3MA transmitter, Mildura. Model 4-SU-112A This STC transmitter would date around early 1970s. In use in 2009 as stand-by for a New Zealand made Blyth 2.5 kW. The STC is used when lightning storms are in the area. It uses 4 valves and many transistors. Just visable in the left window are the push pull modulator valves and RF modulated amplifier; operating at 2,400 Volts for 2.5 kW output. Transistors and an IC are used for the R.F generation driving a 4-125a, which drives a triode in the right of the left window. The rectifiers are solid state.   The modulator output valves differ from the earlier unit above. The modulator valves are not 4/1000A but are QE????. There exciter and other features are similar to the 5 & 10 kW tansmitters below. Photos of this transmitter kindly supplied by Mr David Collins.
The audio and RF power amplifiers are on the left.  Lower on the left are: Audio feedback network, and below are Modulation transformer, front Modulation choke,rear Modulator output coupling capacitor, and 3 phase cooling air blower.	On the upper right are: the high voltage rectifiers. Below that is the overload protection relay panel and indicator lights. On the mid right is the RF oscillator and lower power RF stages.   At the bottom are: power transformer, right. H.T filter capacitors

Is this the last 5 kW MF transmitter made by STC? This transmitter was one of a pair purchased in 1974 for 5KA & 5AU. 5KA Technical Chief, Colin Crowe, came to the STC factory and purchased this transmitter off the factory floor.	Former 5KA transmitter, Cavan Rd, Gepps Cross, Adelaide. The 5kW transmitter was factory modified to operate at 2.5 kW by rewiring the primary connections to the main transformer from 415 Volt "delta" to 240 Volt Y or "star". STC had already deicided to go out of transmitter production, the sales effort had been abandoned.   Since the unit was already built it is that it was converted down to 2.5 kW.   It could easily be converted back to 5 kW if needed in future. Apparently it was last used in the early 1990s as stand-by for a Harris 10 as 5RPH. By early 2007 all transmitters were closed down at the site. The Cavan Rd site was sold at auction in March 2007. It uses 8 valves and many transistors. Just visable in the left window are the push pull modulator valves and RF modulated amplifier; operating at 2,400 Volts for 2.5 kW output. Transistors and an IC are used for the R.F generation driving a 4-125a, which drives a triode in the right of the left window. The rectifiers were solid state.  The output circuit differed to the AWA transmitters above as it used a tuned circuit with an adjustable sliding link to couple the output to the cable to the antenna. The modulator driver and modulator output valves were the same types as in the RF stages.
	Refering to the Photo Left: The audio and RF power amplifiers are on the left.  Lower on the left are: The high voltage d.c. filter Modulator output coupling capacitor, and 3 phase cooling air blower. On the upper right are: the high voltage rectifiers. Below that is the overload protection relay panel and indicator lights. On the mid right is the RF oscillator and lower power RF stages. The modulation transformer (155kg), modulation choke (160 kg) and 3 phase power transformer (173 kg) are all on the lower right. The grey cooling air blower is lower left of centre.   The air is ducted up to cool the valves. The fabric transition duct above the blower were all made at home by an employee's wife; Mrs Tommy Duff.
The box partly in the top of the photo, is for RF generation. The temperature controlled crystal operates at 4 times the transmitter output frequency. The control relays are in the box above the power transformer. 415 V circuit breakers are above the modulation inductor. At the bottom are the modulation inductor, front, modulation transformer, rear power transformer, right. After Easter 2007 the unit was given to a collection and transported to Victoria. In 2009 the unit was reassembled, cleaned & polished, paint touched up, and single phase circuits energised 1 at a time. The valves lit for a few seconds only, & exciter operated. It cannot run as there is no 3 phase power at is new home to run the high voltage nor ¾ h.p. blower. The large valves have become gassy through dis-use.	The 2 manila paper labels on the trasformers are the original factory instructions on how to reconnect it for 5 kW operation.
The glow from the filaments can be seen. The filaments on the top valves each draw 54 amps at 7.5 volts. Without cooling air, the heat from the filaments alone makes the heavy metal anode too hot to touch in a few tens of seconds.	Without forced cooling air, disaster will very shortly follow. Operation of the air pressure switch must be checked regularly. Dirt & dust can build up around the pressure switch and jam it. Its purpose is to shut down the transmitter with loss of cooling air pressure. Perhaps the air pressure switch became fouled up with decades of dust. Every the fan motor will stop working eventually; nothing electrical lasts forever.
"Fast on" Transmitter On the air in less than 6 seconds from cold. The 5 kW and the 10 kW below and the 2.5 kW at Mildura use solid state low level audio and radio frequency stages. The filaments are all directly heated and are ready to go in 5 seconds. From switch on the first thing that happens is the blower starts and runs up to speed and creates cooling air pressure. That takes less than a second. Next the filaments come on. 5 seconds later the high tension is on in 2 stages and the transmiter is on air.

