Laboratory Jottings

Radio Record, Volume III, Issue 5, 16 August 1929, Page 26

Laboratory Jottings

Courier Radio, Mack’s Shortavave Sets | nenaaeemmenmemed

Courier Radio, O*% the night of Friday, August 2; ". / the writer journeyed to Takapuna, Auckland, to hear a demonstration of the "Courier" Sets, The first set was the "Courier QR3," using an aerlal approximately 70 feet long, with a 15-foot lead-in, and haying an earth lead about 8 feet long. 2XA, tuned in about ten minutes past nine, was far too loud, and toningdown became necessary. Turning to 2¥'C a couple of moments later, the reception was good, loudspeaker strength being maintained’ throughout. 4QG was logzed without any difficulty, and 7ZL was more than satisfactory. This set, although only a batteryoperated model, has several distinct features of noteworthv design that should be of interest to those interested in a good, inexpensive receiver. ° A new mode] at present being placed on the market by Messrs. J. Wiseman and’ Sons, Lid., the manufacturers of all "Courier" products, is the model B.S. electric screen grid. receiver. This set incorporates a smoothing circuit, which supplies the electricity at the correct voltage to the valves, and, using component parts suitable to the design of this circuit, a silent and safe operation is ensured. The radio cireuit employs an electric screen grid, special: detector, and pentode valves,

a combination: which gives excellent performance at a low cost. This "Courier" model is made for an electric power supply of 280 volts, 50. eycle A.C., which is the usual electric supply in New Zealand, The "Courier" will not operate on any other supply. Made up in a cabinet of metal, finished in deep bronze,- with a panel of lighter shade, it is extremely attractive, and designéd to fit in with any furnishings. A jack at the side of the cabinet allows for a .gramophone pick-up, thus enabling the "Courier" to be used as an electrical reproducing. machine. On performance, this machine measured up very well, using no aerial. Several New. Zealand stations were logged, and 2FO was received with volume and purity that would be hard to equal. The same may be said of 4QG, 8LO and 7ZL, the other Austrajian stations received. ‘eMiacks" ‘Famous Short-Wave _ Receivers. RRAdI0 construction is developing at a fast rate in New Zealand, and the latest all-New Zealand set that we have tested, Mack’s Famous Radio Sets, are admirable examples ofswhat we can produce, These sets have been designed by Mr. B. R. McCarthy, familiarly known as "Mack," and are assembled by him. The coils are made. by

a New Zealand firm, as is also the very attractive metal case in which they are assembled, Neatness and efficiency are the outstanding qualities of these shortwave sets. _ we The Add-a-phone is a _ two-valve short-wave adapter designed to plug into any set or amplifier. This is a ‘fine that should appeal to all who have a broadeast receiver and wish to adapt it to short-wave. The unit may be used as a separate single valve short-wave set, as an amplifier for a gramophone pick-up, or_as a short-wave unit. The *phones may be plugged in in the usual manner, a station tuned in, and with the ’phones still connected the amplifier of a broadcast receiver may be plugged in. Thus, a pair of phones and speaker are both being used simultaneously, with the amplifier on the ’phones alone, This enables very fine tuning and adjustment. A gramophone pick-up may be plugged in, and the signals superr imposed on those coming in on.short wave on both ’phones and speaker, The "reaction deserves special mention, As -all short-wave enthusiasts know, smooth oscillation is something always desired, but seldom attained. Mack has attained it. -By rotating gradually, the 200/1 yernier dial, the set goes into oscillation with an almost imperceptible hiss. The dials employing a ball-bearing in a unique fashion, are remarkably smooth in their operation, . The larger sets embody audio stages, but the detector circuit is identical with that of the Add-a-phone. Frequencies as high as 800,000 kilocycles (10 metres) may be tuned in. Mack has also designed coils to tune down to 5 metres, , Only first grade components have been used throughout this set, and the result is that every set can be fully guapantead. Hach one is submitted to an individual test before being turned out.