[time-nuts] Lucent GPSDO comments

Bob Camp kb8tq at n1k.org
Fri Nov 14 07:35:58 EST 2014


Hi


That OCXO is doing very well. 

If you look at the plot, it’s doing a few LSB’s on the DAC over the time period. That’s good performance.

Bob

> On Nov 13, 2014, at 9:17 PM, paul swed <paulswedb at gmail.com> wrote:
> 
> Bob the actual pictures and files are large so here is the left screen and
> right screen from the z3811 program. Pretty easy to guess whats in the
> middle.
> Lots of noise on the ti/pps and you can see EFC is rising all the time.
> I will say in the past it had been a steady rise now there is a wave that
> might mean its slowing down a bit.
> But this all looks rattier then I would believe.
> Regards
> Paul
> WB8TSL
> 
> 
> On Thu, Nov 13, 2014 at 5:43 PM, Bob Camp <kb8tq at n1k.org> wrote:
> 
>> Hi
>> 
>> How much is your unit moving?
>> 
>> Bob
>> 
>>> On Nov 13, 2014, at 1:50 PM, paul swed <paulswedb at gmail.com> wrote:
>>> 
>>> On the older units that used a RB to control an Xtal. They created a mix
>> of
>>> 5 Mhz +10 Mhz and that produced 15 out that hit an amplifier to drive a
>> 12
>>> way splitter.
>>> I think I reverse engineered the circuit. Its on paper and filed. Oh that
>>> ends this discussion.
>>> Anyhow it was not hard to figure out.
>>> I am still baking my Lucent in so want to see if it settles.
>>> There is just the barest of hints it may be.
>>> 
>>> So do not want to power down to explore. Happy to dig in if I don't have
>> to
>>> return the unit.
>>> 
>>> Regards
>>> Paul
>>> WB8TSL
>>> 
>>> On Wed, Nov 12, 2014 at 7:21 PM, Bob Camp <kb8tq at n1k.org> wrote:
>>> 
>>>> Hi
>>>> 
>>>> The chain in the Z3810 / 3811 / 3812 Lucent boxes is *much* different
>> than
>>>> the setup in the earlier parts. The phase noise and ADEV on the Z3810’s
>> is
>>>> better than what you got on the earlier versions. That makes keeping the
>>>> noise down in whatever mod you do more important. The existing 10 MHz
>>>> output on the Z3810 setup is a real good example of how a seemingly
>> simple
>>>> thing can add a lot of phase noise and even mess up ADEV.
>>>> 
>>>> I don’t think the 15 MHz is used for much of anything in the Z3810. That
>>>> could be wrong, but I can’t see where it is needed based on poking
>> around a
>>>> little. The 15 MHz buffer appears to be quiet and puts out a lot of
>> power.
>>>> Using it for 10 MHz would give you a *lot* of 10 MHz signal to play
>> with.
>>>> IF the mods are simple it’s an attractive solution. If it involves
>> swapping
>>>> out 30 parts - not so much.
>>>> 
>>>> Bob
>>>> 
>>>>> On Nov 12, 2014, at 5:50 PM, Perry Sandeen via time-nuts <
>>>> time-nuts at febo.com> wrote:
>>>>> 
>>>>> Wrote: At some point we will get into hacking the main board
>>>>> to switch from 15 MHz to 10 MHz.
>>>>> 
>>>>> One doesn’t have to that if one uses the two IC divide by
>>>>> 1.5 circuit I offered the list. I specifically found it so I didn’t
>> have
>>>> to
>>>>> hack the innards.
>>>>> 
>>>>> Wrote: The great news is the oscillator is 5 Mhz.
>>>>> 
>>>>> Don’t bet the rent on that. My early units have 10 MHZ Datum
>>>>> oscillators.
>>>>> 
>>>>> Bob’s point about getting the GPSDO’s if all cost the same
>>>>> is a good point.
>>>>> 
>>>>> Another point. At least on the older units I have: GPSDO,
>>>>> Rubidium, and Crystal oscillator, the output circuitry after the 15 MHz
>>>>> conversion takes place is the same. So if one hacks the 10 Mhz into the
>>>> chain,
>>>>> all one has to do is remove or bypass the 15 MHz filter before the
>>>> output.
>>>>> 
>>>>> Even if you don’t have the rubidium unit but have either/or
>>>>> GPDO or Crystal oscillator email me off list for the rubidium schematic
>>>> as
>>>>> after the logic chips they use the same circuit.
>>>>> 
>>>>> Regards,
>>>>> 
>>>>> Perrier
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