Recent Posts

1

Test Equipment / Re: New 2ch pocket DSO+SG - Zeeweii DSO2512G

« Last post by Aldo22 on Today at 06:05:12 pm »

That's OK, just don't overdo the calibration, it won't be like a multimeter.

For calibration, I need a more or less accurate laboratory power supply and a functional signal generator, which I don’t have.

If you don't want to spend much, I purchased a cheap device like this one https://www.aliexpress.com/item/1005006786894152.html it comes with a hand written paper with the real measured values with good equipment and also states the date and temperature when they were done, it can be used to know how good are the measures of your equipment.

That's certainly nice, but only DC (afaics) and you don't really need that kind of accuracy for the scope.
An average multimeter is perfectly adequate as a comparison.
The scope only has to display approximately the same as the multimeter. So not exactly 1.0000V but e.g. with a battery 1.5xV or 9.xxV

But Autocal is also sufficient imo.

By the way, an FY3224s also has a DC mode and you can output -10V to +10V DC. If you compare this with a multimeter, it should be accurate enough as a reference for the scope.
Of course it can do sine, square etc. anyway.

2

EEVblog Specific / Re: EEVblog 1612 - Siglent SDS1000X HD 12 bit Oscilloscope Teardown

« Last post by skander36 on Today at 06:04:40 pm »

There seems to be another plastic film on the surface of the screen (?). Apparently a residue left on the surface of the screen during installation, and then the film marked with a red ribbon was put on top. Please check  it. Surface need look same half matte as SDS800. Least I have not seen this glossy surface  in SDS1000XHD what can see in your video.

Yes they have a screen protector. Mine had so many bubbles that i was forced to remove it from beginning. Anyway a bench scope shouldn't need a screen protector. His matte screen is pretty comfortable for the eyes.

3

RF, Microwave, Ham Radio / Re: High bandwidth FM signal generation

« Last post by pdenisowski on Today at 06:03:25 pm »

For example, imagine a large number of smart-phones moving around a large campus area and being elements in a vast synthetic aperture phased array able to dynamically beam form in real time while all the elements are moving around randomly!! You can imagine the enormous computational power required for this to work, yet all was condensed into a single ~1 Billion Device chip over a decade ago!!!

And how are the nodes (a) precisely time and phase synchronized and (b) controlled ?

I understand the theoretical part of this, but fail to see how it could practically be implemented on  a large (kilometers) geographical scale.

4

Beginners / Re: Convert US standard 115V to International 230V

« Last post by TimFox on Today at 06:01:03 pm »

As a practical matter, most modern electronic equipment is designed to work equally well at 50 or 60 Hz.
The more likely problem is 100 vs 120 vs. 240 V.
Possible exceptions include "Sola transformers", which are less popular now, that depend directly on the frequency, or motors whose speed depends directly on frequency.

5

RF, Microwave, Ham Radio / Re: High bandwidth FM signal generation

« Last post by pdenisowski on Today at 05:59:24 pm »

Check out the DARPA program Computational Leverage Against Surveillance Systems or CLASS.

Interesting that (to me) at least some of this seems like "security through obfuscation."

1) Waveform Complexity uses advanced communications waveforms that are difficult to recover without knowledge and understanding of the signals itself; 2) Spatial Diversity uses distributed communications devices and the communication environment to disguise and dynamically vary the apparent location of the signal; 3) Interference Exploitation makes use of the clutter in the signal environment to make it difficult for an adversary to isolate a particular signal.

As for "dynamically varying the apparent location of the signal" - I'm not sure what that's supposed to mean.  The apparent location?  I'm guessing they mean having multiple, geographically distributed nodes all transmitting simultaneously on the same frequency, but there are also ways of DF'ing those kinds of signals as well.

https://www.rohde-schwarz.com/us/applications/super-resolution-df-method-application-card_56279-199552.html

6

Beginners / Re: Checking for noise in resistors

« Last post by TimFox on Today at 05:58:27 pm »

To understand resistor noise, I recommend reading Chapter 12 of https://pearl-hifi.com/06_Lit_Archive/14_Books_Tech_Papers/Motchenbacher_Connelly/Low-noise_Electronic_Design.pdf , which is an update of the classic monograph by Motchenbacher and Fitchen: "Low-Noise Electronic Design", Wiley 1973.
I'm not aware of any equipment from that era specifically designed for measuring excess noise in resistors, but the books discuss test equipment designed to measure noise of amplifiers and semiconductors.
The fundamental difficulty is that the excess noise only rises above the unavoidable thermal noise in a resistor at relatively low frequencies, where measurements take a long time.
In some semiconductor devices, the "corner" frequency where excess noise exceeds thermal noise is much higher.

