. QST . Construction The photographs show the construction of abridge l)uilt to \V2ZEs design. As can l)e seen bylooking at the inside view, the unit is not at allcomplicated; however, it is advisable to stick tothe suggested components and layout. Obviouslyit is undesirable to have unnecessary lead in-ductances or capacitances between bridge shown in the inside view of the bridge and inthe photograph of the differential capacitor, acopper shield is placed around the top part ofthe capacitor to shield the stators from the otherelements of the bridge. Since the calibration ac-curacy at
. QST . Construction The photographs show the construction of abridge l)uilt to \V2ZEs design. As can l)e seen bylooking at the inside view, the unit is not at allcomplicated; however, it is advisable to stick tothe suggested components and layout. Obviouslyit is undesirable to have unnecessary lead in-ductances or capacitances between bridge shown in the inside view of the bridge and inthe photograph of the differential capacitor, acopper shield is placed around the top part ofthe capacitor to shield the stators from the otherelements of the bridge. Since the calibration ac-curacy at the upper end of the frequency range islimited by stray capacitances between bridgeelements, the addition of this shielding raises theupper frequency limit at which the bridge main-tains its accuracy. With the shield around thecondenser the frequency error is very small up toat least 50 Mc. The choke in the bridge is a miniature pow-dered-iron-core layer-wound solenoid. The lead. I 111- clidciciilial (Mpiicilor wliich is tlii lirart (il llicliridgc circuit. The copper shielding fastened to therear end plate is to prevent stray coupling to othercomponents in the bridge. Fig. 2 — Bridge circuit using differential capacitorfor adjustment of impedance ratio. Ci — Differential capacitor, 11-161 /x^f. (Millen 28801),C2 — disk ceramic. Ri — 51 ohms, 2-watt composition, 5% — Crystal — Coaxial — Miniature choke, 200 nh., iron core (Millen J300-200).CRi — Germanium diode, 1N34A suitable. between the coaxial input connector and thecapacitor is a short piece of flat copper revision in the layout that results in longerleads will tend to result in increased frequencyerror. The Type 1N34A germanium diode was usedbecause it is satisfactory and because it is gen-erally available. Other types should be equallysatisfactory, however. is introduced into the bridge circuitthrough the crystal socket shown
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
