A fun tidbit about crystal oscillators is that they allowed “un-tethered” sound recording on motion picture film cameras. If both your sound recorder and your film camera are using a crystal oscillator as a reference for their motors - you can sync them up in post without needing them to be physically connected during filming.
for homelab application where extra space & power consumption is not a real concern, "temperature resistance" (tempco) is no longer relevant. you can get a constant temperature controller with +/- 0.01 degree range kind of spec for $65. verified using a reputable digital temperature sensor (outside the control loop) and the performance is pretty solid.
out of interest, what would the physical setup look like? Hard to imagine you could achieve isotropic temperature approaching +/- 0.01 degree over the size of a typical PCB.
Does it have to be isotopic though? The temperature must be constant over time, but a spatial gradient shouldn’t influence the stability of the crystal.
BTW, checkout my other comment in this thread about a GPSDO PCB with a resistor grid on the backside to evenly heat it.
A fun tidbit about crystal oscillators is that they allowed “un-tethered” sound recording on motion picture film cameras. If both your sound recorder and your film camera are using a crystal oscillator as a reference for their motors - you can sync them up in post without needing them to be physically connected during filming.
I imagine that the accuracy requirements for those crystals are not quite as stringent as the one that I’m talking about here!
Was just talking about frequency references last night -- the ARRL Frequency Measurement Test is this Thursday evening
https://fmt.arrl.org/
interesting teardown, thanks.
for homelab application where extra space & power consumption is not a real concern, "temperature resistance" (tempco) is no longer relevant. you can get a constant temperature controller with +/- 0.01 degree range kind of spec for $65. verified using a reputable digital temperature sensor (outside the control loop) and the performance is pretty solid.
I believe it.
This DIY GPSDO has a self-heating PCB to keep the temperature constant: https://www.paulvdiyblogs.net/2023/06/gpsdo-version-4.html?m....
It’s a long blog post, but in the August 24, 2023 update, he mentions that the PCB temperature stays rock solid at 52.9C.
out of interest, what would the physical setup look like? Hard to imagine you could achieve isotropic temperature approaching +/- 0.01 degree over the size of a typical PCB.
Does it have to be isotopic though? The temperature must be constant over time, but a spatial gradient shouldn’t influence the stability of the crystal.
BTW, checkout my other comment in this thread about a GPSDO PCB with a resistor grid on the backside to evenly heat it.