Re: [time-nuts] TAPR TICC boxed

[Bruce Griffiths]

Attempting sub nanosecond timing with an actual 1Mohm source is an exercise in 
futility. There are very few cases where one would want to attempt precision 
timing measurements with such a high impedance source. The 1M pulldown on the 
TICC input is merely intended to maintain a valid logic input should the user 
leave that input disconnected. In actual use with PPS signals the source 
impedance is in most cases a few tens of ohms. If one wishes to have a 1Mohm 
input impedance for use with AC coupled signals then a low noise FET input 
buffer preceding the comparator is required.

Protection diodes in this application not only need to have low leakage,  they 
also need to turn on and off fast enough to be useful.

The propagation delay dispersion (both vs common mode and vs overdrive) also 
need to be considered along with the comparator jitter.


Bruce

> 
>  and overdrive (both vs overdrive and vs input common modeOn 01 April 
> 2017 at 15:34 Scott Stobbe  wrote:
> 
> Fwiw, for a precision comparator you'll probably want a bipolar front end
> for a lower flicker corner and better offset stability over cmos. For
> high-speeds the diffpair is going to be biased fairly rich for bandwidth.
> So you will more than likey have input bias currents of 100's of nA to uA
> on your comparator. Which is not great with a 1 megohm source.
> 
> On Fri, Mar 31, 2017 at 9:08 PM Charles Steinmetz 
> wrote:
> 
> > > 
> > Mark wrote:
> > 
> > > > > 
> > > I thought about using the clamp diodes as protection but was 
> > > a bit
> > > worried about power supply noise leaking through the diodes 
> > > and adding some
> > > jitter to the input signals...
> > > 
> > > > > 
> > It is a definite worry even with a low-noise, 50 ohm input, and a
> > potential disaster with a 1Mohm input. Common signal diodes (1N4148,
> > 1N914, 1N916, 1N4448, etc.) are specified for 5-10nA of reverse 
> > current.
> > Even a low-leakage signal diode (e.g., 1N3595) typically has several
> > hundred pA of leakage. Note that the concern isn't just power supply
> > noise -- the leakage current itself is quite noisy.
> > 
> > For low-picoamp diodes at a decent price, I use either (1) the B-C 
> > diode
> > of a small-signal BJT, or (2) the gate diode of a small-geometry 
> > JFET.
> > A 2N5550 makes a good high-voltage, low-leakage diode with leakage
> > current of ~30pA. Small signal HF transistors like the MPSH10 and
> > 2N5179 (and their SMD and PN variants) are good for ~5pA, while the 
> > gate
> > diode of a PN4417A JFET (or SMD variant) has reverse leakage 
> > current of
> > ~1pA (achieving this in practice requires a very clean board and 
> > good
> > layout).
> > 
> > I posted some actual leakage test results to Didier's site, which 
> > can be
> > downloaded at
> > <
> > 
> > http://www.ko4bb.com/getsimple/index.php?id=download&file=03_App_Notes_-_Proceedings/Reverse_leakage_of_diode-connected_BJTs_and_FETs_measurement_results.pdf
> >  
> > http://www.ko4bb.com/getsimple/index.php?id=download&file=03_App_Notes_-_Proceedings/Reverse_leakage_of_diode-connected_BJTs_and_FETs_measurement_results.pdf
> > 
> > > > > 
> > > .
> > > This document shows the connections I used to obtain the data.
> > > 
> > > The TICC doesn't have the resolution for it to matter or 
> > > justify a
> > > HP5370 or better quality front end. I'll probably go with a 
> > > fast
> > > comparator to implement the variable threshold input.
> > > 
> > > > > 
> > Properly applied, a fast comparator will have lower jitter than the 
> > rest
> > of the errors, and is an excellent choice. Bruce suggested the 
> > LTC6752,
> > which is a great part if you need high toggle speeds (100s of MHz) 
> > or
> > ultra-fast edges. But you don't need high toggle rates and may not 
> > need
> > ultra-fast edges. Repeatability and stability are more important 
> > than
> > raw speed in this application. The LT1719, LT1720, or TLV3501 may 
> > work
> > just as well for your purpose, and they are significantly less 
> > fussy to
> > apply.
> > 
> > Note that the LTC6752 series is an improved replacement for the 
> > ADCMP60x
> > series, which itself is an improved replacement for the MAX999. Of
> > these three, the LTC6752 is the clear winner in my tests. If you do
> > choose it (or similar), make sure you look at the transitions with
> > something that will honestly show you any chatter at frequencies up 
> > to
> > at least several GHz. It only takes a little transition chatter to
> > knock the potential timing resolution of the ultra-fast comparator 

Re: [time-nuts] TAPR TICC boxed

[Scott Stobbe]

Also for interest the 53131a schematic is available at
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/HP/53131.pdf

HP used a low input bias current bjt opamp, the Lt1008 to bias/dc servo a
custom JFET buffer driving an AD96687 comparator.

