PI IRLP Node K1TM - Georgetown TX

Simplex 445.1 Mhz, Tone 100.0

This is a Pi based node using the (modified for 3.3v operation) v3 controller and a BaoFeng UV-5rax+. The whole project was accomplished in an afternoon. I put this page together to add clarity to points I ran into when not using the pre-configured SDcard and building cables for the BaoFeng.


DB-9 Pin Function Lg/Sm Stereo Plug
2 PTT Shell of Large Stereo of Plug
6 Gnd Shell of Sm Stereo Plug
7 COS N/A Internal connection Pin 2
8 RX Audio Tip Sm Stereo Plug
9 TX Audio Ring of Lg Stereo Plug

For connections to the radio I used mini (3.5mm) and micro (2.5mm) stereo jacks from RadioShack and picked up the COS signal from inside the handheld.

UV-5R Connections - pin 2 COS signal

Thanks to KA1MZY for the inspiration. KA1MZY has nice pics on his Pi page with the correct pin outs. KA1MZY PI Setup Page

note: pin 2 must be accessed by disassembling the uv-5R. It is found by locating the 8pin SMT chip just below the display and to the right of the printed circle stamped 5R-C6. The second pin in from the left on the lower row is the pin (when the radio is oriented with the antenna port is at the top left). Disassembly Video>


Instructions and setup information are found in the manual. When in doubt read the manual. I built my software stack from scratch, and then did get-irlp-files and the install. There is one ambiguity around the mixer controls that I encountered. "aumixer -L" is in the environment file and rc.mixer file after install, but alsamixer is used on the pi. I changed the environment file to export "alsactl restore" and commented out the export "ausmixer -L". I also changed the rc.mixer file to "alsactl restore" from aumixer -L. PI Setup Manual

Cleaning up the audio

I decided to adjust the alsamixer transmit adjustment for best signal to noise ratio which meant that the drive level to the the UV-5R would need to be set another way. I elected to use a 10K trim pot to accomplish this. It is configured as a simple voltage divider. See pics below:

Note that the leads to and from the usb sound fob and the controller card are shielded and short. This eliminated unwanted hum.

Controller Jumpers

Controller jumpers are set to factory defaults indicated by the white slim rectangles beside the pins. Be sure to check as my board was not set to the defaults.


The CW ID needs to be configured in the environment file before it will work. The leading "K" of my CW ID was getting clipped off by some radios, so I uncommented TXDELAY in the environment file.

WA3DSP has information on node construction WA3DSP Page
VE7LTD has information on cable construction and mods (pics here) VE7LTD Page

For Quick Reference

BaoFeng follows Kenwood conventions

DB-9 on Controller

73, Todd Moore K1TM