[Linrad] Re: system gain

[Dave Sublette <arrl.net; k4to@xxxxxxxxxxxxxxxx>]

Ok--I am beginng to learn some--I hope....

Leif Asbrink wrote:
> Hi Dave,
> 
> In an old posting you wrote:
>>> In all cases, the IF radio hears 
>>> better and can hear signals that cannot be seen on the waterfall. 
>>> That's good, but with the poorer performance at the waterfall, I feel 
>>> that I am missing off frequency signals that might be calling me.
> Now, knowing that the S/N difference is a bit less than 5 dB I must
> comment to this statement. In case you were able to copy signals that
> were invisible in Linrad you have not selected parameters that give
> optimum visibility for weak signals. You should be able to see CW
> signals that are 5 dB below what you have any chance to copy.
> To do that you need a bin bandwidth in the order of 5 Hz and
> a waterfall averaging of 20 (or more)

What parameter do I use to set the bin bandwidth at 5 hz?  I know where 
the waterfall average adjustment is on the screen, but the bin BW is a 
mystery to me.  I think most of my confusion is not understanding terms. 
I have spent hours reading the material, but just don't seem to get 
it--sorry.
> 
>>> It occurs to me that the band width of the filter in LINRAD's 
>>> demodulation window (sorry I know I am probably not using correct 
>>> terminology here) is affecting the signal to noise of the audio output. 
>>> I have fiddled with the little green ellipses, but can't get them to go 
>>> any narrower and really don't understand how this all works.
> Little green ellipses?

Tee Hee!  Since wrote that I have figured out that they are probably 
yellow arcs in the baseband window that show the filter width and 
offset. You can grab them with the mouse and make them wider and 
narrower to a certain extent...again my problem with proper terminology.


> 
>>> I have read 
>>> W3SR, VK2DU and Leif's instructions until I am cross-eyed. I just don't 
>>> seem to "get it".

This should read W3SZ, VK2KU... maybe I am dyslexic--  ;-)

> 
> Just go ahead and do what seems reasonable to you. Then write to this
> list and tell what you did and in what respect the result is not
> what you expected. That kind of feedback would help me to understand
> where the obstacles are:-)
> 
> 73
> 
> Leif / SM5BSZ

Again--many thanks...

Dave
> 
> 
> 
> 
> > 
> 

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