On Fri, Mar 31, 2017 at 10:34 PM Scott Stobbe 
wrote:

> Fwiw, for a precision comparator you'll probably want a bipolar front end
> for a lower flicker corner and better offset stability over cmos. For
> high-speeds the diffpair is going to be biased fairly rich for bandwidth.
> So you will more than likey have input bias currents of 100's of nA to uA
> on your comparator. Which is not great with a 1 megohm source.
>
> On Fri, Mar 31, 2017 at 9:08 PM Charles Steinmetz 
> wrote:
>
> Mark wrote:
>
> > I thought about using the clamp diodes as protection but was a bit
> worried about power supply noise leaking through the diodes and adding some
> jitter to the input signals...
>
> It is a definite worry even with a low-noise, 50 ohm input, and a
> potential disaster with a 1Mohm input.  Common signal diodes (1N4148,
> 1N914, 1N916, 1N4448, etc.) are specified for 5-10nA of reverse current.
>   Even a low-leakage signal diode (e.g., 1N3595) typically has several
> hundred pA of leakage.  Note that the concern isn't just power supply
> noise -- the leakage current itself is quite noisy.
>
> For low-picoamp diodes at a decent price, I use either (1) the B-C diode
> of a small-signal BJT, or (2) the gate diode of a small-geometry JFET.
> A 2N5550 makes a good high-voltage, low-leakage diode with leakage
> current of ~30pA.  Small signal HF transistors like the MPSH10 and
> 2N5179 (and their SMD and PN variants) are good for ~5pA, while the gate
> diode of a PN4417A JFET (or SMD variant) has reverse leakage current of
> ~1pA (achieving this in practice requires a very clean board and good
> layout).
>
> I posted some actual leakage test results to Didier's site, which can be
> downloaded at
> <
> http://www.ko4bb.com/getsimple/index.php?id=download&file=03_App_Notes_-_Proceedings/Reverse_leakage_of_diode-connected_BJTs_and_FETs_measurement_results.pdf
> >.
>   This document shows the connections I used to obtain the data.
>
> > The TICC doesn't have the resolution for it to matter or justify a
> HP5370 or better quality front end.   I'll probably go with a fast
> comparator to implement the variable threshold input.
>
> Properly applied, a fast comparator will have lower jitter than the rest
> of the errors, and is an excellent choice.  Bruce suggested the LTC6752,
> which is a great part if you need high toggle speeds (100s of MHz) or
> ultra-fast edges.  But you don't need high toggle rates and may not need
> ultra-fast edges.  Repeatability and stability are more important than
> raw speed in this application.  The LT1719, LT1720, or TLV3501 may work
> just as well for your purpose, and they are significantly less fussy to
> apply.
>
> Note that the LTC6752 series is an improved replacement for the ADCMP60x
> series, which itself is an improved replacement for the MAX999.  Of
> these three, the LTC6752 is the clear winner in my tests.  If you do
> choose it (or similar), make sure you look at the transitions with
> something that will honestly show you any chatter at frequencies up to
> at least several GHz.  It only takes a little transition chatter to
> knock the potential timing resolution of the ultra-fast comparator way
> down.  Do make sure to test it with the slowest input edges you need it
> to handle.
>
> Best regards,
>
> Charles
>
>
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Re: [time-nuts] TAPR TICC boxed

[Charles Steinmetz]

Mark wrote:


I thought about using the clamp diodes as protection but was a bit worried 
about power supply noise leaking through the diodes and adding some jitter to 
the input signals...


It is a definite worry even with a low-noise, 50 ohm input, and a 
potential disaster with a 1Mohm input.  Common signal diodes (1N4148, 
1N914, 1N916, 1N4448, etc.) are specified for 5-10nA of reverse current. 
 Even a low-leakage signal diode (e.g., 1N3595) typically has several 
hundred pA of leakage.  Note that the concern isn't just power supply 
noise -- the leakage current itself is quite noisy.


For low-picoamp diodes at a decent price, I use either (1) the B-C diode 
of a small-signal BJT, or (2) the gate diode of a small-geometry JFET. 
A 2N5550 makes a good high-voltage, low-leakage diode with leakage 
current of ~30pA.  Small signal HF transistors like the MPSH10 and 
2N5179 (and their SMD and PN variants) are good for ~5pA, while the gate 
diode of a PN4417A JFET (or SMD variant) has reverse leakage current of 
~1pA (achieving this in practice requires a very clean board and good 
layout).


I posted some actual leakage test results to Didier's site, which can be 
downloaded at 
. 
 This document shows the connections I used to obtain the data.



The TICC doesn't have the resolution for it to matter or justify a HP5370 or 
better quality front end.   I'll probably go with a fast comparator to 
implement the variable threshold input.


Properly applied, a fast comparator will have lower jitter than the rest 
of the errors, and is an excellent choice.  Bruce suggested the LTC6752, 
which is a great part if you need high toggle speeds (100s of MHz) or 
ultra-fast edges.  But you don't need high toggle rates and may not need 
ultra-fast edges.  Repeatability and stability are more important than 
raw speed in this application.  The LT1719, LT1720, or TLV3501 may work 
just as well for your purpose, and they are significantly less fussy to 
apply.


