Radio age (Jan 1927-Jan 1928)

20 RADIO AGE /or January, 1927 ommended that connections be switched until best results are secured. It is also advisable to try more than one position of the rotor coil inside the coupling unit. With the rotor at right angles to the grid and plate windings on this unit there will be least transfer of energy from the oscillator to the grid of the first detector. In this case there is no tendency of the first tube to block under strong signals. However if the inductive relationship of the pickup rotor and the stator coils is such that maximum energy is picked up from the oscillator there is a possibility of overloading the first detector grid and introducing considerable distortion. Tune in a signal of medium strength and then adjust the pickup coil for best results. Also switch the outside terminals of the loop and see if different results are obtained. IN OPERATION we found the simplest method of tuning was to set the oscillator condenser, at the right, to a given point and swing the loop condenser, left, back and forth until a gentle hissing sound is heard. This shows that the loop circuit is then resonant at the frequency for which the oscillator is set. A variation of the rheostat controlling the filaments of three of the intermediate stages will result in changing the volume of the signal. If properly built this receiver will surprise its owner with its LIST OF PARTS 8 Benjamin UX cushion sockets 2 Selectone 410 RF transformers 2 Selectone 400 RF transformers 1 Thor RF coupling unit 2 Remler .0005 mfd variable condensers 2 Yaxley 10 ohm rheostats 1 Jewell dual range voltmeter 0-7 }2 -0-1 50 1 Carter 500,000 ohm resistance, variable 1 Hammarlund .000046 mfd midget condenser 1 Sangamo .006 mfd condenser 2 Sangamo .0005 mfd condensers 1 Samson 125 mh rf choke 3 Sangamo 1 mfd bypass condensers 1 Yaxley base mounting plug 2 Thordarson audio transformers 2-1; 3-1 1 Yaxley filament control jack 1 Radiall }i Amperite 1 Radiall 4-A Amperite 2 National vernier dials 3 X-L Pushposts 1 Quali-tone loop 1 Quali-tone drum speaker 1 Burgess 1V% volt C battery 1 Frost phone plug 1 Formica 7x26x3-16 panel 1 Abox filter 1 Majestic "Super" B eliminator 1 Rectigon 5 amp. charger ability to pick up long distance signals. The audio quality is good with the type of audio transformers shown, although those who are finicky on the subject of quality may find it more to their liking to make use of the larger transformers made by the same manufacturer, such as the R200. For those who like to be relieved of any trouble in the op The Magazine of the Hour eration of a set, we used this receiver with an Abox filter for the filament supply and a Majestic B eliminator for the plate potential. Thus all we had to do was to turn on a snap switch and the filament and plate power was on. What could be simpler? Power for the Abox filter is supplied by a five ampere charger, bulb type. This insures sufficient filament voltage to run the Super 8 even if a UX 210 is used in the last stage. Even on extreme distance when the set is working to its utmost there is no hum of an electrical nature, such as modulation. All bulb chargers have a slight mechanical hum, but this does not affect reception. A few final words. Be sure to solder all connections well. Go over the set twice to make sure that all connections are in accord with the pictorial layout on page 21. When satisfied that all is well, hook up the set to the A and B source and prepare to entertain yourself to your heart's content. To make the loop and oscillator settings track as nearly as possible, the Quali-tone loop was used since it seems best designed for this particular set. Set builders may expect a slight deviation from the published loggings, due to a difference in tubes, loop and the amount of C battery applied to the center tap. However the log shown will serve as a guide for the experimenter who should be able to log his own set in the same manner. 1MW .0005 .006 C 3-6 V 201 A 200 A b o-> o 5+22V B+90V &+67V.C-3-6V. A-B-O C-?iV. A+ M35 Schematic circuit of the receiver described