Product ID: KAIROS
The Radio Activity KAIROS is a continuous-duty, Software Defined Radio (SDR) multi-protocol base station equipped with a native Linux core and an 80 MIPS DSP. It automatically switches between analog FM and digital DMR modes in real time. Featuring dual coherent receivers (Soft Space Diversity), it effectively eliminates multipath fading while delivering a 3 dB sensitivity boost. KAIROS features low power consumption (< 4.5 W in RX), wide-area Simulcast support, and direct SIP/RTP VoIP integration for IP dispatchers and telephone systems.
Product features:
Linux-based Software Defined Radio (SDR) architecture with free software protocol upgrades 
Digital Soft Space Diversity reception boosting sensitivity by 3 dB and overcoming multipath fading 
Automatic, real-time mode switching between analog FM and DMR Tier II/III digital signals on the same channel 
Ultra-low power consumption (< 4.5 W in RX mode), ideal for solar-powered deployments 
Embedded DMR Gateway and SIP agent for direct integration with PABX phone systems and IP consoles • Product description
Built upon rich Italian engineering expertise, the Radio Activity KAIROS represents a modular building block for two-way radio networks, scaling from standalone repeaters to nationwide systems. All physical layer signal processing functions are performed digitally within its DSP core, bypassing hardware limitations. Operating on a full Linux distribution, KAIROS acts as an independent peer node within IP networks, placing minimal demand on backbone bandwidth (transmitting IP packets only when valid RF traffic is present and dropping below 1 kbps in standby).
Multipath fading presents a major challenge in digital mobile communications, as reflected signals interfere with direct signals, increasing the Bit Error Rate (BER) and causing complete audio dropouts. KAIROS addresses this challenge using advanced diversity algorithms proven in cellular and TETRA networks. Equipped with two coherent receiver channels connected to spatially separated antennas, KAIROS performs vector phase addition on incoming signals. This soft diversity process yields a 3 dB sensitivity gain, eliminates coverage nulls, and delivers a stable, uninterrupted digital data stream at the coverage boundary.
KAIROS removes the barrier between legacy analog systems and modern digital standards. By automatically detecting incoming RF modulations, it enables legacy analog radios and modern DMR Tier II/III portables to operate across the same network infrastructure simultaneously. The embedded DMR Gateway converts AMBE+2™ digital voice directly into standard G.711 VoIP streams, registering radio subscribers directly into corporate SIP PABX phone networks as local extensions. This allows dispatch operators and office phone users to establish full-duplex calls with radio talkgroups without external hardware bridges.
Featuring precise delay equalization algorithms and multiple timing references (GPS, PTP IEEE 1588, external references), KAIROS excels in wide-area Simulcast (same-frequency) networks. Operating the entire coverage area on a single frequency pair delivers seamless roaming and automatic handovers without call disruption. Consuming less than 4.5 W in receive mode, with an operating range of -30°C to +60°C, KAIROS can be installed in compact outdoor enclosures mounted directly on poles and powered entirely by solar panels and backup batteries.
The versatility of the KAIROS transceiver makes it ideal for mission-critical operations, including:
Critical Infrastructure & Utilities: power utilities, gas distribution, water management, and SCADA/telemetry networks
Public Safety & Emergency Services: police departments, fire services, ambulance dispatch, and defense sites
Railways & Public Transit: train CAB radio systems, depots, tunnels (operating as a TDMA transponder)
Paging Networks: high-reliability POCSAG digital paging and analog tone alert systems
Tactical & Temporary Deployments: mobile repeaters and tunnel coverage extenders
• Specification
SKU / Catalog Number
KAIROS (KA-040 / KA-080 / KA-160 / KA-350 / KA-450 / KA-500 / KA-900)
Device Type
Multi-Protocol Base Station / Repeater / Transponder
Dimensions (including connectors)
48 x 197 x 220 mm
Dimensions 19" Rack Assembly (2 transceivers)
87 mm (2U) x 426 x 220 mm
Dimensions 19" Sub-rack Assembly (up to 6 transceivers)
215 mm (5U) x 426 x 220 mm
Weight (single transceiver)
1,35 kg
Frequency Bands
KA-040: 30 - 40 MHz KA-080: 66 - 88 MHz KA-160: 136 - 174 MHz KA-350: 350 - 410 MHz KA-450: 400 - 470 MHz KA-500: 450 - 520 MHz KA-900: 865 - 941 MHz
RF Output Power
1 - 25 W (software adjustable; 15 W max for 900 MHz band)