Note that the LTC6752 series is an improved replacement for the ADCMP60x 
series, which itself is an improved replacement for the MAX999.  Of 
these three, the LTC6752 is the clear winner in my tests.  If you do 
choose it (or similar), make sure you look at the transitions with 
something that will honestly show you any chatter at frequencies up to 
at least several GHz.  It only takes a little transition chatter to 
knock the potential timing resolution of the ultra-fast comparator way 
down.  Do make sure to test it with the slowest input edges you need it 
to handle.


Best regards,

Charles


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Re: [time-nuts] TAPR TICC boxed

[Scott Stobbe]

Fwiw, for a precision comparator you'll probably want a bipolar front end
for a lower flicker corner and better offset stability over cmos. For
high-speeds the diffpair is going to be biased fairly rich for bandwidth.
So you will more than likey have input bias currents of 100's of nA to uA
on your comparator. Which is not great with a 1 megohm source.

On Fri, Mar 31, 2017 at 9:08 PM Charles Steinmetz 
wrote:

> Mark wrote:
>
> > I thought about using the clamp diodes as protection but was a bit
> worried about power supply noise leaking through the diodes and adding some
> jitter to the input signals...
>
> It is a definite worry even with a low-noise, 50 ohm input, and a
> potential disaster with a 1Mohm input.  Common signal diodes (1N4148,
> 1N914, 1N916, 1N4448, etc.) are specified for 5-10nA of reverse current.
>   Even a low-leakage signal diode (e.g., 1N3595) typically has several
> hundred pA of leakage.  Note that the concern isn't just power supply
> noise -- the leakage current itself is quite noisy.
>
> For low-picoamp diodes at a decent price, I use either (1) the B-C diode
> of a small-signal BJT, or (2) the gate diode of a small-geometry JFET.
> A 2N5550 makes a good high-voltage, low-leakage diode with leakage
> current of ~30pA.  Small signal HF transistors like the MPSH10 and
> 2N5179 (and their SMD and PN variants) are good for ~5pA, while the gate
> diode of a PN4417A JFET (or SMD variant) has reverse leakage current of
> ~1pA (achieving this in practice requires a very clean board and good
> layout).
>
> I posted some actual leakage test results to Didier's site, which can be
> downloaded at
> <
> http://www.ko4bb.com/getsimple/index.php?id=download&file=03_App_Notes_-_Proceedings/Reverse_leakage_of_diode-connected_BJTs_and_FETs_measurement_results.pdf
> >.
>   This document shows the connections I used to obtain the data.
>
> > The TICC doesn't have the resolution for it to matter or justify a
> HP5370 or better quality front end.   I'll probably go with a fast
> comparator to implement the variable threshold input.
>
> Properly applied, a fast comparator will have lower jitter than the rest
> of the errors, and is an excellent choice.  Bruce suggested the LTC6752,
> which is a great part if you need high toggle speeds (100s of MHz) or
> ultra-fast edges.  But you don't need high toggle rates and may not need
> ultra-fast edges.  Repeatability and stability are more important than
> raw speed in this application.  The LT1719, LT1720, or TLV3501 may work
> just as well for your purpose, and they are significantly less fussy to
> apply.
>
> Note that the LTC6752 series is an improved replacement for the ADCMP60x
> series, which itself is an improved replacement for the MAX999.  Of
> these three, the LTC6752 is the clear winner in my tests.  If you do
> choose it (or similar), make sure you look at the transitions with
> something that will honestly show you any chatter at frequencies up to
> at least several GHz.  It only takes a little transition chatter to
> knock the potential timing resolution of the ultra-fast comparator way
> down.  Do make sure to test it with the slowest input edges you need it
> to handle.
>
> Best regards,
>
> Charles
>
>
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> and follow the instructions there.
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Re: [time-nuts] TAPR TICC boxed

[Alex Pummer]

FJH1100
Ultra Low Leakage Diode

Alex


On 3/31/2017 6:00 PM, Charles Steinmetz wrote:

Mark wrote:

I thought about using the clamp diodes as protection but was a bit 
worried about power supply noise leaking through the diodes and 
adding some jitter to the input signals...


It is a definite worry even with a low-noise, 50 ohm input, and a 
potential disaster with a 1Mohm input.  Common signal diodes (1N4148, 
1N914, 1N916, 1N4448, etc.) are specified for 5-10nA of reverse 
current.  Even a low-leakage signal diode (e.g., 1N3595) typically has 
several hundred pA of leakage.  Note that the concern isn't just power 
supply noise -- the leakage current itself is quite noisy.


For low-picoamp diodes at a decent price, I use either (1) the B-C 
diode of a small-signal BJT, or (2) the gate diode of a small-geometry 
JFET. A 2N5550 makes a good high-voltage, low-leakage diode with 
leakage current of ~30pA.  Small signal HF transistors like the MPSH10 
and 2N5179 (and their SMD and PN variants) are good for ~5pA, while 
the gate diode of a PN4417A JFET (or SMD variant) has reverse leakage 
current of ~1pA (achieving this in practice requires a very clean 
board and good layout).


I posted some actual leakage test results to Didier's site, which can 
be downloaded at 
. 
 This document shows the connections I used to obtain the data.


