[time-nuts] Re: As there a hobby application of precise time or frequency measurement except for being a time nut?

[Jeff Geerling]

Speaking for myself, as a noob to this list, I've seen all these time-related things and never understood how they work.

Especially in media (AES67, SMPTE 2110, genlock, etc) and science, it seems like aspects of time are only growing more important year over year.

If we don't know the fundamentals, how can we advance?

It's also a lot cheaper than cars, guns, etc. (at least that's what I tell myself as I look at masers and old HP gear on eBay...)

-Jeff Geerling

> On Apr 11, 2025, at 6:20 PM, Jim Lux via time-nuts <time-nuts at lists.febo.com> wrote:
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> A lot depends on what you consider "precise" of course...
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> Radio astronomy - more and more people (yeah, probably < 1/2 dozen, but..) are setting up interferometers and precise time knowledge is important.
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> Radio amateurs on microwave frequencies with narrow band signals need good frequency control (1ppm at 10 GHz is wildly insufficient - you'd like to be within 10 Hz - 1E-9)
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> There seems to be a bunch of people doing direction finding with a distributed system (perhaps collaborative drone flight) - it's unclear what their requirements are.
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> There is a hobby radar community with bistatic radars - both at low frequencies (chirp sounders) and at microwave frequencies. The performance of the radar depends on both long term stability (for SAR) and closein (phase noise). 
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> I know a guy with a LTE base station he built in his house - granted he's not putting up multiples, so he doesn't need precise timing (yet). 
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> I suspect none of these are hundreds or thousands of people, but they all have some need to understand time and frequency to a "more than you get with a TinySA or oscilloscope" kind of performance.
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> On Fri, 11 Apr 2025 12:46:12 +0200, Erik Kaashoek via time-nuts <time-nuts at lists.febo.com> wrote:
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> Maybe the subject line is a bit clickbait but this is a serious question.
> Hobby VNA are used to measure impedance for antenna, amplifiers,
> filters, PCB's and cables. Many applications for a VNA outside the
> professional world.
> Hobby spectrum analyzers are user for hunting RFI, measuring harmonics
> of active devices, assessing what part of the spectrum is still
> available for wireless devices, etc... Again many applications.
> But for time and frequency measurement the situation seems to be
> different. What are hobby applications for accurate assessment of
> stability, time or frequency?
> For radio amateurs that operate in the GHz bands the accurate assessment
> of the frequencies of their generators is such an application but what
> other applications do exist and what are their requirements regarding
> accuracy?
> I'm purposely excluding the applications where the accuracy is the goal
> instead of some usage for accuracy.
> Any input is welcome.
> Erik.
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