Radio age (Jan-Dec 1926)

10 RADIO AGE for October, 1926 the panel. The loop terminals come in at the rear of the baseboard at the right, while the Jones base mouting is located at the right rear corner of the baseboard, where also are found connections for the loud speaker and the C battery. Schematically the circuit is shown on page 10. This arrangement is for nine 201-A tubes. It can readily be converted for use with 199's by simply altering the Amperite resistances. Examination of the schematic will show that two intermediate stages are followed by a filter, then another intermediate followed by another filter. This procedure results in maximum selectivity. Further selectivity may be secured by altering the capacity of the midget condenser in the loop circuit. No Body Capacity ON ACCOUNT of using the Remler condensers there is complete absence of body capacity both on the oscillator and loop circuits. These condensers are of the twin rotor type and the shaft extending through the panel (to which are affixed the Marco dials) does not become a part of the circuit since the shaft carries a bakelite gear which engages the rotor plate gears. In previous types of supers this form of condenser has been found highly satisfactory where the oscillator capacity span is from grid to plate. If the oscillator circuit is changed to the grid-filament capacity span body capacity can be eliminated, although the loop might still have a trace. Grid condensers and leaks are not used but instead detection is accomplished by C bias of the detector grid. The bias value for all 201-A tubes was found to be 6 volts, thus simplifying the C battery voltage problem. Using the voltages specified in this article and with the proper C battery value, the total milliampere current used runs from 10 to 16 mills, which is exceedingly low considering the number of tubes and the results secured. A center tap loop, such as the Duro-Metal, is used with the receiver, provision being made at the left rear of the baseboard for the three loop connections. A total of 135 volts of B battery, (three 45 volt blocks in series) will suffice for operation. A good B eliminator may also be used if desired. The Jones 7 wire cable should be connected as follows : Red — A ; Green — A ; Black — B; Brown 22i/2; Pink 67i/2 ; Yellow 112i/2 and Blue 135 volts. It will be noted the LIST OF PARTS 1 — 7x30 panel, 3-16 3 — HFL H210 transformers 2 — HFL H215 transformers 1 — HFL L425 choke unit 2 — HFL F320 audio transformers 1 — HFL L430 R. F. transformer 2 — Remler .0005 mfd variable condensers 2 — Marco dials for above condensers 1 — Clielten midget condenser 5 — Yaxley Imp jacks 1 — Jones base mounting and 7 wire cable plug 1 — Yaxley 6 ohm rheostat 1 — Yaxley filament switch 3 — Amperite resistances 1 — 1-A; 2 — 112 and mountings 9 — Benjamin cushion sockets 1 — Electrad 1 mfd bypass condenser 2 — Muter condensers .0005 mfd 1 — Duro Metal Qualitone collapsible loop 1 — Duro Metal Qualitone loud speaker 1 — Centralab 0-200,000 ohm Rahiohm oscillator is supplied with only 22i/> volts which is very desirable in order to cut down the possibility of the oscillator producing a variety of harmonics. These harmonics are naturally produced at any voltage, but they are weakest at 22 14 volts, whereas with double and triple that voltage these harmonics would be more than bothersome. The range of the oscillator coil with the Remler condenser referred to will be from approximately 190 to 595 meters, which should serve to take in all of the present broadcast channels. To go further down in the wavelength scale another oscillator could be used which would throw the set into the short waves — but that is another subject on which we may have more to say later. The Magazine of the Hour Operation Simple OPERATION of the ninetuber was quite simple. Assuming that all connections have, been made in accordance with the schematic, turn battery switch on; set the midget condenser half way in; turn the (Please turn to page 45)