I arrived at the beach of the River Thames shortly after low tide. The curve of stony beach accessible from Trig Lane Stairs was criss crossed by mudlarkers who hardly noticed me as they bent to the ground and turned over pebbles and pieces of seashell. Arriving at the beach straight from a symposium at the Tate, my head was filled with dialogue about sirens, alarms and states of emergence / emergency. The radio spectrum had its own sirens. Around every two minutes or so, the relatively calm 'ocean' of spectrum in which I tuned my ground station was interrupted by what I can only describe as 'blasts' of energy that drowned out all other signals. The blasts would disappear, allowing a minute or two of calm, before returning. I tried to discern whether they coincided with the Uber Boats traveling up and down the Thames. A mudlarker passerby – who turned out to be an art history professor at a university in London – speculated on this wtih me for a few minutes. As I took a final few photos of my ground station the tide was already beginning to come back in.