Gain tweak question


#1

I was looking at the tweak thread for gain optimizations. Is there a reason the gains selected in the script were selected?

It has gains = “20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6”

Any reason you could not just test with rounded numbers? Was mostly interested in the gap between 44.5 and 48. I could just add 46 and 47, is that going to be a problem?


#2

The dongle gain cannot be set to any value. It can only be set to Supported gain values. If you enter any other gain value, it will be set to the nearest Supported gain value.

To see what are Supported gain value, run the following test:

(1) First stop dump1090 to make DVB-T dongle free.

#stop dump1090-fa, or dump1090-mutability,
#or dump1090 MR, which ever you have
#by using the relevant command 
#from commands listed belown

sudo systemctl stop dump1090
sudo systemctl stop dump1090-fa
sudo systemctl stop dump1090-mutability

.
(2) Next conduct following test

rtl_test -t

.
(3) Check output, which will show Supported gain values

Found 1 device(s):
  0:  Realtek, RTL2832U, SN: 00001000

Using device 0: Generic RTL2832U
Found Rafael Micro R820T tuner
Supported gain values (29): 
0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7
20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 
40.2 42.1 43.4 43.9 44.5 48.0 49.6
Sampling at 2048000 S/s.
No E4000 tuner found, aborting.

#3

I am using the FA Pro Stick Plus. I can stop dump1090-fa but cant run rtl_test -t. I must not have something installed unless there is a different command for the FA pro stick?

I am guessing the gain script was already setup with the supported gain values for the pro stick, so this maybe a mute issue.


#4

Yes, you dont really need to run the rtl_test -t, as the test results I have posted were for Pro Stick, and are same for DVB-T. If you compare results of test with values in optimization script, these are identical.

However just to complete the topic, the rtl_test is part of package rtl-sdr. If you want, you can conduct this test after installing this package by following command:

sudo apt-get install rtl-sdr

.


#5

Got it. Thank you for that.