Hi,

firstly, I should mention that I am not a professional in the
Time/Frequency stuff, just a long time hobbyist.

Good frequency counter is a must. Try to look on EBay for some of those
HP/Agilent 53132A. Not 53131A, but genuine 53132A.
And some GPIB to USB or Ethernet converter for this counter, because you
surely will take some long time measurements (days, weeks, months).

Some bench multimeter like HP34401A with GPIB can be very handy. Or some
more modern multimeter with Ethernet port. But, when it comes to
multimeters, the old one tends to be better than the modern ones.
Sooner or later you will want to precisely measure voltage on some
tuning pin of OCXO/Rubidium/whatever.

NanoPFA -
 https://www.tinydevices.org/wiki/pmwiki.php?n=TinyPFA.Homepage is a
really nice instrument to have and it is cheap.

Also, look at Aliexpress/Ebay/somewhere and buy one of those GPS
disciplined OCXOs. You will need some frequency reference handy, if you
do not have access to some frequency reference like Cesium standard or
hydrogen maser at your university.
Problem with those Rubidium standards from EBay is that 70% of them do
not work properly and basically they works as a not so precise OCXO.

As a starting project, you can try to buy some really good double oven
OCXO like HP-10811A, some time (not position) oriented GPS board a make
your own GPSDO from this.

Best regards

PavelK

Dne 23.09.2025 v 20:09 Austin Dixon via time-nuts napsal(a):

Hi Austin,

On 2025-09-23 20:09, Austin Dixon via time-nuts wrote:

A time-interval counter is a good tool here. Strongly recommend you
getting one and hook it up to the TimeLab software, which is a
ubiquitous tool for time and frequency measurement and analysis. If you
want to be fancy, post-process in Stable32.

A very handy time-interval counter is the TAPR TICC which gives you
about 60 ps resolution, which beats many old counters and cost you 250 USD.

Classical counters include HP5370A/B and SR620 to mention a few. You
might get your hands on a PM6681 / CNT-81 for quite good money too. Some
come cheap because they need a little care, so if you are handy this
could be a path for good performance and a budget. I got started on a
HP5335A, got further down the road on HP5370A, SR620's and Wavecrest
DTS-2070C. For reaching really deep I use a TimePod with dual
references. Being able to measure phase-noise brings extra understanding
than what you can do. A cheap option of phase-noise measurements exist
in the special firmware for a NanoVNA H4.

See my comment above.

Start measuring. Just measure stability of stuff. You make tons of
mistakes first, but you will learn. Once you start to master it, you
start to search for more stable oscillators, better counters and improve
other things. That is the path to the heavier drugs... uhm... basement
lab setup.

Short-term stability is often measured as phase-noise. Noise with
different slopes have known mapping over to the long termstability measures.

Long-term stability is often measured in Allan Deviation (see Allan
deviation wikipedia article), but variants of this is used for various
purposes. David Allan himself wants you to use MDEV as that way you can
separate white phase modulation and flicker phase modulation noises,
which the ADEV fails to separate in a meaningful way.

Oh, we have a bunch of different noise-types. The Allan Deviation
article include those, but the once you see is typically White phase
modulation (WPM) (your thermal noise), Flicker phase modulation (FPM)
(current noise), White frequency modulation (WFM)) and Flicker frequency
modulation (FFM). The noises is explained as you look at the Leeson
model (another wiki-article to look at).

What books have you been recommended? You need more recommendations?

Cheers,
Magnus

Hi Austin

As a project I can recommend to build a GPSDO. For inspiration I'd
recommend to have a look here :
https://github.com/paulvee/Lars-GPSDO-V1?tab=readme-ov-file but there
are many other good (but also bad) DYI GPSDO designs
You already have all the tools needed for building.
For evaluating the performance of the GPSDO (or any 10 MHz source) you
only need Timelab (free from here: https://www.miles.io/timelab/beta.htm
) and this:
https://www.tinydevices.org/wiki/pmwiki.php?n=TinyPFA.Homepage which
will allow you to do highly accurate performance measurements as you
already have a Rubidium frequency  standard
If you are interested in joining a beta test of a two channel
timer/counter with build-in gpsdo contact me off list. (see cc: )

Erik.

