[time-nuts] HP Z3801 RB fun
paul swed
paulswedb at gmail.com
Fri Dec 30 15:42:02 UTC 2016
Magnus
Good afternoon. I am having a hard time following this. Conflicting data I
believe..
Using the FRS-C because its the clearest. On page 3-14 it says +/- 1E-9 for
5V (5V is later in the book) Wouldn't that be 2E-9th for 5V?
The 10811 is far more difficult to pin down as several articles from TVB
and others say the 10811 actually has a wider control range then the
standard. Something like 10 Hz over 10V. Traditional is 1 Hz over 10 V. But
as I say seems to be different answers depending on what you read.
When these details are settled you then came up with the need for a gain of
8. Did you use a rule of thumb?
Thanks
Paul
WB8TSL
On Fri, Dec 30, 2016 at 9:06 AM, Magnus Danielson <magnus at rubidium.se>
wrote:
> I think the numbers given for 10811 sensitivity was grossly incorrect from
> the source I had, so it should be +/- 1E-6 for +/- 5V, thus giving 2E-6
> over 10V thus giving a sensitivity of 2E-7/V. Compare to 4E-10/V fro the
> FRS-C and just redo the work.
>
> I thought the numbers where funny but too tired to do extensive digging,
> but I just wanted to show the general idea.
>
> Cheers,
> Magnus
>
>
> On 12/30/2016 04:05 AM, paul swed wrote:
>
>> Been interesting.
>> Did increase the gain to 8 and remove the attenuation 10:1 needed for
>> the piezo ocxo. Not sure I would say the system locks but it certainly
>> slows the drift down to 10ns/30 minutes. I also added an offset after
>> the amplifier. This allowed the Z3801 EFC to set its range more towards
>> 50%.
>> Though the FRS manual says the range is 0-5V for EFC the FRS is clearly
>> offset with age to the +1.7V for center. (The other FRS was +.6V)
>>
>> Its interesting to see at the startup of the Z3801 the EFC range in the
>> RB. Nice steps down towards a fairly low angle line according to Lady
>> Heather.
>>
>> Have had to stop the experimentation late today to give a hand to a
>> fellow on a HP 70-110GHz signal source. Till today I was a 10 GHz sort
>> of guy.
>> Regards
>> Paul
>> WB8TSL
>>
>>
>>
>> On Wed, Dec 28, 2016 at 6:51 PM, Magnus Danielson
>> <magnus at rubidium.dyndns.org <mailto:magnus at rubidium.dyndns.org>> wrote:
>>
>> Hi,
>>
>> Well, that was the data I was able to find (and I referred to TvBs
>> page where I found it). If you have more accurate data, please share
>> so we can get the numbers right.
>>
>> The Z3801A will do a least square estimate of frequency error and then
>> translate that into an initial DAC setting assuming it knows the EFC
>> sensitivity, and the loop will work out the rest from there
>> (hopefully).
>> Getting EFC in the right neighborhood is probably wise for this
>> reason.
>>
>> Cheers,
>> Magnus
>>
>>
>> On 12/29/2016 12:32 AM, Bob Camp wrote:
>>
>> Hi
>>
>> Ummm ….. errrrr ….
>>
>> The 10811 that is used in the Z3801 has a *larger* electrical
>> tuning range than the standard
>> 10811 not a smaller one. It’s tuning range and the TBolt OCXO’s
>> tuning range are
>> very similar.
>>
>> Bob
>>
>> On Dec 28, 2016, at 6:22 PM, Magnus Danielson
>> <magnus at rubidium.dyndns.org
>> <mailto:magnus at rubidium.dyndns.org>> wrote:
>>
>> Paul,
>>
>> We just want to help you with that curiosity, it sounds like
>> a fun little project. :)
>>
>> The FRS-C [1] has a range of +/- 1E-9 over 0-5V, so EFC
>> sensitivity is 4E-10/V.
>>
>> The Z3801A has a range of 5.20E-10 [2] over -5V to +5V [3],
>> so EFC sensitivity is 5.2E-11/V.
>>
>> So, it looks like you need to have a gain of 8 and raise the
>> EFC 2.5 V.