Max Duty Cycle
100% continuous
Channel Spacing
6,25 / 12,5 / 20 / 25 kHz
Synthesis Step Size
50 Hz
Frequency Stability (without GPS)
0,5 ppm
Digital Vocoder
AMBE+2™
Transmitter Protection
RF power reduction at temp > 85°C; VSWR protection against short/open circuit for min 10 min
Operating Temperature Range
-30°C - +60°C
Storage Temperature Range
-40°C - +70°C
Humidity
Max 80% non-condensing
Standards & Certifications
EN 300 086-2, EN 300 113-2, FCC Part 90, IC RSS119, ETSI TS 102 361 (DMR Tier II / Tier III), EMC EN 301 489-1/-5, EN 50385, Norma kolejowa EN 50498 / EN 50121-3-2 / EN 50155, Dyrektywa RoHS2 / CE
Input Voltage (DC)
10.8 - 15.6 VDC (13.2 VDC nominal)
Power Consumption
Receive (RX): 4.5 W (both Main and Diversity channels active) Transmit (TX): 60 W (at 25 W RF output)
Standby Power Consumption
< 5 W
Power Supply Protections
Polarity reversal protection (up to -70 V), overvoltage (> 15.6 V), undervoltage (< 10.8 V), inrush current limiting (soft start), and short circuit protection
RF & Input Connectors
TX: SMA female RX Main / Diversity: SMA female GPS / GLONASS: SMA female (5V DC phantom power) LAN: Ethernet 10BT/100TX RJ45 (Auto MDI/MDI-X) Auxiliary I/O Port: DB25 female Power & Bus Connectors: 3-pole Phoenix Contact and rear 6-pin bus connector
Local Digital & Analog I/O
8 x Open Collector outputs (up to 20 mA / 40 VDC), 8 x digital inputs (3.3 V pull-up), 1 x analog telemetry input (10 kOhm / 0 - 24 V)
Audio Interfaces
2 x balanced 2/4-wire lines + E&M (600 Ohm impedance, adjustable level -20 to 0 dBm)
Maximum Sensitivity
-116 dBm @ 20 dBp SINAD
BER Sensitivity
Without Diversity: -118 dBm @ 5% BER With Soft Diversity: -121 dBm @ 5% BER
Operating Maximum Input
-10 dBm (damage limit > +10 dBm)
Co-channel Rejection
8 dB @ 25 kHz / 12 dB @ 12,5 kHz
Adjacent Channel Selectivity
73 dB @ 25 kHz / 65 dB @ 12,5 kHz
Intermodulation / Blocking Rejection
75 dB / 80 dB
Intercept Point IP3in
+15 dBm
Audio Distortion & Noise
< 2% @ 1 kHz; -53 dBp @ 25 kHz / -47 dBp @ 12,5 kHz
Adjacent Channel Power
-75 dBc @ 25 kHz / -65 dBc @ 12,5 kHz
Available Modulations
FM, PM, GFSK, 4FSK, 2DFSK
Transmitter Residual Noise
-56 dBp @ 25 kHz / -50 dBp @ 12,5 kHz
FM Distortion
< 1,5%
Analog & Digital Signaling
DTMF, ZVEI I/II, CCIR, EIA, EEA, CTCSS, DCS, FFSK (1200/2000 bps), DSC, POCSAG (512/1200/2400 bps), GMSK (AIS)
Supported System Types
Analog Conventional, DMR Tier II Digital Conventional, DMR Tier III Digital Trunking, MPT 1327, Dual-Timeslot Fixed Station, Simulcast, Paging, TDMA Transponder / Coverage Extender, 1+1 Hot Stand-by
IP LAN Network Requirements
Max delay < 400 ms, Jitter < 200 ms, Packet loss < 0.1%; Required bandwidth: 24 kbps per station in DMR / 70 kbps in Analog
Package Contents
1 x Radio Activity KAIROS Base Station Transceiver 1 x 3-pole Phoenix Contact power connector 1 x Programming utility software & manual documentation
Hardware Modules & Transceivers
KA-080 (KAIROS 66-88 MHz Transceiver) KA-160 (KAIROS 136-174 MHz Transceiver) KA-450 (KAIROS 400-470 MHz Transceiver) KA-500 (KAIROS 450-527 MHz Transceiver) KA-900 (KAIROS 806-941 MHz Transceiver) KA-xxx-RX (RX-only base station variant) KA-xxx-TX (TX-only base station variant) KA_GPS (Internal GPS/GLONASS receiver module) KA_VOC-2 (Internal DMR vocoder 2-line + GPS receiver) KA-TI 02 (KAIROS Audio Gateway module)
Software Licenses
KA_DMR-L (DMR Protocol Software License) KA_GT2 (SIP Gateway SW License for DMR Tier 2) KA_SI-T2 (Simulcast SW License for Analog and DMR Tier 2) KA_P25 (P25 Phase 1 Protocol SW License) KA_P25-SI (Combo Simulcast & P25 Phase 1 SW License) KA_TX_LICENSE (SW license to upgrade RX-only station to full TRX) KA_RX_LICENSE (SW license to upgrade TX-only station to full TRX)
PC Management Software & Tools
KA_MNG (KAIROS Setup & Programming SW) KA_NET (IP-based DMR_NetControl surveillance software) KA_NET-RC (DMR NetControl Remote Control SW License)
19" Mounting Hardware & Sub-racks
KA_RK1 (19" 2U mount panel for 1 KAIROS) KA_RK1v2 (19" mount panel for 1 KAIROS without adjacent panel) KA_RK2 (19" 2U mount panel for 2 KAIROS transceivers) KA_RK6 (19" 5U sub-rack for up to 6 KAIROS transceivers, includes 6x VP-4) KA_VP (Frontal panel 10TE for vertical mounting) VP-10 (Blanking plate 10TE for vertical mounting)
Network & Cable Accessories
GPS-ANT (External active GPS/GLONASS antenna, PCTEL GPS-TMG-SP-40N) KA_1+1 (Cables kit and SW for hot stand-by mode) SWH (19" 8-port Ethernet switch) KIT-CABLES (Cables kit for connecting KA-RK6 and ETH switch) KA_SETUP / SYS-PROG / NTW-PROG (Factory setup and network engineering services)
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