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Mahmood Elnasser
06/09/12 23:08
Read: 774 times
Sacramento
USA


 
#187651 - 20 nsec steps
Responding to: Richard Erlacher's previous message
Yes I tried it with 20 nsec steps and 40 nsec pulse width and it showed the pulses slightly attenuated and you can see the phase shift move clearly. The funny thing is that I couldn't trigger these signals on my analog tektronics I kept fiddling with the knobs for 15 minutes. For some reason it triggered only on normal mode and not auto few days ago.
I have two DDS function generators, one from 0 to 2MHz and the othter from 0-5 MHZ, they are cheap modern type based on FPGA, I also have DDS module 0 - 40 MHz based on AD9850 but it needs a microcontroller circuit and LCD, which I built in the past but it doesn't have output amplifier and amplitude offset. But to be honest FPGA development boards are quite cheap and you can build any signal generator with them quite easily. I used the DCM of my FPGA and raised the frequency to 300MHz , both scopes went blind and I know that the FPGA board is still working because the push button switches and LEDs are still functional.
I guess you need a special probe for high frequency and you need impedance matching to display the high frequency waveform correctly. Do you know how to match the output of FPGA to the 50 ohm scope?
Mahmood

List of 74 messages in thread
TopicAuthorDate
DSO for cheap!      Joseph Hebert      05/11/12 13:35      
   very good      Mahmood Elnasser      05/11/12 14:14      
      Limitations      Joseph Hebert      05/12/12 09:49      
         test results      Mahmood Elnasser      05/12/12 12:46      
            That's valuable information      Joseph Hebert      05/12/12 13:30      
         well, the fact is ..      Richard Erlacher      06/03/12 11:43      
            tektronix 475 comparison      Mahmood Elnasser      06/07/12 10:37      
               Really? Why?      Richard Erlacher      06/07/12 14:51      
               another double post ... sorry      Richard Erlacher      06/07/12 14:51      
   I think ...      Erik Malund      05/11/12 14:34      
      Application dependant      Mahmood Elnasser      05/12/12 05:55      
         Indeed      Andy Neil      05/12/12 09:10      
            It's still too low a bandwidth, wouldn't you say?      Richard Erlacher      06/03/12 11:50      
   just curious, Joe could you try      Erik Malund      05/11/12 14:36      
      Unusual with short pulses for hobbyist projects      Per Westermark      05/11/12 14:53      
         is the clock running?      Erik Malund      05/11/12 16:01      
      Sorry, but no I can't.      Joseph Hebert      05/11/12 16:42      
      10nSec Pulse      Mahmood Elnasser      05/12/12 12:59      
         "at random" means what exactly ?      Jim Granville      05/13/12 18:41      
            Answers      Mahmood Elnasser      05/14/12 07:41      
               more observations      Mahmood Elnasser      06/03/12 10:51      
                  It may not be the sample rate ...      Richard Erlacher      06/07/12 15:07      
                     digital vs analog      Mahmood Elnasser      06/08/12 15:34      
                        Don't get me wrong, here ...      Richard Erlacher      06/08/12 21:34      
                           poor mans's scope      Mahmood Elnasser      06/09/12 02:01      
                              Doesn't it depend on what THEY mean by bandwidth?      Richard Erlacher      06/09/12 20:58      
                                 20 nsec steps      Mahmood Elnasser      06/09/12 23:08      
                                    Well, one thing at a time ...      Richard Erlacher      06/10/12 11:43      
                                    Impulse Tests are better      Jim Granville      06/10/12 16:49      
                                       more capable scope      Mahmood Elnasser      06/11/12 14:03      
                                          I must have missed a step ...      Richard Erlacher      06/12/12 08:07      
                                             TEK475      Mahmood Elnasser      06/12/12 16:16      
                                                here's another alternative ...      Richard Erlacher      06/12/12 22:16      
                                                   DAC and pot in parallel?      Per Westermark      06/13/12 01:07      
                                                      Logically, not physically      Richard Erlacher      06/13/12 07:57      
                                                   new theory      Mahmood Elnasser      06/14/12 00:57      
   3MHz is rather poor Bandwidth ?      Jim Granville      05/11/12 16:51      
      ordinary      Erik Malund      05/11/12 17:20      
         Ther are many params needed      Jim Granville      05/11/12 18:21      
   "only" $200 ?      Andy Neil      05/11/12 23:59      
      Low cost oscilloscopes      Andy Neil      05/12/12 09:18      
         291 > 2*($199)      Joseph Hebert      05/12/12 09:45      
            It doesn't always work that way      Andy Neil      05/12/12 10:48      
               Once upon a time ...      Joseph Hebert      05/12/12 13:28      
   SDS8202      Mahmood Elnasser      06/14/12 13:58      
      Read all the "fine print' first ... and ask any questions      Richard Erlacher      06/14/12 20:31      
         bought it      Mahmood Elnasser      06/16/12 03:07      
            Please let us know how this works out for you      Richard Erlacher      06/16/12 04:19      
               datasheet      Mahmood Elnasser      06/16/12 05:26      
                  2mV/div - but min trig level?      Per Westermark      06/16/12 07:01      
                     Tests      Mahmood Elnasser      06/16/12 09:55      
                        24ns      Per Westermark      06/16/12 11:09      
                           and that's the crux      Erik Malund      06/16/12 11:41      
                              FPGA pulse Expander (edited)      Mahmood Elnasser      06/16/12 12:06      
                                 some love the mother, some love the daughter        Erik Malund      06/16/12 12:13      
                                 Here's omne fairly simple thing ...      Richard Erlacher      06/16/12 15:22      
                                 self calibtrate?      Jim Granville      06/16/12 20:42      
                                    interesting      Mahmood Elnasser      06/16/12 23:01      
                                       yes      Jim Granville      06/16/12 23:15      
                                          glurk      Jez Smith      06/17/12 13:33      
                                             DCMs      Mahmood Elnasser      06/17/12 14:49      
                                                Well....      Jez Smith      06/17/12 15:48      
                                                   I don't know where you're going with this ...      Richard Erlacher      06/17/12 21:25      
                                             xxxxx      Mahmood Elnasser      06/20/12 12:53      
                           333ps      Mahmood Elnasser      06/18/12 00:59      
      SDS9302      Mahmood Elnasser      07/05/12 10:32      
         So, how are you exercising this new 'scope?      Richard Erlacher      07/05/12 10:53      
            so far so good      Mahmood Elnasser      07/08/12 09:45      
               So far so good ...      Richard Erlacher      07/08/12 10:49      
                  rise time      Mahmood Elnasser      08/15/12 13:28      
                     The rise time indicates that high frequencies gets dampened      Per Westermark      08/15/12 16:26      
                     What does "bandwidth" mean?      Richard Erlacher      08/15/12 17:45      
                        good test      Mahmood Elnasser      08/30/12 15:09      
                           Perhaps you should repeat the test ...       Richard Erlacher      08/30/12 23:08      

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