# Re: AGC and Dynamic Range of ADC

**URL:** <https://www.ruby-forum.com/t/re-agc-and-dynamic-range-of-adc/236677>\
**Category:** GNU Radio\
**Created:** [September 24, 2013, 4:32pm UTC](https://www.ruby-forum.com/t/re-agc-and-dynamic-range-of-adc/236677 "2013-09-24T16:32:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [September 24, 2013, 4:32pm UTC](https://www.ruby-forum.com/t/re-agc-and-dynamic-range-of-adc/236677/1 "2013-09-24T16:32:00Z")

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On 09/23/2013 11:07 PM, bob wole wrote:

Can somebody please guide me on this ?

Bob

On Fri, Sep 20, 2013 at 4:44 PM, bob wole [address@hidden](mailto:address@hidden) wrote:

> I have USRPN210 with WBX and RFX2400. Is there any AGC chip on N210  
> motherboard or WBX, RFX2400 before ADC to utilize the dynamic range of ADC  
> ? if yes, which one? If not, then won’t the varying input signal (for  
> example signal from moving object) to ADC affect the performance of ADC ?
> 
> Bob

> > The ADC on an N210 has over 80dB of dynamic range. If that \>\>isn’t  
> > enough, then your application can adjust the RF gain to taste.

> > Only a subset of applications actually benefit from the usual \>\>hardware  
> > AGC schemes, and such schemes are invariably \>\>application-specific, so  
> > there’s  
> > no _automatic_ gain control. But your application can \>\>dynamically  
> > make gain adjustments as it goes.

Hi Marcus thanks for response, If there is no automatic gain control  
then  
how does it is ensured that ADC doesn’t saturate ? I mean what if there  
is  
a signal whose amplitude is greater that ADC’s highest input level ?  
Won’t  
it saturate the ADC ? Also what if the signal is too weak to span much  
of  
the ADC input voltage, then again we are not using all bits effectively.  
Guide please.

Thanks,

Bob

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<div class="post-metadata">

**Author:** ![bob\_wole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/b4bc9f/32.png) [@bob\_wole](https://www.ruby-forum.com/u/bob_wole)\
**Post date:** [September 24, 2013, 4:36pm UTC](https://www.ruby-forum.com/t/re-agc-and-dynamic-range-of-adc/236677/2 "2013-09-24T16:36:41Z")

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On 09/24/2013 10:30 AM, bob wole wrote:

> > ```
> > N210 motherboard or WBX, RFX2400 before ADC to utilize the
> > 
> > ```
> > 
> > > Only a subset of applications actually benefit from the usual  
> > > weak to span much of the ADC input voltage, then again we are not  
> > > [http://www.sbrac.org](http://www.sbrac.org)[http://www.sbrac.org/](http://www.sbrac.org/)

There is nothing to ensure that ADC values are neither “too little” nor  
“too big”. That’s up to your application. There’s an RF gain control  
on the  
WBX, for example, that gives 31.5dB of gain control. If you have  
very weak signals, then you have to use an external LNA. If your  
dynamic  
range requirements exceed the 80dB dynamic range of the ADC, then  
your application has to account for this, and adjust RF gain  
accordingly.