TIPS AND JOTTINGS

Radio Record, Volume I, Issue 32, 24 February 1928, Page 11

TIPS AND JOTTINGS

Many new listeners will be interested to hear that during the currency of the Dunedin Exhibition of 1025-6, the broadcast station, VUDN, at the exhibition employed fairly high power. Transmission was six nighis a week, chiefly of the Argyll and Sutherland Hi¢hlanders’ Band, which, unfortunately, seldom came through as it should have done from the outside bandstand. Items from the concert hall came in at Wellington with good volume and quality, ‘‘Megobm" employing a fivevalve T.A.T. cireuit, The closing ceremony of the exhibition tock place in the afternoon, which was sunny and bright in Wellington, and with the circnit mentioned, the writer, scated some

distance from the loudspeaker, heard quite distinctly every word of tlie yvaledictory speeches. A unit that will interest experimenters and others is known as the ‘‘Abox"’ Filter, now on the Atnerican market. This permits those who have a good two-ainpere or five-ampere charger to conyert it into an A eliminator. The Abox filter smoothes ont the current from the charger, and thus periect A elimination is obtained, sufficient to run six valves of the 201A type, provided that the charger will supply not Jess than two amps. The filaments remain wired in parallel in the usual way. The life of valves and lamps is often quoted as being 1000 hours. ‘This represents twelve months’ service at the rate of nearly 2} hours every night. The object of the fixed "condenser across the primary of the first audio Ltransformer is to shunt to earth the radio frequency currents uecessary to supply reaction, after they have passed through the detector plate circuit. These R.I. currents are earthed to prevent them entering the audio side, from which all R.F. must be excluded A capacity of .001 has no effect upon andio frequencies of as high as 5000 cycles, and larger yalyes may often be used without distortion occurring, but only if necessary to control tone. But in a resistanee capacity coupled amplifier the by-pass condenser lras quite a different effect, and must be kept very small in capacity, say .0001 in a circuit with moving tickler. If howling occurs in a two-stage crystal amplifier, reversing the connections to the primary of the second transformer will often effect a cure. An American radio journal expresses the opinion that manufacturers have of late deyoted more attention to decorating the loudspeaker than to improving its reproducing qualities. When working several salves off a B accumulator, to prevent unequal drain upon groups of cells supplying R.I’, detector, and audio, tle full battery voltage may be taken and resistances inserted in the common plate circuit of valves requiring less than the maximum voltage. This means dealing with the accumulator output in the same way as is done with 3B climinator voltage. In the explanation last week of how to check up B eliminator consumption ‘on the meter, the "hundreds" dial was mentioned, but this should have read "hundredths."

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The New York ‘Times’ says: "I'wo places named Brooklyn, on opposite sides of the globe, were linked recently hy short-wave amateur radio, when station 2APD, of Brooklyn, N.Y., succeeded in operating with the station owned by J. Jolinson, in Fortunas Street, Brooklyn, Wellington, New 'Zealand, according to Nathan Pomerantz, of 1824 Forty-ninth Street, Brooklyn, operator of 2APD,"