03/01/21 16:36:58 UTC
276.500 MHz
Mid air re-fueling training
02/26/21 18:37:21 UTC
238.900 MHz
(Corrected) R135 COBRA55 (62-4129) transiting southern WI
02/26/21 18:35:29 UTC
238.900 MHz
KC135 COBRA55 (62-4129) transiting southwest WI
02/25/21 20:20:31 UTC
252.100 MHz
MASH82 20 min out looking for parking with one writeup
02/25/21 18:52:01 UTC
319.175 MHz
air/air chat and heading for the tanker KC135 just left Grissom on flightradar

02/14/21 02:49:06 UTC
132.550 MHz
02/12/21 07:43:49 UTC
121.500 MHz
02/12/21 07:41:41 UTC
123.300 MHz
02/12/21 07:40:05 UTC
252.100 MHz
02/12/21 07:38:31 UTC
281.025 MHz
02/12/21 07:31:27 UTC
243.000 MHz
02/12/21 07:29:55 UTC
123.550 MHz

Military Air & Space Communications Facebook Group
Facebook Group: Military Air & Space Communications.
2700+ members, logs, how too's & more. Please click the link and join.

Use a Raspberry Pi to Broadcast Internet Streams to Your FM Radio

In this project I'll descripe the steps to turn your Raspberry Pi computer into a low power FM broadcast transmitter. The must useful aspect of this project I've found was to broadcast online scanner streams to an FM radio so I can listen anywhere in the house.

If you don't have any experience using the Raspberry Pi computer you first need to see my article Raspberry Pi - Getting It Ready for Neat Scanner Projects. That article will guide you through installing an operating system, setting up the networking, and getting the Raspberry Pi computer ready for my series of scanner projects.

In the video below the audio you're hearing is coming from my FM radio (cheap clock radio) and being transmitted by the Raspberry Pi. The Raspberry is getting this audio from the LiveATC.net website's stream of JFK airport.

You can see the demo on my YouTube video by Clicking Here

Or just watch it here:

You will need to download the FM Transmitter software from my website. To do this, log into your Raspberry Pi, this should put you in the correct directory which is /home/pi. Next type wget http://www.milaircomms.com/raspberry/pifm.tar.gz. This will download the needed software to the /home/pi directory of your Raspberry Pi computer.

This file is in a compressed format, simular to .zip files on your PC. We now have to un-compress them. To do so type tar -zxvf pifm.tar.gz.

Now we can test out the transmitter. In the pifm.tar.gz file there was included a test .wav file which we can play. But first, you need to attach an antenna to your Raspberry Pi. Nothing fancy is needed here to get coverage throughout your house. Simple connect an 8" piece of wire (length is not critical) to the GPIO4 pin of your Raspberry. To help you locate the correct pin I have included an image below, this is a list of the GPIO pins as if you were looking down on your Raspberry.

To test out your transmitter pick an FM frequency that is clear of noise or other stations. Make sure you're in your home directory by typing cd. Now type sudo ./pifm sound.wav 100.1. Replace 100.1 with the frequency you want the Raspberry Pi to transmit on. Sound.wav is just a sample file I've included so you can make sure you're actually transmitting.

You'll notice that pifm only handles .wav file and not .mp3 files. In the next step we're going to install SOX which will convert .mp3 files (most online streams are in .mp3 format) into .wav files on the fly and pipe them directly into the pifm program.

To install SOX type sudo apt-get install sox libsox-fmt-all

Here is the command you type if you want to broadcast an mp3 file from any website on the internet: sox -t mp3 http://www.milradiocomms.com/audio/021214-293600.mp3 -t wav -r 22050 -c 1 - | sudo ./pifm - 100.1 This command will take the audio file 021214-293600.mp3 found on the MilAirComms.com website and broadcast it on 100.1 MHz. The 22050 is the "samples per second" the audio file was recorded in. If you're audio sounds like its playing faster or slower then it should then the audio file was recorded at a different "samples per second" rate then you're trying to broadcast it in. You'll need to adjust the 22050 value.

This command will allow you to broadcast live streams from the internet. sox -t mp3 -t wav -r 22050 -c 1 - | sudo ./pifm - 100.1 Again the 100.1 is the frequency in MHz which the stream will be broadcast on. The 22050 is the "samples per second" which the internet stream is being sent. In this example the is the direct URL of the stream. This happens to be my audio stream of Air Traffic Control frequeices at Daytona Beach International Airport (KDAB). My KDAB feed is being streamed from a Raspberry Pi. I guess you could say from my Raspberry Pi to your Raspberry Pi would be 𝛑R2. Sorry I just couldn't resist.....

If you want to broadcast LiveATC.net streaming ATC audio to your FM radio you can use the following command: sox -t mp3 http://www.liveatc.net/play/kjfk_gnd_twr.pls -t wav -r 22050 -c 1 - | sudo ./pifm - 100.1. In this case http://www.liveatc.net/play/kjfk_gnd_twr.pls is the url of JFK's Ground/Tower .mp3 stream.

I hope you've enjoyed this article.