Tweaking audio - Raspberry Pi with SDR

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ki6ptn

Newbie
Feed Provider
Joined
May 22, 2014
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3
Location
Oceanside, CA
Hello all,
This is my first post to the forums. I've been providing an amateur radio feed or a few years now. I had dedicated a radio and a laptop running K1PGV's Scanner Cast software. However my radio died and I decided to take the leap to a Raspberry Pi Running the "Raspberry Pi Broadcastify Image" with an SDR attached.
Basically, I combined the steps from here: Raspberry Pi RTL-SDR Broadcastify - The RadioReference Wiki
and from here: Raspberry Pi Broadcastify Image - The RadioReference Wiki

I'm using a Raspberry Pi 2 Model B with the NooElec R820T2 SDR.

I got my feed running. At first the audio playback to Broadcastify was coming through as a rapid playback speed, but I was able to slow it down back changing the lame encoder -s setting to 12. I had it on 28 previously.

I'm hoping to get some help tweaking the feed. when listing via the web or the scanner apps, its pretty noisy.

here's the link to the feed: WF6OCS 144.5050 MHz Oceanside CERT Repeater - Live Audio Feed Web Player

Here is the syntax I'm using in the /etc/rc.local startup file to start the feed automatically.

/usr/local/bin/rtl_fm -d 0 -M fm -f 144.505000M -p 6 -l 65 -g 12.5 -t 2 -E pad -s 12k | /usr/bin/lame -r -s 12 --resample 22.05 -m m -b 16 -F --cbr --lowpass 2.8 - - | /usr/bin/ezstream -c /etc/ezstream_bcfy.xml > /var/log/bcfy2.log 2>&1 &

as I said, my brain is a bit fried and I'm hoping to get some help on recommendations for tweaking the feed to reduce the noise.

Any help would be appreciated.
 

ki6ptn

Newbie
Feed Provider
Joined
May 22, 2014
Messages
3
Location
Oceanside, CA
I was able to clear up the noise by boosting the gain from 12.5 to 38.6
I was able to see the supported gain levels by running the rtl_test command and found that my device supported the following gain levels

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

so now my rc.local file has the following string.

/usr/local/bin/rtl_fm -d 0 -M fm -f 144.505000M -p 6 -l 75 -g 38.6 -t 2 -E pad -s 12k | /usr/bin/lame -r -s 12 --resample 22.05 -m m -b 16 -F --cbr --lowpass 2.8 - - | /usr/bin/ezstream -c /etc/ezstream_bcfy.xml > /var/log/bcfy2.log 2>&1 &

noise is gone and audio sounds pretty good.
 
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