A recent technical article on measuring resistor noise:  https://www.mdpi.com/1424-8220/23/3/1107

Back in graduate school, I measured excess noise in thick-film high-voltage resistors by very carefully applying 300 V from a dry battery (no longer available) and coupling the output through a good capacitor to a low-noise current preamplifier (from Princeton Applied Research, no longer available) into a strip-chart recorder.  One must be very careful not to smoke the input of such a preamplifier with spikes from applying the voltage.

7

Security / Re: Microsoft repackages apps with a telemetry .NET wrapper

« Last post by radiolistener on Today at 05:58:19 pm »

What a myopic, hysterical, uninformed, and untrue claim.

There are definitely some uses for telemetry that are absolutely beneficial to the user: crash reports and usability research. Developers use crash reports to figure out what the most common application crashes are, so they can fix them.

We had telemetry system which was used for the system state monitoring, but as developer I don't remember even one case where I worked with the bug or crash report obtained with telemetry. All this is usually done with usual logging and issue tracker. I remember that we had some experimental telemetry to collect logs, but it was never used in production due to security reason.

I don't see telemetry use case for bug fix and crash report analysis, especially if its about not private system, but about collecting data all around the world. It just will be flooded with false positive and not relevant data for bug fixing.

As operating system user I don't need that someone research usability on my machine. Such an attempt to justify telemetry looks like grant unlimited permission to some random unknown student to allow him to access your private home at any time and examine your genitals while you sleep to research your usability...   

8

General Technical Chat / Re: ultra sonic transducers

« Last post by CatalinaWOW on Today at 05:55:48 pm »

I would not view the claim of 150 feet range by one commercial unit as reliable.  Unless you know a lot more about the company providing this unit, their history, user reviews and published data of results the claim must be treated as possibly false.  The field of ultrasonic control device is rife with charlatans.  Some may be good, solid providers, others are sincere but don't have a sound basis for their devices effectiveness and others are full on lying, with devices that don't even have measurable output. It is a good field for scammers as proof of defectiveness is hard to come by.

9

Beginners / Re: Convert US standard 115V to International 230V

« Last post by sanleontexas on Today at 05:55:15 pm »

The transformer really doesn't care if it's 50 or 60 Hz, it'll run fine either way. If it's a
50Hz transformer it'll actually run slightly cooler at 60Hz because it may have more
copper in it. And a SMPS will generally also run OK at either line frequency.
Unless there's some kind of frequency sampler circuit that wants to see a particular
line frequency(which would be rather odd), it's not worth the bother to design the
device for one or the other.

 

10

RF, Microwave, Ham Radio / Re: High bandwidth FM signal generation

« Last post by mawyatt on Today at 05:54:57 pm »

Check out the DARPA program Computational Leverage Against Surveillance Systems or CLASS.

https://www.darpa.mil/program/computational-leverage-against-surveillance-systems

We developed the computational chip over a decade ago for CLASS.

is there any public available detailed info about used approaches in this program?

Best check with DARPA directly, we can't disclose details on most things for obvious reasons.

One thing that we can disclose is the ability to create dynamic in real time and position elements for phased array beam forming. Think of this as a large physical area and number of moving in position and time phased array individual elements collective forming together in real time for massive beam forming capability

For example, imagine a large number of smart-phones moving around a large campus area and being elements in a vast synthetic aperture phased array able to dynamically beam form in real time while all the elements are moving around randomly!! You can imagine the enormous computational power required for this to work, yet all was condensed into a single ~1 Billion Device chip over a decade ago!!!

Best,