Can Our Two-Way Radio System Share the Building's Existing Mobile/Telco DAS?

No. In almost every Singapore building, the answer is no — your walkie-talkie system needs its own antennas, its own passive network and its own head-end. The telco in-building system carries 700 MHz to 3.5 GHz cellular bands; DMR two-way radio sits at 400–470 MHz, well below the lowest frequency the telco antennas and couplers are specified to pass. You can share pathways, riser space and a single RF survey, but you cannot share the RF network itself.

Why the frequencies don't line up

A telco in-building solution (IBS) in Singapore is built for the operators' bands: 700, 900, 1800, 2100, 2500 and increasingly 3500 MHz. Every passive component in that system — the omni antennas, the directional couplers, the splitters, the point-of-interface — is specified over roughly 698–2700 MHz. Below 698 MHz the manufacturer simply does not characterise the part.

That matters most at the antenna. A wideband cellular omni presents a controlled impedance across its specified band, typically better than 14 dB return loss. Take it 250 MHz below the bottom band edge and the match is uncontrolled — a large share of your UHF power comes straight back down the feeder instead of radiating. Couplers behave the same way: a 10 dB tap at 900 MHz is not a 10 dB tap at 450 MHz, and the tap schedule you designed on paper is no longer the tap schedule you have in the ceiling. The coax itself is the one component that is fine — 1/2" plenum cable runs at roughly 4.5 dB/100 m at 450 MHz against something closer to 9–10 dB/100 m at 1800 MHz, so UHF is the easy case for cable. Verify both figures against the cable datasheet for the specific part.

If the building has an active DAS — fibre to remote radio units rather than a passive coax tree — sharing is not even arguable. Those remote units are band-specific RF modules. There is no port on them that accepts 450 MHz.

The numbers that decide it

• Cellular IBS passive components: specified ~698–2700 MHz. DMR two-way radio: 400–470 MHz — entirely out of band.

• Wideband antenna return loss: typically better than 14 dB in band, uncharacterised below 698 MHz. Verify against the antenna datasheet.

• 1/2" plenum coax: ~4.5 dB/100 m at 450 MHz vs ~9–10 dB/100 m at 1800 MHz. Verify against the cable datasheet.

• Design threshold for reliable DMR voice: −95 dBm at the portable, with 10 dB fade margin for standard commercial coverage and 15 dB where the system is life-safety critical.

• UHF antenna spacing on an open floorplate is typically 25–35 m radius against 12–20 m for 1800/2100 MHz — the cellular layout is roughly two to four times denser than UHF needs.

That last figure is the practical point people miss. Even if the RF worked, you would be feeding a UHF signal into an antenna grid designed for a much shorter cell radius, splitting your repeater output far more times than the physics requires and losing margin for nothing.

There is also an ownership problem, not just an RF one

The telco IBS in your building is not yours. Under IMDA's Code of Practice for Info-communication Facilities in Buildings, the developer or building owner provides rent-free Mobile Deployment Space and access; the equipment inside that space belongs to the licensed mobile operators. Injecting a 40 W UHF repeater into their passive network makes you an unauthorised transmitter on a licensee's infrastructure. That breaches the operator's access agreement and sits badly against your own IMDA station licence conditions. No operator in Singapore will approve it, and you should not want them to — you would be handing responsibility for your security team's radio coverage to a system you have no maintenance rights over.

What you can genuinely share

Coordinate the two systems and you still save real money. One RF survey and one set of floor plans can inform both designs. ELV risers, cable tray, ceiling void routes, ELV room floor space, rooftop antenna positions and mains supply can be allocated once instead of twice. If you are building new and you want a single passive network, the honest route is to specify it that way from day one: wideband antennas and couplers rated from 380 MHz, with a cross-band point-of-interface combining the UHF repeater and the operator feeds. That is a design decision made at tender stage, with operator agreement, not a retrofit you can bolt on later.

Related questions

Can I at least run two-way radio on the same coax as the cellular DAS? Only if the passive network was specified from 380 MHz and combined through a proper cross-band POI. Retrofitting UHF onto a 698–2700 MHz network gives you out-of-band couplers and mismatched antennas, and you will fail the coverage test.

Does the COPIF Mobile Deployment Space requirement cover my private radio system? No. Mobile Deployment Space obligations relate to licensed mobile operators' infrastructure. A private two-way radio DAS is your system, on your budget, under your own IMDA licence. See our explainer on the 2026 COPIF review.

So do I need a second DAS? You need a UHF DAS. It is generally smaller than the cellular one — fewer antennas, longer spacing, one head-end — and it shares the same risers. Our guide to what a DAS is and whether your building needs one sets out the scoping questions.

How Suneast approaches this

Suneast designs and installs UHF DAS for two-way radio in Singapore buildings, and we routinely coordinate the design with an existing or planned telco IBS so the two systems share risers, ELV space and survey data without touching each other's RF. Every design we issue carries the link budget for both the downlink and uplink paths, a floor-by-floor coupler and tap schedule, and a grid coverage test at handover measured against the −95 dBm threshold.