Recent Posts

1

General Technical Chat / Re: $20,000 dollars of software or licences on a thumbdrive ?

« Last post by Siwastaja on Today at 06:14:29 pm »

The story is obviously made-up. Obviously when you buy expensive software, you register your order with the publisher and if you lose your copy, any company would give you a new copy. It's not like you'd anonymously buy a license for a multi-thousand $ software.

2

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by BillyO on Today at 06:14:10 pm »

I meant I get a clean sine wave up to 841MHz.

I've been able to do that that too.  Well, I only went to 840MHz.

3

Manufacturing & Assembly / Re: Advice on adding missing parts to an assembled board

« Last post by Kean on Today at 06:14:10 pm »

Not easy working with small squeeges to fit between components but probably easier and cheaper than what OP was considering: using small stencils.

You would also need to exclude all of any non-JLC placed footprints from the manufacturing stencil used by them, otherwise those pads will already have molten paste and flux residue which has quite possibly spread wider than your new stencil apertures.  The new stencil will not be able to sit properly flat and/or your squeegee won't go over the solder bumps cleanly... meaning the squeegee is lifted off the stencil.

Sounds like a great idea at first, but in practice the process is likely to be far more painful than you can imagine.  Your attempts at paste application will likely be awful.  A bad stencil "gasket" leads to paste leaks causing bridges, and the need to continually clean the underside of the stencil.

You'll wish you either hand-placed the whole thing, or paid a fortune for a local assembly company.   

4

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by KungFuJosh on Today at 06:09:36 pm »

I'd love to play, but I don't have one of these scopes. I have an SDS2504X+ 500MHz scope.

Well, it would still be an interesting data point. What's the lowest samples/sec rate it can do? The idea is to set it to the lowest sampling rate and connect it to a source that outputs a frequency sweep in the range from ~20% to ~60% of the sampling rate.

We can then speculate if the Siglent's 800 HD series have the same wave reconstruction implementation as yours, or not .

I guess, if I feel like procrastinating something else, I could do that. We'll see. 😉

I can sweep up to 841MHz on my scope with the TinySA Ultra.

It can actually output up to 5.4 GHz (or at least so the specs say), but it switches from sine to square wave above 800 MHz.

I meant I get a clean sine wave up to 841MHz.

5

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

« Last post by mawyatt on Today at 06:09:30 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

Imagine the "apparent beam" location being dynamically distributed spatially, even such that it can be "positioned" on an adversary.

In the battlefield an adversary fires a short range radar tracking missile which is quickly sensed and the apparent missile tracking radar signal is dynamically realigned to the missiles origin!!!

Best,

6

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.

7

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.

8

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.

9

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.

10

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