FW: RE: Linrad, some questions (Leif Asbrink Sept 13 2002)

[Leif Asbrink <leif.asbrink@xxxxxxxxxxxxxxxxxxxx]

-----Original Message-----
From: owner-linrad@xxxxxxxxxxxxxxx
[mailto:owner-linrad@xxxxxxxxxxxxxxx]On Behalf Of Leif Asbrink
Sent: Friday, September 13, 2002 10:52 PM
To: linrad@xxxxxxxxxxxxxxxxxxxxx
Subject: RE: [linrad] Linrad, some questions


Hi All,

Larry, VA3LK wrote:
 
> My interest is to use Linrad as part of a tool box of software resources 
> that I can use to examine weak signals, very weak signals.  I 
> would like to 
> examine .wav files using Linrad as well as other FFT based tools with a 
> bandwidth of up to 20 KHz, + and - 10 KHz.  For most of the time 
> I would be 
> looking at the data some time after it has been recorded and other 
> resources have discarded up to 98% of the data that has been collected.
> 
> If I have it right, Linrad can look at .WAV files, but I have no idea if 
> the Linrad SDR can be used to search through a wide band 
> recording and look 
> for weak signals over the whole bandwidth or does one loose detectability 
> through the recording process?  My sense is that this should be 
> possible if 
> the data is recorded at the full bandwidth and not constrained in 
> some way 
> by the Linrad software.
This should work fine. What sensitivity you can get depends on the
signals you look for. If the frequency is very stable and the signal
lasts for a long time sensitivity can be made extremely high.
With only 1024 pixels across the screen and 20kHz total bandwidth, each
pixel corresponds to about 20Hz. Linrad may use 100 data points or more
for each pixel. Spectrum integration is made for each of the data points
which means that signals invisible at 20Hz resolution still can be found 
easily. 

> Next, what might the impact be of transcoding from .WAV to MP3 and then 
> transcoding back to .WAV from MP3 and then using Linrad to look at the 
> data?  What might the transcoding degradation be and how would it 
> manifest itself?
I do not have any experience, but I expect MP3 would be a very bad idea.
 
> If anyone out there in Linradland has done any work with wider bandwidth 
> applications I would appreciate some thoughtful discussion in this area.
If you give more information about what kind of signals you want to look
for I might be able to give some hints how to use Linrad best.


73

Leif  /  SM5BSZ 





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