[hpsdr] WG: New Hermes 2M Board

[Jim Sanford]

Helmut:

Thanks for sharing.  And, to all the developers, please DO keep these 
discussions on the list.

Very 73,

Jim

wb4gcs at amsat.org



On 7/10/2017 11:38 AM, Helmut Oeller wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Isaac,
>
> thanks for your comments. This gives the chance to cancel some myths about
> ADCs. I'll try to do this comparing (my favorite) 75 USD dual 14 Bit, 125
> Msps AD9645 with the 300 USD dual 16 Bit, 310 Msps AD9652 you mentioned.
> Both ADCs are produced by Analog Device and the following data are gathered
> from their data sheet.
> It's not enough or tolerable to compare only the nominal number of bit of
> the ADC. You have to compare the effective number of bits (ENOB) specified
> in the data sheet. We'll find ENOB of AD9645 @70 Mhz 12,0 bits while the
> expensive AD9652 offers @70 MHz 12,1 bits, i.e. 0,1 x 6.02 dB = 0.6 dB more
> DR is no significant benefit.
> Let's compare the spurious free dynamic range SFDR at this frequency (middle
> of HF and considered undersampling bands 70/144 MHz): AD9645 is specified
> with 91 dBc, while the 16 bit AD9656 can only come up with 89 dBc.
> Same story occurs with SNR (74 dB both) and crosstalk between the two
> channels (-97 dB vs. only -90 dB of the AD9652!). Moreover the difference in
> power consumption is dramatically: the 14 bit AD9645 needs 0,24 W, while the
> fast AD9652 consumes 2,16 W.
>
> It's evident that there is absolutely no reason for that fast, hot and
> expensive 16 Bit ADC.
>
> 73, Helmut, DC6NY
>
>
> _______________________________________________
> HPSDR Discussion List
> To post msg: hpsdr at openhpsdr.org
> Subscription help: http://lists.openhpsdr.org/listinfo.cgi/hpsdr-openhpsdr.org
> HPSDR web page: http://openhpsdr.org
> Archives: http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/
>


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus