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

[Martin A Flynn]

Radio astronomy - Check...
Radio amateurs  - check...

https://isec.space/wp-content/uploads/2025/02/IMG_0179.jpeg
https://isec.space/wp-content/uploads/2025/04/tlm_18_lens_flare-1024x724-1.jpg

And looking for a decent cesium clock...

Martin

On 4/11/2025 1:26 PM, Jim Lux via time-nuts wrote:
> A lot depends on what you consider "precise" of course...
>
> Radio astronomy - more and more people (yeah, probably < 1/2 dozen, but..) are setting up interferometers and precise time knowledge is important.
>   
> 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)
>
> 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.
>
> 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).
>
> 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).
>
> 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.
>
>
>
> On Fri, 11 Apr 2025 12:46:12 +0200, Erik Kaashoek via time-nuts <time-nuts at lists.febo.com> wrote:
>
> 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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