Laboratory Jottings

Radio Record, Volume IV, Issue 42, 1 May 1931, Page 12

Laboratory Jottings

ROM Messrs. Crawford and Finlayson we received a Lyratone Midget 2.e, veceiver for test. This is the latest product of Gilfillan Brothers, the wellknown American radio manufacturers. The set has a very neat appearance and is well finished; it has three controls, tuning, volume and tone. Weighing under 22Ib. it is readily transportable, and as it will receive the local station without an aerial, it is an ideal portable set for ‘ those who wish to move it from one room to another as occasion may demand. The circuit consists of three r.f., screengrid stages, screen- -grid detector, feeding through resistance capacity coupling into a single output stage. The detector employs the power linear system. Self-heal-ing, dry, and electrolytic condensers are employed, and this does away with any possibility of filter condenser trouble. We had an interesting example of this in that when examining the internal portions of the machine we accidentally disconnected the speaker with the power on. Normally the set would probably have broken down one of the condensers, but in this case a erackling across the electrolytic condenser was.the only result. When the speaker was connected again the condenser healed. The filament voltages are kept well down, and this is a safeguard against power line surge. The mains are equipped with fuses. The tone of the set is very good and quite. natural. Obviously, using only one stage of 245, the output is limited though it is ample for the average room. The tone eontrol gives a gradual transition from bass to treble. At its minimum setting there is little apparent clipping at either end of the musical scale, In other words, there is neither a boomy bass nor overpronounced treble. ‘The performance on distance quite surprised us. It brought in the main Australian stations at -good strength, and even the smaller ones came in quite well. In the few days we had the set we were able to compile a log of about 80. stations. By adjustment of the balancing condensers the set may be made to oscillate, and thus will go into a state more sensitive than the balanced receiver, Selectivity. is another strong feature, for we were agreeably surprised to find that we could receive 2F'C with no trace

of 2YA. This is one of the most difficult tests any receiver is called upon to pass. The volume control is capable of cutting Wellington down without introduce. ing an obvious amount of distortion. lt operates upon both aerial coupling and the sereen-grid bias. From a fairly searching examination we could detect no weaknesses or eyidences of shoddy construction. Of course some time is necessary before the durability of any set can be ascertained, but, from what we could see of it, the "Lyratone" appears to be well constructed and » would stand long service.