Motor timing help

 Hi, I'm trying to get my motors running with LinuxCNC, and I have an old controller for the machine that can move the motors, but the card reader on it is broken. I have tried many times to get it working with LinuxCNC, but now I've tried to diagnose it with an oscilloscope on the old controller. For the x-axis output, the step pin outputs a constant 20MHz signal when not being told to move, but when being told to move, it outputs a 12MHz signal. Image 1 is the motor not moving (Consistent wave), and image 2 is the motor moving (weird-looking wave). I took a video of them side by side and is linked to a google drive. If anyone knows how I can replicate this signal/frequency in LinuxCNC, that would be greatly appreciated. Thanks. Link to video -->  drive.google.com/file/d/1qQ6TFAT_yjkfDdm...Lns/view?usp=sharing
Image 1 -->      Image 2 --> 

At 75 and 185mVPP, those look like noise, not a signal of any kind, although the first one is weirdly clean sinusoidal.

Yup, that's noise. Your scope settings are so "zoomed in" in time and voltage you probably can't see the real signals.

• Set your scope's Y axis (voltage) range to more like 1V/division. More if the signals are (eg) 24V.
• Set a trigger on a rising or falling edge, with a threshold of something in the middle of your signal voltage range. Eg, if it's a 5V system, set the trigger at 3V or some such.
• Change your X axis (time) to much longer. This depends on how fast you're moving the motor, but 25 ns is way too fast to see the signals you probably care about. Something more in the 100 us or 1 ms range probably makes much more sense.

If you do the above, you'll probably see step/direction signals, or quadrature, or something. Either way, it's very likely something LinuxCNC supports "out of the box". Engineers are lazy and generally don't invent new protocols if they don't have to

After another glance, 17.3MHz !!!
That is the realm of radio frequencies, not something you find on a machine.... usually.

What range of frequencies are usually used by cnc machines?

Signaling usually from 100Hz to 1000Hz, some up to 100KHz, and very rarely up to 1MHz.
There is no recipe for it, depends on a lot of stuff, so not easily framed into an answer, but:
-switching power supplies from 15KHz (older) to 400KHz (new ones)
-CPU inside a PC nowadays 2-6GHz, but almost all use a 100MHz clock
-power lines in USA 60Hz, in Europe 50Hz
-Mesa boards can do up to 10MHz, but most i ever needed was 0.96Mhz or 960KHz
-etc etc