| # | Site Name | Frequency | CTCSS | Location | Elevation | Generator | GPS-locked | Linked |
|---|---|---|---|---|---|---|---|---|
| 1 | Allison | 441.300(+) | 110.9 | Mt. Allison (Alameda County) | 2300' | Yes | Yes | Yes |
| 2 | Woodside | 441.300(+) | 123.0 | Highway 35 (San Mateo County) | 2200' | Yes | No | No |
| 3 | Bonny Doon | 441.300(+) | 94.8 | Empire Grade (Santa Cruz County) | 2600' | Yes | Yes | Yes |
| 4 | Toro | 441.300(+) | 136.5 | Mt. Toro (Monterey County) | 3200' | Yes | Yes | No |
| 5 | Umunhum | 441.300(+) | 146.2 | Mt. Umunhum (Santa Clara County) | 3300' | Yes | Yes | Yes |
| 6 | Bonny Doon Lower | 441.300(+) | 156.7 | Empire Grade (Santa Cruz County) | 2100' | No | No | No |
Technical information about our new voted and simulcast system:
At this point three of the repeater sites are part of the new voted and simulcast system. When you use 100 Hz CTCSS, your signal is received by one or more of the linked sites, digitized by the linking controller, analyzed for signal-to-noise, and sent as VoIP packets to one of the controllers running 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 and the PLL circuitry of the VXR-5000 transmitter has been modified to replace the internal 12.8 MHz reference with the external 10 MHz reference, and a small microcontroller sends the replacement PLL divisor parameters to the PLL chip. 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, no moving parts) 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. All in the spirit of ham radio!
History:
The WB6ECE repeater system has existed since its first repeater on 441.300 (originally tested on 443.050) in Los Altos Hills, installed in about 1984 (moved to Woodside in 1989), and its second repeater in Santa Cruz installed in about 1989 (moved to Bonny Doon in 1999).
Our eventual goal is to provide a voted and simulcast UHF amateur repeater system operating on a single frequency for seamless no-effort wide-area coverage. In order to further that goal, we are initially installing several high-level standalone repeater systems, upgrading those to have GPS-locked transmit oscillators, and then linking the systems together to a voting hub as finances permit.
The system is open to any emergency traffic and all users who respect the operational features and limitations of the system. Most sites have utility power with automatic generator backup. Each standalone site uses a different CTCSS tone for access.
Each site is built with commercial components to reduce or eliminate unscheduled maintenance trips, even when mountaintop conditions get bad: modified Vertex VXR-5000 repeater radios (25 watts out), modified Pacific Research RI-210 controllers, HP Z3801A GPS-locked reference oscillators, Astron power supplies, Telewave (and Wacom) duplexers, Telewave bandpass filters, isolators, and antennas (Telewave 6db omni in Woodside, both Bonny Doon sites and on Mt. Umunhum, Telewave 9db dipole array on Mt. Toro, and Telewave 9db dipole array with electrical and mechanical tilt on Mt. Allison), and Times Microwave LMR-series feedline.
Now you can see more pictures of our sites.
Site Status and News:
April 20, 2009 - Prototype of linking software online - To use the new linked system, select 100.0 Hz CTCSS and try it out
April 17, 2009 - Mt. Allison site online with VoIP linking hardware
April 16, 2009 - Mt. Umunhum site online with GPS-locked transmitter hardware and VoIP linking hardware
April 8, 2009 - An all-new VoIP-based GPS-locked simulcast system is in development for the system, and the first site (Bonny Doon) is online as of today. Hardware for the remaining sites is being built up and software is in development. More news soon.
Mt. Allison - Site online with standalone repeater since September 6, 2003. Transmitter frequency is locked to GPS.
Woodside - Site online with standalone repeater since May 1989.
Bonny Doon - This new site is online as of May 21, 2004. Coverage of the San Lorenzo Valley and upper Bonny Doon should be superior to the previous site, which is now called Bonny Doon Lower and is on CTCSS 156.7 Hz.
Mt. Toro - Site online with standalone repeater since May 2003. Main antenna online since August 24, 2003. GPS-lock conversion completed and 420 MHz link radios installed November 2, 2005.
Mt. Umunhum - Site online with standalone repeater since August 2000.
Bonny Doon Lower - This site went online as the Bonny Doon site with standalone repeater as of February 21, 2004. Converted to backup status May 21, 2004.
Many thanks to our repeater site hosts:
Lance Ginner and the Bay Area Communications Society and Communication & Control Inc. on Mt. Umunhum.
Jerry Zimmer and the Monterey County Office of Education on Mt. Toro.
Dewayne Hendricks and Dandin Group and Communication & Control Inc. on Mt. Allison.
Don Mussell and Broadcast Engineering Services of Bonny Doon in Bonny Doon. (Bonny Doon Lower site)
Our host of the Bonny Doon Upper site
Also thanks to:
Our tower climber JV Rudnick, without whom neither the Mt. Toro antenna nor the Mt. Allison antenna nor the lower Bonny Doon antenna would be on their towers,
and our friends at Telewave who have provided assistance with duplexer and filter selection and custom antenna solutions for each site.
And thanks to our many financal supporters, especially Dennis Mason (N6PDB) who has provided much of the financial support necessary for our site linking project.
Site and installation pictures:
Mt. Toro installation trip of 5/10/2003
More pictures of our sites.
Information about our digital telemetry and pilot tone system used on our 420 MHz links:
(All sites but Mt. Toro have now converted to a VoIP-based linking system)
We transmit a 2000 bit per second MSK data stream. Zero is one cycle of 2000 Hz, One is one-and-a-half cycles of 3000 Hz. The idle synchronization is a 13-bit Barker codeword and is transmitted whenever no voice or telemetry data is available. When voice is sent, the data is muted. When telemetry or identification is sent, it occupies 8 bit data words separated by a single synchronization word. The identification is 8-bit ASCII text and the telemetry format is a direct mapping of input parameters to codewords. When no voice or data is available for an extended period, the transmitter is unkeyed after a turn-off sequence is transmitted. Please ask if you have any additional questions about the digital data format.
Matthew Kaufman, KA6SQG