These magnificent HF transmitters were custom built by Amalgamated Wireless Australasia
Pty Ltd (AWA) for the first twelve standardised
Aeradio stations in 1938-39.
The J2876 (DCA ident Y5/6760) was a multi-channel MF/HF unit for air-ground and, later, point-to-point communications, offering three HF channels and one MF channel, capable of CW Morse and Double Side Band (DSB) speech. The MF channel was usually used as a Non-Directional Beacon (NDB) in the post-war years.
The left hand cabinet contained the power supply, whilst the right hand cabinet contained the RF unit. The transmitter could be operated remotely by control lines.
The units were reliable in operation because of the lack of complicated frequency changing mechanisms and their robust construction. They contained an early form of 'modular' construction. The chassis had multi-pin Jones plugs and sockets for easy access to components by pulling out the faulty shelf/module.
Post-war
these transmitters were often backed up by a lower-powered unit, usually war surplus,
such as an AT20 or MF500. The last units were
removed from service in 1983.
(Photo: CAHS collection)
Specifications:
| Manufacturer | AWA, Sydney |
| Type of transmitter | Wide-frequency range 4 channel transmitter with common modulated amplifier. Manual or remote operation with auxiliary equipment. Orignally 2 x HF & 2 x LF channels, later 3x HF and 1 x MF channel. |
| Frequency range | Original: (1) 5-10 Mc/s (2) 2.5-5 Mc/s (3) 333-500 Kc/s (4) 200-333 Kc/s Later: 3 channels 2-20 Mc/s, 1 channel 150-500 Kc/s |
| Frequency control | Crystal in each range (2 x 2 crystal positions each range with switching) |
| HF Power Output | 400 Watts, channels 1-3 |
| Modulation Characteristics | Normal input not less than -15 db into 600 Ohms. Provision for V.O.C. |
| Type of Keying | For CW buffer Amp. No. 1 HT neg. Keyed to cathode - all other modes signalling key position shorted by relays. |
| Output Coupling | 600 Ohms |
| High Tension Voltage | 1500V - 300V |
| Power Source | 415 Volts, 3 Phase, 50 Cycles |
| Type of Cooling | Forced air |
| Weight | Transmitter units 3,400 lbs (approved Aerial Coupling Units 745 lbs approx.) |
| Dimensions | 7'0" x 7'0" x 2'6" approx. overall |
| Tube Complement | Total 42 |
| Remote Control Equipment | Required
Remote Control Rack and Speech Equipmment Rack at both ends. Also Desk Unit P3892
at cotrol end - 2 pairs lines needed. Line 1, leg 1 - auto switch, impacted. Leg 2 - Speech transmission line. Line 2 - interphone, t/x to control and Keying on CW or ICW (one leg line 2 also available as spare). |
Airways Museum Virtual Tour