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Overview
One of my goals for the new year is dusting off an old hobby and getting back into amateur radio. I got licensed back in the early ’90s, but going to college and having a family took precedence. I’ve been watching a number of videos on YouTube over the last year or so related to both Ham radio and the Raspberry Pi…a small Linux based computer.
It wasn’t until recently that I discovered that it had IO pins on it to allow it to function in a similar way to an Arduino and allow it to control external hardware. It also has more processing horsepower and audio output capabilities. My brain started turning about the possibilities and I thought that it would make a great little repeater controller for setting up a temporary or emergency repeater.
In setting out to develop this project my primary goals and features are to develop a low cost, low power, but feature rich duplex repeater controller suitable for setting up a temporary / emergency repeater systems with radios that can be run on portable power. However with a more complete feature set and a modular design, it could also be used as a primary or a backup controller for a permeant installation repeater. With the low cost, modular design, it would make it easy to keep backup hardware (Raspberry Pi, repeater control board, and a cloned SD card) on site for easy service swap-outs.
The additional circuitry required to interface the Raspberry Pi to the radios would ideally mount on a “shield” or “daughterboard” style circuit board that would mount on top of the Raspberry Pi by plugging into the GPIO connector. This repeater setup is initially intended for use on Amateur Radio, but could be potentially useful on other radio services such GMRS, Commercial, etc.
- Low Cost
- Modular Design
- Low Power Consumption
- Flexible connectivity to various radios
- OPTIONAL - simplex operation.
- Provide all logic control of repeater operation
- Timers (Timeout, Identification, etc.)
- Voice Synthesis for identification
- CW Generation for identification
- Playback of courtesy tones (user selectable)
- Web server Interface for controlling settings - Will be provided by built in ethernet jack. Optionally may add USB/Wifi adapter setup as a wifi hotspot to allow wireless point-to-point communication between the controller and smartphones and tablets.
- PTT Relay
- RX Audio Mute Relay - Used to turn off receive audio in timeout events so that repeater can engage PTT and make announcements such as identification and/or that it is in a timeout condition.
- RX Carrier Detection circuit to tell program that a transmission is being received and to begin repeating and start timeout countdown.
- Passive Audio Mixer Circuit - Independent gain controls for RX audio and Raspberry Pi Audio (Identification & Courtesy Tones)
- OPTIONAL - DTMF Decoder
- OPTIONAL - Real Time Clock for Raspberry Pi to maintain time if not connected to the internet. This would be useful for time announcements and logging/statistics.
- OPTIONAL - Extra Control Relay(s)
- OPTIONAL - Power Lose Detection
- OPTIONAL - Audio In Interface for recording, useful for possible simplex repeater operation or playback or transmissions for “radio check” in a duplex mode.
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