This receiver was
made by Stromberg Carlson in Australia and was intended to be used as an
Amenities receiver. It is a single conversion superheterodyne, covering
the broadcast band from 650 to 1650 kcs and the short wave band 6 to 18
mcs. It has a single RF amplifier and a single IF amplifier at 455 kcs.
All the controls and connections are on the front panel. They are simple and minimal. The Mains cord enters through a grommet on the left hand side. The main front panel features are the speaker grill and the tuning dial, with handles on each side. The tuning dial is a black metal disc, with markings for the broadcast band and the short wave band each using half the dial. There are 5 white markers (or bands) on the short wave dial to indicate the short wave stations, located at 6, 9, 12, 15 and 18 mcs. There is a separate dial pointer for each half of the dial. There are terminals on the left hand side for an external SPEAKER, terminals in the middle for a PICK-UP from a record player, and terminals for AERIAL and EARTH on the right hand side. The 4 controls arranged along the bottom, are: TONE at the left, then VOLUME and TUNING in the centre, and the band switch at the right, marked SW, BCAST and PHONO.
The receiver is housed in a sturdy steel case, painted green, and with a close fitting seal around the edges, to make it dust proof. The radio is held to the case by several clips. It was provided with an internal tray to hold a desiccant like "Silica Gel". This is visible in the internal photograph, just behind the speaker and it has a perforated lid. It uses octal valves mounted on a steel chassis. The valves are: 6U7G for the RF amplifier, 6J8G for the mixer, 6U7G for the IF amplifier, 6B6G for the detector and audio preamplifier, 6V6GT for the audio power amplifier, and a 5Y3G for the rectifier. The case and chassis are heavy steel. All the tuning adjustments have lock nuts. All the control shafts have a gasket.
PERFORMANCE
The radio has a functional look, but is not very pretty. It seems a little larger and heavier than necessary, but has a lot of room inside for easy servicing. It performs OK on a good aerial, although the Short wave stations are a little difficult to tune at the top end of the short wave band. The tuning drive is merely a friction drive to the edge of a semicircular metal disc, and is subject to backlash on the short-wave bands but adequate for the broadcast band. The dial markings would have been better arranged with a horizontal split, that is, the broadcast band at the top, and the short wave at the bottom, rather than split vertically as they are. It is good to have a large speaker. The sensitivity is suitable for its intended function.
RESTORATION
The receiver was in very good condition, and the inside was very clean. The radio was in working condition, but not very sensitive. An alignment was done which improved the sensitivity to 3 micro volts on the short-wave band and 2 micro volts on the broadcast band (for a 10 dB signal to noise ratio). When the volume control was at the minimum, the sound could still be heard, and shorting the volume control to ground actually increased the volume a little! This turned out to be a faulty cathode bypass capacitor on the detector/audio amplifier. There was a slight positive DC voltage on the audio output grid which was due to a leaky coupling capacitor. This particular receiver was used in a public hall after the war, and had a hole cut in the side of the case so that a microphone could be attached. This was welded up and the case repainted. The grey plastic mains cord was replaced with a black rubber cable. The manual I obtained had a circuit for a battery powered version, which uses different valves.
AMENITIES RECEIVER
An "Amenities Receiver" was often provided for entertainment of military personnel during recreation periods. The Amenities receiver was normally more powerful than a conventional domestic receiver, but not as powerful as a communications receiver. It usually had Short Wave bands in addition to a Broadcast Band, and usually had provision for playing records, or connections for a record player or microphone input. It was generally robust, and able to run from a variety of mains voltages as might be the case in forward areas. It would be able to use any aerial provided. They were not normally fitted with specialised functions, like a BFO or selectivity controls. The publication "Australian Telecommunications at War" shows one of this type being used at Moratai in 1945. There were many different types and models, made by many different countries. In the United Kingdom, the Amenities receiver was usually tuned to the BBC and it was often referred to as an "Invasion Receiver" as this was where you heard the first news of an invasion.
CIRCUIT
LAYOUT
MORATAI PHOTO
Copyright
Ray Robinson VK2NO
