[hpsdr] Status of Hermes Gigabit

[Chuck Hutton]

Kok - 
You really didn't address the main point - would you agree that 2 MSPS 24 bit IQ data is in need of GigE?
Chuck

> CC: charlesh3 at msn.com
> From: chen at w7ay.net
> Subject: Re: [hpsdr] Status of Hermes Gigabit
> Date: Sat, 2 May 2015 09:13:21 -0700
> To: hpsdr at openhpsdr.org
> 
> 
> On May 1, 2015, at 3:09 PM, Chuck Hutton wrote:
> 
> > With ham bands less than 400 kHz and 16 bit samples, we can live without GigE.
> > But jump up to 17 bits or more (requiring 3 bytes) and / or move up to wider bands such as the medium wave band (let's say 2 MSPS) or wider ham bands and you will need GigE. 
> 
> The I/Q data from Hermes to the computer is already in the form of a pair of 24 bit numbers (>145 dBDR).  
> 
> The decimated Hermes I/Q data at 96 ks/s rate only has about 110 dB of SFDR and has lots of headroom (5 to 6 bits out of the 24 bits) left before we need to increase the I/Q data width.  
> 
> A faster sampling rate (e.g., 192 ks/s) actually reduces the numerical dynamic range requirement. The raw ("16-bit") ADC at 122.88 Msps starts with just 78 dB of dynamic range (about true 12.5 bits). 
> 
> Hermes' single signal "500 Hz ARRL" dynamic range of 125 dB is achieved when you finally decimate and demodulate inside the desktop computer at 500 s/s.
> 
> 73
> Chen, W7AY
> 
 		 	   		  
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