A single-band 0-20-Mc/s ionosphere recorder embodying some new techniques

The paper describes briefly an ionosphere recorder developed in South Africa by the Telecommunications Research Laboratory of the Council for Scientific and Industrial Research. The first account of it was published in the Transactions of the South African Institute of Electrical Engineers, July 1947. The equipment is considered to possess a number of advantages over previous designs. It is completely automatic and requires a minimum of routine attention. The mechanical moving parts have been reduced to one slowly-moving split-stator condenser, and there is no band-switching. Each record is photographed on a single frame of 16-mm film, thus reducing to a minimum the photographic work required. A panoramic display on a long-afterglow tube is provided. The frequency sweep occupies only 7 sec and enables rapidly changing phenomena to be observed or photographed. Another feature is a crystal-controlled frequency-calibrating circuit, which is independent of the sweeping mechanism and enables the limits of sweep to be set as desired within the range 0¿20 Mc/s.