Re: Efratom LPRO-101 Rubidium question....
Dana,
Just curious, can you share some details on what you are using for the
IQ demodulator? Is this a 'roll your own' solution Gilbert cell mixer, etc?
Thanks,
Dan
On 8/23/2021 3:30 AM, time-nuts-request@lists.febo.com wrote:
Message: 4
Date: Sun, 22 Aug 2021 10:16:56 -0500
From: Dana Whitlowk8yumdoober@gmail.com
Subject: [time-nuts] Re: Efratom LPRO-101 Rubidium question....
To: Discussion of precise time and frequency measurement
time-nuts@lists.febo.com
Message-ID:
CADHrwpeyiqA1PWRVtB_HTmzc8Oxe-wr+fZYz4oZ4VUcnc4h8bQ@mail.gmail.com
Content-Type: text/plain; charset="UTF-8"
C'mon guys- when you speak of a frequency error in Hz, you should also
specify "at
what frequency"in the same breath. Or better yet, always specify
frequency errors in
relative terms.
Hundreds of Hz at 10 Mhz is unthinkable for a Rb. Even at 8.2 GHz, 100 Hz
error is about
12E-9, which is likely to be outside the EFC tuning range of some (if not
most) Rb standards.
Both of my Rbs have a tuning range of only roughly 2E-9 via the EFC input.
Outside that
range, much sterner measures must be taken, which I frankly dread.
The two Rbs that I own (an L-Pro and a PRS-10) both tend to drift upwards
in frequency
to the tune of about 1E-11 or 2E-11 per month. Superimposed on that are
random
variations of around 1E-11 on a time scale of a few hours.
I make phase comparisons between the 10 MHz outputs of a GPSDO and the Rb
under
test using a simple quadrature demodulator, with the I & Q outputs
displayed on a 2-chan
DSO. I use the "roll mode" display feature on the DSO at its slowest speed
(1000 sec/div)
and just leave things running continuously for up to several days. On my
DSO a full screen
width is 14000 sec (slightly under 4 hours), and I just take a glance from
time to time as I
happen to pass by.
Someone suggested a 100 sec measurement with a counter, but that is right
in the realm
where GPSDOs are typically the most noisy, so a single measurement is
likely to have
rather large errors. One would have to record a fairly large number of
such measurements
(several hundreds of them) and plot them out to get a good assessment of
what the Rb is
actually doing. WIth the IQ phase difference display, one can get a pretty
decent estimate of
the needed tuning correction, without doing any real work at all, in a day
or so.
When I'm doing something requiring the best frequency accuracy, I keep the
'scope display
running while I'm doing the serious work, and note the frequency error of
the Rb at the time
for use in correcting the final result. BTW, I don't see much "settling"
effect after making
tuning changes- the correction made seems to take effect essentially
immediately (as best
as one can tell in the presence of GPS noise). By comparing two Rbs, I can
investigate
settling effects quite well without the noise having anything to do with it.
Dana
On Sun, Aug 22, 2021 at 8:41 AM Matthias Welwarskytime-nuts@welwarsky.de
wrote:
Hi,
Has anyone else here had trouble with any of the LaCrosse UltrAtomic
clocks?
I personally purchased one new around early 2017 it worked well until
early this summer. At that point it suffered a mechanical failure where
the minute hand would just swing around the 6 'o clock mark.
Occasionally the gears would hit, and the hand would swing to and fro a
bit. (Yes, we did replace batteries as a test). So, we ordered another
one, and replaced it.
When I pulled the clock down from the wall, there was a lot of white
'plastic' dust everywhere between the glass and clock face. Looks like
these are prone to wearing out quickly. Unfortunately the wife threw out
the dead one without me knowing, so no serous diagnostic surgery was
performed.
Then the clock we bought for work had the second hand quit. We tried a
set of batteries in this one also, which did not help. (Eco mode was
off). This one died a month out of warranty.
