[time-nuts] The home time-lab

Bob Camp kb8tq at n1k.org
Thu Jul 7 21:31:58 EDT 2016


As has been mentioned a few times before …. the best approach is to run batteries to supply the
gear in question off of DC power. Running everything off of it’s own battery may not be practical if
you have gear that is looking for 12V, 15V, 18V, 24V, 28V, 48V and -12V. The practical answer is
to pick a convenient voltage for the battery stack and derive the rest with switchers. 48V and 24V are
pretty good choices if you want to pick up surplus switchers cheap. 


If you decide to go the UPS route, don’t bother with anything that does not produce a sine wave 
output. Modern power factor corrected stuff is a lot happier with sine waves than with weird looking
semi-square wave stuff. 

By far the most expensive gear is the stuff that runs full time. You take the AC line and convert it to DC.
That plus a battery supply the DC to sine wave converter. Everything downstream runs off of the DC to 
sine wave converter all the time. Since it always supplies the gear, it needs to be big enough to supply
whatever surge the gear requires.  That tends to make them a bit large …

None of the UPS systems take care of all issues. There are things like RFI and ground isolation that 
still *could* be an issue. To get into the next layer of that onion you go with stuff like faraday cages and
fairly big filters. 

Lots of choices …. lots of money that could be spent. 


> On Jul 7, 2016, at 8:44 PM, Bob Stewart <bob at evoria.net> wrote:
> I hope this isn't too far off topic, as this is having a big impact on my testing.
> I decided to run an A/B test on one of my GPSDOs: comparing the phase of the two 10MHz output channels.  In the middle of the night, there was a long series of 35ns pops in the phase data.  Strangely enough, there was nothing in the data collected directly from the unit involved.  The preceding two days we had had a number of switching transients where the lights blinked but nothing shut down.  So, putting one and one together, I suspect that a fair percentage of the strange results I've been getting has been power-grid related.
> So, what to do?  I've been looking at UPS devices, and I don't even understand enough to waste my money on a bad one.  The two big questions seem to be "on-line" and "sine wave".  Make that three: can I trust the mfgs claims?  Is there something affordable that could run a pair of 5370s and maybe another 50W worth of DUTs for up to an hour or two and not be prey to power-line transients?  Or would it be more cost effective to somehow monitor the power line for spikes or phase jumps and blow off tests or cut out the offending data?  From time to time we get a thread on power-line nuts.  Should I have been paying more attention?
> Bob - AE6RV
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