[time-nuts] Austron 2201, Tbolt, HP 3801 comparison question

paul swed paulswedb at gmail.com
Sat Apr 7 22:45:02 UTC 2012


Thanks everyone for the comments
Paul
WB8TSL

On Sat, Apr 7, 2012 at 7:54 AM, Tom Van Baak <tvb at leapsecond.com> 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" <
> df6jb at ulrich-bangert.de>
> To: "'Discussion of precise time and frequency measurement'" <
> time-nuts at febo.com>
> 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: time-nuts-bounces at febo.com [mailto:time-nuts-bounces@**febo.com<time-nuts-bounces at febo.com>]
>>> 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 <ed_palmer at sasktel.net> 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
>>>
>>
>
>
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