Radio Broadcast (May 1928-Apr 1929)

p RODUCTS of radio manufacturers whether readers. These pages, which will be a regular feature of Radio Broadcast from this issue on will explain and illustrate certain products which have been selected for publication because of their special interest to our readers. This information is prepared by the Technical Staff and is in a form which we believe will be most useful. We have, wherever possible, suggested special uses for the device mentioned. It is of course not possible to include all the information about \each device which is available. Each description bears a serial number and if you desire additional information direct from the manufacturer concerned, please address a letter to the Service Department, Radio Broadcast, Garden City, New York, referring to the serial numbers of the devices which interest you and we shall see that your request is promptly handled. — The Editor. A Complete A. C. Adapter Unit X21 Device: Marathon A. C. Harness equipment. Consists of a cable conductor, a transformer, supplying the correct voltage for Marathon tubes, type AC 608, and a volume control. The Marathon a. c. tube is of the heater type and is rated at 6 volts and 1 ampere. Manufactured by the Northern Manufacturing Company. Price: $30.00 (5 or 6-tube kit); seven and eight-tube units available. Application: In order to make the conversion of a d. c. set to a. c. operation a simple matter using Marathon tubes, this company is supplying the accessory apparatus (transformer, cable, and volume control) required. It should be understood that this apparatus is made especially for use with Marathon tubes; the transformer voltage is incorrect for other types of a. c. tubes. The Marathon a. c. tube is equipped with two New Apparatus Complete A. C. Push-Pull Amplifier X22 Device: Samson Power Audio Amplifier, Types PAM-16 and PAM-17 for use with radio receivers or phonograph pick-ups. Both types are exactly the same except that the type PAM-17 is equipped to supply 40 milliamperes at 120 volts to the field winding of a Magnavox, or similar dynamic type loud speaker. The amplifier is a two-stage transformer-coupled unit and consists of an input transformer followed by a SAMSON PHONOGRAPH AMPLIFIER OR RADIO THE MARATHON A. C. KIT type 227 a. c. tube which in turn feeds into the primary of a push-pull transformer. Two 210 type tubes are used in the push-pull stage. The filaments of the 210 type tubes are operated on a. c. and plate power for them is obtained from a rectifier-filter system using a type 281 tube. As indicated in the circuit diagram one of the input leads is shielded. This lead connects the input of the amplifier to the output of the detector in the radio receiver (or output of a phonograph pickup if one is used). Electrically the device has been arranged to conform with the underwriters' specifications, all the wiring being entirely enclosed. The terminals' of the audio transformers project down through the base of the transformers into the sub-base, and are therefore unexposed. YAXLEY S POWER CONTROL Manufactured by the Samson Electric Manufacturing Company. Price: $125.00. Application: This amplifier can be connected to the output of the detector tube in a radio receiver, being used therefore instead of the amplifier in the set, or it may be used in conjunction with a phonograph pick-up to reproduce phonograph records. At a recent R. M. A. meeting, Mr. Cotton of the Samson Company demonstrated the amplifier to two of the staff of Radio Broadcast Laboratory and the reproduction from phonograph records was excellent. There was absolutely no hum audible in the Western Electric 540 AW cone used. The unit is beautifully finished and is very well arranged mechanically and electrically. Complete data, blue prints, etc., are available from the Samson Company. HOW TO USE THE YAXLEY POWER CONTROL extra terminals on the side of the tube base and the filament transformer terminals need merely be connected to these convenient terminals using the harness supplied for the purpose in this kit, and the tubes plugged into the regular sockets in the receiver. No adapters are required. This is a distinct advantage when space is limited for these tubes, when installed, will project no higher than the storage battery fype tubes used formerly in the set. When 226 and 227 type tubes are used with the necessary adapters the overall height of the tube and adapter is greater than that of a storage battery tube and this fact will, in some a. c. conversion jobs, give some difficulty and necessitate rearrangement of some apparatus. Shield Symphonic 1 or— Pam, 17> only ' CIRCUIT OF SAMSON AMPLIFIER 35 At Last — Automatic Power Control X23 Device: Yaxley Full Automatic Power Control. For the automatic control of the power units used with a radio receiver. Manufactured by Yaxley Manufacturing Company. Price: $7.50. Application: This device, designed automatically to control a receiver installation operated from a B supply and a trickle-charger storage battery combination, functions (a) to turn on the trickle charger and turn off the B power unit when the set is turned off, (b) turn off the trickle charger and turn on the B power unit when the set is turned on and, (c) cut out the trickle charger when the battery is fully charged. All of