Re: first test comparing FCDpro+ and Airspy at L-band


jdow
 

Go ahead, Alberto, measure it. I dare you. Make sure the signal is large enough
that it occupies a few bits of the A/D converter OR that there is a signal that
large somewhere in the range of the initial sample rate. Then change the sample
rate from 10 MHz to 2.5 MHz and tell us all the measured SINAD at the output on
an NFM, AM, or SSB signal. The final filtered audio step sets the audible SINAD.
It does not matter what the sample rate before that step was.


You are describing the apparent system noise floor in the FFT plot vs the signal
level in the FFT plot. That is not a serious factor in what you actually hear.


Leif posted a nice exposition. Read it. Leif knows what he is doing pretty
darned well.


{^_^} Joanne

On 2015-01-13 08:29, Alberto I2PHD i2phd@weaksignals.com [airspy] wrote:


On 1/13/2015 3:14 PM, 'siegfried jackstien' siegfried.jackstien@freenet.de
[airspy] wrote:

/THATÂ’S the point I wanna know ... if howard include a clever math IN the
dongle then the answer maybe would be yes ... otherwise maybe the answer is
no/
The processing gain depends on the ratio between the initial sampling rate and
the final
sampling rate, no matter where the downsampling is done... so it is immaterial
if it is done
in the dongle or in the SDR software of the PC...


https://dl.dropboxusercontent.com/u/15089947/procgain.gif

--
/*73 Alberto I2PHD*
Credo Ut Intelligam

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