Hello Jay,
The e4k chip has many registers. For example the function
e4k_manual_dc_offset() changes the way the if gain settings
work.
There could also be something that affects the lna gain.
The purpose of the changed code that I made available
is to allow rtlsdr users to have the full performance
of the RTL2832/E4000 dongles NOW. Today.
I do not have access to any data for the chips. Performance
is reasonably close to the theoretical limit and all AGC
functions are disabled so it is now a good radio with Linrad.
The function e4k_manual_dc_offset() is named in a way that
suggests one can change the DC offset on the output from
I and Q. Pointless, at least with the dongle I have because
the E4000 is AC-coupled to the RTL2832. (I checked with
an oscilloscope.)
Regards
Leif / SM5BSZ
On Thu, 5 Jul 2012 08:06:11 -0500
"Jay Salsburg" <jsalsburg(a)bellsouth.net> wrote:
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(a)lists.osmocom.org
[mailto:osmocom-sdr-bounces@lists.osmocom.org] On Behalf Of Leif Asbrink
Sent: Thursday, July 05, 2012 6:27 AM
To: osmocom-sdr(a)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(a)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?