Dear colleagues
I was a bit lazy in the past, so it took way too long to finish the schematics
for my new GPSDO.
I am currently making some first trials on the PCB layout; however, I still
would like to show you guys my schematics and ask what you think about it. See
the attachment.
Page 1
tter too much, should it?
From: time-nuts [time-nuts-boun...@lists.febo.com] on behalf of Achim Gratz
[strom...@nexgo.de]
Sent: Sunday, November 03, 2019 17:45
To: time-nuts@lists.febo.com
Subject: Re: [time-nuts] Question for my new GPSDO
Attila Kinali writes:
> There is
k stability
with the DMTD method - pretty new to me and will be interesting to set up.
Best
Tobias
From: time-nuts [time-nuts-boun...@lists.febo.com] on behalf of Attila Kinali
[att...@kinali.ch]
Sent: Sunday, November 03, 2019 15:57
To: Discussion of precise time and frequency measureme
ed breya writes:
> I think the main need for the overall DAC system in these is not
> linearity, but monotonicity - an increasing digital input always
> causes an output change in one direction only, and never reverses.
An y=x³ (cubic) transfer function is monotonic but not linear, yet you
I think the main need for the overall DAC system in these is not
linearity, but monotonicity - an increasing digital input always causes
an output change in one direction only, and never reverses. The
linearity and other characteristics of the sub-parts comes into play
when you need to combine
Attila Kinali writes:
> There is, as far as I know, only two types of DA converters that
> are inherently linear: single-bit delta-sigma modulators and
> Kelvin-Varley dividers.
No, the Kelvin-Varley is not guaranteed to be linear, same story as a
string DAC actually. Whether a delta-sigma
Hoi Tobias,
On Wed, 16 Oct 2019 16:30:19 +
Tobias Pluess wrote:
> I attached my own schematics of the EFC control circuit. I think with this
> circuit, it should be possible to achieve a similar resolution as you
> mentioned in your thoughts.
>
> D3 is a 16bit resistor string DAC and
Hi
Stepping back a bit here …..
All oscillators have phase noise. It’s going to vary with the offset from
carrier.
What you get at 10KHz will be much better than what you get at 1Hz. As long
as the EFC does not make this any worse, there is no need to get very crazy.
Putting the added noise 40
On Mon, 14 Oct 2019 20:46:14 +
Tobias Pluess wrote:
> For sure the 1PPS output will be generated in hardware. I have made good
> experiences with using a microcontroller timer: One can use an ordinary PWM
> channel and this generates very precise pulses, and no interrupts or the
> like
Hoi Tobias,
On Mon, 14 Oct 2019 11:49:29 +
Tobias Pluess wrote:
> I have now designed the EFC circuit such that it is easily possible to use
> different DAC and voltage reference models. I have also reverse-engineered
> the circuit which is used on the Oscilloquartz GPSDO. They seem to
Tobias Pluess writes:
> Assume a timer is clocked with the 10MHz clock. The timer overflows
> when it reaches 999 (=10e6-1). Further, this timer is used to
> generate the 1PPS pulse output: each time when the timer reaches the
> value of 0, a pulse is generated on one of the output pins. Since
Hi
You (sort of) have run into two problems:
1) The GPSDO takes forever and ever to lock ( = the gain is to low / the time
constant it to long)
2) The GPSDO has to much jitter ( = the gain is to high / the time constant is
to short)
Obviously, you can’t solve both of these problems by
Hi colleagues
thanks to your inputs I could design the EFC circuit for my new GPSDO and I
think its quite clear how that will work.
So in the past days, I spent my spare time on thinking about the control
algorithm. I used FLL previously, which gave unsatisfactory results, so I think
PLL is
nali.ch]
Sent: Wednesday, October 16, 2019 10:17
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Question for my new GPSDO
On Tue, 15 Oct 2019 18:43:29 -0700
Hal Murray wrote:
> You can get a few bits by reducing the tuning range. Suppose you follow the
>
If the DAC update rate isn't excessive a 2nV-sec glitch is unlikely to produce
a significant perturbation at the output of the lowpass filter following the
DAC.
