Show us your square wave

[Electro Fan]

10, 20 and 40MHz square waves from Altera Stratix FPGA Enhanced PLL to Tektronix 2465. CMOS 2.5V IO standard.

The old boat anchor is still beating specs (a little) 30 years after being built (and 10 years after last pro calibration sadly  )

Nice scope indeed and your DUT produces some very good looking square waves.

Is this what you were testing?

http://www.altera.com/devices/fpga/stratix-fpgas/stratix/stratix/features/stx-pll.html

[Rupunzell]

Sounds like an "solid state" version of the Bill Hewlett's audio oscillator with a square wave output made in the UK.

Does design this use a light bulb as a non-linear resistor to regulate feed back in the same way as Bill Hewlett's design and masters thesis at Stanford U.


Bernice

Here is an historic one from a Levell TG150D that I've just been given and hope to restore (it is very noisy at present).

The maximum it can do is 2.5V and 160kHz (nominal 150kHz but the dial goes a bit higher).

EDIT:
I realise that I had the attenuated set for 20dB so I've added a shot with it off below.

Nice to see something old enough to be in KC.   I bet the lamp holder is actual glass.    Any idea on the age?  50s?    I can just see someone driving their high tech relay logic with this back in the day!   

This model actually made it into "Journal of Scientific Instruments" page 34 Vol 38 January 1961.
The particular one I got was rescued from a skip when one of the Cambridge University Physics Labs was having a clear out. So it is 60s rather than 50s and has probably been abused by generations of physics students.

EDIT : I attach a photo of the Journal excerpt.

[EV]

Rigol DS2202, DG4000:

[Rupunzell]

Compare that RG-58 stuff with Gore instrumentation coax.
http://www.gore.com/en_xx/products/cables/coaxialmicrowave/test/gore_phaseflex_microwave_test_assemblies.html


How good does it need to be is the real question. In most cases, RG-58 is OK to use for lower frequency work. Cables are also microphonic which can be serious if small signal are involved.

Using the wrong cable-interconnect often ends in big fat tears and much frustration for trying to figure out why are the signals so very wrong.


Bernice

That's actually contradictory: you can't have RG-58 that's not "chop suey".  The original spec for the stuff is terrible.

Indeed, but the cable I have is slighlty better:
http://www.pasternack.com/images/ProductPDF/RG58C-U.pdf

All I wanted to say is that the cable is not one of the the $2 items from ebay.

[LukeW]

Not mine, but if you want a fast scope, there is some history, teardown pics and discussion of the beautiful Tek 519 here: http://www.timkoeth.com/?p=108

[tautech]

That's actually contradictory: you can't have RG-58 that's not "chop suey".  The original spec for the stuff is terrible.

Indeed, but the cable I have is slighlty better:
http://www.pasternack.com/images/ProductPDF/RG58C-U.pdf

All I wanted to say is that the cable is not one of the the $2 items from ebay.

Compare that RG-58 stuff with Gore instrumentation coax.
http://www.gore.com/en_xx/products/cables/coaxialmicrowave/test/gore_phaseflex_microwave_test_assemblies.html


How good does it need to be is the real question. In most cases, RG-58 is OK to use for lower frequency work. Cables are also microphonic which can be serious if small signal are involved.

Using the wrong cable-interconnect often ends in big fat tears and much frustration for trying to figure out why are the signals so very wrong.


Bernice

Many don't require cable connection for more than a few tens of MHz and as you say RG58 is fine and cheap enough for ppl to use.
More than 100 MHz and signal components with fast risetimes is a different story and quality cables should be sought.

Bernice thank you for your fresh input, no doubt you have more to offer. 
Can I make the suggestion that you quote before your reply as it makes the post easier to read.
Sort of like how I've amended your last post. 

[jpb]

Sounds like an "solid state" version of the Bill Hewlett's audio oscillator with a square wave output made in the UK.

Does design this use a light bulb as a non-linear resistor to regulate feed back in the same way as Bill Hewlett's design and masters thesis at Stanford U.


Bernice

In the circuit diagram the light bulb is only used as a battery check and there is a thermistor for temperature feedback.  Of course the thermistor might actually be another light bulb -  I've not taken it apart to have a look yet.