I took that one home and did some digging. It appears the ID of the
pinion with the magnets (Part of stepper motor mechanism) is wearing.
It's brown plastic part, and there is a lot of brown plastic dust on the
fixed pin it rides on.
In an effort to rejuvenate that clock, some cleaning was done, and small
bit of light oil was applied to the pinion shaft. (I did note, that one
of the other pinion/wheel shafts came from the factory with a bit of
oil). The second hand did start to move again after this cleaning and
lubrication.
I've played with the supply voltage on that clock, and as long as
everything is above 3.0V it seems to operate correctly. Below that it
will sporadically miss steps, and eventually do it's automatic setting
routine. (Maybe drag from the oil applied, or drag from wear, etc...)
Just curious if anyone else has noticed issues with these.
Thanks,
Dan
I’ve not had any issues with mine other than replacing batteries a time or
two.
Jeremy
On Mon, Aug 23, 2021 at 8:55 AM Dan Kemppainen dan@irtelemetrics.com
wrote:
Hi,
Has anyone else here had trouble with any of the LaCrosse UltrAtomic
clocks?
I personally purchased one new around early 2017 it worked well until
early this summer. At that point it suffered a mechanical failure where
the minute hand would just swing around the 6 'o clock mark.
Occasionally the gears would hit, and the hand would swing to and fro a
bit. (Yes, we did replace batteries as a test). So, we ordered another
one, and replaced it.
When I pulled the clock down from the wall, there was a lot of white
'plastic' dust everywhere between the glass and clock face. Looks like
these are prone to wearing out quickly. Unfortunately the wife threw out
the dead one without me knowing, so no serous diagnostic surgery was
performed.
Then the clock we bought for work had the second hand quit. We tried a
set of batteries in this one also, which did not help. (Eco mode was
off). This one died a month out of warranty.
I took that one home and did some digging. It appears the ID of the
pinion with the magnets (Part of stepper motor mechanism) is wearing.
It's brown plastic part, and there is a lot of brown plastic dust on the
fixed pin it rides on.
In an effort to rejuvenate that clock, some cleaning was done, and small
bit of light oil was applied to the pinion shaft. (I did note, that one
of the other pinion/wheel shafts came from the factory with a bit of
oil). The second hand did start to move again after this cleaning and
lubrication.
I've played with the supply voltage on that clock, and as long as
everything is above 3.0V it seems to operate correctly. Below that it
will sporadically miss steps, and eventually do it's automatic setting
routine. (Maybe drag from the oil applied, or drag from wear, etc...)
Just curious if anyone else has noticed issues with these.
Thanks,
Dan
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
an email to time-nuts-leave@lists.febo.com
To unsubscribe, go to and follow the instructions there.
--
Jeremy Nichols
Sent from my iPad 6.
Dan, close but no ceegar! On this one I just needed fair accuracy, at 10
MHz only, and
didn't want to be handling little teeny things and/or laying out an ECB.
Instead I bought
packaged components from Mini Circuits. and cable them up with 0.086"
"hand-flex"
cable I bought from Amazon. I did all this on Cu-clad board, and soldered
down some
BNC connectors from the junk box.
The MCL components are:
1 ea MSC-2-1W+ 0 deg power splitter, used as the LO splitter.
1 ea PSCQ-2-51W+ 2-way 90 deg splitter, used as the RF splitter
2 ea SBL-1 Mixer
This was all wired up in the most naive possible configuration, with no
precautions taken to avoid cross-coupling of harmonic components
between mixers, etc. The only thing a bit unusual is that I did not
terminate
the IF ports in 50 ohms. Instead each is terminated to GND with a 510 ohm
resistor, then a series resistor of 10 k, then a shunt capacitor of 0.1 uF,
to
make an RC lowpass filter of about 160 Hz BW. Then there is a 51 ohm
resistor to the center pin of the I or Q BNC connector (as the case may be),
which is expected to connect to a Hi-Z load such as an o'scope input. This
arrangement yields significantly higher signal voltage output below the
compression point.
