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

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Scanner Audio Controller using Raspberry Pi Computer

These are my notes on building a Scanner Audio Control system based on a Raspberry Pi using a 7" TFT Touchscreen display. This system will be the equivalent / replacment of the famed National Communication Solutions NCS-3230 Multi-Rx system that I've been using for years.

I have had 2 NCS-3230 Multi-Rx systems in my shack for years. They give you the ability to route audio from up to 6 scanners to 2 different speakers, or route scanner audio to both speakers at the same time. The NCS-3230 also provides "Line-Out" audio from any combination of 6 scanners to allow for easy audio recording. Each audio input has an "activity" LED to indicate when there is audio present on any of the 6 inputs. Included are balance and volume controls and a mute feature.

The object of this project is to reproduce the functionality of the NCS-3230 on the Raspberry Pi computer where audio control is done via a 7" TFT touchscreen. One might ask "Why"? Several reasons, first the NCS-3230 has been out of production for many years, I've had problems with the balance & volume pots going bad, and the NCS-3230 while in production sold for nearly $400.00. For far less than $400.00 I think I can create a system tailored to the needs of scanner hobbyist who have multiple scanners in their shack.

For those not familiar with what the NCS-3230 looked like I have included some pictures of my NCS-3230 Multi-Rx's in action.

Click on Picture for larger image

Click on Picture for larger image

The Primary Task for this Project is as Follows:

  • 1) Have 2 speaker outputs via an internal 2 channel audio amp.
  • 2) Have volume, balance, and speaker mute controls on front panel. These will be real knobs, not software via touchscreen.
  • 3) Via touchscreen you will individually be able to route each radios audio to either "left speaker", "right speaker", "both speakers", or mute. The mute button outlined in #2 is to mute the entire system, useful in the event you get a phone call, heard something on another radio not connected to the system..... However via touchscreen you can mute each radio individually, great option in the event a radio "sticks" on a frequency where's its receiving noise, birdie, etc.
  • 4) Provide "blue-tooth" output so you can route audio to your car stereo, iPhone, or any "blue-tooth" audio device.
  • 5) Via touchscreen select any or all radios to provide "line-out" level audio via a "recorder" jack on back of unit. This output could be connected to a PC running your favorite MP3 recording software.
  • 6) Via touchscreen configure each radio to be recorded to the devices internal storage device for later recall-playback. This storage will be an SD Card, amount of recorded audio would only be limited by the size of the SD Card you purchase.
  • 7) Provide an internal Darkcast / Icecast server with WiFi connection to allow you to connect to the device via your PC and listen to scanner audio via streaming. If you're home wifi is connected to the internet you would be able to stream this audio over the internet to any Icecast server, or use its internal Icecast server to allow you or others to connect directly the audio system via the internet and stream the same audio that's being played on the speakers.

75% of the above can be done (and I'm already doing) with pre-packaged free software that runs on the Linux operating system. Its just a matter of integrating each software package together on the same Raspberry Pi CPU and provide a nice touchscreen display for control.

I don't think CPU power will be an issue as currently I'm running 2 individual audio streams on the same Raspberry Pi (see running example here: Live Streaming with Raspberry Pi) and CPU usage is around 10%.

The reason I choose the above options for my project is that over the years of using the original NCS-3230 these are the features that I use and/or wish I had. My scanning environment is made up of listening to 12 (or more) scanners at the same time. All the scanners scan various Military Aviation frequencies, Military bombing ranges, Military Offshore Warning areas, NASA, Customs Border Patrol, Offshore Anti-Submarine operations and more. (Oh public service frequencies....what's that? not my cup of tea). While scanning 1000's of frequencies, searching the UHF MilAir band with 6 to 8 scanners, and listening to audio from several scanners simultaneously (not uncommon for 3-4 scanners to have active audio at the same time) the features described above are the ones I use, I want, and must be very quick to turn-on, turn-off and change configuration.

Over the next few days / weeks I'll me including information about the work I've done or notes to myself. You are welcome to follow along, is there a feature you would like added let me know, maybe we can get a project started together to build the best accessory the scanner world has seen!

Update 3/20/2014
Just a few hours ago I received my 7" TFT Touchscreen and 2nd Raspberry Pi computer. It was easy to get the Raspberry Pi to output video to the little TFT display as seen in the pictures below. However I am still having trouble getting the "touchscreen" portion to function. Some quick research suggests that it might be a kernal problem with the latest build of the Raspbian (Linux style) operating system. I had found where to download a patch however that didn't work. More research is required.

In the pictures below (sorry for quality, hard to take pictures of a "computer" screen), you can see the start of the graphical interface with 6 red boxes. The idea is to have 3 rows of 6, 1 button to route audio to speaker "left", 1 button to route audio to speaker "right", and the final button to route audio to recorder...I'm longer away then thought but progress is still moving in the forward direction.

Click on Picture for larger image

Click on Picture for larger image

Update 3/26/2014
I've been doing more work on the Scanner Audio Controller project. I now have an "almost" working graphical interface working with a 7" TFT Touch Screen. It took longer than expected to get the "touch" portion of the display to work. Now I do have an interface that can turn on and off audio between 6 scanners and 2 speakers. I've uploaded a video of the working interface to YouTube. In the video you'll see where you can select Right Speaker, Left Speaker, and Line Out for each of 6 radios. There are still a few bugs in this software I need to work out, but I am making progress. Once the Graphical User Interface (GUI) is complete then I'll start working on the actual electronics that will route audio based on Digital Inputs & Outputs of the Raspberry Pi computer which are controlled by the GUI.

Update 3/30/2014
After thinking of how to handle the digial I/O between the Raspberry Pi and the Audio Controller Interface board I realized the Raspberry simply didn't have enough digital I/O pins. So I'm going to use the MCP23017 Port Expander I/C. Actually I am using 2 of them to give me a total of 32 extra digital inputs/outputs. I just received 1, so I wired it up on a breadboard and started programming. Using the Graphical User Interfact GUI I programmed a few days ago I added code to switch on Digital Outputs that in turn will direct each radio's (up to 8 radios) to either the "Right Speaker", "Left Speaker", "Both Speakers", and "Line Out".

In the first video you'll see the 7" touch screen display control which radio'ss audio will be directed to "Right Speaker". Left Speaker and Line Out will function the very same way, I just put this circuit together to prove the concept works.

In the second video you'll see me control the audio controller interface's digital outputs via an Apple iPhone via the internet. This proves that my new Scanner Audio Controller can be used over the internet from any computer or smart device connected to the internet. You might have noticed that it took a few seconds from "selecting audio" until the LED (digital output) turned on or off. When I'm finished with the software it should be on the order of 1/2 a second, I have a lot of debugging code running that takes up CPU power, that code will be removed when all is done. I'm thinking of another coding change that will should greatly increase performance. Currently the state of each radio's audio are stored in an SQL database with SQL running on the Raspberry Pi. I will probably replace the SQL database with a simple flat-text-file eliminating the need to have SQL running.

You can see the YouTube video by Clicking Here

Or just watch it here:

You can see the Scanner Audio Controller being controlled via an iPhone on YouTube by Clicking Here

Or just watch it here:

I hope you've enjoyed this article.