The system as it stands right now consists of two sites Fremont Peak and Presson Hill. Both operate on the same temporary frequency pair.
147.405(output) 144.940 (input) PL 94.8
This week was historic for the Salinas Valley Repeater Group, Thursday 9/24/2026 marking the day we put out the first simulcast system on the air!
Over the last 7 years, I’ve been wanting to convert SVRG’s linked system to simulcast. But why simulcast you ask? These systems are hard to build, maintain, and are complex to design. Well let me list out some of the advantages and disadvantages of a simulcast system and you’ll see why I’ve wanted to bring an open VHF simulcast system to the amateur radio community.
- Seamless coverage – users experience better coverage as they move between repeater sites, since all sites transmit the same signal at the same time
- Single frequency – no need to program or scan multiple frequencies/channels for the same system, simplifying radio programming and user operation
- Simpler user experience – users just talk; there’s no need to select a specific repeater, figure out what channel to be on and understand which site they’re nearest
- Efficient spectrum use– Allows SVRG to reduce its spectral footprint and free up repeater pairs in the already frequency congested greater bay area.
That being said there are some Trade-offs worth knowing:
- Simulcast requires precise engineering (GPS timing, phase alignment studies, link reliability) and is more complex/costly to design and maintain
- Linked repeaters (voted or non-simulcast linked) systems are generally simpler and cheaper to deploy, more forgiving
- Linked systems can be easier to expand incrementally site-by-site
All that said, the goal was set. Simulcast was the path forward for SVRG, but how would it be built? Our first experiments were with the Motorola DSM-II T1 based simulcast system developed in the 90’s. After building a test system of 3 sites and mulling over the installation requirements, rackspace constraints, T1 circuit emulation TDMoP, 48v DC power systems. It became quickly apparent that a DSM-II based simulcast system would not be feasible for the system we wanted to build.
So where do we go from here?
DSM-II is off the table, so I started to look into the Motorola MLC-8000 and Micro-Node RTCM. The MLC-8000 requires a 5Mhz 1PPS composite signal that the TRAK-9100 produces (very costly) and the Micro-Node RTCM requires hardware modification to use for simulcast as it requires a 9.6MHz non standard clock, so that’s out too.
Our solution was to design our own simulcast hardware! Dub’d the SV-180, our simulcast board that connects to ASL3’s linking and voting platform. More to come on that in another post.
How does simulcast work?
What equpment makes up a simulcast repeater site?
What are our future plans for SVRG and its simulcast system?
As of right now our plan is to convert all VHF systems to simulcast on 1 frequency pair (excluding Meadow lakes VHF).
This in and of itself is going to be a bigger challenge to work out than the engineering required to design our own simulcast controller and build out a system over multiple counties.
Due to the frequency congestion on the VHF band in our area and with our plan being very aggressive, coupled with the fact that there is no perfect frequency pair for us to land on.
I ask you, the community, for understanding as we work through the next steps of the simulcast system we are going to build for you.
