What is OV marker on S meter?

Comments

• jks

  December 2016

  I updated the "ADC overload" section of the quick start page to talk about the OV indicator (http://www.kiwisdr.com/quickstart/#id-overload), but I didn't elaborate on the "simple way" in which the ADC overflow pin is treated by the software currently.

  
  

  Right now if the ADC asserts the overflow pin, even once, during each ADC sample period (66.7 MHz) it gets latched and passed all the way up to the S-meter code running on the Beagle. Then each time an S-meter reading is sent to the browser for display the latched value (on or off) goes along and then the latch gets reset. Now this is not optimal behavior in a strong signal environment. It is quite possible to have "bad luck" during a single sample period where all the signals (0-30 MHz) happen to add up and overflow the ADC even though the ADC is not really under a chronic overload condition that would show as wide-band distortion. The OV indicator will flicker as signal levels increase. Finally it will be on all the time. But even then there may not really be a problem.

  
  

  What you really want is a counter showing how much of the time during the S-meter sample interval the ADC overflow pin was asserted. Was is 1%, 50% or 99%? Then you could make a much better decision about when to light the OV indicator.

  
  

  
  
• W5UXH

  December 2016

  Thanks for the information.   At my level, just knowing that it is ADC overload means I don't need to wonder about it anymore.  I should have gone back through the quick start and been able to learn that though:)