Radio Broadcast (Nov 1926-Apr 1927)

482 RADIO BROADCAST MARCH, 1927 diagram. All of the dotted lines in this latter drawing represent wires run below the base panel. The solid wires are run above the base panel. This scheme forms a very neat layout as well as automatically affording some separation between the grid and plate wires. Specific types of tubes are recommended with miles from weaf and 25 from wjz. The excellent selectivity, even at the long waves, is at once apparent. While wjz and weaf blanket any distant reception between them, the dials do not have to be turned very far either side to bring in the remote stations without interference. The location where the tests were conducted in ^I'l'h^l'I'M'I'I'H'I'I'^^l'H'H " A"1""* a + ~~ n + FIG. 3 To identify the various units as indicated here it is well to refer to Fig. 1. The same identification letters have been used for this diagram and Fig. 1. This schematic circuit gives one the general idea of the circuit employed while the wiring diagram shown in Fig. 5 is a direct aid in the actual wiring of the receiver this circuit design for very definite reasons. The high efficiency of the receiver is obtained through coordinate operation of the various parts — including the tubes. This applies particularly to the detector. To insure the same exceptional performance as obtained here in our laboratories, use'the tubes recommended. These are given in Fig. 1. It is fully realized that it is no easy matter to Staten Island is even worse than the mileages indicate. The New York stations come in with practically undiminished volume, traveling the intervening distances mainly over water, while the distant Western stations must pass through a high ridge that runs north and south through the center of Staten Island. This locality is thus favorable to the reception of New York locals and unfavorable to Western reception. Several well-known standard radio receivers have failed to bring in even one distant station in this locality under modern congested conditions of the air. The following is a list of parts necessary for the construction of the R. G. S. receiver described in this article: Ci — 1 National Single Condenser, 0.0003 5-Mfd C2, C3 — I National Double Condenser, 1 0.0003 5-Mfd. Each Section . . . > $26.50 2 National Dials Ti, T2, T3 — 3 National-Grimes Tuning Coils, with Antenna Switch T4 — 1 Samson 2-1 Audio Transformer 5.00 T5 — 1 Samson 6-1 Audio Transformer 5.00 4 Spring Sockets 3.00 C4 — 1 Hammarlund Vernier Condenser, 15-Mmfd 1.25 1 Dejur Resistance-Coupler (with Condenser) 1.50 R2 — 1 Centralab Modulator 200,000 Ohms 2.00 Rs — 1 Lynch 2-Meg. Resistor . A R4 — 1 Lynch i-Meg. Resistor . . > 1.75 R3 — 1 Lynch 25,000-Ohm Resistor . ) C6, C7, Cs, C9, C10 — 5 Sangamo Condensers (3 — 0.001-Mfd. and 2 — 0.00025-Mfd.) 2.30 1 Front Panel (Drilled and Engraved). 6.00 1 Base Panel (Drilled) 4.00 Li — 1 Grimes R. F. Filter Coil . . 2.50 L2 — 1 Grimes R. F. Grid Choke . . 2.50 8 Eby Binding Posts and Drilled Terminal Strip 2.00 Co — 1 Dubilier Grid Condenser, 0.00025-Mfd .25 Ri — 1 Dejur Rheostat, 2 Ohms . . 1.10 Acme Connecting Wire .75 R. G. S. — Grimes Blue Prints and In 4.50 structions Total $71.90 The above selection of parts may be obtained in kit form complete with front panel and base panel drilled and engraved. DX. N.Y.C. Throuoh Locals Locals FIG. 4 In this representation of a tuning dial are shown the Greater New York locals in one group while the distant stations which were received through the locals are shown in the outside band fairly present the real performance of a radio receiver because so much depends upon local conditions. This has led to the generally accepted practice of comparative demonstrations between some well-known receiver and the one under test, so that, other conditions being equal, the actual performance of the new receiver could be judged in terms of some standard. Many such tests, conducted in many difficult localities have revealed the high selectivity of the R.G.S. Inverse Duplex receiver. Fig. 4 shows at a glance the performance of an R.G.S. receiver tested at Grasmere, Staten Island, while all the locals wer« on the air. Grasmere is about 10 FIG. 5 This wiring diagram, aside from showing the point to point wiring, coincides with the parts layout shown in Fig. I. As an aid in wiring, the two should be referred to constantly. The dotted lines show those wires which are run below the base while the solid lines indicate those connections which are made above the base