THE WIRELESS WORLD.

Otago Daily Times, Issue 19259, 25 August 1924, Page 8

THE WIRELESS WORLD.

NEWS AND NOTES. (By Magna VoxA [ltems of news, comment, suggestions, •to., will be welcomed by “Magna Vox.’3 At the monthly mooting of the Otago Radio Association on Monday night, a letter was received from Mr E. A. Adams, St. Clair, enclosing £5 to assist the association in broadcasting. The concerts broadcasted from JAB have of late shown a considerable improvement, and reports have been received from Russell (Bay of Islands), Upper Moutere. (Nelson), and elsewhere congratulating the association on the excellence of the transmissions. The action of Mr Adams, which is one to be commended, shows that the efforts of the association on behalf of the radio amateurs are appreciated. The lecture given by Mr J. T. Cooper at Jhe conclusion of the business at the meeting of the Radio Association certainly deserved a much larger audience. Mr Cooper, who spoke on “Wireless’ Topics,” dealt lucidly with various wirless apparatus, and, as his remarks were not too technical they could be appreciated by the youngest amateur. It is to bo regretted that the members of the association do not. take a more active interest in its affairs, and, when such interesting and educative addresses are given they should avail themselves of the opportunities of gaining expert knowledge of the science. Mr John Coolidge, father of the President of the United States, is now an ardent radio fan, although 79 years of age. A radio manufacturing company has presented him with a neutrodyne sot, the screws and jacks of which are of gold. Mr Coolidge, sen., now listens to his son’s speeches at a distance of ■ hundreds of miles. Transmission by amateurs is prohibit'd during broadcasting hours b” the Uni States Government. According to a New York radio man, “In connecting up a receiver, whether it be a single-tube ‘blooper’ or a six-tube super, always keep the high potential wires away from the panel. If a set is correctly wired in this respect it Is not necessary to shield the panel. It is not good practice to shield a panel when not necessary, as the shield forms one plate of a condenser, with the wires that are not at ground potential as the other, and will result in a broader tuning.” POINTS IN OPERATING VALVES. The importance of properly taking care of a valve is so great that it is surprising so little is said on the subject. Tubes cost so much and they burn out so easily for one reason or another (much quicker than do the electric light bulbs, as a rule) that we ask ourselves: “What is the secrettThe operator tries to make his valve last as long as possible, but very often he unconsciously shortens its life. lie figures that it is necessary to cut in the resistance when he leaves off operating, so that when he starts operating again the vpltuge of the accumulator won’t have the chance of burning out his filament due to recovered voltage. However, do not make this mistake, because the voltage does not recover enough to burn out the tube. Only before connecting up a re-charged cell should the rheostat have most of its resistance thrown in, and apart from that it should only be varied slightly for very fine tuning purposes after the best operating point has been found. Flash your tube instantaneously to its operating temperature. The electric light is done this way. The filaments are made of the same material. Note how long the bulbs last compared with the amateurs’ valves Do not forget that it is not good for your tube to bo burned lower than its proper operating temperature, except in filaments other than tungsten. An increase in filament life result if the above is read and practised.—From Radio News.

HONOLULU TO NEW ZEALAND. » TEST FOR AMATEURS. Following are the details of a test arranged by Mr Cantin, 6TQ, Honolulu, between Hawaiian and New Zealand amateurs. The times given are i>ew Zealand Mean Time, and the wave lengths to be used are from 165 to 180 metres. Aujgust 24. —7.30-8 p.m., Hawaii calls New Zealand; 8-8.30 p.m., New Zealand calls Hawaii. August 31.-8-8.30 p.m., Hawaii calls, 8.30-9 p.m., New Zealand replies. September 14.-8.30-9 p.m., New Zealand calls: 9-9.30 p.m., Hawaii replies. September 21. —9-9.30 p.m., New Zealand calls; 9.30-10 p.m., Hawaii replies. September 28.-9.30-10 p.m., New Zealand calls; 10-10.30 p.m., Hawaii replies. All New Zealand amateurs are invited to take part, and.it is hoped to establish two-way communication. EARTH CONNECTION. No small part of the falling of! in signal strength about which most _ wireless ' men complain in summer time is due to the earth connection. The long hours of daylight, the prevalence of atmospherics and the screening of aerials by trees now in full leaf, have a great deal to do with the falling off that takes place in the quality of One’s receptions, especially on short waves; but the condition of the earth is one of the most iiriportaot factors. During the hot days the soil becomes parched, at first on the surface and then for some distance below; Dry ground has a very pour degree of conductivity, hence an earth contact- that is left to look after itself may become the seat of a very high resistance.