The TICC doesn't have the resolution for it to matter or justify a 
HP5370 or better quality front end. I'll probably go with a fast 
comparator to implement the variable threshold input.


Properly applied, a fast comparator will have lower jitter than the 
rest of the errors, and is an excellent choice.  Bruce suggested the 
LTC6752, which is a great part if you need high toggle speeds (100s of 
MHz) or ultra-fast edges.  But you don't need high toggle rates and 
may not need ultra-fast edges. Repeatability and stability are more 
important than raw speed in this application.  The LT1719, LT1720, or 
TLV3501 may work just as well for your purpose, and they are 
significantly less fussy to apply.


Note that the LTC6752 series is an improved replacement for the 
ADCMP60x series, which itself is an improved replacement for the 
MAX999.  Of these three, the LTC6752 is the clear winner in my tests.  
If you do choose it (or similar), make sure you look at the 
transitions with something that will honestly show you any chatter at 
frequencies up to at least several GHz.  It only takes a little 
transition chatter to knock the potential timing resolution of the 
ultra-fast comparator way down.  Do make sure to test it with the 
slowest input edges you need it to handle.


Best regards,

Charles


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-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.8012 / Virus Database: 4769/14211 - Release Date: 
03/31/17


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Re: [time-nuts] GPS first LO need to be locked?

[Bob kb8tq]

Hi


There are a lot of GPS chips that do an I/Q mix down to a low IF. It’s then 
(re) sampled from there. The “LO” in this case would down convert to the low IF 
….

Bob

> On Mar 31, 2017, at 6:08 PM, Magnus Danielson  
> wrote:
> 
> God natt Attila,
> 
> On 03/31/2017 11:29 PM, Attila Kinali wrote:
>> God kväll Magnus,
>> 
>> On Fri, 31 Mar 2017 21:19:00 +0200
>> Magnus Danielson  wrote:
>> 
>>> Still fills the function of LO, as the sample and hold operates as a
>>> mixer and the fold-down can be seen as an overtone mix followed by a
>>> sampling of the mix product, so well, it's about the same thing.
>> 
>> "Harmonic mixer" is the word you are looking for :-)
> 
> Not necessarily. It could be a locked oscillator too.
> Harmonic mixer is another way to go.
> 
> Cheers,
> Magnus
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Re: [time-nuts] GPS first LO need to be locked?

[Magnus Danielson]

God natt Attila,

On 03/31/2017 11:29 PM, Attila Kinali wrote:

God kväll Magnus,

On Fri, 31 Mar 2017 21:19:00 +0200
Magnus Danielson  wrote:


Still fills the function of LO, as the sample and hold operates as a
mixer and the fold-down can be seen as an overtone mix followed by a
sampling of the mix product, so well, it's about the same thing.


"Harmonic mixer" is the word you are looking for :-)


Not necessarily. It could be a locked oscillator too.
Harmonic mixer is another way to go.

Cheers,
Magnus
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Re: [time-nuts] GPS first LO need to be locked?

[Attila Kinali]

God kväll Magnus,

On Fri, 31 Mar 2017 21:19:00 +0200
Magnus Danielson  wrote:

> Still fills the function of LO, as the sample and hold operates as a 
> mixer and the fold-down can be seen as an overtone mix followed by a 
> sampling of the mix product, so well, it's about the same thing.

"Harmonic mixer" is the word you are looking for :-)

Attila Kinali

-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
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Re: [time-nuts] more of a time distribution question

[Bob Darlington]

I'm happy to run a group buy for just the 8736.My last quote from the
vendor was just a bit under $27 each, and that does not come with the board
connector.  I picked these boards for compatibility with Motorola
footprint, but also because it doesn't insist on goofy 3.0 volt power and
logic levels for communication.   It's happy with and rated for 3.3 volts
which is desirable.

I'll start a new thread for a group buy with details once I get a fresh
quote from the vendor.

-Bob
N3XKB

On Fri, Mar 31, 2017 at 12:45 PM, Bob Camp  wrote:

> Hi
>
> The 8736 is a very nice part. I think some sort of group buy would be a
> good idea.
>
> Bob
>
> Sent from my iPhone
>
> > On Mar 31, 2017, at 12:14 PM, Bob Darlington 
> wrote:
> >
> > I guess it's time for me to finish up that NTP cape for the BeagleBone.
> > I'm using a Furuno GT-8736 ( http://www.furuno.com/en/
> > products/gnss-module/GT-8736 )
> >
> > I built up a prototype about two years ago but... got married very
> shortly
> > after that and haven't played with it since.
> >
> > Is there any interest in something like this?   As with past group buys,
> I
> > never charge a penny of profit and sell at cost.   I want to say the
> brand
> > new GT-8736 boards are $26 a pop (my cost) from the vendor.
> >
> > Is there a better board from Furuno for timing applications?
> >
> > -Bob
> > N3XKB
> >
> > On Fri, Mar 31, 2017 at 1:03 AM, David J Taylor <
> > david-tay...@blueyonder.co.uk> wrote:
> >
> >> From: Hal Murray
> >>
> >> That should work.  I haven't found a GPS with PPS for the beaglebone.
> What
> >> level of accuracy do you want?  If you only need 100 ms or so, then a
> >> normal
> >> junk GPS (no PPS) on USB should work.
> >> ==
> >>
> >> This works with the BeagleBone:
> >>
> >> https://www.adafruit.com/product/746
> >>
> >> Cheers,
> >> David
> >> --
> >> SatSignal Software - Quality software written to your requirements
> >> Web: http://www.satsignal.eu
> >> Email: david-tay...@blueyonder.co.uk
> >> Twitter: @gm8arv
> >> ___
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> >> ailman/listinfo/time-nuts
> >> and follow the instructions there.
> >>
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[time-nuts] HP 5090A Frequency Standard manual available

