[time-nuts] HP 5087A distribution amplifier
Just a note to say that a HP 5087A distribution amplifier arrived yesterday purchased from a seller on eBay (http://www.ebay.com/itm/300903865292). I initially emailed him requesting the option information on the unit or if he could give information as to what option modules are installed inside. Unfortunately I received a simple reply that he did not have information on either. So, I went ahead anyway and took the chance and purchased one knowing full well that it may have an odd combination of modules (I will say that I am normally not much of a gambler). After pulling the unit out of the box and checking it over, I was surprised to find that it is in nearly new condition sans a couple of small patches of sticker goo on the front panel that quickly went away with goo remover. It virtually has no scratches or dings. Opening the unit up I was more pleased to find that it has option 033 (one 10 MHz input buffer module and 12 - 10 MHz output modules). A perfect buy. Yes, it was a bit pricey and he also takes best offers. If the other remining two are of the same condition as this one and have the same option, it is a nice buy. Greg ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Cheap 1588 cards Was: Re: Net4501
Well you sent me on a search. I know virtually zip about ptp, but this page lists a few ethernet cards that allow time stamping. Is this the same as having a 1588 card? https://github.com/richardcochran/linuxptp-as/blob/master/README.org -Original Message- From: Doug Calvert Sender: time-nuts-boun...@febo.com Date: Fri, 7 Jun 2013 20:58:20 To: Discussion of precise time and frequency measurement Reply-To: Discussion of precise time and frequency measurement Subject: [time-nuts] Cheap 1588 cards Was: Re: Net4501 On Thu, Jun 6, 2013 at 8:48 PM, Bob Camp wrote: > 1588 compatible network cards are capable of time stamping everything > that goes in and out. They are pretty common these days both as stand > alone cards and as peripherals on MCU's. There's no real need to do > hardware, just come up with drivers (and all the other software goop) > to make them work with NTP. More or less the same work you would have > had to do once the FPGA was done and debugged. > > Bob > Can anyone recommend a cheap 1588 compatible card? I just recently saw that the linux kernel PPS support for the cards. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Cheap 1588 cards Was: Re: Net4501
On Thu, Jun 6, 2013 at 8:48 PM, Bob Camp wrote: > 1588 compatible network cards are capable of time stamping everything > that goes in and out. They are pretty common these days both as stand > alone cards and as peripherals on MCU's. There's no real need to do > hardware, just come up with drivers (and all the other software goop) > to make them work with NTP. More or less the same work you would have > had to do once the FPGA was done and debugged. > > Bob > Can anyone recommend a cheap 1588 compatible card? I just recently saw that the linux kernel PPS support for the cards. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Have 10 MHz need 19.2 MHz
On 07.06.2013 19:23, Perry Sandeen wrote: List, Another hardware possibility. Double the 10 MHz to 20 MHz. With another circuit of 74HC390’s divide 10 MHz to 200 KHz. Then double it twice to 800 KHz with LM 1496 DBM’s. Apply the two frequencies to a LM 1496 DBM and use a LPF to get the 19.2 MHz. Hardware complicated? A bit. Only a bit? Only the filter to rejetct the products that you will have spreaded in all places, spaced 200kHz, and mainly to remove the 20.8 MHz spurious that you will have as a result of the last mixing, makes this approach difficult. I would favour a PLL, and since for the application, short-term stability seems unrelevant, even using a conventional VCO and not a crystal would be enough. A 74HC4046 can reach 19.2MHz, and you only need a couple of dividers to get a 200kHz reference to feed it. However one doesn’t have to search for a microprocessor that you program and may not be available in a couple of years. The IC’s are cheap and have been and will be around forever. The LM1496 was discontinued long ago it was a second source of the MC1496 (that is in production). But never think it will be around forever (yes, as a hobbyist, surely you can find a single piece forever, more if price does not matter too much). Also, I'm not a bit fan of PICs, quite the contrary, but for example the PIC16F84 has been available from more that 16yr and it is on production... so following your LM1496 criteria, will be available forever :) IMHO sometimes an older *brute force* circuit proves that more can be less in implementing what you desire to accomplish. Brute force is usually brute :) Regards, Javier Regards, Perrier ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Have 10 MHz need 19.2 MHz
Since the actual crystal frequency appears to be 19.2 MHz rather than 19.5, my original suggestion of injection locking it would have to be modified. For example, you could divide the 10 MHz by 25 ( a single 74HC390 could do it) to make 400 kHz, so 19.2 MHz could sync to the 48th harmonic. Ed ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Have 10 MHz need 19.2 MHz
