Finding dropped tags

Tagging
1

Hi Motus Community!

I am a Master’s student at Thompson Rivers University doing a study on Mountain Chickadee natal dispersion and overwintering flock movements. We tagged nestlings in June (with glue as other tagging options weren’t working) and since then I have been using handheld telemetry with a Lotek SRX1200 receiver and 3 element Yagi antenna to do the main tracking.

Problem: Many tags have either been pulled off by the parents or simply fallen off. I spent 2 months doing routine telemetry surveys (and looking for lost tags) with a whip antenna and 3 element Yagi to triangulate some tags, but just couldn’t find the physical tag.

Solution: New Antenna and SDR Console software on a laptop (Media attached)

With help from a physics technician at my university:

  1. He made a loop antenna (with a 50ohm semirigid line) with an N connector that fits into the FunCube dongle for Motus stations, which I then connect to a laptop. **The loop antenna is extremely sensitive and only works with a strong signal strength**
  2. I downloaded a software called “SDR Console”, (SDR Console Download), which was programmed by a radio enthusiast to analyze and visualize radio signals at any frequency.

FYI

  • Using the proper adapter from BNC to N, you can also attach a Yagi antenna to the FunCube and use that instead. Just keep in mind that the Yagi won’t provide the same accuracy as the loop antenna.
  • With the SDR console, you can also visualize a signal that may be getting lost in surrounding radio interference (which we have encountered a lot at my study site).
  • SDR console only works with a windows operating system. You need at least a windows 7 64bit with a minimum Core I3 processor and 4GB RAM

In The Field:

I triangulate a tag with the usual receiver and yagi set-up, then once I have a clean estimate of where the tag may be, I switch to the loop antenna and laptop. Within the SDR console, you set your radio as the FunCube, preferred frequency (166.380 MHz) and press start. As it starts scanning, it provides 2 default views, a horizontal (real-time only) and cascade (real-time and historical); when a tag is detected, it will appear in both views and in the cascade–depending on tag pulse rate, will show you the strength of your previous detections. To determine how strong a signal is, you can visualize on dbm scale in the horizontal view, or by colour and brightness on cascade. If you’re really close, each time the tag pulses, you will get a significant peak in the horizontal graph, and a large, bright yellow line on the cascade. If it’s weak then the peak will be smaller, and the line will be almost non existent and blue.

Results: Every time I have taken this setup to the field, I have found physical tags within ~45 minutes of searching. This is once I have already pre-determined a general location and includes triangulating with the Yagi antenna. Definitely beats the 2 months spent looking for tags and not finding anything apart from general locations!

I am just beginning my thesis, so this is highly preliminary, but this new method has been a life changer and I hope it helps others doing handheld telemetry!

Feel free to reach out if you want to know more, I would love to help!

Lorena Munoz

lorena.m.comparan@outlook.com

(Google drive link in case media doesn’t upload properly SDR Console - Google Drive )

1 Like
2

Very cool and general method. Thanks for posting. I have had success with using the Lotek receiver and removing the Yagi to allow you to use the BNC cord as a probe. It is not perfect, but it can allow you to narrow from a several square meter area to a much smaller area. You can put the end of the cord into bushes and near the ground, trying to increase signal strength. If the tag is in contact with the ground, you will get a very strong signal when you touch the ground near it.

While your method won’t tell you the tag ID, it does suggest a way to detect tags without the big expensive Lotek receiver.

3

Of course!

Oh nice, that’s a very cool idea! I still have a few more tags to hunt for so I’ll give that a shot too.

Yes, it doesn’t provide tagID, but it hasn’t been an issue because by the time you attach the loop antenna, you’re already searching for an individual tag–for which you know the ID of from the triangulation with the Yagi and receiver.

4

Hi Lorena.

Have you tried putting the tags with a backpack?

5

Hi @user1234 thanks for sharing this!

6

When we originally ordered the tags, we didn’t realize that we had to specify the loops, and we tried a few other harness techniques (figure 8 loop, adjusted rappole by creating our own loops on the tags), but none of them worked. The biggest issue was that the chickadees were still growing in their tail feathers so the harness was slipping off too easily.

We’re tagging again this winter but with adults this time, so hopefully we can use the rappole or at least maybe other backpack types will fit better.