On 23-9-2025 20:09, Austin Dixon via time-nuts wrote:

Hi Austin,

On Tue, 23 Sep 2025 18:09:39 +0000
Austin Dixon via time-nuts time-nuts@lists.febo.com wrote:

Welcome to the time-nuts community. Please fasten your seatbelt,
fold up your tray and bring your seat into an upright position :-P

That sounds like a good start. You have all the basic equipemnt
that you'd need. Now the question is where you would want to go?
There are many parts of the time & frequency community that one
could enter. Some people do high stability or low phase noise
oscillators (e.g. Jeremy Everard at University of York).
Some people do precise phase noise measurement (e.g. Enrico
Rubiola at FEMTO-ST in Besançon or Craig Nelson and Archita Hati
at NIST). Some do low noise electronics (e.g. Claudio Calosso
at INRIM in Turin). Some do time and frequency transfer with
GNSS (e.g. Gerard Petit BIPM emeritus) or fiber optical (e.g.
Gesine Grosche at PTB Braunschweig). Some do modeling of
atomic clock stability (e.g. François Vernotte at FEMTO-ST)
or how noise propagates in electronics (yours truly).

Which one of these do you want to peruse?

I would go for a simple time-frequency counter
(e.g. Pendulum CNT-90 which was also sold as Fluke PM6690,
these are usually quite a bit cheaper than the
HP/Agilent/Keysight ones, while giving similar perfomance).
Something like the TAPR TICC would be also a low-cost option
to do some measurements.

I would also get a GPSDO, if you can get a cheap one, so you
have a reference to compare against, that is long-term stable.
Do not go for the Chinese ones that are available on ebay.
They perform not so well. Some of them have bugs where they
have a small frequency error. There are several GPSDOs out
there that are GPSDOs taken from base stations and repackaged
for home use. Go for one of these.

If you haven't already, get yourself a copy of Enrico Rubuiola's
book "Phase noise and Frequency stability in Oscillators". That
will introduce you to a lot of terms and methods in describing
phase noise in oscillators and atomic clocks. You can find a
digital copy at the usual places.

There is so much stuff out there! So! Much!
So it really comes down to your interests. Try to figure out
what you want to be doing and go after that.

How about designing and building your own GPSDO?
These are pretty simple devices.... on the surface. So you
get something working very quickly. Then figuring out why
it doesn't perform well for different time scales and improving
the perofmance teaches you a lot on how electronics for precision
metrology works and where the pitfalls are.

BTW: One thing that you have to keep in mind is, that a lot of
time and frequency work in the US is focused on military applications.
This means, if you are going into time and frequency, you wil
likely do some work for military use as well. If that's morally
a problem for you, I would recommend aiming for the many smaller
companies in the field, as there are many that do not go for
military contracts. Or go for research: There are many universities
and institutes that do research in time and frequency. I know
that NIST is always looking for people with good skills in
electronics who know a phase noise plot from an ADEV plot.

HTH

		Attila Kinali

--
The driving force behind research is the question: "Why?"
There are things we don't understand and things we always
wonder about. And that's why we do research.
-- Kobayashi Makoto

Inspired by some posts in another thread…
Austin, maybe making precise (which is quite the rabbit hole to dive into) measurements of the local power frequency would be interesting.  Here’s a weird aspect that I just thought of.  These days, there’s a lot of grid tied solar generation. So the local frequency (or phase, probably)  at a given house will be slightly different than the neighbor’s house, etc., because there has to be a slight difference to get the power to flow the right direction.

There’s two problems that has been occupying me recently:
#1 If you have multiple inexpensive SDRs (RTL-SDR), how do you synchronize the digitized data streams coming out of them (if you don’t just distribute the sampling clock among the them).  There’s a lot of ideas floating around out there from people who want to do things like phase based direction finding or beam forming.  But what if you want to compare data from two sites that are far enough apart that you can’t just send a common reference to them.  GPSDO is part of one solution.

