[time-nuts] Lucent RFTGm-II-XO / Lucent RFTGm-II-Rb / NT BW50AA

[Jeff Blaine]

OK.  I would still be interested to see if anyone has plots on the close 
in noise profile of the Lucents.  The XO part has an Efrom OCXO and I 
can assume it's similar to a generic OCXO.  But the RB is an unknown - I 
have no idea what to expect from that.

On a separate task, one of these days I would like to build up a set of 
125 & 500 Mhz sources for lab and gear use disciplined by a GPSDO 10Mhz 
feed.  The current source is a 125 Mhz homebrew OCXO and a pair of 
doubler/amp/filter sets.  I assume they are pretty clean close in but 
the frequency moves around a bit more than I would like as the OCXO part 
of the equation is nothing special.  They drive some SDR and DDS sig 
gens here in the shack so the PN is a factor as well as the frequency 
accuracy.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com

On 12-Feb-19 5:15 PM, Bob kb8tq wrote:
> Hi
>
> None of the GPSDO’s out there are great for multiplying direct to microwaves. It’s not so much
> the phase noise as all the spurs (though phase noise does vary a bit). For an instrument frequency
> source, they *assume* the input will be dirty and clean it up inside the device. So again, pretty much
> any of the gizmos likely will do ok.
>
> As you go to longer gate times than one second, the accuracy changes a bit on most GPSDO’s.
> Just how much is a “that depends” sort of thing. If you get out around 200 seconds it’s a good
> bet that your 0.1 ppb is more like 0.01 ppb.
>
> Bob
>
>> On Feb 12, 2019, at 4:30 PM, Jeff Blaine <KeepWalking188 at ac0c.com> wrote:
>>
>> Hi Bob,
>>
>> Thanks for your comments.  The highest precision thing in my lab is a 5338a and that's only if I set the gate time to something really long so that it renders a full 12 digits of info.  Other than a "I wanna be a time nut so let's see what it will do" - I never need anything near that in reality.  So let's say what I want to be able to see is 0.1 Hz resolution on a 50 Mhz test frequency.  So your 0.1 ppb is a good observation.
>>
>> Do you have any thoughts on PN of the 3?  Ive not found plots yet for the Lucent boxes but know the NT I have is middling on a good day.
>>
>> 73/jeff/ac0c
>> alpha-charlie-zero-charlie
>> www.ac0c.com
>>
>> On 12-Feb-19 9:17 AM, Bob kb8tq wrote:
>>> Hi
>>>
>>> Pretty much all of these big old telecom beasts are “good enough” for “typical use”. The gotcha
>>> is that both of those terms are very much lacking in precision. Since this is a precision sort of
>>> thing, that may not be ideal :)
>>>
>>> If 0.1 ppb is good enough for what you are doing, then they all should be fine. If you need 0.001 ppb,
>>> then none of them are likely to do what you need to do. Between those two limits, things like antennas,
>>> survey locations, lab temperature, and the accuracy definition you use all get into play. Yes, you *can*
>>> have some unusual cases (your lab goes from -20 to +90 (F of course …) on a daily basis. For anything
>>> reasonable, the limits above are pretty good.
>>>
>>> If time rather than frequency *is* the goal, then one of these GPSDO's is not really what you want.
>>> The time pulse output from a good GPS module is likely closer to UTC (after some math) than the
>>> output of the GPSDO.
>>>
>>> Bob
>>>
>>>> On Feb 11, 2019, at 9:57 PM, Jeff Blaine <KeepWalking188 at ac0c.com> wrote:
>>>>
>>>> I have these 3 systems operational here and wonder what is the "best" of the sources?
>>>>
>>>> The local use for the reference is as a time base for test equipment.  Nothing hyper critical in the way of end-use requirements - but after running the NT GPSDO for a few years and watching the Lucent box collect dust, I wonder if I have got that backward?
>>>>
>>>> The lucent has a 10 Mhz output on the front panel of the RB but the XO would need a tiny bit of modification to have 10 Mhz instead of the current 15 Mhz.
>>>>
>>>> There is a lot of data on http://leapsecond.com/u/sims/gpsdo17/ but I don't see the RFTG XO on there - which I assume is due to it's native 15 Mhz Fo vs. 10 Mhz for the rest of the field.
>>>>
>>>> Appreciate any advice you may have for a (very) novice 'nut.
>>>>
>>>> 73/jeff/ac0c
>>>> alpha-charlie-zero-charlie
>>>> www.ac0c.com
>>>>
>>>>
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