Add streaming audio to OP25 RPi scanner

Thanks to Graham Norbury, here is how to set up a Raspberry Pi OP25 scanner to stream audio to an icecast or other streaming server. I have updated my plug-and-play op25-rpi.img image at http://febo.com/os_images/ to include this capability (look for the 2018-03-18_op25_rpi.zip or later-dated file). 1. Copy the following into a new file /etc/asound.conf on the Raspberry Pi (you’ll need to do this as root): # output device pcm.loopout { type dmix ipc_key 328211 slave.pcm “hw:Loopback,0,0″ } # input device […]

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RTL-SDR.com Dongle Measurements (Part 1 — background)

I’m using several USB “dongle” SDR sticks from RTL-SDR.com. These nifty $20 devices can receive from 100 kHz to above 1700 MHz. They have a low noise amplifier in the front end that is adjustable from 0 to about 50 dB gain. I wanted to determine the impact of the gain setting on receiver performance, and the results are below. First, some introduction. The dongles use an 8 bit analog-to-digital converter (“ADC”). The number of bits sets the dynamic range, […]

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