[time-nuts] How does one actually do Allan variation graphs?

Bob Camp lists at rtty.us
Mon Nov 15 12:52:50 UTC 2010 

Hi

The only reason the check list is any good is the - gee if I'd checked that I would not have bought this one syndrome ...

------------

The same socketed ROMs on the A that have issues while they are "live" are easier to replace if / when they go bad. 

-------

Many of these counters (any model) spent their life on an external standard. Having an OCXO that's a ppm or two off is not unusual. What you want to watch out for is the one that's 30 or 40 ppm off.

Bob

On Nov 14, 2010, at 11:15 PM, John Miles wrote:

> Bob's checklist is a good one, all right.  It is important to get a solid
> working example because they are quite challenging to troubleshoot and
> calibrate.
> 
> The only problem with the 5370A as far as I'm aware is the reduced
> reliability caused by the larger number of socketed ROM chips.
> 
> It seems that many, if not most, 5370s were used with external 10 MHz
> references.  If you're patient, you can wait for one to show up on eBay with
> a display that is blank except for one bright LED.  Buy it cheap, and flip
> the external-reference switch back to internal-reference mode when you get
> it.  Easy "fix!"
> 
> -- john, KE5FX
> 
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>> Behalf Of paul swed
>> Sent: Sunday, November 14, 2010 8:01 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] How does one actually do Allan variation
>> graphs?
>> 
>> 
>> Really good advice on what to checkout.
>> 5370s are the devil to fix if somethings wrong such as jitter.
>> Good luck.
>> Paul
>> 
>> On Sun, Nov 14, 2010 at 12:40 PM, Bob Camp <lists at rtty.us> wrote:
>> 
>>> Hi
>>> 
>>> Like a lot of stuff, the going price for these has dropped.
>> They get less
>>> and less respect every day ...
>>> 
>>> One thing that may be specific to me - I do not consider a
>> 5370A to be any
>>> more or less valuable than a 5370B. They both do pretty much
>> the same thing.
>>> The 5370B might have fewer hours on it, it might not. On average 5370A
>>> prices seem to run slightly higher than 5370B prices. Why is a
>> mystery to
>>> me.
>>> 
>>> Bob
>>> 
>>> 
>>> On Nov 14, 2010, at 11:57 AM, William H. Fite wrote:
>>> 
>>>> Thanks, Bob
>>>> 
>>>> He's asking $400 but I can tell by the look in his eye that he'll take
>>>> substantially less.
>>>> 
>>>> He's a lousy poker player, too...
>>>> 
>>>> I asked him to turn it on about 0900 this morning and I'm
>> going over in
>>> an
>>>> hour or so to check it out.
>>>> 
>>>> Thanks again,
>>>> 
>>>> Bill
>>>> 
>>>> 
>>>> 
>>>> 
>>>> On Sun, Nov 14, 2010 at 11:44 AM, Bob Camp <lists at rtty.us> wrote:
>>>> 
>>>>> Hi
>>>>> 
>>>>> Assuming:
>>>>> 
>>>>> 1) All the knobs and switches are intact and working
>>>>> 2) All the led's in the display work
>>>>> 3) All the alarm and indicator LED's work
>>>>> 4) The input amps are good
>>>>> 5) All the connectors are intact
>>>>> 6) The OCXO is good / on frequency
>>>>> 7) It passes the diags
>>>>> 8) Jitter is down below 100 ps ( should be below 40)
>>>>> 9) You can check all this out before purchace. Let the beast
>> warm up for
>>> at
>>>>> least an hour before you check it.
>>>>> 
>>>>> Something in the $180 to $260 range is probably fair depending on
>>>>> cosmetics. You might start out at $150 in order to
>> compromise at $200. I
>>>>> certainly would not pay over $300. I know the list sounds a bit long,
>>> but
>>>>> I've seen 5370's with problems in each of those areas. Pretty much
>>> anything
>>>>> damaged / non-functional would knock a pretty good chunk off
>> the price.
>>>>> 
>>>>> Bob
>>>>> 
>>>>> 
>>>>> On Nov 14, 2010, at 11:29 AM, William H. Fite wrote:
>>>>> 
>>>>>> Gentlemen,
>>>>>> 
>>>>>> What is a reasonable price for a 5370A?  Local guy here is trying to
>>> hawk
>>>>>> one to me.  Not cosmetically perfect but fully operational.
>>>>>> 
>>>>>> Yes, I know someone is going to say, "I got one for 50 bucks."  But
>>>>> really,
>>>>>> what is a fair price?
>>>>>> 
>>>>>> Thanks,
>>>>>> 
>>>>>> Bill
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> On Sun, Nov 14, 2010 at 10:48 AM, Magnus Danielson <
>>>>>> magnus at rubidium.dyndns.org> wrote:
>>>>>> 
>>>>>>> On 11/14/2010 09:41 AM, John Miles wrote:
>>>>>>> 
>>>>>>>> 
>>>>>>>> I’ve looked at Wikipedia and I am as lost as when I started.
>>>>>>>>> 
>>>>>>>>> Could someone walk me through the process step by step and also
>>>>>>>>> tell me what test equipment is required?
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>> Besides the pointers at www.leapsecond.com , I've collected a few
>>>>> links
>>>>>>>> at http://www.ke5fx.com/stability.htm that may be helpful.
>>>>>>>> 
>>>>>>>> The first .PDF link on that page is my presentation from the
>>> Microwave
>>>>>>>> Update conference a few weeks ago.  It was meant as an
