IRLP Naked Node
By: Ramon Gonzalez (KP4TR)
Welcome to the pIRLP Naked Node page! This was an idea I conceived after installing the very first pIRLP node (4085) back in January of 2013. Once Dave Cameron (VE7LTD) assisted me with getting my node up and running on the Raspberry Pi platform, I found myself with a messy IRLP setup with cables, IRLP boards, and a “naked” Raspberry Pi sitting on my desk. I needed to find a way to get the whole setup packaged up in an elegant way.
I initially went with a standard “Raspberry Pi” case and the IRLP board sitting on top, with a USB powered hub powering it all. It was still messy and ugly. This was my setup for a few weeks, but I was still unhappy. After assisting the ARRL State Convention in Puerto Rico in 2013, I got an idea from another project. It was the W8AK “mini repeater” project. This project was 2 Motorola radios, a duplexer, and a circuit wired to be a portable repeater. I took this project and added an IRLP node to it, but it was bulky and I really wasn’t interested in a “repeater” with an IRLP node in it. The “repeater” portion was useless for my needs.
That’s when I decided to build just a portable node. My idea was to have a single radio, IRLP board, and make it as small and portable as possible, that could operate off of 12 volts powered from a car cigarette lighter, and using a wireless USB device. The Raspberry Pi in itself only required 5Volts, but the radios I decided to use were powered by either 3.7V or 7.4 Volts.I also decided to remove all cases off the radios and Raspberry Pi and IRLP card. This would make it easy to interconnect, plus it looked pretty cool and “naked”.
I decided on using the Baofeng BF-666S UHF radio. It proved to be the perfect radio for use as a single portable node. They are cheap ($20-$25), easy to disassemble, and very easy to wire cables into. Plus if you burn them, replacing them would be very cheap to do. These radios are easy to get from Amazon or Ebay. Do not use the Baofeng BF-600S, as the antenna connector is very weak and will loosen over time! The BF-666S, BF-777S and BF-888S all work very well.
To the left is the wiring to the radio. The red cable is the PTT cable. Next to it is a 4.7K resistor going to the microphone input. And the next resistor is a 10K, where audio is taken and fed to the IRLP board and the sound card microphone input. Power is fed to 3.7V input, and use any ground point for power and wiring. See diagram.
Next the wiring goes to the IRLP board. Observe where the audio to IRLP board goes (pin 8). The PTT goes to pin 2, and COS from radio goes to pin 3. The COS jumper must be set to “H” since it goes +3v when active. See picture to left.
The audio out and mic in cables both go th the soundcard. The audio out requires a 10K resistor go to both the pin 8 of IRLP board, and to mic input of sound card. The audio out from soundcard goes to mic-in ofr radio, using a 4.7K resistor.
Once all is assembled, this is the layout of radio. I use a 3.7V and a 5V step-down (buck) adapter to convert 12V to 5V and 3.7V. The 5V is for the Raspberry Pi and the 3.7V is for the radio. The 12 volts comes from an Anderson Powerpole connector. You can use a car lighter adapter to use in car. Use a micro USB cable to take power to the Raspberry Pi. Do not use any other means to power the Raspberry Pi. I cut a microUSB cable and wired it to the 5V buck-down adapter. In the USB cable, use the red for +5V and black for ground. The green and white data cables are not used.
The assembled radio will look like this. The radio is at to, next the IRLP board, and on the bottom the Raspberry Pi. I use 6/32 inch bolts to interconnect everything, and use Aspect Metal sheets to build the top and bottom platform. Aspect Metal is used to decorate kitchen walls. They are brushed aluminum sandwiched with a composite material. Very easy and lightweight!
I hope this article is of help for those building pIrlp nodes.