Linrad with rtlsdr with and the e4000 tuner.

Jay Salsburg jsalsburg at bellsouth.net
Thu Jul 5 13:06:11 UTC 2012


I assume everyone involved in constructing the Control Code for the Tuner
Dongles started out by recording the I2C stream on the Dongle coming from
the Original Dongle Software that comes with the Dongle for watching TV and
FM Radio.

-----Original Message-----
From: osmocom-sdr-bounces at lists.osmocom.org
[mailto:osmocom-sdr-bounces at lists.osmocom.org] On Behalf Of Leif Asbrink
Sent: Thursday, July 05, 2012 6:27 AM
To: osmocom-sdr at lists.osmocom.org
Subject: Re: Linrad with rtlsdr with and the e4000 tuner.

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.)

Regards

Leif / SM5BSZ

On Thu, 05 Jul 2012 02:06:31 +0200
la at tfc-server.de 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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