SHARK TRACK

Tracking Porirua's rig sharks

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Tag aerial angles

30th May, 2015

Transmission success rates from tag aerial at different angles

This week I've been learning how many shark GPS positions (transmitted from my tags) might I not be receiving because the tag aerial is at a poor angle to the network of receivers I've placed throughout the harbour. The tag (aerial) angle changes, when the tag is towed over or through the waves as the rig shark swims with it around the harbour. Because the transmitted positional data signal transmits from the tag aerial like a donut (see picture) its important to know if your positions are being sent, but not received by the surrounding network of routers. 

I make the aerials from coaxial cable and very carefully remove exactly one quarter of a wavelength at 1.6 GHz  (31.25 mm of shielding) from the coaxial, if not exact that tag transmission distance drops and my shark positions won't be able to be received by my network of receivers.

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