MARS operates several repeater systems, including a VHF simulcast system. Check the Repeaters page for the latest information.
What is a voice repeater? A voice repeater is an automatically controlled amateur station that facilitates voice communications between other amateur stations, that are separated by distance or terrain. Repeaters do this by receiving incoming signals on one frequency and re-transmitting audio from the received signals on a different frequency. Repeaters do this by using special filters to separate the received and transmitted signals, called duplexers. Repeaters are usually installed where they have wide receive coverage areas. Repeater users listen on the repeater output frequency, and transmit to repeater’s input frequency. Most repeaters require a sub-audible access tone (CTCSS) to transmitted on the input frequency, to re-transmit a signal from a user.
What is a simulcast system? Simulcast is the simultaneous operation of two or more transmitters with overlapping coverage on the same frequency. This means that several repeaters operating on the same frequency are deployed to cover the area required. In our world that would be north, south and west portions of Marin County. By combining three repeaters into one system, Big Rock, Mt Tam and Mt Barnabe, we will dramatically improve our coverage area. In our system, we have different access tones (CTCSS) for each repeater in the system, but all transmitters are linked, so any received signal by one of the repeaters, is retransmitted by all three.
So, isn’t that what we had before? Well, not exactly. What we had was one repeater, on Big Rock, with multiple receivers spread around the county. That was good for being heard by the repeater, but not so good if you wanted to hear the repeater. Replacing the satellite receivers with a full repeaters will improve both transmit and receive performance in those areas.
The Timeline: On Saturday June 1, 2013 we took the first big step by upgrading the Big Rock repeater, making it the first member of the simulcast system. The new Big Rock repeater is now operating on a new frequency of 146.700 MHz, minus offset, with a CTCSS tone of 203.5. That’s the same access tone as the old Big Rock, only the repeater frequency has changed. Mt Tam went online Saturday June 8th, 2013 also on 146.70 MHz with a tone 179.9. The last site to become part of the simulcast system was Mt Barnabe, on 146.70 MHz with a tone of 167.9 which was completed in July 2013.
Where did the old 147.330 go? The old Big Rock frequency, with a changed CTCSS tone, has been relocated to the west peak of Mt Tam in Building 402, where it will function as a stand-alone repeater. 147.330 went live on Mt. Tam on 6/10/2015, and has great coverage into Mill Valley, west into Stinson Beach.
What’s working today? All 3 sites VHF Simulcast sites are operating today, as are the stand-alone UHF repeaters, which were not affected by this upgrade. The 147.330 VHF repeater (PL 179.9) on Mt. Tam went live, with new equipment, on 6/10/2015.
Any future plans for changes? We are planning enhancements to the Simulcast system, adding more receive sites (one enhancement has been approved, to date). We have purchased and are planning to install a Yaesu Fusion (digital) in place of the UHF repeater on Mt. Tam (443.250 MHz). There is a firmware update for the Yaesu Fusion repeater, which is a factory installed update. We will update the webpages as we implement changes.
What is a digipeater? A digipeater is a store-and-forward device used in APRS and Packet modes.
A digipeater receives and stores data packets, and after a short period re-transmits the information, on the same frequency.
Updated 2020-08-08 KG6VMT
