Announcing ...The "Super-Six"...

Radio Record, Volume V, Issue 21, 4 December 1931, Page 16

Announcing ...The "Super-Six"...

An easily built six-valve battery-operated super-heterodyne giving amazing results

HE "Super-Six" is a sixvalve . super-heterodyne of revolutionary design. Though as simple to tune as a onevalve set, Australian stations may .be. brought in on the frame’ aerial at full loudspeaker strength, while the selectivity is remarkable. First of all a word to those constructors who think superhets are complicated to build, and are thus to be avoided.’ ‘In: some cases this is undoubtedly so. The "Super-Six," however, is definitely much easier to build than an ‘ordinary ‘battery-operated set using the same number of valves, and no technical ‘knowledge whatever is necessary for its construction, provided, of course, that the circuit and lay-out diagrams are closely followed. The circuit is based on a well-known Mnglish circuit which has been remodelled to suit New Zealand conditions and to comply with the P. and T. regulations. Commercial super het. eoils of standard English make are tused throughout, and thus the construction of this receiver is greatly simplified. The three long-wave shielded coil units are. accurately matched by the ‘makers. All the user has to do is to plug them into valve-holders appropriately wired in the set. Ganging and trimming are not needed. It will be noted that the knob on the top of the oscillator coil may be set to three posi-tions-viz., long, medium and short. As there are no stations out here onerating on wavelengths above 550 metres the "long position" will not be used. How ever, it is always there if the con structor is keen on dxing and would like to try to log some of the long-wave European stations, which would possibly be best heard in New Zealand in the hours of 5.0 a.m. and 7 a.m. For performance on dx the "SuperSix" is unrivalled. No benefit would be achieved by publishing the huge list of stations we have received on this set,

but those who know a little about (xing will realise something of the set’s capabilities when they learn of the fact that 2iFC, Sydney, has often been picked up in the early afternoon at good speaker strength, in the heart of Wellington. The set is remarkably easy to handle. There are only three controls-two for tuning and one for volume. The first (ial tunes the frame aerial and the second the oscillator, while the volume control is in the form of a potentio-

meter which controls the screen-grid voltages of the two intermediate frequency amplifier valves. In tuning, the dials are kept in step by listening for the characteristic "live’ sound from the speaker, which indicates that the set is in the most sensitive position for receiving and is picking up "mush" and other extraneous noises. As the dials are rotated, the stations come in and out within a degree, with no how] ing or overlapping. Another very attractive feature of

this remarkable set is that, by the use of a suitable frame aerial, which may be purchased ready made,, shortwave stations all over the world may be tuned in at good loudspeaker strength. On short waves the receiver is remarkably well behaved, but of course the tuning dials must be rotated much more slowly, in order to avoid passing over stations. Hand capacity is nonexistent. Finally, and this from the homeconstructor’s point of view is very ign portant, the total "B" battery current of this receiver is no more than 12 to 15 mamps., or about equal to that of the ‘usual three-valve receiver. The Circuit.

OW for the circuit and a word or two about the principle on which the "Super-Six" operates. It’s action is indeed the action of any straightforward super-het. First of all the signals are picked up by the frame aerial and are handed to an anode-bend detector. A separate valve is arranged as an oscillator in such a way that the energy from it is fed into the frame aerial by means of a coupling coil. The first detector therefore receives the in-coming signals and oscillations from the separate oscillator valve. In this way the signals picked up by the frame / are converted into others having a/ wavelength of 2400 metres, or a frequency of 126 k.c.-the frequency for which the coils were designed. Our signals, which now have a new frequency of 126 ke, are passing through the long-wave (intermediate frequency) amplifier. To give a concrete example of the principle involved up to this point. Say we wish to re-

Parts List for the " Super-Six." EXbonite Panel, 18in. x Zin. Aluminium Baseboard, 9in. x 18in. _ X iin. Two .0005mfd. Var. Condensers, Two Vernier Tuning Dials. One 50,000-ohm Potentiometer. Five imfd. Fixed Condensers. Two .001imfd. Fixed Condensers. One .0002mfd. Fixed Condenser. Six UX Valve Sockets. Three English Valve Scckets. Set of Four Special. Super-het, Coils. One Grid Leak Holder. One .75-ohm Grid Leak. One 15,000-ohms Spaghetti Type Resistance. Two 20,000-oluns Spaghetti Type Resistances. One 3-point Filament Switch. One Audio Transformer, 5-1, 7-Wire Battery Cable. One Distribution Strip, 44in. x Zin., with 7 soldering lugs. One piece of Ebonite, 3in. x 3in. Three Banana Plugs and Sockets. Speaker Plug and Jack. Aluminium Shielding Box for Oscillator Tuning Condenser, 5in. x Siin. x 24in.

beive a station on 300 metres, or 1000 _ ke. First of all.the variable condenser +. tuning the frame aerial ig adjusted to ‘this frequency, Next the oscillator dial iis adjusted to "beat" with this fre‘quency, and produce a new one of 126 | ke, Thus the oscillator.can be tuned ! to 1000 ke. plus, or minus 126 ke. This explains why some stations may be heard at two settings of the oscillatér dial. Now, in the grid circuit of the first valve, which is working as an anode bend detector, we have two signals, the broadcast from the frame and the oscillations from the oscillator. These together are rectified, and in the anode circuit we have a signal of 126 ke. This is magnified by the long-wave amplifier, and then, in the normal way, ---_,

rectified by the second detector and passed to the power valve. One of the greatest advantages of ‘the super-heterodyne type of receiver is the enormous amplification which may be obtained with complete stability, in the long-wave amplifier, An additional feature incorporated in the "Super Six" is the fixed tuning of the long-wave amplifier-thus obviating the need for ganged conden-

Sers and other complications-and the band pass characteristics of the coils themselves. Unusually high quality of reproduction is thus obtained. Building the Set. HIS week we are publishing the complete list of parts, with measurements of baseboard, panel, ete., so that by next week’s issue the constructor will be ready to assemble his set. A complete list of parts is given in a panel on page 16. A word of caution about the valve-holders. The three intermediate frequency amplifier coils are designed to plug into English valve sockets. Three of these will be needed. For the six valves, however, UX valve bases should be used, as with Iinglish sockets some modification of the lay-out would be necessary. The panel, which is. of ebonite, measures 18in. by Tin., and is 3-16in. thick. The baseboard is shaped from 20-gauge aluminium, and is 18in. long by 9in. wide and lin. deep. All wiring runs under this baseboard, with the result that the above baseboard appearance of the sect has a marked professional appearance. Accompanying the next and concludimg description of this instalment in next week’s issue will be several photographs and: layout diagrams, so that the constructor will have no difficulty whatever is assembling the "Super Six" correctly.

DX’ers! Write for that verification on D.X. notepaper and avoid missing out important details. Takes a quarter of the time to write out, too. Obtainable from P.O. Box 1032, Wellington, in two-dozen lots (minimum order), price 1/6, or six dozen for 4/-, post free. Special paper for club members.