[hpsdr] Status of Hermes Gigabit

[Helmut]

...and even the LTC2208-14-Bit, which is used in the ANAN10-E offers only
4-5 dB less dynamic range (ENOB typ.11.7). Without precise test equipment
nobody will discover this fact in practical operation.

73, Helmut, DC6NY

-----Ursprüngliche Nachricht-----
Von: Hpsdr [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Kok
Chen
Gesendet: Samstag, 2. Mai 2015 18:13
An: hpsdr at openhpsdr.org
Cc: Chuck Hutton
Betreff: Re: [hpsdr] Status of Hermes Gigabit

***** High Performance Software Defined Radio Discussion List *****


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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