[jancumps]

Metex MS-9150 2 MHz

Square wave output loaded with 50 Ohm:


TTL output:

[MartyD]

A few screenshots from my Siglent SDG1025, taken with the SDS1102CML, 1m Coax, 50Ohm terminator:

[Wuerstchenhund]

Many don't require cable connection for more than a few tens of MHz and as you say RG58 is fine and cheap enough for ppl to use.
More than 100 MHz and signal components with fast risetimes is a different story and quality cables should be sought.

The problem with RG-58 is that the original spec was very poor. Many modern variants are much better but the variation between RG-58 cables can be huge. I'd always use a good quality cable (Gore is fine, although I prefer Huber & Suhner and Pasternack).

Bernice thank you for your fresh input, no doubt you have more to offer. 
Can I make the suggestion that you quote before your reply as it makes the post easier to read.
Sort of like how I've amended your last post. 

Save your breath. He's pretty deaf on that ear 

[Electro Fan]

Hi, Thanks to all the posters for the good examples and info.  There are lots of questions that could be asked about what constitutes a "strong" square wave (I think "strong" is probably NOT an official technical term  ).  (And certainly, one set of questions revolves around the ability to generate and render excellent rise times but I'll leave that for another post.)

I realize that there are many setup variables that can contribute to how waveforms render (generator equipment, cabling, termination impedance, scope capabilities, etc, etc.).  My questions here are somewhat less about the equipment and setup - and more about how to read/interpret what is displayed.

Below are two examples:  one from a Rigol DG1032Z and one from a Rigol DG1062Z - presumably similar other than bandwidth.  Admittedly, they are each hooked to different scopes (the 1032 to a Rigol DS2022A and the 1062 to a LeCroy 7300A) and likely with different cables.  Additionally, I could be wrong but I think the  1032 was probably terminated into 1 Mohm on the Rigol vs. 50 ohms on the LeCroy.  (The bandwidth on a Rigol 2202 is typically 200MHz and I think it's 3GHz (with 20GSa/s!) on the LeCroy 7300 - big difference and probably there is a healthy difference in price too.)

Given all that my questions are about the level of detail seen on the two images.  In particular, the images from the 1032 on the 2202 are pretty distinct (sharply detailed?).  They show a pretty defined ringing at the tops and bottoms.  The images from the 1062 on the 7300 don't seem to convey the ringing as distinctly.  Perhaps there is less ringing shown on the 1062/7300 because of 1) the 50 ohm termination? (doubtful but maybe?), 2) the extra bandwidth of the 1062 vs. the 1032? (doubtful but maybe?), 3) better cabling?, or 4) the extra bandwidth and sampling of the 7300? (I don't know the specs on the display resolution - maybe that's better too on the 7300 but I'm betting it's the outstanding bandwidth and sampling of the 7300 that we are seeing), or 5) maybe it's something else?  On a related observation, the tops and bottoms of the 1062/7300 combination appear much thicker than the tops and bottoms of the 1032/2202.   Perhaps this is due to the ability of the 7300 to process and resolve (and ultimately display) noise more accurately beyond what the 2202 can resolve and display.  Interestingly, the thicker tops and bottoms on the 7300 seem to be of an amplitude roughly similar to the ringing that is seen on the 2202.  Perhaps that is why the ringing is not so evident on the 7300 (ie, the ringing is hidden in the noise)? 

Net, net:  which setup (the 1032/2022 or the 1062/7300) most accurately represents the phenomenon occurring?  Is the waveform on 1032/2022 setup cleaner/more defined/more accurate or is it missing information that is being revealed by the 1062/7300 setup?  I'm betting the difference is that the 2022 simply can't render the information as accurately as the 7300 but I'm curious to know...

Thanks, EF

PS, one other observation:  the Rigol seems to use square divisions and the LeCroy uses rectangular divisions - a bit off topic but an observation...

[Pjotr]

Don't see much different about the ringing. With the LeCroy it's more buried in the noise of the scope.

[G0HZU]

Jeez... Some of the low frequency squarewave plots from the modern stuff from Rigol and Siglent are less than impressive.

