Polo Marconi PMR Cavity Duplexer

At a radio communications repeater site, the duplexer is the component that determines whether the system can use a single antenna to transmit and receive simultaneously without the transmit signal saturating the receiver. Without a quality duplexer, the repeater transmit power (typically 25-50 W) reaches the receiver mounted in the same cabinet directly, causing permanent desensitization or destruction of the receiver front-end. Polo Marconi resonant cavity duplexers solve this with TX/RX isolation exceeding 90 dB — a signal reduction factor of 10^9 between the transmit port and the receive port.

Polo Marconi's machined aluminum resonant cavity design guarantees resonant frequency stability with temperature: at an outdoor site without climate control, the temperature variation between day and night can shift a lower-quality duplexer's resonance out of the useful range, degrading isolation and causing intermodulation. Polo Marconi cavities compensate for this effect through controlled resonance temperature coefficients, maintaining the specified isolation across the complete operating temperature range of the site.

Polo Marconi offers duplexers in 2, 4, and 6 cavity configurations for different isolation and TX/RX separation requirements, and integrates them with their combiners and bandpass filters in complete systems for multi-system repeater sites (police + fire + civil defense on the same tower and antenna), reducing antenna-sharing infrastructure cost.