Each site is built with commercial components to reduce or eliminate unscheduled maintenance trips, even when mountaintop conditions get bad:
- Tait TB8100 Repeaters
- Trimble Thunderbolt GPS-locked reference oscillators
- NewMar battery management systems
- SOK LiFePO4 battery systems (some sites)
- Telewave duplexers
- Telewave bandpass filters and isolators
- Telewave and Sinclair antennas
How our Voted/Simulcast System works
When you use 100 Hz CTCSS, your signal is received by one or more of the linked sites, digitized by the linking controller, analyzed (in software) for signal-to-noise, and sent as VoIP packets to one of the controllers which is also running the central voting software.
That controller picks the best signal for each interval and sends that back out to all of the controllers where it is transmitted.
The frequency of each transmitter is locked to a GPS-disciplined 10 MHz oscillator. The same GPS-disciplined oscillator also provides a 1 pulse per second timing signal to the linking controller.
Each linking controller is a Soekris net5501 (500 MHz AMD Geode processor, 512 MB of RAM, 2 GB of Compact Flash) runnning Linux and equipped with an M-Audio Delta 44 audio card. The audio card records and plays back 4 channels of 24 bit audio at 96 kHz. One of the audio inputs is used to sample the 1 PPS signal from the GPS, another is used to sample the looped-back output of the card itself, and two duplex channels are available for link audio. A software FLL/PLL algorithm is used to lock the audio sample timing for both audio capture and playback to within about 10 microseconds of GPS-derived time. This allows the audio sent to the transmitter to be in phase with all other sites, and also allows the voter inputs to be in phase so there's no detectable transition between receivers.
All audio processing, signal-to-noise determination, tone detection and generation, and so forth is done in software, and because the GPS phase locking is also done in software there is no requirement for specialized DSP hardware. With the exception of the cables, everything is "off the shelf" hardware.
For more details, see Matthew Kaufman (KA6SQG)'s 2014 Pacificon presentation, "Voting and Simulcast for Repeaters"
The original modified VXR-5000 repeaters and Pacific Research RI-210 controlled have been replaced with Tait TB8100 repeaters with integral controllers.
When you use 100 Hz CTCSS, your signal is received by one or more of the linked sites, digitized by the linking controller, analyzed (in software) for signal-to-noise, and sent as VoIP packets to one of the controllers which is also running the central voting software.
That controller picks the best signal for each interval and sends that back out to all of the controllers where it is transmitted.
The frequency of each transmitter is locked to a GPS-disciplined 10 MHz oscillator. The same GPS-disciplined oscillator also provides a 1 pulse per second timing signal to the linking controller.
Each linking controller is a Soekris net5501 (500 MHz AMD Geode processor, 512 MB of RAM, 2 GB of Compact Flash) runnning Linux and equipped with an M-Audio Delta 44 audio card. The audio card records and plays back 4 channels of 24 bit audio at 96 kHz. One of the audio inputs is used to sample the 1 PPS signal from the GPS, another is used to sample the looped-back output of the card itself, and two duplex channels are available for link audio. A software FLL/PLL algorithm is used to lock the audio sample timing for both audio capture and playback to within about 10 microseconds of GPS-derived time. This allows the audio sent to the transmitter to be in phase with all other sites, and also allows the voter inputs to be in phase so there's no detectable transition between receivers.
All audio processing, signal-to-noise determination, tone detection and generation, and so forth is done in software, and because the GPS phase locking is also done in software there is no requirement for specialized DSP hardware. With the exception of the cables, everything is "off the shelf" hardware.
For more details, see Matthew Kaufman (KA6SQG)'s 2014 Pacificon presentation, "Voting and Simulcast for Repeaters"
The original modified VXR-5000 repeaters and Pacific Research RI-210 controlled have been replaced with Tait TB8100 repeaters with integral controllers.