. QST . nsitivity control maybe adjusted to provide a noticeable meterdeflection. Aside from ordinary signal-strength work,the S-meter may be used to advantage whenaligning converter or receiver circuits, and it isworth its weight in gold in adjusting antennatrap circuits to suppress QRM from signalfeed-through in converters.^ Mobileers interested Arofahr, Unidirectional Loops for Transmitter Hunt-ing, QST, March, 1955. 2 Abel, The Hidden Gem, QST, March, 1955. •Chambers, Bandswitching a Crjstal-Controlled Mo-bile Converter, QST, January, 1955. in transmitter hunting will find the indicat
. QST . nsitivity control maybe adjusted to provide a noticeable meterdeflection. Aside from ordinary signal-strength work,the S-meter may be used to advantage whenaligning converter or receiver circuits, and it isworth its weight in gold in adjusting antennatrap circuits to suppress QRM from signalfeed-through in converters.^ Mobileers interested Arofahr, Unidirectional Loops for Transmitter Hunt-ing, QST, March, 1955. 2 Abel, The Hidden Gem, QST, March, 1955. •Chambers, Bandswitching a Crjstal-Controlled Mo-bile Converter, QST, January, 1955. in transmitter hunting will find the indicatorindispensable when used in conjunction with adirectional loop. Circuit The circuit of the S-FS Indicator is shownin Fig. 1. A 12AX7 is used in the S-meter grid is returned directty to chassis and thesecond grid is connected to the sensitivity con-trol, Ri. The input end of Ri is returned, via J2and a shielded cable, to the line in receiver. The plates of the 12.\X7 are con-. A front view of the S-FS Indicator. The zero-adjustcontrol is to the right of the toggle switch. Si. Themeter registers either signal or field strength, dependingupon the setting of the toggle switch. nected in parallel and then, through a singlelead, to J2. Fig. 1 shows heater wiring for both6- and 12-volt operation. Pin 9 of the tube is notused in the 12-volt circuit. For S-meter operation, the meter and R2 areswitched across the cathode terminals of thetube by Si. The 500-ohm potentiometer, R2,becomes a zero-adjust control. Zero reading isobtained -nath R2 adjusted for equal voltageat Pms 3 and 8 of the 12AX7. After an initialzero adjustment, the application of voltagethrough Ri will drive the cathode of Fia nega-tive with respect to the cathode of F2B, thusupsetting the meter balance and causing anupward deflection. For a given voltage. September 1955 19
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
