Thanks everyone for the comments Paul WB8TSL On Sat, Apr 7, 2012 at 7:54 AM, Tom Van Baak <[email protected]> wrote:
> Hi Ulrich, > > I want to re-iterate how difficult it is to compare one make of GPSDO > with another. A lot depends on antenna, and software configuration, > environmental controls, and the particular OCXO that you happen to > get with the unit. You can see significant difference in N TBolts; you > can see significant differences in N HP Smartclock's. > > I don't believe there's anything magic about the hp Smartclock. The > main goal back then was to reduce the effects of S/A. Maybe that > was clever 15 years ago, but S/A hasn't been around for a decade. > > In order to investigate the Smartclock algorithms in detail it would > be possible to replace their algorithm with your own. That is, take > a 58503 or Z3801 and keep the Oncore, keep the OCXO, keep > the DAC, keep the p.s., but insert your own TIC and your own > PC-based disciplining algorithm. FYI: here's info on their DAC: > http://leapsecond.com/pages/**z3801a-efc/<http://leapsecond.com/pages/z3801a-efc/> > > If without too much effort you match HP's performance, then there > is no magic in Smartclock. In other words, the performance they > get is mostly the Oncore and the 10811 and a decent TIC & DAC > and nothing extraordinary about the software. > > On the other hand, if after weeks of work HP still beats your best > effort, then I would agree there's something clever and hidden in > their implementation. > > Realize that the HP Smartclock was one of the very first GPSDO. > Since then there have been tens (hundreds?) of different GPSDO > products, both commercial and amateur. It's really hard for me to > believe that any stone has been left unturned. > > Still, I welcome anyone who wants to test the Smartclock algorithm > as suggested above. If you have the time but not the Smartclock, > let me know and I'll make a loaner available. > > Thanks, > /tvb > > ----- Original Message ----- From: "Ulrich Bangert" < > [email protected]> > To: "'Discussion of precise time and frequency measurement'" < > [email protected]> > Sent: Saturday, April 07, 2012 3:13 AM > Subject: Re: [time-nuts] Austron 2201, Tbolt, HP 3801 comparison question > > > > Gents, >> >> one of the things that MAY be responsible for the differences in >> performance >> is that the Z3801 uses HP's Smartclock technology while the TBolt does >> not. >> The TBolt works with a fixed set of parameters (unless we change them) >> which's default values are far from optimal but ensure a fast lock of the >> pll. The Smartclock in difference seems to be able to adapt regulation >> parameters to its "measurements" of ocxo stability and long term drift. >> Unfortunately there are only a very limited number of publications >> available >> about Smartclock technology with most of them only scratching the surface. >> That is why I believe that HP & Agilent still make a big secret out of it >> even today. I guess we time nuts could learn a lot if we had an in depth >> description available on how Smartclock works. >> >> Best regards >> Ulrich Bangert >> >>> -----Ursprungliche Nachricht----- >>> Von: [email protected] >>> [mailto:time-nuts-bounces@**febo.com<[email protected]>] >>> Im Auftrag von paul swed >>> Gesendet: Samstag, 7. April 2012 02:09 >>> An: Discussion of precise time and frequency measurement >>> Betreff: Re: [time-nuts] Austron 2201, Tbolt, HP 3801 comparison question >>> >>> >>> A lot of great comments. >>> Hope I do not drop any responses. >>> I am sure its older also it was $135 and picked it up recently. Have to >>> say for the $ its actually quite fine and I am happy. >>> >>> I have had the 3801 at least 10 years now. Picked it up early on and did >>> some of the original tinkering and reverse engineering. So perhaps is does >>> have the better oven. I m looking at what the 38xx software program says >>> its doing at the numbers match the 2201 very nicely. So beginning to >>> believe that what the 2201 says may be pretty accurate.. >>> >>> Tom asked if someone was going to make down converters. I might believe >>> that I was involved in those threads. But it would have been attempt to >>> make. Not produce. I have produced 2 main approaches with a number of other >>> sub approaches. They do not emulate the RF down converter but are dependent >>> on older less integrated receivers. The key is being able to get to the >>> signals. >>> >>> First version >>> Used the odetics antenna and then up converting the 35.42 to 75.42 Mhz. >>> Easy to say harder to implement then imagined. plus building a 10 Mhz to 40 >>> Mhz multiplier. though this all worked for a year I don't think many could >>> reproduce it. >>> >>> Second most recent approach thats really working very well. >>> A novatel starview 2 receiever provided by another Time-nut. The G2015 >>> chips quite a jewel. Its made by zarlink now for $7.50. Any how it produces >>> a 40 Mhz clock and has nice filtering and such for the 35 Mhz. Mix them and >>> you are in business. Though I had been using active mixers with mixed >>> results. (Pun) I went brute force a week or so ago using a minicircuits >>> SRA1 type mixer. Boy does that work nicely in fact every things rock solid. >>> No muss no fuss. Thats the right kind of design. The hardest part of this >>> effor is attaching the IF wire and 2 wires for the pecl 40 Mhz clock. Right >>> about at my limits for soldering. >>> >>> So I do believe the 2201s are really quite a good receiver. There are >>> numbers of tricks to actually getting them going. But after all the work I >>> do believe worth it. I have made an offer for a second antenna-less unit. >>> Considering my first was $5 I am offering more then that. But not going >>> crazy either such as the silly prices I see on e... for a faulted unit. >>> >>> Hope every things covered and thanks. >>> regards >>> Paul >>> WB8TSL >>> >>> >>> >>> >>> On Fri, Apr 6, 2012 at 5:43 PM, Ed Palmer <[email protected]> wrote: >>> >>> > Hi Paul, >>> > >>> > I'm sure you've followed the discussions in the past on Tbolt > >>> performance tuning. Have you jumped through all the appropriate > hoops? >>> Things like precision survey, autotune the oscillator > parameters, good >>> antenna visibility, mask angle, etc. come to mind. > Having said that, >>> I've found that my Z3801A performs somewhat better > than my Tbolt. For >>> example, the 1 PPS out of my Tbolt has a Standard > Deviation of ~ 550 ps >>> and a max-min range of ~ 4 ns. My Z3801A is > ~200ps and ~2 ns. so call it >>> twice as good. >>> > >>> > FYI, my best GPSDO is a Z3817A with a Standard Deviation of < 100 ps > >>> and a max-min range of < 1 ns. That one has an E1938 oscillator. >>> > >>> > Ed >>> > >>> > >>> > >>> > On 4/6/2012 2:24 PM, paul swed wrote: >>> > >>> >> Recently I put a 2201 back into service with a home brew down >> >>> converter. I am a bit surprised that when I use it to measure the >> Tbolt >>> and then the HP 3801. The 3801 comes out always better by a >> decade >>> actually. Granted what I am seeing is way down below a e-12th >> and in >>> fact what I am reading seems nuts to me. >>> >> But can a 3801 run that much better then the Tbolt? >>> >> I kind of thought they would both be in the same region. >>> >> Thanks >>> >> Regards >>> >> Paul >>> >> WB8TSL >>> >> > > > ______________________________**_________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