The best way of making sure that the earth contact is good is to make a practice of giving it a bucketful of w'ater once a week during the summer months. A most reliable earth can be made from a 6ft length of old stove piping. A number of holes are punched in it and it is buried in an upright position so that the last foot of its length protrudes above the surface of the ground. It is filled up for about half its length with riddled earth, the top 3ft being left empty. It it is filled to the brim at regular intervals with water a good moist contact of very low ristsance will be secured, for the water will leak away through the holes in the sides as well as through the bottom. It would be an improvement to make a pipe of either sheet zinc or galvanised iron rolled ur>, for these will not suffer so severely from the effects of corrosion. AND THE; AERIAL. The aerial also requires attention. In winter the rain washes the insulators to some extent and keeps them fairly free from dirt. But if there is little rain, dust and soot settle on them; these attract moisture when the air is humid, and the sun bakes them into a hard cake. It is a good “tip” to lower the aerial every now and then and to give the insulators a thorough cleaning. For short-wave work two or three insulators should bo used in series. Those of shell, ring, or barrel types, even if they are perfectly clean, are. responsible for losses by capacity. If we have the aerial wire separated from a supporting rope or wire by the material of the insulator, a. condenser is formed with a dielectric of porcelain. By placing condensers in series wo can reduce their total capacity to very small figures; hence the addition of two or three insulators at each end of the suspended wire may make all the difference between receiving and not receiving weak signals. THE SERIES-PARALLEL SWITCH Every set. should be provided with a seiies-parallol switch so that the A.T.C. and the tuning inductance may be used to the greatest advantage. In tuning we should always endeavour to use the largest amount of inductance, and the smallest of capacity possible. Short-wave coils have a much larger self-capacity in proportion to their inductance value than those wound for the lower frequencies. When the A.T.C. is in parallel its capacity is added to that of the aerial and the inductance; when it is in series the total capacity in the circuit is reduced. Thus if we use a parallel condenser with a very small coil we have an undue ratio of capacity to inductance with consequent reduction of grid voltage. With the larger coils there is no such loss in efficiency, for even ifihe condenser is a big one the proportion between inductance and capacity never becomes unreasonable. The S-P switch enables one always to have tiro condenser in the right place. It also nearly doubles the range of one’s A T.l. coils. —“Lambda” in Modern Wireless. WIRELESS CONCERT. A first-class programme by the 3rd Artillery Band and party was broadcasted from Station 4YA, Dunedin, on Wednesday evening. The following items were contributed Pianoforte solo, “The Waltz from Faust,” Miss Kathleen Whelan; songs—- “ Away in Athionc.” Mr D. Caldwell; “Impromptu,” Mr S. Higman; “Don’t Be Quite Forgetting,” Miss K. M'Callum; cornet solo, “Answer,” Mr A. Whitburn; trombone trio, “Comrades in Arms,” Messrs Hancock, Inder, and Ker; song, “Homeward Bound,” Mr A, Quennell; euphonium solo, “An Old German Air,” Mr M. Clark; pianoforte solo. Miss K. Whelan; song, “What Am L.Love,” Mr Bay Butler; cor-

net duet, “Wind and Wave," Messrs A. Whitburn and D. Scott; bass solo, “Interi mezzo from Rusticana,” Mr Ij. Fogo; solo, “Home Song,” Miss Kitty M’Callum; trombone solo, “Death of Nelson,” Mr H. Inder; cornet solo, “Killarney,” Mr Whitburn; song, “Shipmates o’ Mine,” Mr A. Quennell; cornet solo, “The Devout Dover,” Mr D. Scott; song, “For You Alone,” Mr Ray Butler; bass solo, “Reverie No. 2,” Mr L. Togo; and trombone trio, by Messrs Hancock, Inder, and Ker,