[time-nuts] time-nuts Digest, Vol 45, Issue 55
Ronald Held
ronaldheld at gmail.com
Fri Apr 25 10:30:48 EDT 2008
On 4/25/08, time-nuts-request at febo.com <time-nuts-request at febo.com> wrote:
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> Today's Topics:
>
> 1. Re: GSyncQ GPS Evalution Kits && NTPns (Bruce Griffiths)
> 2. Re: Disciplining Rubidium (Bruce Griffiths)
> 3. Re: GSyncQ GPS Evalution Kits && NTPns ( Pekka Niemel? )
> 4. Re: GSyncQ GPS Evalution Kits && NTPns (Bruce Griffiths)
> 5. Re: GSyncQ GPS Evalution Kits && NTPns (Bruce Griffiths)
> 6. Re: GSyncQ GPS Evalution Kits && NTPns (Didier Juges)
> 7. Re: GSyncQ GPS Evalution Kits && NTPns (Bruce Griffiths)
> 8. RS485/422/232 Chip (Don Bradbury)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 25 Apr 2008 20:12:22 +1200
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] GSyncQ GPS Evalution Kits && NTPns
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <48119266.2000203 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Pekka Niemel? wrote:
> > Hi, and thanks for your replies PHK and Bruce,
> >
> >
> >
> > Yes, I'm looking for a Quatech card from a Finnish dealer. So, I need the 2
> > serial port version of the card to get everything I need? I'm not sure how
> > and what should be fed to the rs-422 connector, can't I use a rs-232c from
> > the computer run through a max232? Sorry for asking these stupid questions,
> > but I'm kindof out of luck. Synergy says they have something called Deutsch
> > connectors from the antenna and receiver. I'm not familiar with this kind of
> > connector. Synergy says there is a rs-422 connector, do they provide
> > something like a adapter which will turn the Deutsch thing into a RS-422
> > connector and separate wires for 1PPS and apparently a second power source?
> >
> > I'm thrilled that NTPns will work with this setup. :)
> >
> > warm regards,
> > P. Niemel?
> >
> >
> Pekka
>
> If you want, you can easily construct your own external RS422 to RS232
> transceiver.
> Just use a Max 232 to convert the RS232 signals to TTL/CMOS and connect
> RS422 receiver and transmitter chips to that.
> RS 485 transceivers chips can also be used instead of RS422 transmitters
> and receivers, just connect them as drivers or receivers as required.
> If you need a circuit schematic I can send you one.
>
> Novatel also use Deutsch connectors on some of their enclosures.
>
> Bruce
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Fri, 25 Apr 2008 20:36:38 +1200
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] Disciplining Rubidium
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <48119816.80702 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Said
> SAIDJACK at aol.com wrote:
> > Hi Bruce,
> >
> > the 1ns performance per second was mentioned by someone else in the previous
> > threads.
> >
> > When you lock a BVA OCXO to carrier phase, I would still expect the PLL loop
> > time constant to be >>20s, thus the 8E-014 / 2s you mentioned is very likely
> > the performance of the BVA Crystal, not likely the carrier phase real-time
> > system output.
> >
> More complete specs are:
> 8E-14 @ 1 sec
> 8E-14 @ 10 sec
> 2E-13 @ 100 sec
> 5E-13 @ 1000 sec
> 4E-14 @ 10,000 sec
> 1E-14 @ 1 day
>
> Loop time constant is probably somewhere around 1000 sec or so.
>
> >
> > For example, our Fury with double oven has an ADEV of a couple of parts per
> > E-012 1s to 20s, but that performance is entirely generated by the OCXO, not
> > the M12+.
> >
> > I would expect the carrier phase to improve things at the point where the
> > BVA starts having a rising ADEV. Maybe around a couple 100s? If for example the
> > phase comparator has 1ps resolution (that's really quite a high resolution)
> > to compare the OCXO and carrier phases (1E-012) then it would take >12s
> > averaging intervals in the PLL just to prevent the measurement errors from
> > affecting the system performance above 8E-014.