>> introductory
>>>>>>>> "Stability Measurement for Radio Nuts" talk, discussing
>> the state of
>>>>> the
>>>>>>>> commercial art in light of what's available to hobbyists.
>>>>>>>> 
>>>>>>>> The NIST links under "General timing and noise metrology", in
>>>>> particular
>>>>>>>> this one ( http://tf.nist.gov/general/pdf/2220.pdf ) are
>> excellent.
>>>>>>>> 
>>>>>>>> If you have an HP 5370A/B counter and a GPIB interface
>> you can do a
>>> lot
>>>>> of
>>>>>>>> good measurement work.  With the appropriate software you can make
>>>>>>>> conventional strip-chart style plots of frequency and
>> phase, as well
>>> as
>>>>> ADEV
>>>>>>>> and similar plots.  Unless you are a software nut you
>> probably do not
>>>>> want
>>>>>>>> to homebrew the necessary code to do this.  Most people
>> don't use the
>>>>> same
>>>>>>>> program for acquisition and plotting; a script or batch
>> file does the
>>>>> job of
>>>>>>>> reading the data from the counter and spooling it to a text file,
>>> while
>>>>> a
>>>>>>>> program like Stable32 or Ulrich Bangert's (search on
>> df6jb plotter)
>>>>> renders
>>>>>>>> the graphics.
>>>>>>>> 
>>>>>>>> My own app (TimeLab) is an exception, in that it attempts to do a
>>> good
>>>>> job
>>>>>>>> at both data acquisition and rendering.  It's still under heavy
>>>>>>>> construction.  Right now I'm rewriting all of the acquisition
>>> routines
>>>>> to
>>>>>>>> support, among other things, the use of more than one
>> GPIB counter at
>>>>> once.
>>>>>>>> 
>>>>>>>> Given that you have an HP 5370 available, if you wanted a
>>> walkthrough,
>>>>> you
>>>>>>>> could try something along these lines:
>>>>>>>> 
>>>>>>>> 1) Get an NI or Prologix GPIB adapter, install per manufacturer's
>>>>>>>> guidelines.
>>>>>>>> 
>>>>>>>> 2) Download the current TimeLab beta.  You have two options here:
>>>>>>>>    http://www.ke5fx.com/timelab/setup.exe -- Graphically ugly but
>>>>>>>> better tested
>>>>>>>>    http://www.ke5fx.com/timelab/setup_temp.exe -- Nicer looking,
>>>>> but
>>>>>>>> more likely to have bugs, and some features have yet to be ported
>>> over
>>>>> to
>>>>>>>> the new codebase.  Use this one for the instructions below.
>>>>>>>> 
>>>>>>>> 3) Decide whether you want your HP 5370A/B to run in
>> talk-only mode
>>> or
>>>>>>>> addressable mode and set its DIP switch accordingly.  The software
>>> will
>>>>> work
>>>>>>>> either way since it doesn't actually try to control the
>> counter, but
>>>>> for a
>>>>>>>> 5370 I'd use addressable mode unless you have a reason not to.
>>>>>>>> 
>>>>>>>> 4) Set up a basic frequency measurement to begin with.
>> Feed a 10 MHz
>>>>>>>> signal or whatever into the STOP jack, and hit FREQ and 1s.
>>>>>>>> 
>>>>>>>> 5) In TimeLab, select Acquire->Acquire from HP 5370A/B, and then
>>> select
>>>>>>>> the NI interface or the Prologix interface's COM port
>> from the list.
>>>>> Hit
>>>>>>>> the "Monitor" button and you should start seeing the counter's
>>>>> frequency
>>>>>>>> readings scroll by.  If not, find out why before going
>> any further.
>>>>>>>> 
>>>>>>>> 6) Hit "Start Measurement."  After a few readings have
>> come in, you
>>>>> should
>>>>>>>> see your ADEV plot start to take shape.
>>>>>>>> 
>>>>>>>> 7) Hit the 'f' key to switch to a frequency-difference
>> chart, or the
>>>>> 'p'
>>>>>>>> key for a phase-difference chart.  The 'y' key will
>> toggle the Y-axis
>>>>>>>> between easy-to-read round numbers and full display range.
>>>>>>>> 
>>>>>>>> You can get somewhat cleaner measurements from the 5370 if you use
>>>>>>>> time-interval mode rather than frequency mode, but time-interval
>>>>>>>> measurements require a 1-pps or similar source and some additional
>>>>> setup
>>>>>>>> effort.
>>>>>>>> 
>>>>>>> 
>>>>>>> 0) Essentially whatever source you have (crystal, Rubidium, Cesium,
>>>>> GPSDO)
>>>>>>> unless you haven't done it before, turn it on well in advance. I
>>> prefer
>>>>> days
>>>>>>> over hours. Locked crystals such as Rubidium, Cesium and
>> GPSDOs will
>>>>> cancel
>>>>>>> the last part of the oscillator drift but depending on details
>>>>> performance
>>>>>>> may be more or less compromised by this drift. I think
>> this is one of
>>>>> the
>>>>>>> practical details one should not miss.
>>>>>>> 
>>>>>>> I for one thinks that using a trigger signal such as the
>> PPS or more
>>>>>>> preferably a higher frequency trigger is worthwhile, as
>> you get a more
>>>>>>> stable rate of read-outs. Also, it gives a larger amount
>> of raw data,
>>>>>>> allowing for the increased degrees of freedom and quicker
>> convergence
>>> of
>>>>>>> estimator(s).
>>>>>>> 
>>>>>>> Do use TimeLab, I think it is a great way to get going.
>> It's also fun
>>> to
>>>>>>> see the curve converge as more data comes in...
>>>>>>> 
>>>>>>> Cheers,
>>>>>>> Magnus
>>>>>>> 
>>>>>>> 
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