I wrote a really simple app for Android phones that acts as a telemetry receiver using the RTL-SDL dongles.  First version was 5 years ago, and I will admit I didn't really understand what I was doing with the signal processing at the time.  I have improved it some, but haven't added all the features I have wanted quite yet.  A big change I made was integrating the RTL-SDR android driver directly into my code so a separate package doesn't have to be installed.  Some concerns have been brought up, that making a cheap receiver could lead to bad actors using it to find animals, and I have had to sit and debate that.  Still, the code for the projects is here:

https://github.com/donfbecker/Telemetry-Receiver

I saw mention of tracking BPM with AI, and I have to say, you don't need AI.  Code for this one will not be released until after we finished up a project or two using it (publishing is competative, sometimes you have to keep your advantage).  The hardware has a cellular modem in it, so we get updates on BPM (which translates to Body Temperature), every 20 minutes.  I had it at 5 minutes, but the solar panels don't keep up as well then.  Like I said, no code, but I can give you a teaser of what I have been watching the last few days as our snakes emerge from over wintering.

The main issue with the RTL-SDR is that with the 8bit sampling, you have a noise floor around around -50dB, so you have to have a signal stronger than that to detect it.  The built in amplifier amplifies it's own noise as well, so isn't always great.  The wideband LNAs that are sold for software radios amplifies EVERYTHING, which sounds great, but isn't.  Tracking frequencies often aren't too far off from local FM radio stations in my area, so the LNA amplifies them too.  If they get too strong, they saturation the amplifier, and the RF front end on the SDR, basically erasing your signal.  The solution is to put a good bandpass filter in front of the LNA, but I've never been able to find one for the frequencies we use, so had to resort to building my own.  I only recently figured out the black magic that goes into LC filters, and dealing with all the extra capacitance added by PCBs.  I finally have a filter working in the range I need, and will be testing it out on my hardware soon to see how it helps with range.

Overall there is a lot of utility in using the RTL-SDR dongles, but the more I get into it, the more I am trying to design my own SDR hardware.  I don't need it to be as capable as the commercially available hardware.  I've made a few basic ones already just feeding the output of mixers in to the ADCs on an STM32 microcontroller, using an SI5351 to generate an LO signal for direct converstion.  I am going to start playing with using a TLV320ADC audio codec chip to sample signals.  It does 32bit sampling, which lowers the noise floor down to -130dB or so, assuming I don't introduce a bunch of noise from my hardware.  The sampling rate wouldn't be as fast, but still plenty for picking up the CW pulses from wildlife transmitters.

--Don

P.S. I am recovering from the flu, please ignore typos

How far did you end up taking this project?

HI Chittakon, 

Have you tested the dB gain as that is a measurement of how sensitive the receiver is to pick up a VHF signal.  Most commercial grade VHF receiver from telemetry manufacturers are in the -150dbm with a maximum noise figure of 3 dB.  

What was the type of VHF transmitters you were using and what was the length of the antenna of the transmitter?  Was the transmitter on the ground or position above the ground and if so what height and polarization plane?

There are a lot of variables which determine field range.

Chris Kochanny

www.vectronic-aerospace.com

Hi Simon, this sounds so interesting and is something I've been thinking about for my work in the past.
My team tracks Temminck's pangolins in Malawi using VHF and satellite tags. These animals have been rehabbed and released so we conduct welfare checks on them following release.
Our biggest challenge is that sometimes the satellite tag dies prematurely and then we struggle to pick up VHF signal without knowing an approx sat location. If the terrain is especially hilly then the distance we can pick up VHF signal from is really reduced, especially if the animal is in a burrow. I've previously wondered if a VHF monitoring system is possible with our drone (DJI Mavic 3T).

Your system sounds great and I'm definitely interested in learning more. A 50-100m real-time estimate would work well for us.

Surprised no one has recommended Bushnell. In Indonesia we use Bushnell 30MP Core DS-4K No Glow  119949C and Bushnell 32MP Core DS-4K Double Sensor 119987C, both are now the same price here. Depending on where you are they may be more expensive, but they retail in North America for close to USD 100. No wifi but in remote locations that doesn't matter. Low flash and good image/video quality. Definitely recommend getting a case for protection against animals (we have macaques and Sun bears). They like to grab hold and scratch a little but we've never had serious damage. 

Hi Stephanie, We are manufacturing an innovative AI-powered trail camera called DeterCam, and we are based in the UK: https://innovfactory.com/ 

The camera is equipped with our Edge AI technology, which allows it to detect only animals and send media (pictures/videos) only when an animal is present in front of the camera. This significantly reduces false triggers and power consumption.

Our Edge AI architecture allows the camera to operate for up to 1 year on battery power (assuming approximately 5 triggers per day). The system also allows full remote control from our cloud platform, including:

• Video duration
• PIR trigger settings
• Detection configuration
• Camera management and updates

The camera is equipped with a 4G module, allowing all media and detections to be uploaded directly to the cloud, meaning there is no need to physically collect data from the SD card.

