WHAT IS THE DIFFERENCE BETWEEN RECEIVER OVERLOAD AND ADC OVERFLOW?
This is an excerpt from Varian VNMR News dated 11-18-2001. Some users wonder why occasionally they observe an ADC overflow without a receiver overload, or why sometimes they see a receiver overload that is not also causing an ADC overflow. While it is obvious that with an ADC overflow the incoming (audio) signal could not be digitized properly (which usually causes severe spectral distortions), it is often unclear what the significance of a receiver overflow is. The difference between receiver overload and ADC overflow is more than the fact that an ADC overflow is a “digital” measure for “too much signal”, while the receiver overload is measured with an analog method: additionally, the ADC samples the signal after the programmable audio filter, while the receiver overload is derived from the signal level just before the programmable audio filter. This gives us two reasons why the two signals may appear at different levels: • there may be large signals outside the audio filter bandwidth
