Linrad with rtlsdr with and the e4000 tuner.

Leif Asbrink leif at
Thu Jul 5 11:27:00 UTC 2012

I changed the numbers to get a reasonable agreement with
the gain values I observed on the dongles I have.

I did not care to match the gain setting to the real gain
better than within 3 dB (the gain step size in Linrad.)
The reason is that I assume that the routines from osmocom
will be changed and that other softwares that support
rtl dongles will allow gain setting in a reasonable way and
that the performance will become similar to the current
Linrad performance. When that happens I will rewrite Linrad 
to use the library as intended. 

I see two alternatives, there could be lna gain as well as IF
gain as separate controls. 

The other alternative would be a single gain control, but 
in that case both lna and if gain have to be controlled. 
The first few gain reduction steps have to be on the IF because 
the most common problem is close range interference and the 
improved dynamic range is useful. (In case the lna gets blocked 
one should install a filter.)


Leif / SM5BSZ

On Thu, 05 Jul 2012 02:06:31 +0200
la at wrote:

> > The gain setting is clumsy
> If it only was your gain setting function, but no, even your gain values 
> for the lna are just plain wrong.
> I just have to ask: Why? What made you "improve" them?

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