Recent Posts

1

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

« Last post by Mechatrommer on Today at 06:11:55 pm »

i tuned my sim files to this setup, 220MHz sampled at 500MSps (f = Sr / 2.27), here is what i come up with. so it seems Rigol and VisaDSO got broken implementation.

That interpolation looks broken indeed. It seems to assume that the sampled data points are alway the extrema of the curve. Why would that be the case? Whatever that "smooth" interpolation is, it's not sin(x)/x, I would say.

Edit: Did you ask for a sin(x)/x interpolation through all the linearly interpolated datapoints, by any chance? That might explain the strange results. Of course only the actual sampled points must be fed to the interpolation.

i just copied lanczos resampler code lying around in the internet somewhere, i dont have skill to code real Sinc filter nor i know how lanczos resampler is coded/works, assume its a black box functions. and yes i feed it with sampled points visible on screen and it returned like 10X points (sampled + interpolated points) and then plot on screen. i can guarantee those curve will pass through real sampled points... open source code like this... https://gist.github.com/kode54/6338299

2

General Technical Chat / Re: Russia and China to Build a Nuclear Plant on the Moon.

« Last post by strawberry on Today at 06:11:02 pm »

dont know some say that earth could be overheated by sun if didnt radiate excess heat to space
energy conservation law

maybe some fraction converts into kinetic energy

3

Beginners / Re: Checking for noise in resistors

« Last post by CatalinaWOW on Today at 06:07:46 pm »

In today's world the conceptually simplest way to test is to sample the voltage often enough to meet Nyquist for the frequencies of interest to you, and sample long enough to get solid data on 1/f noise and then data whip the resulting file.  You still have to do tests along the line that Tim mentioned to isolate the source(s) of the noise you find, and you have to assure that your sampling system is not the dominant noise contributor.  The latter requires either a lot of thought or a lot of money, or some combination thereof.

4

3D printing / Re: could anyone please print me a microscope Head adaptor ring

« Last post by davebb on Today at 06:03:54 pm »

ok thanks i will try,
Good idea using a tack head,
it should be good
i will let you all know how it works
Thanks again Roger for your good work,
Dave 2E0DMB

5

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

« Last post by ebastler on Today at 06:03:08 pm »

i tuned my sim files to this setup, 220MHz sampled at 500MSps (f = Sr / 2.27), here is what i come up with. so it seems Rigol and VisaDSO got broken implementation.

That interpolation looks broken indeed. It seems to assume that the sampled data points are alway the extrema of the curve. Why would that be the case? Whatever that "smooth" interpolation is, it's not sin(x)/x, I would say.

Edit: Did you ask for a sin(x)/x interpolation through all the linearly interpolated datapoints, by any chance? That might explain the strange results. Of course only the actual sampled points must be fed to the interpolation.

6

Test Equipment / Re: Siglent SDS800X HD 1Specifications

« Last post by mawyatt on Today at 06:01:30 pm »

Just put an order for a SDS804X HD scope.  Seems out of stock in Europe, but hope I will get delivery in a month or so.

Just got the scope today.

Discussion about clock time accuracy, anyone who has any open NTP-server IP to recommend for the scope?

We use 129.6.15.26 from here in Florida USA, believe site is in Maryland.

Best,

7

Beginners / Re: Checking for noise in resistors

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

But what do you want to find? As I understand, the noisier the tube amp is - the better. Or not? If you don't want noise at all - use metalfilm resistors.

8

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

« Last post by KungFuJosh on Today at 05:57:43 pm »

All 4 channels on.

this is what i meant... perfect sine reconstruction.. i tuned my sim files to this setup, 220MHz sampled at 500MSps (f = Sr / 2.27), here is what i come up with. so it seems Rigol and VisaDSO got broken implementation.

Well, it looks pretty cool anyway! 😉

9

Beginners / Re: Checking for noise in resistors

« Last post by Calambres on Today at 05:56:52 pm »

Well, while I agree it should be easier to change all old carbon resistors for newer and better ones, I still would like to have (build) some type of testing device. I feel courious...

10

Other Equipment & Products / Re: Different bases on Amscope microscope

« Last post by KE5FX on Today at 05:54:23 pm »

The arm itself is fine, but yes, that clamp is not great.  I mounted mine with a couple of heavy carriage bolts:



If I had clamped it to the edge of the workbench, rather than securing it directly to the surface where two benches are strapped together, it would probably be shaky enough to bother me, as the 'workbenches' are just folding tables.   (It would also rip the edge off and fall to its death sooner or later.)

Another disadvantage of the articulating boom is that you can't really parfocus the microscope, because it doesn't end up in the same horizontal plane every time you reposition it.  That's probably my biggest complaint, but it is what it is.  The advantages overcome the annoyances by a big margin.