The "Ranger Two"

Radio Record, Volume IV, Issue 48, 12 June 1931, Page 22

The "Ranger Two"

Simple, Cheap, Efficient |

| HE recently-described ‘"Differential" series of receivers has proved exceedingly popular-so much s0, in fact, that for several weeks great difficulty was experienced by many readers in securing differential reaction condensers. Fresh shipments of these are now to hand, however, and may be obtained from any radio dealer. For smooth, efficient control ‘of ascillation, especially in short-wave work, where reaction is critical, differential condensers possess a distinct advantage over the older type, and for this reason were incorporated in the "Differential" series of receivers. A number of correspondents, however, who have ordinary reaction condensers on hand, and who do not wish to go to the expense of purchasing the differential type, have written in asking for a modified version of the "Night Hawk" two, for use only ou the broadcast band. In response to these requests, we publish below a description of the "Ranger Two." It is a receiver of the det. audio type, and, while exceedingly easy to construct, gives excellent results. Good loudspeaker strength from the local gtation, provided it is not too distant, may be expected, as well as headphone reception of the main New Zealand and Anstralian stations. The Coil. "RHE coil is of the conventional threewinding type,,and is so easy. to wind that even those for whom radio ig-a new hobby will experience no difficulty whatever in its construction. -A three-inch length of cardboard or ebonite former two inches in diameter is first secured, and about 3-8ths of an inch distant from one end, two small ‘holes are drilled, about 1-8th of an inch apart. One end of-the 28 gauge d.s.c. wire is passed through these in turn, and then doubled back and passed through the first hole again, thus leaving the free end inside the former. A short length is left’ projecting for

connecting purposes 25 turns, nspaced. are now carefully wound on, and the end passed through two more holes similar to those made at first. If any difficulty is experienced in keeping the windings -tight while the holes are being made, a dab of seccotine or a drawing-pin used as a temporary anchor will overcome it. Some three or four inches of wire are allowed for connecting purposes, and the remainder eut off. The primary is now complete. Bxactly 1-8in above the primary winding make two further holes, and, just as before, anchor the free end and wind on, in the same direction, 72 turns of 26 gauge d.s.c. wire. This is the secondary, and it is finished off in exactly the same manner as that deseribed for the primary. Now for the third and last windingthe reaction or tickler coil. This is wound on in exactly the same manner as the other two, and is commenced 1-8in.. above the secondary coil. It consists of 35 turns of 28 gauge (.s.¢c.,

und should be wound In ube same alrection’ as the other two. Except for the connection. of the ends to the metal tags, which are mounted m the former, the coil is now complete. Reference to the lay-out and coil diagrams indicate clearly the mounting of the tags. It will be noticed that "G," or the top end of the secondary winding, is mounted on top of the

former, and all the others on the bottom. Also "HB," the bottom of the secondary and the bottom of the primary, are taken to a common tag. Unfortunately this is not shown very clearly on: the coil diagram, Those who do not wish to wind their own coils may have them made up or purchase them ready made from a radio dealer.

Condensers. HILE the original model was. constructed for a .00035 tuning condenser, it is now somewhat difficult to obtain these, and so our specifications are prepared for.a..0005. Generally speaking, however, it is advisable to keep the size of the condenser down. Nevertheless, when it comes to actual performance, there is very little’ difference between the set using a .0005 and that using a .00035 condenser. For a .00035, 15 extra turns should be wound upon the secondary coil, and the primary and tickler increased by 3 each. ' } ‘The Lay-out. HH lay-out of the set should not give anyone difficulty, as the placing of every component is ‘very clearly illustrated in the accompanying illustration. The order of: procedure is generally to commence with the drilling of the panel, then attach the two condensers, the rheostat, switch, and. the jack, The two condensers are 3in. from the top and 23in. from the side. The switch and jack are din. from the side and 2in. above the base board. The rheostat is in the dead centre, lengthwise, and 5in. from the top. 4 Having done this, lay out the .components on the baseboard which, for convenience, might be a piece of din, timber, 8in. x 9in. It is wise to make.the base board a little smaller than/ the panel, so that if at any later date it is desired to put a box round the set, the protruding panel makes a neat finish. Note particularly the way the coil is turned round and its proximity to other components. Do not screw the grid condenser (.00025 on the right) to the base board ‘unless it is one of the wholly insulated type, such as a T.C.C. It is not a bad plan to suspend this between the grid terminal of the coil and the two megohms grid-leak. However, if the constructor decides to do this, this operation is performed during the. wiring. For the two megohms grid-leak it is necessary to use a grid‘leak. holder, as the method of returning it to the filament is slightly differ-