> >
> > It's late, and I may just be wrong about all this.
> >
> > bye,
> > Said
> >
> Yes the carrier phase measurement resolution is very high (typically 1/4000 of a ~635ps L1 carrier period) however the measurement noise is around 20ps the oscillator performance is so good in comparison a very large time constant is used.
>
> However if one had an OCXO whose performance ADEV was around 1E-11 for tau from 1 to 100 sec or so then a much shorter time constant would be appropriate.
>
> When the GPS receiver LO is phase locked to the OCXO, the GPS receiver has all the hardware necessary to do the phase comparisons using either via code phase or carrier phase methods.
>
> The following Chinese implementation appears to use a commercial receiver, they just replaced its crystal oscillator:
>
> http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/19/30540/01408297.pdf?arnumber=1408297
>
>
> They also use a neural net for modeling prediction of atmospheric delays.
>
>
> Perhaps the ultimate is to implement a custom GPS receiver (apart from the RF front end and ADC) in a large FPGA.
> One could then use L1, L2C, L5 etc plus the Galileo signals when they become available.
>
> Bruce
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Fri, 25 Apr 2008 12:47:13 +0300
> From: " Pekka Niemel? " <pniemel at gmail.com>
> Subject: Re: [time-nuts] GSyncQ GPS Evalution Kits && NTPns
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Message-ID:
> <4f0fb16b0804250247x542de252o42a5e17897354b4a at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Hi Bruce, thanks for bearing with me. :)
>
> On 4/25/08, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> >
> >
> > Pekka
> >
> > If you want, you can easily construct your own external RS422 to RS232
> > transceiver.
> > Just use a Max 232 to convert the RS232 signals to TTL/CMOS and connect
> > RS422 receiver and transmitter chips to that.
> > RS 485 transceivers chips can also be used instead of RS422 transmitters
> > and receivers, just connect them as drivers or receivers as required.
> > If you need a circuit schematic I can send you one.
>
>
> Hmm, if you would have schematics that would be really great. Can I download
> them from somewhere? I'm not 100% that I understand what you're saying, but
> I guess the schematics talk more than thousand words. :)
>
> The other option is ofcourse to just buy the transciever. But even in that
> case I would need to drop the voltage with the max 232? That is, the 1PPS
> signal that we drive into the Soekris?
>
>
> Novatel also use Deutsch connectors on some of their enclosures.
>
>
> Hmm, so it's an industry standard? Wikipedia doesn't know anything about it.
> Strange.
>
> warm regards,
> P. Niemel?
>
>
> Bruce
> >
> >
> >
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at febo.com
> > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
>
>
> ------------------------------
>
> Message: 4
> Date: Fri, 25 Apr 2008 22:06:58 +1200
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] GSyncQ GPS Evalution Kits && NTPns
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <4811AD42.6060409 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Pekka Niemel? wrote:
> > Hi Bruce, thanks for bearing with me. :)
> >
> > On 4/25/08, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> >
> >> Pekka
> >>
> >> If you want, you can easily construct your own external RS422 to RS232
> >> transceiver.
> >> Just use a Max 232 to convert the RS232 signals to TTL/CMOS and connect
> >> RS422 receiver and transmitter chips to that.
> >> RS 485 transceivers chips can also be used instead of RS422 transmitters
> >> and receivers, just connect them as drivers or receivers as required.
> >> If you need a circuit schematic I can send you one.
> >>
> >
> >
> > Hmm, if you would have schematics that would be really great. Can I download
> > them from somewhere? I'm not 100% that I understand what you're saying, but
> > I guess the schematics talk more than thousand words. :)
> >
> >
> I need to create them first, I can then place them with my collection of
> circuits, references etc on Didier's site:
> http://www.eds-fl.com/~bruce/ <http://www.eds-fl.com/%7Ebruce/>
>
> Should be ready by 1200 UTC.