[GandalfG8--- via time-nuts]

I've just uploaded a pdf version of the HP 5090A Ops and Service manual to  
Didier's site at.
 
http://www.ko4bb.com
 
For now at least it's also available at
 
https://www.mediafire.com/?u0bf1eips89uo3h
 
The 5090A was an HP product designed in the UK in the early  1960s and was 
an off air frequency standard intended for use with the  BBC Droitwich 
broadcast service when it was broadcasting on 200KHz.
 
If anyone has a copy of the 5090B manual they'd be willing to scan and  
share that would be very much appreciated, the A and B versions of the  5090 
are quite different.
 
Nigel
GM8PZR
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Re: [time-nuts] GPS first LO need to be locked?

[Magnus Danielson]

Hi Jim,

On 03/31/2017 01:07 AM, jimlux wrote:

BTW a lot of GPS receivers don't have a "first LO".. they are more like
a Tuned RF receiver - an input BPF for L1, L2, or L5, then direct
sampling at around 30-40 MHz -  something that makes the GPS signals
alias down somewhere convenient (and always have positive frequency
offset from zero, even at max negative Doppler)


Still fills the function of LO, as the sample and hold operates as a 
mixer and the fold-down can be seen as an overtone mix followed by a 
sampling of the mix product, so well, it's about the same thing.


Cheers,
Magnus
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Re: [time-nuts] more of a time distribution question

[Bob Camp]

Hi

The 8736 is a very nice part. I think some sort of group buy would be a good 
idea. 

Bob

Sent from my iPhone

> On Mar 31, 2017, at 12:14 PM, Bob Darlington  wrote:
> 
> I guess it's time for me to finish up that NTP cape for the BeagleBone.
> I'm using a Furuno GT-8736 ( http://www.furuno.com/en/
> products/gnss-module/GT-8736 )
> 
> I built up a prototype about two years ago but... got married very shortly
> after that and haven't played with it since.
> 
> Is there any interest in something like this?   As with past group buys, I
> never charge a penny of profit and sell at cost.   I want to say the brand
> new GT-8736 boards are $26 a pop (my cost) from the vendor.
> 
> Is there a better board from Furuno for timing applications?
> 
> -Bob
> N3XKB
> 
> On Fri, Mar 31, 2017 at 1:03 AM, David J Taylor <
> david-tay...@blueyonder.co.uk> wrote:
> 
>> From: Hal Murray
>> 
>> That should work.  I haven't found a GPS with PPS for the beaglebone.  What
>> level of accuracy do you want?  If you only need 100 ms or so, then a
>> normal
>> junk GPS (no PPS) on USB should work.
>> ==
>> 
>> This works with the BeagleBone:
>> 
>> https://www.adafruit.com/product/746
>> 
>> Cheers,
>> David
>> --
>> SatSignal Software - Quality software written to your requirements
>> Web: http://www.satsignal.eu
>> Email: david-tay...@blueyonder.co.uk
>> Twitter: @gm8arv
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
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>> ailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
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Re: [time-nuts] GPS first LO need to be locked?

[Magnus Danielson]

Hi,

On 03/30/2017 03:46 PM, paul swed wrote:

I am curious if the first local oscillator on a GPS receiver must actually
be locked or coherent to the reference oscillator in the GPS receiver
typically running at some 10 MHz approximately. Or as long as the first LO
is quite stable it doesn't matter because the receiver can track the code.
This is a question for very classic receivers like Austrons, Odetics etc.
Discreet. Modern fully integrated receivers are not in question.
Thank you for your insights.


If you only do a code receiver, you can do this, but the carrier 
tracking will need to compensate the LO. This is naturally possible, but 
some of the precision will be lost. You can play some tricks to average 
this from the channels and sort things out.


If you want to do a carrier phase receiver, you would suffer too much, 
then you would need to lock the LO to get the gain.


For old receivers, I'd just assume the LO is locked, as it saves 
compensation tricks later, which would save computation cycles.

However, there where some crude receivers back in the days.

Cheers,
Magnus
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[time-nuts] TAPR TICC boxed

[Mark Sims]

I thought about using the clamp diodes as protection but was a bit worried 
about power supply noise leaking through the diodes and adding some jitter to 
the input signals...  I'm probably just being paranoid.  The TICC doesn't have 
the resolution for it to matter or justify a HP5370 or better quality front 
end.   I'll probably go with a fast comparator to implement the variable 
threshold input.