	Former 3XY transmitter 1422 kHz until 1991 then 693 kHz as 3EE & 3AW . The 3XY site at Viewbank was redeveloped for housing in early 1990s The building and 318 foot(97 m) mast was shared with 3AW.  The red brick building was a few metres in from where Bartram Rise now meets Banyule Rd. The transmitter made in 1974 is a 10 kW STC but operated at 5 kW. Last used on stand-by (for 3AW) until 1 May 2006. "It was a damn good transmitter" said the station's technical director. It uses 9 valves and many transistors and an IC. Just visable in the left window are the push pull modulator valves and 2 by valve RF modulated amplifier; operating at 4,800 Volts for 10 kW output. Transistors and an IC are used for the R.F generation producing 5 watts that drive a 5-500A pentode driving 2 triodes in the right of the left window. The rectifiers were solid state.  The output circuit differed from the 2.5 & 5 kW transmitters above as it used a pi-coupler style network. The output circuit was made simple since only 2 were being made and they were on similar frequencies of 1280 & 1420 kHz and STC were getting out of the transmitter business.
	The audio and RF power amplifiers are on the left.  Lower on the left is the 3/4 hp 3 phase cooling air blower. On the mid right is the RF oscillator and lower power RF stages up to 5 watts. Below that is the RF driver valve on the left. The modulator output valves were the same type, 3CX2500F3, as the RF power amplifier. The modulation transformer (191kg), modulation choke (209 kg)and modulator output coupling capacitor,are on the lower right. Serious Australian transmitter production would have closed down not long after this transmitter was manufactured. The Whitlam Government virtually eliminated tariffs on imported electronic equipment, at the same time as wages rapidly escallated; many electronic industries soon closed. Unemployment, interest and inflation grew rapidly.
The box in the top of the photo, is for RF generation. The temperature controlled crystal operates at 4 times the transmitter output frequency. Below that on the right is the control in the box, minus its cover. The RF driver valve is on the left. Nearby are the 415 V circuit breakers above the modulation capacitor. At the bottom are the modulation transformer , Modulation inductor (rear)and modulation output coupling capacitor on the left.
Rear R.H.S of cabinet. The tarnished output tuning coil.	Death of 3XY After moving from Viewbank, in March 1991, 3XY set up a temporary transmitter and mast radiating 2.5 kW from half way along the south side of Ajax St, Altona. The hired mast was about 100 ft with wire 4 top load. The counterpoise was 60 insulated wires laid out on the soil. Antenna current was 10.8 Amps This transmitter was moved to storage in the former Corio Whiskey distillery in Corio, Geelong. I first saw the transmitter there in 1991. 3XY transfered to AWA Media at noon, Monday, 23 September, 1991 for $500,000. The old owners played a song with "I'll sing my song and I'll be gone." and "Its a long way to the top if you want to rock and roll" just before noon. The new owners, AWA, played a 1 hour special on the history of Australian Rock and Roll then closed down. 3XY had been in liquidation since April 1991.  It sold for almost $16,000,000 in 1986. The new owners obtained a licence 3EE, for 693 kHz and reused the pictured transmitter on 693 kHz from late June 1992. 3EE operated as "Magic 693" then eventually became 3AW's transmitter channel and site. 3EE was the first 4 mast broadcast station in Australia.  It's masts are 90 metres and it has 72 km of buried earth wire.
	10 kW Transmitter Power Supply The 800 pound (364 kg) 3 phase power transformer is too large to fit in the main cabinet so a separate compartment on wheels is provided. The small transformer in the middle is a 3 phase step down auto trans4mer of from 400 Volt to approx 300 Volts. Schematic diagram of last STC 10kW MF transmitters made. (3XY & 3AW) If the drawing does not open on your computer then try opening it from "Paint". The Viewbank site was powered Heidleberg Council Electricity Supply using a 3 phase step down transformer from 22,000 Volts to 415 volts. The transformer was one of 3 specially purchased for the radio stations, one transformer each for 3AW-3XY, 3DB and 3UZ. They were 50 kVA transformers of star-interstar connection made in Heidleberg by Machinery Construction.
3 STC Transmitters 10 kW nearest, 5 centre and 2.5 kW incomplete in background.

3WV, Western Victoria transmitter during erection approx 1962. The transmitter upgraded the power of the station from 10 kW to 50 kW. Photo used with the kind permission of Mr R Leerson.

This transmitter used mostly transistors.	There were only 5 valves, all were 5-500A. The blower motor was ¼ h.p. i.e. approx 190 Watts.

STC Compressor / Limiter I kept one of these as a limiter for years; it had a tag with "PMG Broadcast Station Sydenham"? then I threw it away ; I wish I hadn't now, I didn't have the room then. They were used to protect AM broadcast transmitter from excessive audio input signal. The unit had octal valves and a seperate power supply, not shown.	Photo courtesy Mr Mat. Robins
	STC Modulation Monitor (transistorised) It is built like a battleship.  It contains so much thick metal that it must have been expensive. The carrier control knob is not original. The monitor required about ¼Watt of RF. The colour of the front panel is actually green grey, similar to this background.

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	2CO in 1987 The original 1931 building and antenna are shown. The antenna is one of 3 built. The others are at Crystal Brook S.A. and Perth W.A. The antenna is an example of the historic Multiple Tuned Downlead type. This antenna predates the vertical mast and radial earth systems developed later in the 1930s. When 2CO started, it used the then lowest broadcast frequency of 560 kHz in Australia. The original power was 7,500 Watts. Motor generator equipment was used to generate the DC voltages for the original equipment. The antenna has a sign on it; "Manufactured for Standard Telephones and Cables A/Asia Ltd Johns and Waygood Ltd Engineers South Melbourne" The white building was the original 1931 transmitter building. It has been replaced by a transportable hut with "Ifco"or similar on it. The Antennas page has more information on this antenna. Link to antennas page