Bruce
> On 16 October 2019 at 21:01 Attila Kinali wrote:
>
>
> On Wed, 16 Oct 2019 15:04:31 +1300 (NZDT)
> Bruce Griffiths wrote:
On Wed, 16 Oct 2019 15:04:31 +1300 (NZDT)
Bruce Griffiths wrote:
> Consistency of the glitch independent of DAC output is more important than
> its size. A constant amplitude glitch occurring at the dac update rate is
> more benign in its effect than a glitch whose amplitude varies with DAC
>
On Tue, 15 Oct 2019 18:43:29 -0700
Hal Murray wrote:
> You can get a few bits by reducing the tuning range. Suppose you follow the
> DAC with an OpAmp with a gain of 1/8 while the reference is adjustable. That
> adds 3 bits of resolution by decreasing the output range. The downside is
>
On Tue, Oct 15, 2019 at 10:00 PM Hal Murray wrote:
>
>
> You can get a few bits by reducing the tuning range. Suppose you follow
> the
> DAC with an OpAmp with a gain of 1/8 while the reference is adjustable.
> That
> adds 3 bits of resolution by decreasing the output range. The downside is
>
Consistency of the glitch independent of DAC output is more important than its
size. A constant amplitude glitch occurring at the dac update rate is more
benign in its effect than a glitch whose amplitude varies with DAC output.
Brruce
> On 16 October 2019 at 08:02 Attila Kinali wrote:
>
>
>
On Tue, 15 Oct 2019 18:57:30 +0200
Attila Kinali wrote:
> Assuming
> your OCXO has a tuning range of 1ppm (I've seen 0.1 to 20ppm for OCXOs)
> that would mean you have to controll the EFC voltage better than parts in 1e-9
> or 30 bits. Yes, this is kind of unreallistic, but that's what the
Hoi Tobias,
On Mon, 7 Oct 2019 21:06:37 +
Tobias Pluess wrote:
> I am planning to make a new version of my own GPSDO. I have attached the
> schematic of the OCXO and DAC. Because the stability of my previous design
> was not yet optimal, I now chose better components; my main criteria was
-nuts-boun...@lists.febo.com] on behalf of Tom Van Baak
[t...@leapsecond.com]
Sent: Monday, October 14, 2019 18:08
To: time-nuts@lists.febo.com
Subject: Re: [time-nuts] Question for my new GPSDO
Have a look at the TAPR/TICC design as an example how to use the TDC7200
as a timestamping / time interval count
On Mon, Oct 14, 2019 at 12:09 PM Tom Van Baak wrote:
> ...
> One other comment, do read the archive time nuts postings and blog
> entries by Nick Sayer. He did a nice work with an affordable, not
> extremely high-end but open source, GPSDO and that would be useful
> background reading for you.
>
gt; HB9FSX
>
>
>
>
> From: time-nuts [time-nuts-boun...@lists.febo.com] on behalf of Bob kb8tq
> [kb...@n1k.org]
> Sent: Wednesday, October 09, 2019 16:25
> To: Discussion of precise time and frequency measurement
> Subject: Re:
16:25
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Question for my new GPSDO
Hi
Indeed some OCXO’s have VCXO return pins. If you take a look at how they
get used ….hmmm…. the pin doesn’t get used properly. From trying to *get*
designers to use that sort of pin,
Hello: proportional controllers from the Old Country are also available
for around $15 on ebay. The one i have uses type K thermocouple.
Don
On 2019-10-12 18:13, Perry Sandeen via time-nuts wrote:
Yo Bubba Dudes!,
The suggestion was made to use a ebay item number 192112054053 heater
for this
I created a temperature test setup for my TCXOs. Relay control did not last
long because the relay was operating once a second or so and the Peltier
uses a lot of current. The relay contacts welded in a few hours. Luckily I
was watching when it happened. A PID controller running H bridges works a
Yo Bubba Dudes!,
The suggestion was made to use a ebay item number 192112054053 heater for this
project.
Now it's cheap and has a digital reading.
BUT
It is a bang- bang controller using a relay. At some point that relay will
stop working. Also all designs I've seen for good temperature
> From: time-nuts [time-nuts-boun...@lists.febo.com] on behalf of Bob kb8tq
> [kb...@n1k.org]
> Sent: Tuesday, October 08, 2019 17:18
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Question for my new GPSDO
>
> Hi
of Mark Sims
[hol...@hotmail.com]
Sent: Wednesday, October 09, 2019 04:08
To: time-nuts@lists.febo.com
Subject: [time-nuts] Question for my new GPSDO
The BME280 does temperature, humidity, and pressure. They are very nice.