#2 - Protocols like NTP allow you to synchronize (and syntonize) the clocks on multiple computers on a network.  Now think about the problem of synchronizing a clock that is on the Moon (or orbiting the Moon, or Mars) with clocks on Earth. Perhaps through a network where the links are not continuous (which is the case for a lot of relay orbiters).  So you have a series of problem: How do you “transfer time”? How do you adjust the local clock (smoothly, or not) when you get an update? How do you deal with relativistic effects The Moon is different gravity, and is moving relative to the Earth, so there are both special and general relativity effects.  (See Project GREAT for a demonstration of the latter, using a minivan.).  It’s easy to write a proclamation that says “We shall use Lunar Coordinated Time” but there’s a lot of interesting aspects to defining just what LTC would be, and then even more interesting aspects to actually implementing it.

On Thu, 25 Sep 2025 11:17:40 +0200, Attila Kinali via time-nuts time-nuts@lists.febo.com wrote:

Hi Austin,

On Tue, 23 Sep 2025 18:09:39 +0000
Austin Dixon via time-nuts  wrote:

Welcome to the time-nuts community. Please fasten your seatbelt,
fold up your tray and bring your seat into an upright position :-P

That sounds like a good start. You have all the basic equipemnt
that you'd need. Now the question is where you would want to go?
There are many parts of the time & frequency community that one
could enter. Some people do high stability or low phase noise
oscillators (e.g. Jeremy Everard at University of York).
Some people do precise phase noise measurement (e.g. Enrico
Rubiola at FEMTO-ST in Besançon or Craig Nelson and Archita Hati
at NIST). Some do low noise electronics (e.g. Claudio Calosso
at INRIM in Turin). Some do time and frequency transfer with
GNSS (e.g. Gerard Petit BIPM emeritus) or fiber optical (e.g.
Gesine Grosche at PTB Braunschweig). Some do modeling of
atomic clock stability (e.g. François Vernotte at FEMTO-ST)
or how noise propagates in electronics (yours truly).

Which one of these do you want to peruse?

I would go for a simple time-frequency counter
(e.g. Pendulum CNT-90 which was also sold as Fluke PM6690,
these are usually quite a bit cheaper than the
HP/Agilent/Keysight ones, while giving similar perfomance).
Something like the TAPR TICC would be also a low-cost option
to do some measurements.

I would also get a GPSDO, if you can get a cheap one, so you
have a reference to compare against, that is long-term stable.
Do not go for the Chinese ones that are available on ebay.
They perform not so well. Some of them have bugs where they
have a small frequency error. There are several GPSDOs out
there that are GPSDOs taken from base stations and repackaged
for home use. Go for one of these.

If you haven't already, get yourself a copy of Enrico Rubuiola's
book "Phase noise and Frequency stability in Oscillators". That
will introduce you to a lot of terms and methods in describing
phase noise in oscillators and atomic clocks. You can find a
digital copy at the usual places.

There is so much stuff out there! So! Much!
So it really comes down to your interests. Try to figure out
what you want to be doing and go after that.

How about designing and building your own GPSDO?
These are pretty simple devices.... on the surface. So you
get something working very quickly. Then figuring out why
it doesn't perform well for different time scales and improving
the perofmance teaches you a lot on how electronics for precision
metrology works and where the pitfalls are.

BTW: One thing that you have to keep in mind is, that a lot of
time and frequency work in the US is focused on military applications.
This means, if you are going into time and frequency, you wil
likely do some work for military use as well. If that's morally
a problem for you, I would recommend aiming for the many smaller
companies in the field, as there are many that do not go for
military contracts. Or go for research: There are many universities
and institutes that do research in time and frequency. I know
that NIST is always looking for people with good skills in
electronics who know a phase noise plot from an ADEV plot.

HTH

Attila Kinali

--
The driving force behind research is the question: "Why?"
There are things we don't understand and things we always
wonder about. And that's why we do research.
-- Kobayashi Makoto

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