Have you found yourself wondering what a digital receiver is lately?

11. December 2023

Over 10 exiting years with digital receivers! Learn more here:

Thelma Biotel has made digital receivers for over 10 years, where both the older TBR 700 and the new TBR 800 family are digital. Follow us through this short article to learn more about the digital receiver technology.

TBR 800 is a digital receiver, what does that mean?

The digital processing of acoustic signals opened up many possibilities 10 years ago! The short description here is that everything the receiver hears, the sounds in the water, are picked up and analyzed digitally. The on-board receiver’s computer constantly calculates the frequencies of the detected sound, the phase and the intensity. How it’s sampled and calculated can be changed through firmware and is not dependent on hardware tuning! This makes the digital receivers very flexible and allow for more precise and sensitive detection than what’s possible through analog signal processing.

Our digital receivers can run detection on several frequencies at once (multifrequency) and they supress signal collisions. Traditionally the high performance of digital signal processing has come with high power consumption and short battery lifetime, but that has been possible to overcome through smart programming and cutting edge microprosessors.

So how do the traditional analog receivers work?

An analog receiver compares the detected sound energy to a specific tuned reference frequency, e.g. 69kHz. Sound matching the frequency is treated as signals and is the input of the on-board computer. The receiver will only respond to this pre-set frequency and most of the noise rejection is done in the factory tuned electronics and does not allow for much flexibility. The analogue receivers generally lack information about the signal intensity and can’t efficiantly handle multiple frequencies at once or provide effective means of supressing signal collision.

What about the acoustic transmitters, are they also digital?

Acoustic transmitters are already as digital as they can be, and shouldn’t be mixed in with the digital receiver technology. Most of the pre millenium tags ran fixed transmit intervals and didn’t have microcontrollers, but that changed with the introduction of more advanced sensor options and coded transmit protocols.

Photo by: Catrine Schulze

What other perks are there to the TBR 800 being a digital receiver?

Behind the black rugged casing of the TBR 800 are refined and well thought through solutions to create a state of the art acoustic receiver. Below are some of the other benefits of the digital signal processing in the TBR 800:

  • Reduce signal collisions: Multichannel reception ensures that weak signals do not interfere with stronger signals, significantly reducing the number of signal collisions, which is often seen with similar technologies. The TBR 800 logs the signal intensity of every detection, which provides information on signal detection conditions and the approximate range/distance.
  • Mitigate background noise: The digital receivers from Thelma Biotel is based on digital technology which includes tools to filter out and mitigate background noise, assuring researchers are able to study all kinds of areas of interest, whether you find your species in noisy river systems or in lively coral reefs. With dynamic adjustments of the signal threshold levels the TBR 800 increases performance in challenging conditions where high noise levels are present, such as ambient and biological noise.
  • SNR/Signal to noise ratio: The digital signal processing offers great sensitivity, and thus a large detection range for tags. The digital signal processing also allows the receiver to analyze the received signal strength, this is stored as SNR with every signal detection in the memory. The SNR, the signal strength, is reduced with increasing distance and increased background noise. That’s why it’s such a powerful tool in range testing and general analysis of your final data.

Other things you might not know about the TBR 800:

  • Modular design: The modular design allows you to transform a standard logger into a release or a deep version release – or the other way aorund! If your needs change, we want you to be able to use the equipment you have already invested in. This is why we strive for a durable design with the possibility of updating both firmware and hardware in existing equipment.

You can always contact us at mail@thelmabiotel.com for more information!