WIRELESS CORNER.

New Zealand Herald, Volume LXVIII, Issue 21036, 21 November 1931, Page 4 (Supplement)

WIRELESS CORNER.

CONSTRUCTION OF THE ALL-WAVE LOUD-SPEAKER SET.

BY B. S. JONES.

For tho construction of this set tho following parts will be required: 1 Aluminium Panel—9 x 6 inches. 1 Baseboard—B x 7 inches. 1 Midget Condenser, 5-plate. 1 Variable Condenser (tuning), .00015 mfd. 1 Variable Condenser (reaction), .00025 mfd. 1 .0002 m.f.d., fixed (grid) condenser, with clips. 1 G meg. grid leak. 1 Set " Pilot Wasp " plug-in coils—l 7to 500 metres. 1 Vernier Dial for tuning condenser. 2 UX Valve Sockets. 1 UY. Valve Sockets (for coils). 1 RF Choke. 1 Audio Transformer. 12 Terminals and Terminal Strip. 1 Battery Fuse. 1 Battery Switch (with insulated shaft). 1 PH. 2 DX. Valve (detector). 1 PM. 22-Valve (pentode). « a," " B " and " C " Batteriei. Screws, Connecting V/ires, etc.

Connectors joining. Commence by mounting the component parts on the aluminium panel and the baseboard in the positions indicated in Fig. 1. On referring to this diagram it will be seen that the grid and plate leads of both valves are as short as possible, this being an essential condition for successful working, particularly with short waves. Use tinned copper wire to connect the various components, and make these connecting leads as short as possible; if there is any chance of these bare wires coming into contact with each other at any time, it would be as well to slip lengths of " spaghetti " over the conductors at these particular points. All joints should be well soldered.

Tho connections are as follows From the A (aerial) terminal to the fixed plate!' of the midget condenser (C); from the A3 (aerial) terminal to the C terminal of tho coil holder (L); a lead from this connection is taken from tho movable plates of the midget condenser. From the earth (E) terminal to Ax terminal, to the Fx terminal of both valves holders (VI and V2), to F1 of coil holder to the movablo plates of both the tuning (C2) and reaction (C 3) condensers. From the A—connection in the terminal strip to Cx terminal, to one side of the battery fuse (F), to one side of the battery switch (SW); from the other side of the fuse to B~ terminal; from tho other side of the i;witch to the F— terminals of the twovalve holders (VI and V2) connect the grid condenser and leak (OCL)' between tho G terminals to L and VI, the former being also connected to the fixed plates of the tuning condenser (C2). A lead connects the plate (P) terminal of V, to the P terminal of the coil holder (L'|. From the F2 terminal of L to one terminal

Connectors crossing. of the choke coil (RFC) and to the fixed (F) plate of the reaction condenser (C2); the other choke coil terminal connect to P of the transformer (T). From B terminal of the transformer to Bx det. terminal on the strip. G on transformer to G terminal of amplifying valve (V2); F on transformer to C— terminal on strip. Ihe plate terminal on Y2 take to speaker terminal (Sl),,the other speaker terminal (S2) being connected to Bx amp., and also._ by means of a flexible lead to the auxiliary grid (AG) of-the pentode valve (V2). This completes the wiring, and in the next article full information will be given on the proper operation of the set. In the meantime, if builders experience any difficultv in the construction of this model will they please write to me in care of the Editor of this page, enclosing a stamped self-addressed envelope.