Comparing Standalone DMR & Trunked Radio Systems for Large Sites 

Most sites size a radio system by headcount and coverage. ISED sizes it by channel count and drew that line in 1983. RP-003 puts a 120 km radius around the Kitchener, London, Hamilton and Toronto census metropolitan areas. Inside those circles, a new system needing more than three channels must trunk as a condition of licence.

The comparison behind a trunked radio system for large sites narrows faster than most operations managers expect. Below four channels, the choice is real and worth arguing. Above it, in this part of Ontario, the choice belongs to the licence.

What still gets decided locally is when a site crosses that line, and nobody there is watching for it. Channel count creeps up with a night shift, a contractor crew, a second building. The threshold arrives before anyone runs the numbers.

Coverage and capacity get conflated throughout this decision, though coverage only tells you whether a radio reaches the repeater. Capacity decides whether your operator can transmit while the rest of the site is keyed up.

Every Channel Stays Reserved Until Someone Lets Go

In a conventional DMR setup, each talkgroup gets a channel and reserves it for the duration of the conversation. The DMR standard from ETSI gives you two-slot TDMA in a 12.5 kHz channel. A single licensed frequency therefore carries two simultaneous talk paths. Shipping occupies one, maintenance occupies the other, and the third talkgroup waits its turn.

Under light traffic, that configuration is efficient and inexpensive to operate. It's also predictable, which is why it has held up for decades on single-building sites. A supervisor internalizes the rhythm of the channel within a week and works around it without thinking.

That discipline is real, and it decays. New hires and contractors arrive without it, and the channel configuration absorbs the difference.

Then comes 3 p.m. Outgoing supervisors, incoming leads, maintenance and the yard all key up inside the same two minutes. A radio channel busy at shift change isn't a fault code. The system is performing exactly as designed, holding each path until the person transmitting releases the button.

Headcount Is the Wrong Number to Size On

Most sizing questions arrive as a headcount, asking how many radios a standalone system will hold. There's no reliable answer, because loading depends on how many talkgroups transmit simultaneously and how long each transmission runs.

ISED does publish a loading benchmark. RP-003 sets the guideline at 90 mobiles per channel for commercial applicants, 50 for safety services. Those figures describe expected spectrum efficiency, not the point where your operators stop waiting.

A facility can sit well inside that guideline and still block calls every afternoon. The benchmark counts radios against channels. It doesn't count how many of those radios transmit inside the same ten-minute window.

Headcount gets answered because headcount is easy to count, but the number that decides the system is a different one. Identify the talkgroups requiring simultaneous transmission at the busiest moment of the operating day.

A Trunked Radio System for Large Sites Pays Off at Peak, Not Average

Trunking pools the available channels rather than allocating them permanently. A dedicated control channel receives the request, identifies an unoccupied path and allocates it. That path returns to the pool once the conversation finishes.

The ETSI standard covers this as Tier III, and Motorola builds trunking into MOTOTRBO through Capacity Plus and Capacity Max. Its own documentation puts Capacity Plus at single-site trunking for up to 1,000 users. Call queuing ranks an emergency ahead of a shipping update rather than making both wait in the same line.

We've broken down how trunking assigns channels on demand in more detail, including what the control channel does between calls. The gain isn't more coverage, but more conversations through the same licensed spectrum at the hour that matters. A site running six talkgroups across four paths stops rationing airtime by department.

Standalone DMR Doesn't Log What It Refused

Here's the part that keeps this problem alive on otherwise well-run sites: nobody owns the threshold. A facility adds a night shift, then a contractor crew, then a second building, one hire at a time. The system was specified correctly on the day it was bought, and nothing since has produced a report saying otherwise.

A standalone DMR system doesn't record blocked calls, delivering a busy tone to the operator and continuing to operate normally. Ask a plant manager how many times a supervisor couldn't get through last month. The honest answer is that nobody counted, because there was nothing to count.

Purchasing sees a functioning radio fleet with no fault history attached, while operations sees people walking to find each other. Neither picture is wrong, and neither one is complete on its own. Those positions reconcile only when somebody monitors actual channel activity for a complete week.

That gap is why the standalone DMR versus trunked radio decision gets made after an incident instead of before one.

Trunking Adds a Layer That Can Fail

Pooling channels means something has to do the pooling. A control channel is one more part of the system, needing planning, redundancy and money. Motorola supports alternate control channels for that exact reason, which tells you the risk is real enough to design around.

For a facility running 20 radios across two channels, that additional complexity earns nothing back. Two repeaters and disciplined talkgroup allocation will outperform a trunked deployment at a fraction of the capital cost. The money is better spent on coverage in the corners of the building where people go quiet.

The threshold sits around four or five distinct talkgroups, or the point where congestion becomes regular rather than occasional. Below that, the control layer is cost without load. Spending the same capital on a coverage correction usually delivers more for operators, and it delivers it sooner.

The genuinely hard cases sit just under the three-channel line. A site there can remain conventional legally and still queue at every handover. Nobody should determine that from a headcount alone, because it takes a week of channel data.

Above Three Channels, ISED Has Already Decided

ISED's RP-003 guidelines count the channels a system needs within its first three years, not the channels it opens with. A facility anticipating growth is assessed on that projection, not on day one.

Trunking also consumes more spectrum, not less. RP-003 assigns trunked systems a minimum of four frequencies and a maximum of five. The licensee is expected to reach 70% of the minimum loading criteria during the licence term.

Falling short of that permits ISED to take corrective action on the assignment. The system is also expected to be operating within one year of the licence being granted. In the 800 MHz band, licensees reaching 90% of the loading criteria can request additional trunked frequency pairs.

The application asks more of you as well. ISED wants a justification, a technical description, a five-year growth plan, implementation dates, and expected quality of service. Applications are processed first come, first served, against whatever channels remain free in the area. The 421 to 430 MHz band is tighter again. ISED authorizes one system per licensee in a given area, capped at five duplex channels. That paperwork runs on its own clock, separate from your capital approval.

Southwestern Ontario Buildings Make Capacity Look Like Coverage

Much of the manufacturing and warehousing stock through the Kitchener, Cambridge and London corridor was constructed in stages. A poured-concrete core from the seventies, a metal-clad addition, a mezzanine office that went in later. Signal behaves differently in each section, and staff memorize the weak locations over time.

An operator hears a busy tone in the north stairwell and reports a dead zone. Maintenance gets sent to check the antenna, which is performing correctly, and the sweep confirms it. The facility continues chasing coverage while the actual problem sits in the channel configuration.

An RF coverage study in Southwestern Ontario separates those two failures before anyone signs a purchase order. Device choice won't. Handing every supervisor, a MOTOTRBO R7 improves audio in a noisy bay, and it adds exactly zero talk paths.

What To Measure Before the Capital Request

Record busy-tone occurrences across your two busiest operating windows for a complete week. Count active talkgroups at those same moments, not on paper but in practice. Note how long a typical transmission runs, because short dispatch traffic and long maintenance exchanges produce different systems.

Then add your headcount plan for the next two years, including contractors. Seasonal crews load the system identically to permanent staff, and they rarely appear in the sizing conversation. Facilities migrating to trunking too early pay for a control layer they never fully load. Sites that trunk too late discover it during an incident.

Public safety agencies made this move years ago for exactly the same reason. Much of why trunking suits high-volume users reads the same for a two-way radio system for a manufacturing campus. Three shifts produce the same crush, and the traffic pattern is different in scale rather than in kind.

If shift change is producing busy tones nobody logs, book an RF coverage study with our team. We'll measure traffic and coverage separately, then tell you which problem your site actually has.