[time-nuts] Spectracom 8161 "Standard Frequency Receiver - Oscillator" for WWVB (and question...)

[Bob kb8tq]

Hi

You *can* do all the work to get a WWVB based device running, it’s not impossible. 

Compared to a GNSS based device, the WWVB has a number of issues. The biggest
is the twice a day ionosphere based disruption. There is no practical way to get around
that. The net result of the this and the other stuff create a device that is several orders of 
magnitude worse than a GNSS system.

To put some numbers on it, you get 10’s of ns of “wander” in a typical GPS setup over 
a day. On a WWVB setup you get 10’s of us ( yes microseconds) of movement at sunrise
and sunset. You get as much as 10us between day and night. 

The normal operation process with a WWVB based setup was to look at data spaced 
24 hours apart. Even then single digit us sort of systematic drift was not uncommon. That’s
based on a *lot* of years using one of those Spectracom boxes …..

Bob

> On Oct 4, 2020, at 7:41 PM, Bill Notfaded <notfaded1 at gmail.com> wrote:
> 
> Is this why so many really high end devices are basically dumped on eBay
> now?  I wondered why SRS device was so cheap now considering price of the
> SR620.  It's too bad they don't work anymore.  I'm sure when this happened
> it was a HUGE let down to many here that were using them?  What's the best
> modern one of these for metrology use?  Or has GNSS basically ended it?
> I'm very interested in your knowledge about these because I've really
> wondered how a modern one would compare to GNSS?
> 
> Thanks,
> 
> Bill
> 
> .ılılı..ılılı.
> notfaded1
> 
> On Sun, Oct 4, 2020, 2:54 PM paul swed <paulswedb at gmail.com> wrote:
> 
>> Agree with Bobs comment. The 180 degree phase flip killed all of the gear
>> unless significant mods are done or the d-psk-r is used. Great old boxes
>> though.
>> Regards
>> Paul
>> WB8TSL
>> 
>> On Sun, Oct 4, 2020 at 3:15 PM Bob kb8tq <kb8tq at n1k.org> wrote:
>> 
>>> Hi
>>> 
>>> This is another of the many devices out there that pre-date the
>>> “modern” 180 degree phase modulation approach on WWVB. Getting
>>> one of these to run properly with the new modulation approach would take
>>> some major mods …..
>>> 
>>> Bob
>>> 
>>>> On Oct 4, 2020, at 10:23 AM, Magnus Danielson <magnus at rubidium.se>
>>> wrote:
>>>> 
>>>> Hi,
>>>> 
>>>> I got a bit curious, so I dug up the manual (Available from Orolia that
>>>> Spectracom is part of):
>>>> 
>>>> 
>>> 
>> https://www.orolia.com/sites/default/files/document-files/8161_manual.pdf
>>>> 
>>>> It is apparent that the reference oscillator is actually free-running
>>>> but compared to the WWVB, so you manually tune it to make the
>>>> strip-chart become more of a flat line.
>>>> 
>>>> This is interesting, because the receiver locks up another 10 MHz
>>>> oscillator.
>>>> 
>>>> Now, there is a 45 degree (2.1 micro) modulation on the WWVB signal,
>>>> that shows up as time-tags on the strip-chart, so it is not trivially
>> so
>>>> that you just replace the simpler 10 MHz oscillator with the more
>>>> advanced, unless you can live with that modulation at which time it is
>> a
>>>> fairlly trivial hack. You can be a bit more cunning to add hardware to
>>>> compensate the modulation, but I wonder if that is what is done.
>>>> 
>>>> To figure it out, one has to pop the lid to figure out. That is however
>>>> not for me to do.
>>>> 
>>>> Anyway, I thought the manual pointer and quick analysis would maybe be
>>>> appreciated.
>>>> 
>>>> Good luck!
>>>> 
>>>> Cheers,
>>>> Magnus
>>>> 
>>>> On 2020-10-04 09:37, Kirk Bailey wrote:
>>>>> I ran across an interesting widget in my ongoing "find the bottom of
>> the
>>>>> pile" task.  Has a label indicating it was modified for "WWVB
>> Continuous
>>>>> Monitored".  I thought these were all for WWVB, so what does
>> "Continuous
>>>>> Monitored" mean?  See attached pic.  If anyone is interested in being
>>> the
>>>>> new owner please contact me directly.
>>>>> 
>>>>> Thanks,
>>>>> 
>>>>> Kirk Bailey
>>>>> bailey at peak.org
>>>>> 
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