>
> What I am really saying is that if one uses a few chips on a circuit
> board one can just connect the GPS cable to the 2 RS422 receivers and RS
> 422 transmitters on the card.
> A Soekris serial port would then connect to the RS232 transceiver chip.
> The TTL/CMOS signals from the 2nd RS422 chip would connect to the
> appropriate Soekris header pin so you can use the higher resolution timer.
>
> No plug in RS422 card is then required.
>
> Remember of course that the RS422 signal is differential and the cable
> pair associated with each RS 422 signal has to be terminated in in the
> correct characteristic impedance at the receiver (~100 ohms).
>
> Can you buy components from Farnell or RS components these appear to be
> good sources for some parts of Europe (for Germany at least)?
> If so I can easily check the availability of the required parts.
> > The other option is ofcourse to just buy the transciever. But even in that
> > case I would need to drop the voltage with the max 232? That is, the 1PPS
> > signal that we drive into the Soekris?
> >
> >
> > Novatel also use Deutsch connectors on some of their enclosures.
> >
> >
> > Hmm, so it's an industry standard? Wikipedia doesn't know anything about it.
> > Strange.
> >
> > warm regards,
> > P. Niemel?
> >
> >
> > Bruce
> >
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Fri, 25 Apr 2008 23:58:15 +1200
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] GSyncQ GPS Evalution Kits && NTPns
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <4811C757.90905 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Pekka
>
> Circuit schematic now at:
> http://www.eds-fl.com/~bruce/GPS_RS232_RS422_Transceiver.html
> <http://www.eds-fl.com/%7Ebruce/GPS_RS232_RS422_Transceiver.html>
>
> Bruce
>
>
>
> ------------------------------
>
> Message: 6
> Date: Fri, 25 Apr 2008 07:01:55 -0500
> From: "Didier Juges" <didier at cox.net>
> Subject: Re: [time-nuts] GSyncQ GPS Evalution Kits && NTPns
> To: "'Discussion of precise time and frequency measurement'"
> <time-nuts at febo.com>
> Message-ID: <021a01c8a6cc$287737a0$0a01a8c0 at didierhp>
> Content-Type: text/plain; charset="windows-1250"
>
> One issue with RS-485 is that the Tx and Rx lines are shared and the driver
> chip has to be told which direction it is supposed to work. This is usually
> done in the serial driver code using one of the modem control lines. I am
> not sure if the NTP code provides that signal. If that signal is not
> available, you can use a 555 timer to turn the driver around when it is done
> transmitting. Of course, if data flows in only one direction (I do not see
> why the PC should talk to the GPS receiver for an NTP application, but there
> may be good reasons for that), you can simply tie the driver so that it
> works in that direction only.
>
> In a pinch, I have made a RS-485 (one pair Rx/Tx) to RS-232 bi-directional
> "converter" with only 3 resistors... I would not pretend it is good
> engineering practice, but it works over a few feet (very useful for a quick
> verification) and it requires the software in the PC being able to get back
> what it sends without throwing its arms up in the air (the human equivalent
> of an exception)... I use that "solution" for a project I am working on
> right now, and it is nice not to have to carry a bunch of cables/wall warts
> and assorted hardware when I carry my project from work to home back and
> forth every day.
>
> http://www.ko4bb.com/Test_Equipment/RS-485_Converter.jpg
>
> On that schematic, the right side connector would be the standard serial
> connector of a PC. When the RS-485 driver is in the receive mode, it
> receives data on the inverting input through the 1k resistor and the other
> input is biased to a fixed DC level with the other two resistors. When the
> RS-485 driver is talking, it swamps the 1k resistor and drives the Rx pin of
> the RS-232 connector directly.
