WIRELESS NOTES

Evening Star, Issue 19386, 21 October 1926, Page 16

WIRELESS NOTES

[By Electron.] AUDIBILITY STANDARD. El. — Faint signals, just audible. R2. —Weak signals, barely readable. R3.—Weak signals, but readable. R4.—Faint signals, easily readable, R 5 strong signals. R6,—Strong signals. R7.—Good signals, readable through interference. RB.—Very strong signals (several feet from phones), R9.—Extremely strong signals. B BATTERY LIFE. In the average receiving set, using five American type valves, the current consumed will bo six mill! amperes for each radio frequency valve, two milli amperes for the detector, and for each audio frequency valve six milli amperes, without C battery bias, or throe to four milli amperes with the correct C battery bias. The total current for five valves will thus bo twenty-six milli amperes, without C battery, and twenty to twentytwo milli amperes with the C battery. The life of the standard three types of 11 battery will, bo as follows, provided the batteries have not at any time been damaged:—Light typo: 10 m.a.; life, 9) months; 15 m.a., G months; 20 m.a., 4 months; and 25 m.a., 24 months. Heavy type: 10 m.a., 15 months; 15 m.a., 10i months; 20 m.a., 74 months; and 25 m.a., s'j months. Extra heavy type: 15 m.a., 1H) months;,.2o m.a., 9] months; and 25 m.a., 7) months. These figures are the result of actual test on the stated load for two hours per day, and should give a good guide to the actual cost of dry typo li batteries against storage celts. AMP L 1 hi CATION OUTFIT. Comparing a single tube against two tubes in parallel and two in push-pull wo obtain tbo following results:—One valve only; Voltage amplification, 18; output, .01125 watts. Two valves parallel; Voltage amplification, 2-1.5; output. .0225 watts. Two valves pushpull: Voltage amplification, 12.7; output .0025 watts. It is thus scon that both push-pull and parallel tubes will deliver twice as much power as a single tube with the same input, hut the pushpull gives lower voltage amplification. Greater input voltage can there!ore be supplied, and 25 per cent, more overload can he tolerated. The only advantage of parallel tubes is that the output impedance is lowered, and more power can bo delivered to a low impedance loud speaker. With the pushpull amplifier the output impedance is doubled.

APPROVED RADIO RECEIVERS. The following sets have boon tested and approved for use in Now Zealand by the Telegraph Department. It must ho understood that sets of the _superbetrodyne typo not mentioned in this list must bo used only on a loop aeriai. On no .account may they bo used wiGi outdoor aerial or earth connection, it will be noticed that some ol tin; sets use direct or auto coupling with the aerial. but in tho cases mentioned the sets bare been tested by the department and found non-radiating:— Colin B. Kennedy, Model V. —Thrccvalvo direct coupled neutralised. Gcrophnnc.—Two-valvo direct coupled tuned anode neutralised receiver. Marconi Y2A.—Two-valvo direct coupled neutralised. Eada. —Eivc-valvo ncutrodync. Freed Kiscraann K.D.50. —Eivc-valvc ncutrodync. Giliillan.—Eivc-valvo, ncutrodync. Hanscom.—Loosely coupled and neutralised super-ueutrodyne. King.—Five-valve neutrodyne. Pago 6.—Six-valvo neutralised receiver. Radiola Model 20. Five-valve neutrodyne. , , Radiola Model 26.—Loose coupled super-hetrodyne. Sonora. —Five-valve neutralised. Stewart Warner.—Five-valve loose auto-coupled potentiometer controlled. Grebe Syncrophaso.—Eivc-valvo neutralised. Atwater Kent Model 20.—1' ive-valve receiver. Branston Super-diet.—Only under special conditions. 3LO GHOST STORIES. Writing from 3LO, Melbourne. “Hello” states: “I have been amused at some of the letters sent in to 3LO about the ghost stories. Most people, whether they believe in ghosts or not, get a decided thrill from tho exciting denouement of a skilfully-told ghost story. A ghost story, if it is to ho successful, should make the most sceptical feel just a little reluctance to leave tho bright room and climb the dark stairs to bed. If it doesn’t thrill it is a dire failure. In spite of this, correspondents have written to 3LO complaining that these stories are very bad for nervous people. Why on earth the nervous people, knowing that for fifteen minutes a ghost story is to bo on the air, do not tune out and put the cat out or mix up the supper toddy is more than I can say! It would seem that it is as impossible for these nervous wrecks to go without their ghost yarn as for a dipsomaniac to go without his whisky. They sit with twittering nerves ready to scream at _a shadow, possibly with the lights out in obedience to tho programme order, and then write to the station about it being so bad for them. People are genuinely funny; there’s no doubt of it.”