[hpsdr] Subject: Measuring SDR Dynamic Range

[Alessandro Santucci]

Hi all,

I read the post and decide to post my message too in order to discuss with
guru's and not... about this topic.

It's clear the we have different problems of IMD and noise floor when we use
the sound card as 2nd IF of our SDR receivers. But what I mean is that we
can have different IMD reasons and different noise sources in order to get a
low noise floor in a SDR RX. But mainly, what we are now going to do is
simply to substitute the analog or tubes (why not?..hi) receiver with the
new digital-based RX. 
The "on the air" performance we need are the same as previous receivers
(i.e: in a crowded band during a contest) and so I don't understand why we
cannot test the receivers as we made in past with the analog.  
Otherwise we'll use to manage different numbers but we'll able to make
comparisons between SDR and analog receivers. Apart we'll find also
different and new measuring methods, and specific measures with the aim of
evaluate the SDR performance (i.e.: the sound-card A/D dynamic range and so
on). 
Obviously we'll be forced to specify what PC equipment we'll use (i.e: the
Delta 44 performance will be different from the on board sound-card), so we
can specify the test conditions or maybe a couple of different conditions
(i.e.: with Delta 44 card used ad it's a standard at now, and the on board
card used, that's the cheap condition we have in every pc). In this manner
we'll make also PC equipment improvements on the SDR equipment (if with a
new sound card I'll be able to improve de IMD or noise floor performance of
my Delta 44 card, it will be clear I'll have a new better block of my
system, as when we made the famous mods and adds on the Drake C receiver).

My opinion is that if we now change the measuring tests and loose what we
use for classic transceiver we can loose the perspective of receivers
performances and we cannot understand what we have to improve in order to
make SDR competitive with analog.
I think we can use the old test sets and add new measures in order to make
more complete the data we have from performance check of our systems.

I'm not a guru but I'm interested in high performance receivers since 1975,
and I'd like to learn from gurus and from other normal tech hams, like me,
what are the opinions: I'll be glad to learn more...

Thanks to all replays!

73 

Alex I0SKK


email: i0skk at eco-lavoro.com
 
Web: www.eco-lavoro.com/i0skk




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