216.430 MHz Once Per Second for Six More Weeks

The RDF receiver was still in the field case where I’d left it after the meteorite beacon test failed. Charged the battery. Swept 216-217 MHz just to see if anything was transmitting.

216.430 MHz: beep… beep… beep…

One pulse per second. Steady. Someone’s tagged something.

Rotated the three-element Yagi. Signal got louder, then quieter, then—nothing. Complete silence. Rotated past it, signal came back. That null point, where it goes dead silent? That’s the perpendicular to the transmitter. Way more precise than hunting for the loudest beep.

Walked fifty metres west. Took another bearing. Drew two lines on the benchmark datasheet map. They crossed in the river valley, maybe 800 metres northeast.

This is exactly what the meteorite beacons were supposed to do. Same frequency range. Same Yagi. Same triangulation math. The difference: I’m not trying to guess where a rock will land three days from now. The transmitter’s already out there, already placed, already pulsing. Someone else solved the positioning problem.

Called the university wildlife biology department. Yes, they have rock ptarmigan tagged in that drainage. 216.430 is bird PT-47, a two-year-old female, 0.4-gram transmitter, battery good for another six weeks. Would I log coordinates if I get a fix?

Logged into the Motus network dashboard while I was on the phone. Forty thousand transmitters. Fifteen hundred automated receiver stations across North America. It’s APRS for birds—same packet radio methodology, same coordinate logging, but instead of ham operators reporting their positions, it’s warblers and sparrows pinging towers as they migrate from Alberta to Texas.

The researcher said beginners always hunt for the loudest signal. That’s the wrong target. The null is narrower, more definitive. You’re looking for silence, not noise.

Front-back ambiguity is the other thing. The Yagi produces identical signal strength whether the bird is in front of or behind the antenna. One bearing gives you a line. Two bearings give you a point. Three confirms it. It’s the same triangulation problem from amateur radio fox hunts—exactly the skill set, just applied to biology instead of hidden transmitters in parks.

The equipment that failed for meteorites works perfectly here. The problem wasn’t the RDF technique. It was trying to track something that didn’t exist yet, in terrain I couldn’t predict. Birds with 0.4-gram transmitters? Already placed. Already transmitting. The optical observation from the sextant monocular couldn’t follow that rough-legged hawk past the ridge line.

Radio waves don’t care about line-of-sight the same way.

PT-47 is still out there. 216.430 MHz. Beeping once per second. I have two bearings logged and a third position to try tomorrow before the battery dies in six weeks.