. QST . d appreciably. Try and end up with anantenna length that serves the purpose as faras jour own installation is concerned and alsoprovides enough pick-up to permit makingmeasurements of a more sensitive nature. Thelatter would include measuring the field strengthfrom the mobile transmitter of a fellow ham whois parked alongside of your vehicle. Li should ordinarily require adjustment onlyif the indicator is used for checking at 75 that case, it is advisable to increase thesensitivity to maximum by resonating the has explained \vh.\- a tuned circuit is notrequired at t
. QST . d appreciably. Try and end up with anantenna length that serves the purpose as faras jour own installation is concerned and alsoprovides enough pick-up to permit makingmeasurements of a more sensitive nature. Thelatter would include measuring the field strengthfrom the mobile transmitter of a fellow ham whois parked alongside of your vehicle. Li should ordinarily require adjustment onlyif the indicator is used for checking at 75 that case, it is advisable to increase thesensitivity to maximum by resonating the has explained \vh.\- a tuned circuit is notrequired at the higher fretiuencies. The function switch is tothe left of the zero-adjustcontrol in this bottom view ofthe S-FS Indicator. R\ is atthe rear of the unit, just be-low the 1-mh. choke, /i,on the rear wall of the chassis,is a miniature nylon tip back cover for the metalbox that normally enclosesthe meter is punched to clearthe components mounted onthe rear wall of the chassis. September 1955. A Low-Cost Code-Practice Oscillator Power with Safety Features BY ROBERT E. FOLTZ,* W9GBT IN looking for a good design for a code-practiceoscillator, certain requirements were estab-lished: The unit must be powered from line yet provide complete isolation for safety;there should be no shock hazard in the keyingcircuit; and in addition, speaker operation was de-sired without added cost or circuit complication. Units have been described using a filamenttransformer for the tube heaters, with the platevoltage obtained from batteries or a rectifiersupply. A study of transformers available dis-closed a type used in TV boosters having a platewinding of 110 to 150 volts at 15 to 25 ma., inaddition to a filament winding, at a cost of onlyfifteen cents more than a single filament trans-former. A selenium rectifier was first considered for ob- I2AU7
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
