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Show (KJ't0j bV ' DOUBln" Wtt""P. 'tor orCMrand'iring.)1 ' ' ioH 1 i A SIT ! il Ti r !adP , f?GC vli0;e " " J This Diagram Illustrates How the Double Pole, Double Throw Switch Is Em lilt. ployed. Wave Lengths Depend Upon Position of Switching Device test By FRANCIS H. ARMSTRONG nil, One of the problems troubling many s It radio fans at the present time is the lolly adjustment of their sets to cover the mi higher wave lengths, especially of 402 ccej and 52G meters. One method that may rue- be applied to most receivers in pres ent day use, and particularly those of J, the two variometer and varlocoupler ia, type, is by the addition of instruments to called condensers. Where such load ed ing of capacity is resorted to great lie- Care must be exercised in securing re in generation over the wave length bands ing desired. la- Most receiving sets embodying radio er frequency will remain just ns they st- are. These instruments are governed lie by the range of transformers Included ly in the construction of the set, and the general practice of most manufac- a turers has been to design their radio frequency transformers to cover a le wave length range of from 300 to 550 ir meters. There is no question regard- a lng most of the transformers made e today, as the majority run as high as n the new wave length of 526 meters, s In some cases where a loop aerial Is h mployed In conjunction with a radio frequency set more turns of wire on ' the loop may have to be added in or der to secure sufficient added inductance induc-tance in this part of the circuit to ' reach the wave desired. The reason for this is that the loop acts in this case as a tuning inductance. Should the loop aerial be deficient In it3 inductance in-ductance value, then there is no resident resi-dent point to work on for the higher wave lengths. Better service may be had if the original loop is supplied with a sufficient number of turns on Its frame, which are then varied by means of a suitable tapping or a switching arrangement. Loading Three-Circuit Tuner. Under this type of regenerator comes the well-known two variometer and varicoupler circuit. This type of apparatus has become the prize receiver re-ceiver of many a radio fan, since it contains the elements which give a set selectivity, but since some new stations were Injected into the ether It seems that most of the variometer sets fall short of bringing in concerts con-certs on the longer waves. With this set an arrangement can be made to secure se-cure shorter waves with their maximum maxi-mum signal strength just as efficiently efficient-ly as when using the longer wave length bands. This arrangement consists of em- ploying a double pole, double throw switch, or by the use of an antica-Paclty antica-Paclty switch. The 'first arrangement would be the better of the two for the beginner or novice, since it appears ap-pears to be much simpler. In the accompanying ac-companying diagram (Figure 1) one may get an idea how the double pole, double throw switching arrangement Is employed. The wave lengths depend de-pend entirely upon the position of the switching device. In Figures 1 and 2 the condensers are represented by C. These condensers con-densers may be made at home or they can be purchased at any radio shop at the option of the builder. If purchased pur-chased the fixed type condenser Is to be preferred. In shopping around the fan will run into various types of fixed condensers, many of them consisting con-sisting of paper and tinfoil. This type of condenser should not be considered, as Its capacity is not uniform. In recent tests some of these paper pa-per condensers gave no fixed reading whatsoever; capacities varied anywhere any-where from .0002 to .001 mfd. merely by pressing the condenser together with the fingers. Due to their loose construction, moisture creeps in and varies the capacity to the same degree de-gree of inaccuracy. What the fan should buy Is a condenser constructed of mica and copper foil machine pressed or firmly clamped. Load Circuit Carefully. Where loading is resorted to great care must be exercised to procure regeneration re-generation on the higher wave bands. A double pole double throw switch is shown in Figure 1. When the position po-sition of the switch is such that It neither cuts in or out condensers the set Is standard and will operate normally nor-mally over its limit of wave length range. Should the condenser switch be thrown to a position indicated for the "600-meter" stations, then two condensers in series are cut into the circuit and placed across the grid variometer vari-ometer and secondary of coupler. The switch thrown to the position of "1,000 meters" has a different effect. ef-fect. It disconnects all previous connections con-nections and adds capacity from the plate circuit to the grid circuit. The two condensers are connected In series, the connection being made from the plate hack to the filament. Another connection Is then taken from the center of both condensers and placed to a point just prior to the grid condenser, but in the grid circuit. This then provides for capacltatlve regeneration re-generation over the entire wave length range up to 1,000 meters. The condenser values should average aver-age about .00025 capacity, and, as explained, ex-plained, should be of the mica and copper foil type. Why most of the sets failed to function properly Is due to the fact that regeneration was not available on the higher wave bands. In Figure 2 a cam switch or anti-capacity anti-capacity switch arrangement is Illustrated, Illus-trated, but this is merely a method of accomplishing the same result as the previously mentioned switch. The appearance and arrangement of the cam switch appeals to most radio fans, and therefore Is more often employed. The amateur who is willing to "make his own" must bear in mind that for proper results regeneration is essential essen-tial on the higher wave bands. New York Sun. A 1 0 Mi-Capacity i L O.V. Jllr "J FIG. 2 Rcc Cam Switch cr Antl-Capacity Switch Arrangement Is Merely a Method of Ac complishlng Same Result as Double-Throw Switch. |