Laboratory Jottings

Radio Record, Volume IV, Issue 48, 12 June 1931, Page 41

Laboratory Jottings

Gulbransen Combination -- From Messrs. H. W. Clarke, Lid., we have received a Gulbransen three-in-one model. combination radio receiver, incorporating a super-heteorodyne short-wave converter, which gives the set a worldwide range. . The receiver has a handsome appearance, and the short-wave adapter, in the model we tested, fits unobtrusively on one side. In other models, and in. some ways this is preferable, a sepanate adapter rests on the top of the receiver. As a gramophone amplifier, the set leaves nothing to be desired. On a frequency test it gave strong responses from 50 to 7000 cycles. These were by no means the extremes, for more or less weak responses were obtained above and below this, illustrating that the set is capable of reproducing faithfully almost any. type of musical instrument or voice. There is a marked absence of base predominance, though the tone control will give this if desired. The gramophone part of the outfit employs a Hammond motor, which incorporates several ‘new principles, among these being the absence of a stopping and starting device. One starts the turntable revolving merely by flicking it. It is-stop-ped by the automatic stop on the record. There is a complete absence of noise, it: is permanently lubricated, beautifully finisled, requires no governor, and maintains constant speed. It is indeed a highclass motor. , The volume control is smooth, and will control 2YA at close range satisfactorily \ without having to remove the aerial. ‘.. The sensitivity of the set is very high, and on the local switch we could listen to all we desired. 2FC and 2BL could be brought in with the set adjusted in this manner, and for pleasurable listening we found it advisable to use this swiitch on all stations to which we were listening. One evening when conditions were’. not particularly good, we ran down the dial and brought in fifteen stations, any one of which might be listened to with pleasure. We did not attempt to do DX-ing with the set, though an ample reserve of power was available had we wished to 0 SO. The short-wave equipment seems to us to be, perhaps, the most logical solution of the converter problem. By using a super-heterodyne converter all the valves of the main set are employed, as this adapter is placed between the aerial and the aerial terminal of the set. The shortwave coils cover all the bands from 17 ‘v 100 metres. Tuning is very critical, but with a little practice, stations from all over the world can be brought in. We listened ‘to Sydney and Melbourne stations, 5SW (London), W8XAL, and many other Americans, to say nothing of the. many. amateurs that came in at good strength. __ . ° There is much to be explored in short wave, and it takes time and patience. We are convinced, however, that the adapter is an excellent one, and the combination left little to be desired.