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Broadcastify/Live Audio Administration - Administration topics for live audio broadcasting on Broadcastify.com. This forum is for feed providers to get support. Other audio questions go here: Streaming /Broadcasting / Audio Recording forum

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  #101 (permalink)  
Old 05-14-2017, 1:36 AM
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Not sure what happened with the end of line formatting with my last post. The code should look like this:

sudo /usr/local/bin/rtl_fm -d 0 -M fm -f 482.863M -g 20 -p 19 -l 75 -t 10 -s 12k -E pad | \
/usr/bin/lame -r -s 12 --resample 22.05 -m m --cbr --lowpass 4 --highpass 0.241 - - | \
/usr/bin/ezstream -q -c /etc/ezstream_bcfy.xml > sudo reboot &
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  #102 (permalink)  
Old 05-14-2017, 6:34 PM
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Found out what was happening with the copy and paste problems in the #50 post above. Using VNC with low resolution screen does strange things to text lines that are pasted from a remote computer if it doesn't fit inside the rpi's nano editing window. To over come the problem, I sliced up the line length by adding backslashes. Also created an executable file called "/etc/startstream.sh" and pasted the code into the new file as follows:

#!/bin/bash
sleep 20
sudo /usr/local/bin/rtl_fm -d 0 -M fm -f 482.863M \
-g 20 -p 19 -l 75 -t 10 -s 12k -E pad | \
/usr/bin/lame -r -s 12 --resample 22.05 -m m \
--cbr --lowpass 4 --highpass 0.241 - - | \
/usr/bin/ezstream -q -c /etc/ezstream_bcfy.xml > sudo reboot &

then just added one line to the default /etc/rc.local file near the end just before the 'exit 0' line:
sudo /etc/startstream.sh

Also had to set the file permissions for executable. At a command prompt type:

sudo chmod +x /etc/rc.local
sudo chmod +x /etc/startstream.sh

Now it seems to work. Can reboot and rpi automatically logs on and restarts the stream. Should also work to restart the stream if only the internet connection is lost but haven't confirmed that yet.

ps: The sleep 20 (seconds) line is to give the rpi time to establish a network connection and a safeguard against a headless infinite loop that could be hard to break out of with a remote control connection.

Last edited by JACK26; 05-14-2017 at 7:20 PM..
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  #103 (permalink)  
Old 05-14-2017, 7:29 PM
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Would appreciate feedback from anyone else who has this working (rtl-sdr narrow band fm feed to broadcastify). I have this background hum of about 150Hz and I think it might be a difference signal artifact of mixing different encoder sample rates. I don't hear this hum with a windows computer using SDR# and scannercast. But it is possible that it's a channel artifact that is part of the transmission. Without feedback from someone else who has this working, I don't know.

For now I'm back online with the rpi3 and rtl-sdr USB stick only. I'm using the 'lame' high pass filter with a cutoff off of 250Hz to minimize the prominent 150Hz buzz but it cuts a lot of low audio frequencies and is not that good a solution:
Milpitas Police Dispatch

Last edited by JACK26; 05-14-2017 at 7:36 PM..
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  #104 (permalink)  
Old 05-25-2017, 10:06 PM
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Default Using rtl-sdr USB for AM Air Traffic

Regarding the original topic of this thread, I tried to receive the local Air Traffic Control radio frequencies in my area with a RTL2832 compatible rtl-sdr USB with a 1/4 wave whip antenna. I'm pretty close to SFO and SJC airports in CA and both were flooded out by local 88-108 MHz commercial FM stations . Since the AM ATC voice frequencies are just above the commercial FMW radio band, the FM side freqs flood out the rtl-sdr receiver since it has no front end filtering. In my case the FM noise is about 30dB below saturation which is just below the level of the received ATC signals.

So if you're trying to make the Air Traffic Control AM voice frequencies work with a simple RTL2832 style sdr USB dongle and you see a high level of background noise, you might want to try this notch filter from the original rtl-sdr blog guys:

https://tinyurl.com/y8voo8ze

I haven't tried it myself yet but looks pretty slick and designed for this application. If anyone already has experience with this filter, feedback is appreciated .

Last edited by JACK26; 05-25-2017 at 10:24 PM..
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