-

> As protection circuit I have used a 51ohm  from the front panel input to the 
> TICC input than two diodes one from TICC input to gnd , other from TICC input 
> to +5V.
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Re: [time-nuts] GPS first LO need to be locked?

[David C. Partridge]

links [2] and [3] give 404 errors

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Attila Kinali
Sent: 31 March 2017 12:35
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS first LO need to be locked?

 [2] "A Prototyping Platform for Multi-Frequency GNSS Receivers", by Akos, Ene 
and Thor, 2003 
http://waas.stanford.edu/~wwu/papers/gps/PDF/AkosIONGPS033FreqRX.pdf

[3] "Design of a GPS and Galileo Multi-Frequency Front-End", by Parada, 
Chastellain, Botteron, Tawk, Farine, 2009 
http://202.194.20.8/proc/VTC09Spring/DATA/04-04-01.PDF


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Re: [time-nuts] more of a time distribution question

[Bob Darlington]

I guess it's time for me to finish up that NTP cape for the BeagleBone.
I'm using a Furuno GT-8736 ( http://www.furuno.com/en/
products/gnss-module/GT-8736 )

I built up a prototype about two years ago but... got married very shortly
after that and haven't played with it since.

Is there any interest in something like this?   As with past group buys, I
never charge a penny of profit and sell at cost.   I want to say the brand
new GT-8736 boards are $26 a pop (my cost) from the vendor.

Is there a better board from Furuno for timing applications?

-Bob
N3XKB

On Fri, Mar 31, 2017 at 1:03 AM, David J Taylor <
david-tay...@blueyonder.co.uk> wrote:

> From: Hal Murray
>
> That should work.  I haven't found a GPS with PPS for the beaglebone.  What
> level of accuracy do you want?  If you only need 100 ms or so, then a
> normal
> junk GPS (no PPS) on USB should work.
> ==
>
> This works with the BeagleBone:
>
>  https://www.adafruit.com/product/746
>
> Cheers,
> David
> --
> SatSignal Software - Quality software written to your requirements
> Web: http://www.satsignal.eu
> Email: david-tay...@blueyonder.co.uk
> Twitter: @gm8arv
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/m
> ailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] GPS first LO need to be locked?

[jimlux]

On 3/31/17 4:35 AM, Attila Kinali wrote:

On Thu, 30 Mar 2017 20:00:31 -0700
Peter Monta  wrote:


BTW a lot of GPS receivers don't have a "first LO".. they are more like a

Tuned RF receiver - an input BPF for L1, L2, or L5, then direct sampling at
around 30-40 MHz -  something that makes the GPS signals alias down
somewhere convenient (and always have positive frequency offset from zero,
even at max negative Doppler)




True.  I've been wanting to try this with an FPGA transceiver; even the
cheap ones go to 6 Gb/s now, but binary only.  The newest transceivers
support PAM-4, which would be great, but they're not affordable yet.  Also
that's a lot of gain at one frequency.


I guess you know of [1] already?

Alternatively, instead of using a MAX2021, you can use a discrete
mixer and use the high analog bandwidth of todays ADCs to use them
as downmixers. [2] and [3] describe how to do this in detail.

The epitome of this is using direct sampling of the signals without
previous downmixing (e.g. [4]). Though I have no idea how easy or hard that
is with todays electronics. It will definitely need good preselection
filters to keep SNR high.



Our space GPS receiver flying on SCaN Testbed/ISS is a direct sampling 
at 38 MHz. Filters are nothing special as I recall.  A chain of 
amplifiers with filters - Lots of gain into the thresholders, so good 
layout is important.


https://trs.jpl.nasa.gov/handle/2014/41781

https://trs.jpl.nasa.gov/bitstream/handle/2014/41781/11-0046.pdf?sequence=1&isAllowed=y




Attila Kinali

[1] http://www.aholme.co.uk/GPS/Main.htm

[2] "A Prototyping Platform for Multi-Frequency GNSS Receivers",
by Akos, Ene and Thor, 2003
http://waas.stanford.edu/~wwu/papers/gps/PDF/AkosIONGPS033FreqRX.pdf

[3] "Design of a GPS and Galileo Multi-Frequency Front-End",
by Parada, Chastellain, Botteron, Tawk, Farine, 2009
http://202.194.20.8/proc/VTC09Spring/DATA/04-04-01.PDF

[4] "Design and Implementation of a Direct Digitization GPS Receiver Front End",
by Akos, and Tsui, 1996



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Re: [time-nuts] GPS first LO need to be locked?

[Attila Kinali]

On Thu, 30 Mar 2017 19:56:31 -0400
Bob kb8tq  wrote:

> > Doppler is pretty big when the spacecraft is coming or going at the 
> > horizon, about 5 kHz (out of 1.5 GHz, so 4-5 ppm).
> > Relatively speaking, GPS satellites are moving slowly (a few km/s)
> > 
> 
> So somewhere in the baseband processor code somebody said “we’ll handle +/- 5 
> KHz”. If your LO is < (say) 500 Hz it’s still inside the likely doppler 
> handling range. 
> 
> If you want to do carrier phase then maybe you want to get a bit fancier ….

