyone, certainly not to me, just how big
a role that LH plays in the world of GPSDOs. So, here
Mark,
I haven't had the time to look at the LH code yet, but is there a sort of
natural interface that would most easily fit? I'm speaking about both sides of
the conversation: receiving data streams and sending commands. It seems a bit
strange to me that NMEA would be the preferred type of da
One thing I've never really understood is who actually uses the high-quality
1PPS output from a GPSDO. I have spent a lot of time, effort, and money on
developing my GPSDO without a whole of thought to the user base. It was just a
quest for the best result I could obtain with a particular tech
ject: Re: [time-nuts] 1PPS users?
On 12/18/16 3:16 PM, Bob Stewart wrote:
> One thing I've never really understood is who actually uses the high-quality
> 1PPS output from a GPSDO. I have spent a lot of time, effort, and money on
> developing my GPSDO without a whole of thought t
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