We have just done another test of the lost model tracker transmitter and the new yagi antenna. To make it interesting, a night test; in the dark.
Waterproof the tracker transmitter
Ready to drop
I armed a transmitter using the servo tester, put it in a piece of bubble wrap and into a plastic bottle. Driving along what we call “the River Road” which is dark (no street lights) we threw the bottle out the window into the grass. Then went about 1.5KM back and parked the car. We knew approximately where the tracker was, to within about 300 meters.
Begin Tracking
From the car we wandered off with the receiver and yagi. The road is raised above the river so there was some raised land between us and the tracker which was at ground level in wet grass, so the signal was very distant and intermittent. To begin with, I think it was only clear when a car went past and we got a reflection.
The test area. 1.5Km
There was a good moon so the track was easy to walk. When about 700 meters from the tracker the obstruction was less significant and the signal was clear enough to follow easily. At about 500 meters out the signal was very strong even with maximum attenuation on the receiver. About 100 meters out the yagi was too sensitive and direction finding didn’t work. It was still dark and we didn’t know exactly where the tracker transmitter was.
Time to switch to the short whip antenna, body shielding and slowly rotating to get closer. About 40 meters out the signal was strong enough to not need an antenna at all. By walking up and down the track a couple of times and noting the points at which the signal disappeared, walking at right angles from the centre lead straight to the tracker.
Yagi Performance
It was easy enough to find, even at night. Which was good because I don’t have to go back the next day to locate it.
The yagi performed very well. Close in, it was not much use as the signal was too strong and the yagi could be pointed in any direction and still receive an overpowering signal. Out beyond 500 meters (in this case) it was easy to determine the direction towards the tracker transmitter.
A low gain whip antenna (a simple piece of wire) is still needed for close in tracking. You hold the receiver and antenna close to your chest and slowly rotate, listening for the weakest signal. At this point the tracker transmitter is directly behind you because your body is providing maximum shielding of the signal.