Beware of BME280 boards sold on Ebay, etc. A lot of sellers ship BMP280s
on behalf of Bob kb8tq
[kb...@n1k.org]
Sent: Tuesday, October 08, 2019 17:18
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Question for my new GPSDO
Hi
What is the temperature stability of the OCXO you plan to use? In the case of
open windows, what is th
Hi,
On 2019-10-08 14:35, Tom Van Baak wrote:
> Hi Tobias,
>
> 2) I suspect one can spend a great deal of time picking and testing
> optimal parts in a GPSDO based on tempco specs. But at what point is
> it cheaper to just control the environment of the GPSDO board itself?
>
> You mention opening
The BME280 does temperature, humidity, and pressure. They are very nice.
Beware of BME280 boards sold on Ebay, etc. A lot of sellers ship BMP280s.
One way to tell is the BME280 is in a square package and the BMP280 is more
rectangular.
Also be aware that some BMP/BME280 libraries seem to
Tobias: along the path suggested by TVb, might I suggest something like
a small heater/cooler for your car?
lots at https://www.amazon.com/s?k=car+cooler+6+pak=nb_sb_noss
a simple controller such as
eBay item number:
192112054053
can be applied as well.
and Bob's your uncle.
Don
On
tter of cost than something else. In
> > this case I think I am fine with a DAC8501 or DAC8560, which are both
> based
> > on a resistor string, and therefore are also monotonic by design.
> > >
> > > Tobias
> > >
> > > ___
; Tobias
> >
> > ____
> > From: time-nuts [time-nuts-boun...@lists.febo.com] on behalf of Bruce
> Griffiths [bruce.griffi...@xtra.co.nz]
> > Sent: Tuesday, October 08, 2019 00:19
> > To: Discussion of precise time and frequency m
ists.febo.com] on behalf of Bruce
> Griffiths [bruce.griffi...@xtra.co.nz]
> Sent: Tuesday, October 08, 2019 00:19
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Question for my new GPSDO
>
> Detecting the steep drop in oven heater cu
Another sensor you might consider for measuring ambient temperature is the
LM34 or LM35. These have an analog output calibrated in degrees F for the
LM34 or C for the 35.
They are less expensive than the DS1620 and you can feed the output into a
spare A/D channel. I prefer the LM34 because
Hi Tobias,
Very interesting project you have. Not just that it's a fresh GPSDO, but
interesting because you seem to be taking so much care in the design. A
couple of comments:
1) The need for ultra low tempco is more important if you expect your
GPSDO to be in holdover often; less so if it
ruce.griffi...@xtra.co.nz]
> Sent: Tuesday, October 08, 2019 00:19
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Question for my new GPSDO
>
> Detecting the steep drop in oven heater current when the temperature
> regulator loop assumes cont
]
Sent: Tuesday, October 08, 2019 01:11
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Question for my new GPSDO
Tobias,
You have not shown the rest of your GPSDO, but presumably it includes a
phase detector and processor which implement a phase locked loop
[bruce.griffi...@xtra.co.nz]
Sent: Tuesday, October 08, 2019 00:19
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Question for my new GPSDO
Detecting the steep drop in oven heater current when the temperature regulator
loop assumes control shouldn't require
Tobias,
You have not shown the rest of your GPSDO, but presumably it includes a
phase detector and processor which implement a phase locked loop that
compares the oscillator phase with a 1 pps signal from the GPS.
For open loop VCXO testing, you will certainly need to be concerned with
the
Detecting the steep drop in oven heater current when the temperature regulator
loop assumes control shouldn't require an extremely low tempco sensing resistor.
In principle PWM DACs can offer high resolution at relatively low cost, one
tradeoff being the settling time of the low pass filter
Hi Guys,
I am planning to make a new version of my own GPSDO. I have attached the
schematic of the OCXO and DAC. Because the stability of my previous design was
not yet optimal, I now chose better components; my main criteria was the lowest
tempco I found.
As one can see, I plan to use the
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