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I worked as a trainee technician at both Brooklyn Park and Pimpala in the 1960s. Neither main transmitter at Brooklyn Park was 50kW, but whether they were 2 or 5 or even 10kW I don't remember; there may have been one of each. The two main transmitters at Pimpala were nominally 55kW, and I could swear to that on a stack of ARRL handbooks; at each site there was a standby transmitter of more modest power, readily retunable to either frequency. At Brooklyn Park there was one transmitting antenna (a bottom-loaded vertical mast) for each frequency; Pimpala had (and still has) the one mast with a "top hat" and capacitor loading just below the top section, designed for "anti-fading", ie. minimising "skywave" radiation. Both sites had a standby antenna in the event of a problem in the coupling or tuning hut or during antenna maintenance, eg replacement of aircraft warning lights. Transmitter maintenance was in those days accomplished after hours (only 5KA had 24-hour service in those days, the ABC transmitters were shut down between midnight and 6am). Broadcast transmitters were staffed in those days; a mostly boring occupation with a lot of routine jobs (around 100 meter readings taken hourly) to keep staff (and trainees) busy, and broadcasts were monitored continuously and any break in program or quality problem logged. But come a failure, service had to be resumed in minutes. Any break longer than 5 minutes or any break at all during news or Parliamentary broadcasts (yes, all sessions of Parliament were broadcast on AM radio - tedious in the extreme) had to be reported to Canberra by a "breakport" telegram. Installation and maintenance of National Broadcasting Services transmitters, for which the Australian Broadcasting Commission supplied the programmes, was the responsibility of the Postmaster-General's Department (later Telecom Australia) until the late 1970s or early 1980s, by which time I was out of the service.
Humorous trivia: The tuning hut at Brooklyn Park was surrounded by a man-proof Cyclone fence with a locked gate. The sign outside read "Danger High Voltage. Before entering, operate the earthing switch located within the tuning hut."Doug butler (talk) 00:09, 21 April 2016 (UTC)