You have a carrier PLL anyways. What we call "carrier phase" is just
using the information from that subsystem to get a better estimate
for the time differences.

Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] GPS first LO need to be locked?

[Attila Kinali]

On Thu, 30 Mar 2017 20:00:31 -0700
Peter Monta  wrote:

> > BTW a lot of GPS receivers don't have a "first LO".. they are more like a
> >> Tuned RF receiver - an input BPF for L1, L2, or L5, then direct sampling at
> >> around 30-40 MHz -  something that makes the GPS signals alias down
> >> somewhere convenient (and always have positive frequency offset from zero,
> >> even at max negative Doppler)
> >
> >
> True.  I've been wanting to try this with an FPGA transceiver; even the
> cheap ones go to 6 Gb/s now, but binary only.  The newest transceivers
> support PAM-4, which would be great, but they're not affordable yet.  Also
> that's a lot of gain at one frequency.

I guess you know of [1] already?

Alternatively, instead of using a MAX2021, you can use a discrete
mixer and use the high analog bandwidth of todays ADCs to use them
as downmixers. [2] and [3] describe how to do this in detail.

The epitome of this is using direct sampling of the signals without
previous downmixing (e.g. [4]). Though I have no idea how easy or hard that
is with todays electronics. It will definitely need good preselection
filters to keep SNR high.

Attila Kinali

[1] http://www.aholme.co.uk/GPS/Main.htm

[2] "A Prototyping Platform for Multi-Frequency GNSS Receivers",
by Akos, Ene and Thor, 2003
http://waas.stanford.edu/~wwu/papers/gps/PDF/AkosIONGPS033FreqRX.pdf

[3] "Design of a GPS and Galileo Multi-Frequency Front-End",
by Parada, Chastellain, Botteron, Tawk, Farine, 2009
http://202.194.20.8/proc/VTC09Spring/DATA/04-04-01.PDF

[4] "Design and Implementation of a Direct Digitization GPS Receiver Front End",
by Akos, and Tsui, 1996

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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[time-nuts] TAPR TICC boxed

[Mark Sims]

(this might be a duplicate post...  the last time I sent this, the message 
bounced)

What did you do for input protection?

I want to build an input system for the TICC that incorporates some input 
protection, switchable terminator,  possibly  settable threshold and edge 
selects, and a switchable PICDIV divider like the TADD-2 Mini.  That would 
allow inputs of <1 .. 100 (or maybe up to 1000) PPS and  1/5/10/15 MHz inputs.

The main problem I'm having is coming up with an input squarer circuit that is 
simple and cheap but can handle basically DC-15 MHz.  Anybody got any ideas?
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Re: [time-nuts] more of a time distribution question

[David J Taylor]

From: Hal Murray

That should work.  I haven't found a GPS with PPS for the beaglebone.  What
level of accuracy do you want?  If you only need 100 ms or so, then a normal
junk GPS (no PPS) on USB should work.
==

This works with the BeagleBone:

 https://www.adafruit.com/product/746

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 


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Re: [time-nuts] TAPR Oncore M12+ kit

[Art Sepin]

Norm and Bob,

The M12+ GPS receivers mounted on the motherboard are indeed the timing units. 
Chapter 5 of the Motorola M12+ User's Guide is here:
http://www.synergy-gps.com/images/stories/guides/m12+userguide.pdf
The binary commands and output messages, including timing related commands, are 
in Chapter 5 starting on page 59.

The M12+ timing receiver can also be used for navigation applications - simply 
don't use the Position Hold mode. The main difference between the M12+ 
navigation receivers and the M12+ timing versions is that the navigation boards 
have a faster TTFF.

Motorola didn't refer to the M12+ timing version as "M12+T" That designation 
was used by Synergy, and others, to clearly differentiate the timing version 
from its navigation counterpart.

We recently forwarded information to TAPR on where to purchase front and rear 
end plates for the housing and also dimensional information on the hole sizes 
and locations. Until that info is available from the TAPR.ORG web site, we'll 
be happy to forward that information to anyone interested off list.

Art Sepin
 


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Norm n3ykf
Sent: Thursday, March 30, 2017 8:11 AM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] TAPR Oncore M12+ kit

Bob,

Couldn't find a part number on the .jpg of the gps rx to to cross reference. 
Have a few +T's. Don't need another timing rx. Would take a few positioning 
rx's as the M12+ units are good for balloon launches.
Reads out >65535ft.

See top comment.

