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How to reduce noise on digital oscilloscope?

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indman:

--- Quote from: pcprogrammer on October 22, 2024, 08:34:57 am ---Looking at the photo showing the probe connection on the board, there are three coils besides the probe tip, and with the ground lead "miles" away from the scoping point, it easily picks up the signals the coils may emit. Looking at the signal on the scope it shows switching spikes. So are these coils part of a switching supply?

--- End quote ---
You are right, and if you look even more closely, you can see to the right of the probe a large row of relays, which also have windings with wire and can be sources of interference. ;)


--- Quote from: Fungus on October 22, 2024, 08:40:42 am ---It's normal

--- End quote ---
This video is a must watch for anyone who owns a digital oscilloscope. Then there will be fewer questions about noise. ;)

Kean:
I agree regarding the probing of the PCB being a potential problem.  The probe is close to potentially radiating components, and has a very long ground lead that will pick up noise.

The PCB that the OP is probing appears to be this Indonesian transceiver kit: https://products.ajetronic.com/2024/06/kit-radio-bitx-allband-tanpa-power.html

--- Quote ---Allband Bitx Radio Kit without Power Amplifier (Just Exciter, need additional linear amplifiers to be able to transmit)
--- End quote ---

A video showing it (Indonesian):

Found via text labels of "ye3cif.com" and "AJE-101".  I didn't find a schematic for this, but there are schematics of other PCBs on an Indonesian amateur radio site ye3cif.com

Aldo22:
Nevertheless, I still wonder how an intact scope in AC coupling mode can produce such an offset, as tautech mentioned.

Kean:

--- Quote from: Aldo22 on October 22, 2024, 04:06:43 pm ---Nevertheless, I still wonder how an intact scope in AC coupling mode can produce such an offset, as tautech mentioned.

--- End quote ---

The fact the trigger level is above the signal could maybe mean this trace was captured with different settings than shown?

indman:

--- Quote from: Kean on October 22, 2024, 04:14:30 pm ---The fact the trigger level is above the signal could maybe mean this trace was captured with different settings than shown?

--- End quote ---
Is it also likely that the user himself shifted the signal higher or lower after the capture? ;)

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