[time-nuts] Next upgrade

[Bob kb8tq]

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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