Norm n3ykf

On Thu, Mar 30, 2017 at 7:33 AM, Bob kb8tq  wrote:
> Hi
>
> At least from a quick read of the TAPR page it’s not real clear if the GPS 
> modules are M12+T or just M12+ boards. I believe that if they don’t have the 
> T on the end, they don’t have sawtooth / PPS (?).
>
> Bob
>
>> On Mar 30, 2017, at 2:11 AM, Mike Cook  wrote:
>>
>> I would like to add mention of the M12+ interface board that Tom Wimmenhove 
>> offered on this list. I am using them to lock PRS10s. Very happy with it.
>> Here is a link to some of his performance measurements. < 
>> https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Ftomwi
>> mmenhove.com%2Fotherstuff%2FOncore%2F&data=01%7C01%7Cart%40synergy-gp
>> s.com%7C66da3e2206114ff5dd4d08d47785fbd8%7Cc81f9fdec0e04d8c95779afaa0
>> cad9ed%7C1&sdata=nPeS%2B%2F4n9wz9ySHtYGu45yfpDpUWkE8C1NvAj%2FZ5Pug%3D
>> &reserved=0 >
>>
>>> Le 28 mars 2017 à 20:47, Gregory Beat  a écrit :
>>>
>>> Larry -
>>>
>>> Interface Boards for Motorola (and Garmin) receivers have been discussed 
>>> (and sold) by TAPR since late 1990s.  TAPR archives all of this 
>>> documentation, for discontinued GPS kits, can be seen on the left margin.
>>> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww
>>> .tapr.org%2Fgps_exp-kit.html&data=01%7C01%7Cart%40synergy-gps.com%7C
>>> 66da3e2206114ff5dd4d08d47785fbd8%7Cc81f9fdec0e04d8c95779afaa0cad9ed%
>>> 7C1&sdata=sdfgbaFtA%2FQMThFy1V4ZOtmTsABU1GMPosgXSixusvs%3D&reserved=
>>> 0
>>>
>>> Tom Clark, W3IWI Total Accurate Clock (TAC) project (1996) covers the 
>>> entire topic.
>>> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww
>>> .tapr.org%2Fkits_tac2.html&data=01%7C01%7Cart%40synergy-gps.com%7C66
>>> da3e2206114ff5dd4d08d47785fbd8%7Cc81f9fdec0e04d8c95779afaa0cad9ed%7C
>>> 1&sdata=SI%2FiUk0o0cZMXc8FYUxbnfXlgNG9pUKeLHuLM2gE%2F4w%3D&reserved=
>>> 0
>>>
>>> Simple interface board schematics (Serial Level converters, and voltage 
>>> adjustments for external antennas/ 3.3 or 5 V) can be found throughout the 
>>> Internet since mid-1990s.
>>> Numerous radio amateurs DIY their own (breadboard) or sold small interfaces 
>>> at hamfests (1996-2006), until newer GPS solutions became surplus (and 
>>> smartphones with built-in GPS appeared after 2007).
>>>
>>> Doug McKinney, KC3RL (SK, December 2006) offered interface boards for the 
>>> Garmin (GPS-25) and Motorola receivers until about 2005.  I have one of 
>>> Doug's boards in my GPS parts box.  These were sold by TAPR until their 
>>> inventory was exhausted.
>>> --
>>> Garmin
>>> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww
>>> .tapr.org%2Fgps_garminib.html&data=01%7C01%7Cart%40synergy-gps.com%7
>>> C66da3e2206114ff5dd4d08d47785fbd8%7Cc81f9fdec0e04d8c95779afaa0cad9ed
>>> %7C1&sdata=Lp1MR2jjmusu9vBJKJwIaGFPinECe9yfPBV1qvPszSw%3D&reserved=0
>>> Motorola
>>> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww
>>> .tapr.org%2Fgps_vpib.html&data=01%7C01%7Cart%40synergy-gps.com%7C66d
>>> a3e2206114ff5dd4d08d47785fbd8%7Cc81f9fdec0e04d8c95779afaa0cad9ed%7C1
>>> &sdata=O1OXhJqYA2s9uYBkRIGxvQdqqWfZ0Q7oE1troYDasnM%3D&reserved=0
>>>
>>> Synergy M12-MB board (web link to photo [jpg] below) IF you look 
>>> closely at the Synergy Board, you see the board outline and 2x5 
>>> (10-pin) header for the earlier 8-channel Motorola receivers
>>> https://na01.safelinks.protection.outlook.com

Re: [time-nuts] TAPR TICC boxed

[timeok]

   As protection circuit I have used a 51ohm  from the front panel input to the 
TICC input than two diodes one from TICC input to gnd , other from TICC input 
to +5V. A swichable 51ohm from front panel input to gnd allow to have 1M or 50 
ohm as input impedance.
   The front panel leds are drived from 2N3904 transistors connected to:
   A14 for the channel A
   A15 for the channel B
   PPS for reference 10MHZ (close to the pic divider)
   PW1 for the TX data (a 2N3906 instead 04 is used as not inverting function)
   Luciano
   www.timeok.it


   Da "time-nuts" time-nuts-boun...@febo.com
   A "time-nuts@febo.com" time-nuts@febo.com
   Cc
   Data Thu, 30 Mar 2017 20:15:09 +
   Oggetto [time-nuts] TAPR TICC boxed
   What did you do for input protection?

   I want to build an input system for the TICC that incorporates some input 
protection, switchable terminator, possibly settable threshold and edge 
selects, and a switchable PICDIV divider like the TADD-2 Mini. That would allow 
inputs of <1 .. 100 (or maybe up to 1000) PPS and 1/5/10/15 MHz inputs.

   The main problem I'm having is coming up with an input squarer circuit that 
is simple and cheap but can handle basically DC-15 MHz. Anybody got any ideas?
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