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Choose the Proper Transmitter Model for Your Project.

We divide our VHF transmitter models by species types. Avian transmitters are designated Axxxx, mammal as Mxxxx, etc. We then divide up each species type into different series' by attachment types e.g. collars, glue-ons, etc., and by form factor, which depends on the size and shape of the battery used.

The Product Finder  and the species pages can help you filter transmitter characteristics by weight and battery life.

Below are additional details that will help you understand transmitters better. As always, call us and we are happy to help you.

Transmitter Weight

  • For birds, transmitter weight should not exceed approximately 3% of the body weight.
  • Fish, weight should not exceed 2 - 3%.
  • Reptiles and amphibians, 3 - 5%.

We publish the average weight for each transmitter model. There will always be a degree of variablitiy in the final transmitter weight; we try to keep it to 15% or less of spec.

Please note that some model series' weights do not include attachment material weights. Also, requested "deviations" to the production design can significantly change the final weight.

Battery Type and Size

  • The trade-off is between transmitter weight and life; a larger, heavier battery will last longer than a smaller, lighter one.
  • Most transmitters use lithium batteries and have a shelf life of several years.
  • Smaller transmitters using tiny button-sized silver oxide batteries have a very limited shelf life.

Program and Power Options (e.g. mortality)

  • Smallest transmitters use simple circuits and cannot be programmed (designated as “astable circuit” transmitters)
  • Larger transmitters can be programmed (designated as micro-processor controlled) and can include features like mortality, duty cycle, etc.
  • Some models offer an increased range option (a two stage vs. a three stage circuit), indicated with a “B” suffix.
  • Higher pulse rates and widths reduce transmitter life, lower increase life.
  • The faster the pulse rate, the easier to track and home-in on the animal (the "beep- beep" tone).


  • Each finished transmitter is labeled to identify its unique frequency.
  • We space the transmitter frequencies 10 to 20 kilohertz (kHz) apart. If there are other researchers using nearby frequencies in your planned study area, tell us and we can avoid them.
  • Smaller transmitters using silver oxide batteries have limited storage life and should be deployed within 1-3 months of delivery. Otherwise transmitter shelf life is about 5 years.
  • All transmitters are turned on and off by removing or replacing a small magnet taped to the unit.

100% Satisfaction, Guaranteed

We provide a 100% satisfaction guarantee on all transmitters equal to one half the battery life (in days), up to two years; up to three years on select collars.