I'm glad I asked this question. I was hoping to get ideas I'd never think of. It's going to be hard to beat that TI PLL chip especially because TI offers free samples. The injection idea seems almost like cheating. I might use part of the idea below to divide down 10MHz then inject that into the 19.2 crystal and let the crystal itself do the rest. On Fri, Jun 7, 2013 at 10:23 AM, Perry Sandeen wrote: > List, > > > Another hardware possibility. > > Double the 10 MHz to 20 MHz. > > With another circuit of 74HC390’s divide 10 MHz to > 200 KHz. Then double it twice to 800 KHz > with LM 1496 DBM’s. Apply the two > frequencies to a LM 1496 DBM and use a LPF to get the 19.2 MHz. > > Hardware complicated? A bit. However one doesn’t have to search for a > microprocessor that you program > and may not be available in a couple of years. The IC’s are cheap and > have been and will be around forever. > > IMHO sometimes an older *brute force* circuit > proves that more can be less in implementing what you desire to accomplish. > > Regards, > > Perrier > > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Have 10 MHz need 19.2 MHz
List, Another hardware possibility. Double the 10 MHz to 20 MHz. With another circuit of 74HC390’s divide 10 MHz to 200 KHz. Then double it twice to 800 KHz with LM 1496 DBM’s. Apply the two frequencies to a LM 1496 DBM and use a LPF to get the 19.2 MHz. Hardware complicated? A bit. However one doesn’t have to search for a microprocessor that you program and may not be available in a couple of years. The IC’s are cheap and have been and will be around forever. IMHO sometimes an older *brute force* circuit proves that more can be less in implementing what you desire to accomplish. Regards, Perrier ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Net4501
Hi All of the MCU based 1588 interfaces I have seen allow you to "get at" the internal 1588 stamping clock. You can stuff your pps in there and compare it directly to the stamps it puts on the incoming and outgoing packets. If you are on an MCU, the 1588 clock can easily be the same as your CPU clock (or at least derived from the same source). Stamping with the 1588 counter in that case is no different than stamping with the cpu clock. Doing the same thing on a pc is a bit more complex. If you can get at the stamping inputs and outputs, it's another layer, but still doable. Bob Get the free running 1588 counter 1 pps output to agree with your local clock output. On Jun 7, 2013, at 12:16 AM, Chris Albertson wrote: > Network time stamping is a different issue. You are thinking of time > transfer over a network. What the above is about is capture the pulse per > second from a GPS. We actually do NOT want to time stamp the PPS. We > want to capture the computer's internal clock so that it can be compared to > the PPS. The purpose is to adjust that internal clock. > > Then one this is none is some set of stratum 1 NTP server, then you can > transfer the time over Ethernet. > > > On Thu, Jun 6, 2013 at 5:48 PM, Bob Camp wrote: > >> Hi >> >> 1588 compatible network cards are capable of time stamping everything that >> goes in and out. They are pretty common these days both as stand alone >> cards and as peripherals on MCU's. There's no real need to do hardware, >> just come up with drivers (and all the other software goop) to make them >> work with NTP. More or less the same work you would have had to do once the >> FPGA was done and debugged. >> >> Bob >> >> On Jun 6, 2013, at 8:32 PM, Ralph Smith wrote: >> >>> On Jun 6, 2013, at 1:59 AM, Chris Albertson >> wrote: >>> Yes, that is exactly what I meant by "remove the temperature issue" >> that means using a clock derived from a laboratory standard like GPS >> disciplined OCXO or a rubidium oscillator. Once you do this the next bottle next is the uncertainty in the interrupt latency and the granularity of the >> clock that is being sampled. So practically you are limited to about >> microsecond level performance. >>> >>> The Net4501 is capable of about 1/8 microsecond performance, the >> limiting factor here is clock granularity. >>> I think to get better than that you need to eliminate the interrupt and have some kind of deterministic hardware where the PPS directly samples >> the counter. Perhaps hosting NTP on a soft CPU inside an FPGA, then you >> could implement the PPS interrupt in gates rather then in software. I've not read of anyone doing this yet. >>> >>> If you look at PHK's code in FreeBSD this is what is done. The PPS >> signal gates the timer, so no interrupt is involved in the time stamp >> precision. But yes, it would be interesting to do something on a FPGA. >> Unfortunately I wouldn't be able to get to anything like that myself in >> this lifetime. >>> >>> Ralph >>> ___ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > > > -- > > Chris Albertson > Redondo Beach, California > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Net4501
On 06/07/2013 02:48 AM, Bob Camp wrote: Hi 1588 compatible network cards are capable of time stamping everything that goes in and out. They are pretty common these days both as stand alone cards and as peripherals on MCU's. There's no real need to do hardware, just come up with drivers (and all the other software goop) to make them work with NTP. More or less the same work you would have had to do once the FPGA was done and debugged. The ntp.org NTP daemon also have some support for such timestamping, using the socket option(s) as provided by the kernel. I have not tried it myself, but seen traces of support throughout Linux and NTP. Should not be too hard to get the pieces together and actually try it. NTP isn't all software timestamps anymore. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
