[time-nuts] Next upgrade

Jerry Hancock jerry at hanler.com
Wed Nov 22 19:23:58 EST 2017


Adrian, when you stated it didn’t work, what were the results?  

I had mine running in HA mode, if you can call it that, because only one has a GPS.  Actually now that I think about it, the separate but modified REF0 and modified REF1, assuming separate power and antennas, is probably closer to HA than the original application.  I have both mine running now with Lady Heather tracking each and I’ve been playing around with comparisons.  Now in my case, if either goes down for any reason the other can take over.  I guess in order to make them truly HA, we would need a diode or relay switched transfer to the active unit.

Jerry

> On Nov 22, 2017, at 4:10 PM, Adrian Godwin <artgodwin at gmail.com> wrote:
> 
> Yes, I cross-connected  the pins, but I didn't cut any short.
> 
> 
> 
> On Wed, Nov 22, 2017 at 11:36 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
> 
>> Hi
>> 
>> I have run a number of the REF0 / REF1 combos. They all seem to work fine.
>> The standard cable has some odd short pins on it. If you are not hot
>> plugging
>> the cable I don’t think they matter at all. If anything, the system is
>> more reliable
>> with a normal length pin on the connector.
>> 
>> Bob
>> 
>>> On Nov 22, 2017, at 6:08 PM, Adrian Godwin <artgodwin at gmail.com> wrote:
>>> 
>>> I've got several of the Ref 0 boxes but none of the Ref 1. I've added an
>>> Oncore GPS receiver to one of them as per Peter Garde's notes and it
>> works
>>> well.
>>> 
>>> But I'd like it to run with an unmodified Ref 0 too in the ref0/ref1
>>> configuration. Not that I need an HA reference but just for interest.
>> I've
>>> only had a quick look so far and found that connecting the two together
>>> with a 15-pin cable didn't work.
>>> 
>>> Has anyone looked into this ?
>>> 
>>> 
>>> On Wed, Nov 22, 2017 at 11:01 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
>>> 
>>>> Hi
>>>> 
>>>> 
>>>> 
>>>>> On Nov 22, 2017, at 5:16 PM, Jerry Hancock <jerry at hanler.com> wrote:
>>>>> 
>>>>> Three questions:
>>>>> 
>>>>> 1) Now that I’ve split my Lucent RFTG-U into a REF0 and REF1 unit with
>>>> both supplying 10Mhz and 1PPS, is there a way to combine the outputs or
>>>> some other technique to improve the short and/or long term performance?
>>>> 
>>>> You can monitor one against the other. Ideally you would want three
>>>> GPSDO’s and a
>>>> monitoring setup. That way you can figure out which of the three has
>> gone
>>>> bad.
>>>> 
>>>>> 
>>>>> 2) I’ve become interested in Rubidium Disciplined Oscillators recently
>>>> and was now thinking of purchasing one of the PRS-10 that I see on
>> Ebay. If
>>>> I did that and replaced one of the DOCXOs from one of the Lucent boxes,
>>>> what impact would this have on the overall performance both with and
>>>> without (when in hold-over)?
>>>> 
>>>> If you go into holdover, you are the exception. Most setups rarely go
>> into
>>>> holdover. When they
>>>> do, it’s because a hurricane just went over the house. Generally that’s
>>>> not when the focus is going
>>>> to be on timing experiments.
>>>> 
>>>>> Basically, is it worth the money to upgrade one of the boxes to a
>>>> Rubidium disciplined oscillator assuming the GPS signal is rarely lost?
>>>> 
>>>> Not worth the money if you are only looking at holdover and have a
>> typical
>>>> setup.
>>>> 
>>>>> 
>>>>> 3) Figuring the PRS-10 will cost around $250 when all is said and done,
>>>> is there a better option to improve my GPSDO system?
>>>> 
>>>> 
>>>> Disciplining implies continuously correcting. Rb standards age much less
>>>> than a typical
>>>> OCXO. Oddly enough their temperature stability may not be as good as a
>>>> high end
>>>> DOCXO. It is fairly common to try to stabilize the environment your
>>>> standards operate in.
>>>> To the extent you are successful this reduces the need to deal with
>>>> temperature.
>>>> 
>>>> The net effect is that disciplining an Rb at a rate (filter / control
>> loop
>>>> / manual tweak) of less than
>>>> a few days actually makes the Rb worse. Coming up with software to “back
>>>> off” on the tuning is
>>>> not as simple as it might seem.
>>>> 
>>>> This comes back to the fact that the GPS signal (or any of the sat
>>>> signals) are quite noisy. You
>>>> need to average them over a *long* time to get good performance. Rb’s
>> are
>>>> enough better than
>>>> a GPSDO OCXO that the time ranges really stretch out ….
>>>> 
>>>>> 
>>>>> I basically use the GPSDO as a reference for any equipment that takes
>> an
>>>> input. I have no monetary need for a reference, just an interest.
>>>> 
>>>> For most normal test equipment, a GPSDO output is “plenty good enough”.
>> As
>>>> a source for fancy
>>>> timing experiments … maybe not so much. As a phase noise reference or a
>>>> spur free source for
>>>> microwave games … also not the best way to go.
>>>> 
>>>> Bob
>>>> 
>>>> 
>>>>> 
>>>>> Thanks.
>>>>> 
>>>>> Jerry
>>>>> 
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