Just wanted to know if the unit is faulty because in the images posted by you (and others) it looks like the noise is lower, but it may be that I'm in a noisy environment..I'll check this.
cex:
About possible noise problem in CH1.
Do next:
Insert 50 ohm terminator to CH1 and CH2 if you have 2 pcs terminator.
set acquire to peak
memory 10k - 10M
speed 10ms/div.
CH1 and CH2 x1, 10mVac,
Both channels on.
Both channels noise need look same amount. (<0.3div (typically 0.15 - 0.2div)
If you have only 1 terminator.
Do test first with CH1 and then same test with CH2.
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With FFT:
First do "default" for oscilloscope settings.
Insert terminator to CH1
Set CH1 x1, 10mVac / div
(speed is as is)
go to FFT,
Turn CH1 V/div so that there read 10dB (one click counterclockwise)
Turn CH1 vertical position so that trace bottom is one div up from bottom line.
Turn frequency (horizintal speed)
So that middle is 25MHz.
Can you see small peak just right from center line. (position around 26 MH)
Wait a short time and watch if there is this peak. (maybe example 10dB over random noise or even more)
If you see this peak, wait more and look if there can see sometimes many random peaks both side of this peak and even more high... (these do not appear continuously becouse they need occure just this time when sampled)
If you can not see these and you continuously see only around 1 - 2 div high random noise then you do not have this special problem what is ONLY in first produced units what are these "new generation" improved HW models. Later this problem have solved in Owon.
If have not 50ohm terminator, it is not so easy to see this problem but it can try also with probe.
Set probe 1x, connect probe tip and GND directly together without scope GND wire. (take short part of wire and wound it over probe tip and together with GND surface near probe tip. Put probe on the table directly away from any EMI source.
CH1.
If you can not see clear difference firts in CH1 and CH2 comparison with peak acquire and then also if can not see this 26,6MHz peak on the FFT then you have not this special "problem". FFT you can switct to CH2 and you see there is not this problem or it is just barely visible... after solve CH1 problem it also solve CH2 if it can also see there. (if unit have this problem, typically it can not see in CH2)
If you have this problem please contact seller or directly to Owon for more instructions.
Solution is easy but
it need do in Owon accepted service using Owon mechanical part for this small HW EMI problem.
It was extremely nice that very fast Owon solve this problem and solution is enough good. It seems that only part of units suffer this small noise problem. Now in manufacturing there is this solution in use and not problem in new units now.
I do not know how before but this I know sure that units what have serial SDS7102
1152xxx or later they do not have this problem.
Owon have been very good and responsible and helpful for quickly solve this problem.