[time-nuts] The home time-lab

Bob Camp kb8tq at n1k.org
Fri Jul 8 09:00:56 EDT 2016


A 5335 / 5334 generation counter will spot a 30 ns blip. A modern MCU demo board
probably can to the same sort of thing. The cost of another (cheap) couple of counters
is probably less than mucking around with power line monitors and giant banks of batteries. 

The most likely output of a *really* good monitor: There is a blip of some sort about every
5 to 10 minutes forever and ever ….When there is bad weather they happen every few seconds up to
a few a second. Not a lot you can make sense out of ….


UPS’s (except for the continuous type) are designed with an “acceptable dropout” in mind. The assumption 
is that the gear downstream is OK with a cycle / half cycle / couple of cycles missing. Compared to the 
sort of things a really good line monitor catches, those are giant blips. Does a 5370 chug on through a 30 ms full
line drop out and go nuts on a 3.1 (or 30 or 0.3) us wide spike at 203V? Seems unlikely. If it does, the answer is a really 
good (screen room grade) line filter rather than a UPS of any sort. 


Here’s something to try that has not yet come up:

Grounding is more likely to be the issue than anything else. Having an isolated / independantly grounded test space is a really 
good idea. You can get surplus isolation transformers into the couple of KVA range for mighty cheap prices. 
Coupled with a good  line filter they will take out a lot of mains related issues. They will also force you to
cable up everything to the new “good ground”. It might also drive you to look at how the GPS and other 
antennas are grounded  and isolated from the test system. Keep in mind this is *not* an un-grounded
system. There still is a proper ground on it. It just isn’t grounded who knows where and who knows how.


> On Jul 8, 2016, at 12:25 AM, Bob Stewart <bob at evoria.net> wrote:
> Nothing looks good at the moment.  It may be that I just have to trust the equipment testing and if there's a big blip that's not repeatable, then it didn't happen.  No, I don't like it either.
> Bob -----------------------------------------------------------------------------------
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>      From: Hal Murray <hmurray at megapathdsl.net>
> To: Bob Stewart <bob at evoria.net>; Discussion of precise time and frequency measurement <time-nuts at febo.com> 
> Cc: Hal Murray <hmurray at megapathdsl.net>; hmurray at megapathdsl.net
> Sent: Thursday, July 7, 2016 11:18 PM
> Subject: Re: [time-nuts] The home time-lab
> bob at evoria.net said:
>> So, since I need to power the 5370 (preferably both) I'm looking at a deep
>> cycle battery, a charger, and an inverter?  At this point in the process, a
>> power line monitor is looking like a good solution.  At least it would tell
>> me to ignore the test results.
> Yes, you can build your own UPS.  It would be interesting to see what the 
> parts cost totals out to.
> What did you have in mind for a power line monitor?
> I didn't look very hard, but I didn't see anything interesting under $100.  
> My manual says the 5370 is 250 VA.  2 of those cuts out some of the low end 
> UPS units, but there are still several left under $100.
> They will fix the blinking lights glitches.  They won't fix real power 
> outages that last for more than a few minutes.
> -- 
> These are my opinions.  I hate spam.
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