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Oscilloscope probe ground leads act as FM attennea
Martin72:
--- Quote --- Is this why people wear tinfoil hats?
--- End quote ---
;D
Do you have a metal box ?
You could put the scope in there and then see if the irradiations become less.
But I am afraid that the probe will still be the "antenna".
dmulligan:
--- Quote from: Martin72 on October 30, 2023, 09:45:58 pm ---
--- Quote --- Is this why people wear tinfoil hats?
--- End quote ---
;D
Do you have a metal box ?
You could put the scope in there and then see if the irradiations become less.
But I am afraid that the probe will still be the "antenna".
--- End quote ---
Tinfoil hats and metal boxes are just two different styles of faraday cages. I am thinking about wrapping a cardboard box in foil, grounding the foil then using the web interface to look at the results.
ledtester:
[quote author=dmulligan link=topic=398355.msg5143530#msg5143530
A few days ago I reported that I turned everything off and unplugged all the things in this room with no significant change. I am waiting for an opportunity to shut off all breakers in the house and turn them back on one at a time. There are so many devices in my home, it could be coming from anywhere. Is this why people wear tinfoil hats?
[/quote]
Just don't go too crazy trying to find it...
Coppola - The Conversation - ending
https://youtu.be/SEo7FGkmRx0
dmulligan:
I finally found the opportunity to shut down the power to the rest of the house. I didn't set the scope up in the same location due to travel time to my normal work area. I regret not doing that as the last step. I was only seeing 35mV of noise with my scope plugged in beside the breaker which wasn't good for testing for lower noise. I tried a few more outlets around the basement with similar luck. Eventually I decided to use an extension from the outlet where I saw the lowest noise from and located my the DHO804 at the top of the stairs. I was only seeing 80-100mV of noise but at least the FFT showed the same peaks across the FM band. Shutting down all other circuits yielded no change.
Learnings:
1) Noise source doesn't seem to be local.
2) Noise improves the lower down I get. The other way to think of that is the noise improves the further I get the scope away from line of sight to the towers.
3) (Separate from this test) Twisting the ground leads around the probe lowers the noise, often significantly.
I would really like the convenience of both working upstairs and using ground leads at least sometimes. I wonder what other mitigation methods I can use. I have some more split ferrite beads of unknown value coming from Amazon today that I can try on my bench power supply cable, ground, scope AC and scope DC cables. I've read that a grounded antistatic mat has helped with some types of probe noise, I don't know if that could help mine. I suppose that I could simulate that with some foil or a cookie sheet and a ground wire.
Are shorter or lower inductance ground leads available? LeCroy makes a "HF Compensated Ground Lead", I wonder if I can find them for Rigol probes or if I can find affordable probes with some. I wonder what sort of sorcery makes them special and how effective they are. From the probe datasheet "A passive network in the lead itself reduces the loading effect of any resonance." At 35USD I really hope they are special and at that price I don't think I'll be buying one to test if it even fits my probes let alone helps with my problem.
ebastler:
--- Quote from: dmulligan on November 27, 2023, 08:16:45 pm ---Are shorter or lower inductance ground leads available?
--- End quote ---
Do the Rigol probes come with ground springs which you attach right to the front of the probe (after pulling off the hook attachment)? If so, have you tried what difference these make? They are not applicable in every situation, since a ground connection needs to be available very close to the measurement point -- but should work on the 1 kHz reference output, and will give you another data point.
EDIT: Ah, sorry -- just saw your older post a page up where you already mention that you successfully tried these.
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