I only picked 1 mV as an EXAMPLE.
I fully understand that the designer can make it whatever he or she wishes,
limited only by the capabilities of the devices available.
Gary
> On Sep 11, 2016, at 4:40 PM, Carl Moreschi <n4py3@earthlink.net> wrote:
>
> There's no law that says the step size has to be 1 mv. It can be whatever
> the design allows.
>
> Carl Moreschi N4PY
> 58 Hogwood Rd
> Louisburg, NC 27549
> www.n4py.com
>
> On 9/11/2016 5:04 PM, Gary J FollettDukes HiFi wrote:
>> I understand and appreciate this discussion of NOISE dynamic range. This
>> does not explain how one can get SIGNAL dynamic range higher than ~96 dB
>> with 16 bits. These are different quantities.
>>
>> If the A to D has say, 1 mV per bit response, then the largest input signal
>> this 16 bit A to D can measure should be ~65,000 mV. That’s about 96 dB.
>> Please tell me what I am missing here…
>>
>> Is the input amplifier compressing the RF input signal dynamic range range
>> to make this work? This was done on Vinyl records to compress the roughly
>> 120 dB dynamic range of an orchestra down to the 70 dB or so that Vinyl
>> records could carry.
>>
>> Gary
>>
>>
>>
>>> On Sep 11, 2016, at 6:49 AM, shristov<shristov@ptt.rs> wrote:
>>>
>>>
>>> Gary J FollettDukes HiFi wrote:
>>>
>>>> How is it that a 16 bit A to D can now handle a
>>>> dynamic range of 132 dB (in band)?
>>>
>>>
>>> A perfect 16-bit ADC would have a difference of 97.8 dB
>>> between the average noise level and the level of the full-scale
>>> sinusoid. This is a basic fact, and it is NOT violated by ADCs
>>> used in SDR receivers. In fact, a real-life 16-bit RF ADC
>>> has substantially less than 97.8 dB.
>>>
>>> Under certain conditions, not very difficult to fulfill,
>>> ADC noise spectrum density is uniform, i.e., there is
>>> the same average noise level in each Hz of the ADC output.
>>>
>>> Now, if the ADC output goes through a filter with
>>> the bandwidth smaller than half of the sampling
>>> frequency, the average noise power AFTER the filter
>>> will be decreased in proportion to bandwidth reduction.
>>>
>>> For example, if the bandwidth gets reduced from 50 MHz
>>> to 500 Hz, i.e. 100,000 times, the resulting average noise
>>> level will be decreased by 50 dB.
>>>
>>> So, one might say that the ADC dynamic range got increased
>>> from 97.8 dB to 147.8 dB (minus imperfections).
>>>
>>> Such an interpretation would not be correct if the essential
>>> factor of bandwidth reduction is omitted.
>>>
>>>
>>> 73,
>>>
>>> Sinisa YT1NT, VE3EA
>>>
>>>
>>> _______________________________________________
>>> TenTec mailing list
>>> TenTec@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/tentec
>>
>> _______________________________________________
>> TenTec mailing list
>> TenTec@contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|