[time-nuts] Re: Water in connectors

[Dana Whitlow]

My own belief is that almost everything can be blamed on GPS, but then much
if not
most is my own fault for using an indoor antenna only about 6 or 7 feet
above ground
level.

Except when excessive lightning activity is around, I run a
continuous setup comparing
10 MHz phase between a T'Bolt GPSDO and a Rb, showing I & Q waveforms on a
very
slow roll-mode 'scope display which shows the most recent 4 hours.  It just
sits there
and runs, and I glance at it many times per day in passing.  It gets very
messy much
of the time.

A month-long recording could net you quite a bit of couch time  :-)

Dana


On Sat, Mar 27, 2021 at 11:21 AM Ole Petter Rønningen <opronningen at gmail.com>
wrote:

> Active HM, yes - nothing in the logs that corresponds, except a .5 degC
> diurnal temperature change - which roughly coincides with the outdoor temp,
> so no help there..
>
> This was meant as a quick-and-dirty check, so a months is not in the cards
> - but that second antenna/receiver is climbing on my list of priorities, in
> imminent danger of surpassing «doing nothing on the couch»! :)
>
> > 27. mar. 2021 kl. 16:52 skrev Dana Whitlow <k8yumdoober at gmail.com>:
> >
> > Ole,
> >
> > If you can stand the suspense, a time error recording of a month or more
> > duration
> > would probably be pretty informative (and interesting for us to see).
> >
> > And when you speak of the maser, is that an active hydrogen maser?  If
> so,
> > you're
> > a lucky man (unless it's in the process of dying).  But there should be
> > scads of
> > diagnostics being logged, which should be enough to enable making a
> fairly
> > good
> > confidence check on it.
> >
> > Dana
> >
> >
> >> On Sat, Mar 27, 2021 at 8:33 AM Ole Petter Rønningen <
> opronningen at gmail.com>
> >> wrote:
> >>
> >> Hi, Dana
> >>
> >> Thats the peculiar thing - these last 48 hors theres been a pretty clear
> >> 24 hour cycle, pointing to temperature as the culprit; but the
> preceeding
> >> 48 hours the phase shift did not follow a 24 hour period at all; the
> >> wheather has been all over the place, so it is hard to say.. More data
> >> needed! As always..
> >>
> >> (of course, there is always a possibility that I’ve somehow bungled the
> >> data, and the period has been 24 hours all along)
> >>
> >> This is why I am looking for ballpark figures for the two main suspects;
> >> water and temperature.
> >>
> >> I guess I should bite the bullet and rig up a second receiver/antenna
> so I
> >> can take the maser out of the equation.. (and reseal the connectors
> >> properly)
> >>
> >>
> >>>> 27. mar. 2021 kl. 14:04 skrev Dana Whitlow <k8yumdoober at gmail.com>:
> >>>
> >>> Ole,
> >>>
> >>> You did not mention whether this timing anomaly is periodic or steadily
> >>> growing.
> >>> That information could be of considerable diagnostic significance.
> >>>
> >>> Dana
> >>>
> >>>
> >>>> On Sat, Mar 27, 2021 at 6:08 AM Ole Petter Ronningen <
> >> opronningen at gmail.com>
> >>>> wrote:
> >>>>
> >>>> Hi, All
> >>>>
> >>>> I am trying to chase down a 2-3-4 ns/day "anomaly" in a gpsdo I am
> >> working
> >>>> on - it could be temperature sensitivity in the antenna (cheap patch
> >>>> jobbie), or I suspect my sealing of the outside connectors may not be
> >>>> watertight. I just wanted to ask the list of anyone know of/has an
> >> estimate
> >>>> of how much the propagation delay on an N and/or SMA can reasonably be
> >>>> expected to change in the presence of water? is 3 ns in the right
> >> ballpark,
> >>>> or would that effect be way bigger/smaller?
> >>>>
> >>>> Likewise, does anyone have reasonably accurate figures for how much
> >>>> temperature could be expected to affect the delay of signals? 20 ps?
> 20
> >> ns?
> >>>> Looking for some rough figures so I can look in the right direction..
> >>>>
> >>>> I've used the same gpsdo, cable and location with a high quality
> antenna
> >>>> without seeing these effects, so I am fairly certain it is the antenna
> >> (or
> >>>> my reference maser giving up the ghost..)
> >>>>
> >>>> Thanks!
> >>>> Ole
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