>>
>> Cheers,
>> Magnus
>>
>> [1] http://www.to-way.com/tf/frs.pdf
>> <http://www.to-way.com/tf/frs.pdf>
>>
>> [2] http://www.leapsecond.com/pages/z3801a-efc/
>> <http://www.leapsecond.com/pages/z3801a-efc/>
>>
>> [3] http://www.realhamradio.com/joe-geller.htm
>> <http://www.realhamradio.com/joe-geller.htm>
>>
>> On 12/28/2016 11:42 PM, paul swed wrote:
>>
>> Magnus and Bob,
>> Thank you for your response. As far as the original HO
>> 10811 oscillator
>> goes there is some well written details on it behavior
>> and sensitivity. It
>> was not the same as a standard 10811. A far smaller
>> range as I recall. But
>> the data is there.
>> Its funny on the RB I have the EFC range from the spec
>> sheet. It really
>> tunes from 0-5V. But I find it interesting that the best
>> alignment with
>> other references is sub 1V. Its an old FRS C and I have
>> others that may
>> present a more centered range.
>>
>> I'll have to compare the detials that I have on the
>> 10811 and FRS C. But I
>> actually pulled out a 100:1 antenuator I was using on
>> the Piezo crystal
>> that indeed does lock.
>>
>> Goal in all of this is nothing special simply curiosity.
>> Thanks again. When I have some real numbers to share I
>> will.
>> Regards
>> Paul
>> WB8TSL
>>
>> On Tue, Dec 27, 2016 at 10:26 PM, Bob Camp
>> <kb8tq at n1k.org <mailto:kb8tq at n1k.org>> wrote:
>>
>> Hi
>>
>> The loop gain (as Magnus mentions) needs to be
>> “correct” for the Rb. Since
>> the firmware was written for an OCXO with a PPM(ish)
>> trim range, tacking it
>> on to a PPB(ish) Rb will require everything to scale
>> by 1000:1. That’s 10
>> bits.
>> You may (or may not) have enough resolution in the
>> math to handle that wide
>> a range of gains.
>>
>> If it really locks, the next challenge is to get it
>> to run out to ~ 4 days
>> or more on
>> the loop. Again, the firmware may or may not be able
>> to do this. Unless it
>> does,
>> the Rb really will not lock as well as it could.
>>
>> With the Rb correctly locked, you still have the
>> issue that the Rb is a
>> 2x10^-11
>> device (ADEV) at 1 second and the OCXO probably is
>> 2x10^-12 (or better).
>> For
>> driving a counter with a normal gate, the Rb may not
>> show much (if any)
>> improvement.
>> There is the slight chance the ADEV will get the
>> firmware confused…..
>>
>> Since the firmware source is running around
>> somewhere, you *could* dig into
>> all of this wonderful stuff :)
>>
>> Bob
>>
>>
>> On Dec 27, 2016, at 8:33 PM, paul swed
>> <paulswedb at gmail.com
>> <mailto:paulswedb at gmail.com>> wrote:
>>
>> OK so could not resist. The replacement of the
>> HP 10811 with a PIEZO ocxo
>> went very well. So in for a penny in for a
>> pound. Why not an RB. Having a
>> few around. Choice efratom FRS-c. Lot of thought
>> went into this choice.
>>
>> Not
>>
>> really it was there. It has a inverse frequency
>> to EFC voltage just like
>> the piezo and opposite the HP 10811.
>> Well it connects runs and locks using the simple
>> 1 opamp level ofset and
>> and phase inverter.
>> But locked is a funny comment. According to
>> HPsatstat and LH. Its pll is
>> locked. But both scope and the LH graph shows a
>> very slow frequency drift
>> that with the offset I can make positive or
>> negative. A cycle at 10 ns
>> takes quite some time about an hour compared to
>> a TBolt and another non
>> modified Z3801. At this level of resolution some
>> things start to become
>> questionable.
>>
>> I almost wonder if the modified z3801 under some
>> level of drift assumes
>> everything is locked and fine. Can it be pushed
>> beyond expectations. I
>> suspect it can.
>> Anyhow as I say a bit of GPSDO fun.
>> Regards
>> Paul
>> WB8TSL
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