Radio age (Jan 1927-Jan 1928)

RADIO AGE for Dec-Jan., 1927-28 The Quadrode Super-Heterodyne A Super-heterodyne in the simplest form, with new features and new merits, that make it an outstanding performer among super receivers Builders everywhere were deeply interested in the description of this circuit in the November issue of Radio Age. By Frank Freimann T? VERY month brings a "new" cir•*-* cuit of some "dyne" or other into creation, so new in fact, and so wonderful, that, according to its creator, it will send everything else into oblivion. The public has been so overfed within the last few years on circuits that petered out on test that they have finally ceased to bite. There have in reality been very few new circuits invented or created, although there have been great strides made towards better radio in the development of better apparatus. Comparison of our present tubes, audio transformers, loudspeakers, and other devices with those of the past years will confirm that. Is it a wonder then that we should hesitate in proclaiming a new super-heterodyne? We did so last month in the November issue, and the interest displayed by readers who built the set gives us no cause for regrets. The super-heterodyne described is new, not for novelty's sake, but because there is actual merit in its newness. — The Editor. THE Quadrode super-heterodyne — so named because a quadrode or four element vacuum tube is used in the mixer circuit — made good all that has been claimed for it. In a two weeks test for consistent reception at least two West Coast stations were brought in nightly, and on fair nights as many as a half dozen stations west of the Rockies were heard. Broadcasts from the states of Washington, Oregon, and California came in with sufficient volume to entertain a room full of people. A small Bodine loop or the house lighting system was used to pick up the energy, an outside wire was never used at all. One enthusiastic fan wrote a letter containing a log of some 52 stations outside of Chicago and the surrounding stations area, which were received in a two nights' vigil, through the maze of locals. These and other verifications are a sure proof of the pudding. Nothing about the set or circuit is radically different from the usual super-heterodyne receiver. The present change is, however, obviously an advantage over the usual super-heterodyne. The highest grade of material was chosen for the make-up of the set, and this, together with the su The Quadrode Super-Heterodyne installed in Ehlert cabinet. The Temple speaker is enclosed. Note the substantial elegance of the complete installation. perior design, make it a better superheterodyne. Very likely, the principal feature that has put this set into good graces with radio set builders, is the minimum of effort required to build and operate it, with the minimum strain on the money pouch, and the maximum efficiency that is derived from it. The departure from the customary superheterodyne, as has already been pointed out in the article which appeared in the November issue of Radio Age, lies in the mixer circuit. Why run the loop or grid lead all over the set to pick up energy from the osci'lator tube and mix it in the detector tube to obtain a beat frequency, when this can be accomplished in one tube with less wiring? That is what we wanted to know. The first progressive step was taken by some designers by using direct coupling from the plate circuit of the oscillator tube to the detector tube plate circuit. But why the extra tube? — we still ask. Attempts were made a few years ago to popularize a circuit in which one regular three element tube was used for a mixer. Careful balancing of condensers and other tedious adjustments were necessary, and then what was the result? The circuit