Radiometrix VHF Bird Alarm Transmitter

The BAT1 On-Off-Keying (OOK) transmitter is intended for the tracking of small animals such as birds and operates in the 150MHz and 173Mhz bands dependant on country specifics. It is designed to meet ETSI EN 300 220-2 radio standard.

Lemos International Technologies Radiometrix Bird Alarm

Functional description

The BAT1 transmitter consists of an OOK modulated crystal Oscillator and frequency multiplier with
two stage RF filter and antenna matching. It has a microcontroller, which controls the main functions
of the transmitter. Activity monitoring is achieved by the use of an omni-directional tilt and vibration
sensor, This senses movement regardless of orientation of the transmitter.

The transmitter has 2 pre-defined modes, Mode 1 is Normal Mode and transmits a single 20ms RF
pulsed carrier and is repeated every 1.5 seconds. Mode 2 is controlled by the activity sensor, which is
activated when the pre-determined activity timer has been exceeded, typically this will be 18 hours.
When there has been no movement during this time, Mode 2 is then activated, this gives two 20ms
transmitter pulses which are separated by 150ms, this gives the effect of a “double beep” on the
Receiver and is repeated every 1.5 seconds. If any activity is detected when in Mode 2, the 18 hour
counter is reset and then returns to Mode 1.

On board is a magnetically operated Single Pole Normally Open (SPNO) dry-reed switch and requires
the use of a small magnet brought close to the unit to turn the transmitter on or off, no visual indication
is provided as this would consume extra power and shorten the battery life for this reason a tracking
receiver should be used to confirm if the transmitter is on or off.


  •  Standard frequencies in 150MHz to 173MHz bands.
  • Other frequencies available subject to custom crystal lead times.
  • Modulation OOK (on off keying).
  • 2 modes of operation – Normal, Inactivity/Mortality.Low power requirements
  •  Activity sensor
  • 2 grammes weight excluding coin cell


  • Small tracking transmitters for game and wildlife research and management

Technical Summary

  • RF Power output: >-10dBm
  • Pulse width: 20ms
  • Pulse rate: 40 pulses per minute (ppm)
  • One-touch ON/OFF switching by magnet
  • Tilt & Vibration sensor built in for mortality / inactivity detection
  • Supply 3V lithium coin cell
  • Battery life 12 months typical (dependant on model)
  • Integral 30cm long nylon coated stainless steel wire antenna
  • Microcontroller controlled