Since launching our range VHF wildlife transmitters we are often asked if we can supply the circuit boards without any encapsulation or attachment materials. This not only allows the user to design and build their own attachment method to better fit their study species but it also saves them money! We have also supplied the transmitter boards for attaching to other equipment. In addition to being attached to a wide range of wildlife equipment to help locate it after deployment e.g. drop-off cameras and GPS collars, our transmitter boards have also been used as an inexpensive, discrete and long lasting security device for remotely stored equipment such as farm and construction machinery.
The PERDIX small VHF transmitters are built using a round double-sided PCB board with a diameter of 20 mm. The board also has two 5 mm x 5 mm ‘wings’ with 2 mm diameter eyes that can be used for mounting or simply cut off depending on the application. The transmitter antenna is 300 mm of 7/7 stainless steel cable with nylon coating.
How it works
The PERDIX transmitter consists of an OOK modulated crystal Oscillator and frequency multiplier with two stage RF filter and antenna matching. It has a processor which controls the main functions of the transmitter. Activity monitoring is achieved by the use of an omnidirectional tilt and vibration sensor, this senses movement regardless of orientation of the transmitter. A magnetically operated switch is used to turn the transmitter on and off. By placing a small magnet that requires close to the unit the transmitter is activated or deactivated. No visual indication of the unit being on or off is provided as this would consume extra power and therefore shorten the battery life. A VHF tracking receiver should therefore be used to confirm if the transmitter is activated.
Standard transmitter settings
The transmitter has two predefined modes, mode 1 is normal mode and transmits a single 17.5 mS RF pulsed carrier and is repeated every 1.6 seconds. Mode 2 is controlled by the activity sensor which is activated when the predetermined activity timer has been exceeded, typically this is 18 hours. When there has been no movement during this time period, mode 2 is then activated. This gives two 17.5 mS transmitter pulses separated by 150mS to produce a “double beep” on the VHF receiver and is repeated every 1.6 seconds. If any activity is detected when in mode 2, the 18 hour counter is reset and the transmitter returns to mode 1. The TX power of our standard transmitter is range from 2.5 mAh.
Battery type and life
The PERDIX small VHF transmitter boards have been designed so that either a Panasonic CR2025/HFN or Panasonic CR2032/HFN lithium coin cell can be easily attached to them. The CR2025 coin cell weighs 2.5g and has a capacity of 165 mAh while the CR2032 weighs 0.5g more but has a greater capacity of 225 mAh. Using our standard transmitter parameters above, the CR2025 cell has a calculated battery life of up to 195 days. The CR2032 cell has a life of up to 265 days. The battery life of the transmitters can be altered depending on the TX current setting (please see below). Please note that battery life can vary depending on environmental conditions.
Currently we have frequencies available in 150, 151 and 173 MHz ranges.
Can any of the settings be changed?
Although the settings cannot be changed by the user, we are able to adjust some of the parameters during manufacturing to meet a particular projects needs (MOQ applies). These include the non-activity period (1.5 seconds to 30 days), pulse spacing and total current (2.2 – 4.2 mAh). Please contact us to discuss your requirements further.