Hacker News Reader

Comment by darkhorn | Hacker News Reader

Also may depend on what kind of watch you wear, like quarts watches are sensitive to magnetic field.

Sadly no. That would be a convenient and nifty way to vary frequency for ham radio applications if it were the case. Even just a couple dozen PPM in a magnetic field would be sufficient for transmit receive switching but it just doesn't work. Also if that were the case mounting a crystal nearby a power transformer or fan would generate massive noise in the output signal unless magnetically shielded, which also doesn't happen.

I would imagine magnetizing a mechanical watch would really mess things up, so at a "just under really messed up" threshold it would probably have the claimed effect.

You may be thinking of YIG garnet oscillators which are very dependent on magnetic field but they haven't been common tech in maybe 30 years. Even used on ebay they cost more than modern new microwave VCOs which is annoying. I have a box of old YIG osc in my basement which I actually used for ham radio experiments before modern solid state VCOs took over.

Yeah, they're not sensitive to magnetic fields. But they do drift with temperature. Which leads to fancy semi-improv solutions, like placing the quartz in a small case, together with a heating element and a temperature sensor, to keep that sucker incubated at constant temp. A lot of HAMs used to do this back in the day - or maybe they still do, I dunno.

Also, placing a small variable capacitor in series with the quartz is an easy way to tune it, if it's too fast. I actually have a wall clock that looks nifty but is too fast, and I'm gonna tune it by trial and error, inserting small caps in series with the crystal.

The heating setup is still used today. In fact, you can get integrated components called OCXOs (Oven Controlled Crystal Oscillator) that do the whole job in one small package with precision over time on the order of 1ppb. Cheaper, and less precise, are TCXOs (Temperature Compensated Crystal Oscillators) where a crystal is paired with a circuit that has an opposite dependency on temperature so that the errors tend to cancel each other out.

> Yeah, they're not sensitive to magnetic fields. But they do drift with temperature

Also, gravity: https://www.youtube.com/watch?v=zILwgQhjC_Q

Degauss? You can speed up some clocks with degauss. So isn' it sensitive to magnetic field?

Relativistic time effects are changes in the rate of time itself, not changes in the mechanism of a clock. If there was a magnetic field effect, that's a different, additional thing.

Yeah clock, not time.

Reply on news.ycombinator.com