Repeater Site Selection: Height, Duplexer, Duty Cycle
A 50 W repeater in the wrong place performs worse than a 25 W repeater in the right one. Three decisions set the outcome before the model number matters: where the antenna sits relative to the coverage area, whether the duplexer can hold the isolation your split demands, and what duty cycle the site actually asks of the box. Each one is cheaper to fix on paper than after installation.
| Specification | What drives it.. | How to check.. |
|---|---|---|
| Decision | What drives it | How to check it before ordering |
| Antenna height | Height buys coverage faster than watts do - roughly doubling height at fixed power extends usable range far more than a 3 dB power increase | Survey the proposed mast against the worst-served point, not the site centre |
| Duplexer isolation | The transmit and receive paths share one antenna, so the split must be wide enough and the duplexer selective enough to stop the transmitter deafening its own receiver | State the TX/RX split in the RF plan; ask for the duplexer's isolation figure at that split |
| Duty cycle | A repeater rated for continuous transmit can run at full power all day; a lower-duty unit must be derated, which changes your effective coverage | Read the duty-cycle line, not just the wattage. SLR5500 publishes 50 W maximum adjustable 1-50 W in a 1U chassis |
| Rack and depth | 1U does not mean shallow. Both units are 483 mm wide but 366-370 mm deep | Measure the cabinet, not the rack unit count |
| Channel capacity | 64 channels on SLR5500 against 1024 on HR106X decides how many sites and talkgroups one box can host | Count talkgroups and sites, then add headroom for growth |
| Band split | A repeater is band-specific. HR106X publishes UHF 350-400, 400-470, 450-527 MHz plus 851-869 and 935-941 MHz TX | Match the split to the licence before comparing prices |
Repeater
The first mistake in repeater procurement is ordering watts. Coverage is dominated by antenna height and by what sits between the antenna and the handheld. A 50 W box feeding a mast that is below the roofline will lose to a lower-power unit on a higher mast almost every time, because the limiting factor is the path, not the amplifier. The practical test is a walk survey against the worst-served point on the site - the basement stairwell, the far end of the yard, the back of the cold store - rather than a coverage circle drawn from the site centre.
Site Planning
The second mistake is treating the duplexer as an accessory. It is the component that lets one antenna transmit and receive at once, and its isolation at your specific split is what keeps the receiver usable. If the split is narrow the duplexer must be more selective, and a cheap duplexer at a narrow split produces a repeater that hears nothing while transmitting - a fault that looks like a radio problem and gets diagnosed as one for weeks. The third is duty cycle. A repeater running at full power through a twelve-hour shift is not the same duty as one carrying occasional calls, and a unit rated below your duty must be derated, which quietly removes the coverage you bought. On hardware: SLR5500 publishes 50 W maximum adjustable 1-50 W, 64 channels, 8.6 kg and 370 mm depth in 1U. HR106X publishes 5.8 kg and 366 mm depth in 1U with 1024 channels and DMR Tier II/III, but does not publish an RF power figure. If your submittal needs a wattage line, only one of these two can answer it in writing.
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Data Source: Motorola Solutions SLR5500 datasheet and Hytera HR106X product page (links on the SLR5500 and HR106X product pages). Coverage and duplexer behaviour described are engineering principles, not measured results for a specific site.
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