We supply the complete solution, including manufacturing the battery packs ourselves. The total internal battery capacity can reach up to 32,500 mAh. To date, we have sold over 10,000 units worldwide.

Please let me know if you have any questions.

You can email me if you have any further questions: [email protected] 

Hi, are you looking to import these? Do you have any import tax considerations? This could impact which models you buy. I have been using Acorn models, very reliable and provide photo and 4K video with sound options.

Best wishes

Susan

That's a great idea @MandyEyrich ! Similar to your idea, I wrote up an article with geospatial highlights from ICTC 2026: https://wildlabs.net/en/article/wildlabs-geospatial-group-ictc-2026. 

Is the Human-Wildlife Coexistence article available yet? Would love to read it and share it with colleagues at Fauna & Flora.

See the solution below. If the island is within Globalstar’s coverage area, this is definitely the cheapest option: https://interrex-tracking.com/flex-globalstar 

Greetings Lisa, it is interesting to see to the project you are working on.  If there's anything I can do to help with my skillset let me know.

Thanks, Mike

Hi Kristof,

 Very cool that you made your own app like this! I'm not a movement ecologist, but I'd generally say this sort of thing will be more nice to look at than solves research questions. For example, most statistical models will show that proximity to water and human development are the strongest predictors of elephant movement. But it's still a very cool tool for outreach and communication with the general public or conservation decision makers! 

I can imagine a visualization like this being very helpful in communicating drivers of human-elephant conflict in SE Asia, where elephant movements outside of protected areas may be explained by the combination of attractive food crops, accessible water and shade refuge in tree plantations, and repulsive hazing by farmers. These sorts of things that can be modeled statistically don't necessarily translate well to the public - so visualization is really important! 

On a non-geospatial note, I would say that AR/VR also has a lot of potential for increasing public engagement/support for conservation. Getting individuals who may never go to East Africa to experience visually how increasingly severe droughts affects the landscape and promotes conflict between pastoralists and agriculturalists and wildlife could be really powerful. That's perhaps an area where game development expertise would be particularly useful. 

Cheers,

Brandon

I am glad to see more programmers coming into the conservation field.  The first big project I did that really got me involved with conservation work, was taking the path finding algorithms I used from learning game programming, and using them to detect and measure the distance of routes that turtles traveled up and down streams in a river drainage.  

Wolves, cool!

Will this then need collared wolves ?

Hi, 

Perhaps this is a tad late for you Maggie, but sharing in case this post comes up in a future search. Project CETI just released a fully open-source biologger, both hardware and software. Pretty cool. Here are the links:

Read "An open-source bio-logger for studying cetacean behavior and communication | PLOS One" on

An open-source bio-logger for studying cetacean behavior and communication | PLOS One

Over the past decade, bioacoustics associated with diverse marine life has become the focus of increasing research. While fixed acoustic devices play important roles in characterizing localized soundscapes, animal-worn devices that record audio alongside physiological metrics provide richer portals to understanding cetacean communication and characterizing sounds in their environment. To facilitate scaling the collection of such multimodal datasets for deep learning applications and to encourage rapid prototyping for new recording capabilities, we present an open-source non-invasive bio-logger that can be deployed on marine animals to record high-quality audio synchronized with an extensible suite of behavioral and environmental sensors. The current implementation is tailored to investigating sperm whale communication and biology. It features four suction cups, three high-bandwidth synchronized hydrophones for audio analysis including directionality, GPS logging and transmission, and sensors for pressure, motion, orientation, temperature, and light. Its hardware and software are both open-source, with designs, fabrication details, and code available online. Lab-based experiments characterize and validate performance including shear adhesion forces, withstanding pressures equivalent to 560 m depths, battery life up to 16.8 hours, audio sensitivity of –205 dB re FS/μPa with a 96 dB dynamic range, multi-threaded data acquisition, drone-based deployments, and GPS-based recoveries. Field experiments record sperm whale vocalizations and behaviors spanning 10 deployments, 44 hours of recording, 20 dives, and up to 967 m depths. Altogether, this platform aims to advance the understanding of marine animal biology and communication within the rapidly evolving and intersecting areas of robotics, bioacoustics, and machine learning.

Read "Tapping Into Whale Talk" on Harvard SEAS

Tapping Into Whale Talk

Open-source bio-logger captures underwater cetacean conversations

Harvard SEAS

I found this article on Hackaday a while ago: 

Read "The Gladys Hydrophone : 12 Steps (with Pictures) - Instructables" on Instructables

The Gladys Hydrophone : 12 Steps (with Pictures) - Instructables

The Gladys Hydrophone: It is time to update my Hydrophone Instructables. My first Hydrophone Instructable is a few years old at this point. Many were built and used around the globe. One of the first things I learned was that there needs to be a ground connection fro…

Instructables

It may be possible to install some of these in a semi-fixed location and then use them to generate baseline data in conjunction with observations.

For example, six or seven locations along with a population study would let you get a very coarse heatmap of areas that animals avoid.

This option looks to be a lower-cost hydrophone 

Read "Make a DIY Hydrophone" on

Make a DIY Hydrophone