nt from the ordinary method of placg it in parallel with the grid condenser. Note particularly how the detector and audio sockets are turned round, that is, with the plate and the grid terminals and the detector valve toward the left hand side in the case of the audio valve. Be quite sure, too, that the transformer is not turned round, but that the primary Winding is facing the front of the set, the secondary toward the back. _. Having fastened the components and the base board in position, raise the panel and screw it to the base board, passing one inch screws through it into the end of the base. There is no need to use angle brackets for such a small set. ‘ Just one thing more and the set is ready to commence the wiring, that is, a short piece of ebonite about once incKk wide and two inches long is plated at the rear of the set, as shown, and two terminals are mounted on this. These are the only two terminals used in the set, as it.is much’ better to make all connections to the set with a cable. . Wiring. * , THE wiring is best carried out with some insulated. wire, such as glazite, although ordinary. cottoncovered wire of about 18 gauge can be used. Buzbar is not altogether to be recommended, as it is difficult to work, and unless one-has been very carefully soldered, the joints do not hold. If buzbar wire is used, or any other bare wire for that matter, spahgetti must be Slipped over the wires in order to insulate them. f

The constructor cannot go wrong in the wiring if he follows the sketch, where everything is plain and clear. Note in the sketch that:all wires do not go direct, but that there are rightangled bends. Do not put these in when the set is made. They are shown right-angled and straightened in order to make things clear. Further, it will be found that when the panel is raised at right-angles to the base board, the wiring from the latter will be very much shortened and straightened. Grid and plate wire particularly should be kept short and clear of one another. Do not take them half-an-inch further than they should go. It will be found. that the cable is best connected by stripping about a foot and stapling it to the centre of the back of the baseboard. The wires can then be taken out to their destinations and cut to the right size. They are shown in the diagram .with tags attached. These are, of course, optional, for the wire can be twisetd round the terminal to which they go. ‘ Note in connecting up the batteries that "A-"’, "B-", and "O--" ate all connected together outside the receiver. For batteries, the following are commended :-"A" battery depending upon

the valves. If 2-volt type is used, such as the new Radiotron 230, two number 6 cells (or an air cell) must be provided and the voltage controlled by the rheostat. Remember if this type is

used, two volts must under no circumstances be exceeded. For this reason the rheostat should never be turned on full. It is advisable to use a voltmeter ‘with these valves. The other types of 2-volt valves are not quite so delicate, though in general the rheostat ‘should not be turned on fully. A good rule is to start operating your set with the rheostat turned so that the maximum resistance is in and bring it up gradually, stopping when the station listened to is at its maximum. Do not turn pass this point under any circume. stances. Possible Faults. DETAILING possible faults is always a difficult plan because, if the in structions have been followed carefully, there will be no faults, and if they have not been followed, it ‘will be impossible for us to say where the constructor might have gone wrong, Always try varying the detector voltage. Probably the best results will be obtained with 224 to 45 volts on this valve.

Rough and ploppy oscillation indi¢ cates that the voltage is too high. Reduce until oscillation is smooth and even. Ploppy oscillation is also due to a defective grid leak or wrong coupling between primary and second». ary coils. However, if the instruc. tions are followed and a space of 1-8in-: left between these coils, there will be no difficulty. It is usual to keep the. number of tickler turns fairly ‘ high,. and the detector voltage fairly low.. When the set will not oscillate it is‘ due, in nine cases out of ten, to the tickler connections being reversed. If the windings are put on the wrong. why, or if the ends are connected "about face," then the set will not oss: cillate, but just reverse these and it. will be found to be quite satisfactory,

HERE is the list of parts:-One° * 0005 variable condenser; one~~ 00025 variable condenser; two dials; -> one 30 ohms. rheostat; one battery ~’ switch; one single-way jack and plug; ©’ one h.f. choke; two UK valve sockets; ’' two terminals; one .0005 or .0003 condenser; one 2 megohms grid-leak; .- one A.F. transformer; Coil Glazeite; | one 5-wire battery cable; panel, 10 x 7; baseboard, 9 x 8; solder lugs if | required; a small piece of ebonite, « "4 3in. wide by about 2i4in, long; a" small quantity of 28 d.s.c. wire; ilb.. 7) 26 d.s.c. wire. vA