Illuminated range scale used on Chain-Home (Low) Radar plan position indicators, c.1940. Science Museum Collection.

from death ray to radar:

on atmospherics
direction finding
thermionic valves         field strength measurements

an ionised reflecting

at the height of

and another                   unpublished memorandum

detect by means of
the energy re-radiated
from a transmitter
on the ground

Daventry Experiment


signature tracking

intercept and dismiss
if not to be found within
the expected register

of voice