>
> Didier KO4BB
>
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com
> > [mailto:time-nuts-bounces at febo.com] On Behalf Of Bruce Griffiths
> > Sent: Friday, April 25, 2008 3:12 AM
> > To: Discussion of precise time and frequency measurement
> > Subject: Re: [time-nuts] GSyncQ GPS Evalution Kits && NTPns
> >
> > Pekka
> >
> > If you want, you can easily construct your own external RS422
> > to RS232 transceiver.
> > Just use a Max 232 to convert the RS232 signals to TTL/CMOS
> > and connect
> > RS422 receiver and transmitter chips to that.
> > RS 485 transceivers chips can also be used instead of RS422
> > transmitters and receivers, just connect them as drivers or
> > receivers as required.
> > If you need a circuit schematic I can send you one.
> >
> > Novatel also use Deutsch connectors on some of their enclosures.
> >
> > Bruce
> >
>
> Internal Virus Database is out-of-date.
> Checked by AVG.
> Version: 7.5.519 / Virus Database: 269.22.5/1358 - Release Date: 4/3/2008
> 6:36 PM
>
>
>
>
>
> ------------------------------
>
> Message: 7
> Date: Sat, 26 Apr 2008 00:16:46 +1200
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] GSyncQ GPS Evalution Kits && NTPns
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <4811CBAE.5070508 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Didier Juges wrote:
> > One issue with RS-485 is that the Tx and Rx lines are shared and the driver
> > chip has to be told which direction it is supposed to work. This is usually
> > done in the serial driver code using one of the modem control lines. I am
> > not sure if the NTP code provides that signal. If that signal is not
> > available, you can use a 555 timer to turn the driver around when it is done
> > transmitting. Of course, if data flows in only one direction (I do not see
> > why the PC should talk to the GPS receiver for an NTP application, but there
> > may be good reasons for that), you can simply tie the driver so that it
> > works in that direction only.
> >
> > In a pinch, I have made a RS-485 (one pair Rx/Tx) to RS-232 bi-directional
> > "converter" with only 3 resistors... I would not pretend it is good
> > engineering practice, but it works over a few feet (very useful for a quick
> > verification) and it requires the software in the PC being able to get back
> > what it sends without throwing its arms up in the air (the human equivalent
> > of an exception)... I use that "solution" for a project I am working on
> > right now, and it is nice not to have to carry a bunch of cables/wall warts
> > and assorted hardware when I carry my project from work to home back and
> > forth every day.
> >
> > http://www.ko4bb.com/Test_Equipment/RS-485_Converter.jpg
> >
> > On that schematic, the right side connector would be the standard serial
> > connector of a PC. When the RS-485 driver is in the receive mode, it
> > receives data on the inverting input through the 1k resistor and the other
> > input is biased to a fixed DC level with the other two resistors. When the
> > RS-485 driver is talking, it swamps the 1k resistor and drives the Rx pin of
> > the RS-232 connector directly.
> >
> > Didier KO4BB
> >
> >
> Didier
>
> Look at the new circuit I've just added to the miscellaneous section.
> I've just used the RS485 drivers not the RS485 standard.
>
> The GPS receiver actually uses dedicated RS422 transmit, PPS, and
> receive pairs.
> I've merely used RS485 transceiver chips for convenience and their
> higher current drive capability.
> The RS485 transceiver signal levels are RS422 compatible.
>
> Bruce
>
>
>
>
> ------------------------------
>
> Message: 8
> Date: Fri, 25 Apr 2008 23:17:27 +1000
> From: "Don Bradbury" <vk3yv at netspace.net.au>
> Subject: [time-nuts] RS485/422/232 Chip
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Message-ID: <000801c8a6d6$b5dfbbd0$0301010a at your6516987ce9>
> Content-Type: text/plain; charset="iso-8859-1"
>
> The MAXIM MAX3162E will do RS485/422 and RS232 in the one chip , get samples from maxim.com.
> Don VK3YV....
>
> ------------------------------
>
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> End of time-nuts Digest, Vol 45, Issue 55
> *****************************************
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