I usually drive the RF input at about -18 dBm ((IRC) and get I & Q outputs
of
about 60 mV p-p. I should be driving the LO input at about +10 to +11 dBm,
but it seems to work OK at levels of +8 to +9 dBm, which is all I can
usually
manage to give it.
If I plot I & Q on an X-Y 'scope display through at least one full cycle of
phase
difference, the expected circle is visibly slightly distorted into an
ellipse slanted
at approx 45 deg, but it's not real bad. I would not use this as-is for
precision
phase measurement, but for my present purposes of tuning an Rb onto GPS it's
more than good enough.
For my precision work at "all" frequencies, I use a Signal Hound SA44B (USB
Spectrum Analyzer). It does a nice job in terms of IQ accuracy, but
finding out
exactly where it's tuned can be a bitch.
Hope this helps...
Dana
On Mon, Aug 23, 2021 at 10:33 AM Dan Kemppainen dan@irtelemetrics.com
wrote:
Dana,
Just curious, can you share some details on what you are using for the
IQ demodulator? Is this a 'roll your own' solution Gilbert cell mixer, etc?
Thanks,
Dan
On 8/23/2021 3:30 AM, time-nuts-request@lists.febo.com wrote:
Message: 4
Date: Sun, 22 Aug 2021 10:16:56 -0500
From: Dana Whitlowk8yumdoober@gmail.com
Subject: [time-nuts] Re: Efratom LPRO-101 Rubidium question....
To: Discussion of precise time and frequency measurement
time-nuts@lists.febo.com
Message-ID:
<
Content-Type: text/plain; charset="UTF-8"
C'mon guys- when you speak of a frequency error in Hz, you should also
specify "at
what frequency"in the same breath. Or better yet, always specify
frequency errors in
relative terms.
Hundreds of Hz at 10 Mhz is unthinkable for a Rb. Even at 8.2 GHz, 100
Hz
error is about
12E-9, which is likely to be outside the EFC tuning range of some (if not
most) Rb standards.
Both of my Rbs have a tuning range of only roughly 2E-9 via the EFC
input.
Outside that
range, much sterner measures must be taken, which I frankly dread.
The two Rbs that I own (an L-Pro and a PRS-10) both tend to drift upwards
in frequency
to the tune of about 1E-11 or 2E-11 per month. Superimposed on that are
random
variations of around 1E-11 on a time scale of a few hours.
I make phase comparisons between the 10 MHz outputs of a GPSDO and the Rb
under
test using a simple quadrature demodulator, with the I & Q outputs
displayed on a 2-chan
DSO. I use the "roll mode" display feature on the DSO at its slowest
speed
(1000 sec/div)
and just leave things running continuously for up to several days. On my
DSO a full screen
width is 14000 sec (slightly under 4 hours), and I just take a glance
from
time to time as I
happen to pass by.
Someone suggested a 100 sec measurement with a counter, but that is right
in the realm
where GPSDOs are typically the most noisy, so a single measurement is
likely to have
rather large errors. One would have to record a fairly large number of
such measurements
(several hundreds of them) and plot them out to get a good assessment of
what the Rb is
actually doing. WIth the IQ phase difference display, one can get a
pretty
decent estimate of
the needed tuning correction, without doing any real work at all, in a
day
or so.
When I'm doing something requiring the best frequency accuracy, I keep
the
'scope display
running while I'm doing the serious work, and note the frequency error of
the Rb at the time
for use in correcting the final result. BTW, I don't see much "settling"
effect after making
tuning changes- the correction made seems to take effect essentially
immediately (as best
as one can tell in the presence of GPS noise). By comparing two Rbs, I
can
investigate
settling effects quite well without the noise having anything to do with
it.
Dana
On Sun, Aug 22, 2021 at 8:41 AM Matthias Welwarsky<
wrote:
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
an email to time-nuts-leave@lists.febo.com
To unsubscribe, go to and follow the instructions there.