I'm not really into pulse risetime races but I do have some ancient and low spec pulse generators from the 1970s here. eg the bargain basement 10MHz models from HP or Datapulse and they produce nicer square waves at 1MHz and 5MHz. (HP8002A and Datapulse 101) The Datapulse claims a risetime of 5ns and the HP is about 10ns. I paid £5 for each of them about 20yrs ago at a ham surplus sale.

Do people really accept that level of performance from Rigol? Looks woeful compared to basic old school stuff that was designed and built about 40 years ago.

Note: I just noticed that the later plots from the Siglent gear look to be better. So maybe the first plot was poorly set up?

[Yago]

With all the talk of cable and connector quality, what (and where from in UK) would qualify as reasonable up to say 150Mhz, for a BNC to BNC patch?
 
Cheers

[jancumps]

Jeez... Some of the low frequency squarewave plots from the modern stuff from Rigol and Siglent are less than impressive.

I'm not really into pulse risetime races but I do have some ancient and low spec pulse generators from the 1970s here. eg the bargain basement 10MHz models from HP or Datapulse and they produce nicer square waves at 1MHz and 5MHz. (HP8002A and Datapulse 101) The Datapulse claims a risetime of 5ns and the HP is about 10ns. I paid £5 for each of them about 20yrs ago at a ham surplus sale.

Do people really accept that level of performance from Rigol? Looks woeful compared to basic old school stuff that was designed and built about 40 years ago.

Note: I just noticed that the later 5MHz plots from the Siglent gear look to be better  so maybe the first plots were poorly set up?

I'd be careful to draw too much conclusions out of this thread.  We're all having good fun - but not all of us may have used state-of-the-art measuring methods.
Mainly looking at myself here

[BloodyCactus]

well, the 1032 screen shot is mine, I used the cable that came supplied with the unit (1032Z), and it was into the rigol at 1Mo, the square wave was 5vpp, 50% duty cycle. rigol dont give specs on the provided cable.

note, if I use the 300mhz option the ringing is much worse.

here is the 50mohm of 1mhz.

[G0HZU]

I took a quick image of the HP8002A generator response on my Tek 465 when the HP8002A is giving a 10MHz squarewave. This is on (50ns/div x10) so it is 5ns/div.

It doesn't look bad for a basic 10MHz pulse gen that was made about 40 years ago. I expected the modern gear to be far better than this?

[N2IXK]

Hewlett Packard 3312A function generator @ ~7.5 MHz, displayed on Tektronix 7904 w/7A26 amplifier. Connected directly to scope input via 3' of RG-58, terminated w/50 ohms via T connector at scope input.

[miguelvp]

Rigol DS2202, DG4000:

I hope your DG4000 wasn't set to 50% duty cycle

[G0HZU]

Here's the old Datapulse 101 (1970s vintage?) at 10MHz on 5ns/div and you can see it just meets its published spec for 5ns risetime. However, the Tek 465 risetime will be starting to limit the performance here.

However, the quality of the squarewave isn't as nice as the HP8002A as it looks quite lumpy.

[pedroteck]

70s hung chang 5502 20 MHz cro .

[Yago]

What frequency signal Pedro ?

[tautech]

EF
That both DSO's display the ringing artifacts of the waveform is the inportant thing, even though they are from 2 FG's.
This ringing implies a cable or termination problem.
Have you set the FG output for 50 Ohms or Hi Z as required by the termination available?

Yes the LeCroy will resolve and display more info as a result of its much higher sampling rate.

Your LeCroy has 10 horizontal divisions as was the norm until recently whereas the Rigol has 12.
MartyD's Siglent SDS1000 series shows 15 with the Menu out, 18 with the menu hidden.
https://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg588973/#msg588973

Accuracy.
Set your AWG to a P-P level and read the resultant P-P level on the scope.
Termination method WILL influence result.
Carefull study af preceeding posts will display these errors as a result of sub-optimal connections.

[Electro Fan]

Rigol DS2202, DG4000:

I hope your DG4000 wasn't set to 50% duty cycle

That was from a Rigol DG4000 series at 40MHz with a rise time less than 2ns?  Must be either a DG4162 or maybe a DG4102.  Either way, impressive.  (I'm betting you had it set to something other than 50% duty cycle.)

[AlfBaz]

Here's a shot of a Wavetek 395 at 20Mhz into 50ohm. It can go up to 50Mhz but it's pretty much sine looking beyond 25Mhz