THE HONGKONG TELEGRAPH.
THE BUICK MODEL "50"
LIMOUSINE SEDAN.
Combining the qualities of a chauffeur-driven car with those of a closed car for family use, the Buick Limousine Sedan is a distinctive addition to the Buick line for 1924. It is another evidence of Buick's policy of furnishing a car for the majority of motoring needs.
The one-piece curved glass that separates the driving compart- ment from the tonneau can be lowered completely out of sight by simply turning a small handle on the back of the front seat. The car is then converted into a Sedan for the use of the owner or members of the family.
Sole Agents :
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Telephone No. 1036.
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RADIO FOR BOATRACE CROWDS. A musical Boat Race is the latest development in broadcast ing.
SCHOOLMASTER ABROAD--BY
WIRELESS.
Negotiations between the Bri tish Broadcasting Company and the educational authorities have brought very noar experimente in the nse of wireless in schools...
WEDNESDAY, APRIL 16,
RADIO NOTES AND NEWS.
Distortion in Loud Speakers.
BS
The announcement of the natural frequency of vibration B.B.C. that they propose to open five more relay stations should give a fillip to the sales of low- power rucniving sots, such crystal and one-valve Hots: At the same time it should increase the field of potential users of loud- speakor equipment, says a writer in the Manchester Guardian Commercial. People In the theso relay areas served by
with who, slations or three valve sots, could only obtain suflicient power to operato headphones, with the samo equip ment will now be able to operato loud speakers.
two
ቤ
|
|
of Its own, and its ampll- of vibration under tho tude action of the impressed signal will vary with the frequency of muxinium the signal, being whon the two coincide. The boxt nikers of loud speakers attempt to overcome this by corrugating the diaphragm and in some CASCH making it, not of metal, but of somo pressed paper composition n largo extent, is which, to
tends
to solf-damping" and reduce the discrepancy in the response to signals of different frequencos. This is evidenced by the almost univeral tendency to blast on certain notes, theso corresponding LE the notes natural frequencies of constituent moving parts of the loind speakor. Damping could bo introduced deliberately with beneficial re- sults to the quality of the reproduction, but mainly owing to the low acoustic efficiency of the diaphragni, demands of
011
in
A type of ounipimont which has receive considérable attention from amateurs with varying degrees of success, but which up to the present doos not appear to have been exploited by, manufac turers to the extent which it pos- sibly doserves, is the combination of a crystal detector and a single- valve retiex circuit. This com- bination is comparatively inox-sensitivity preclude the possibility ponsive in first cost, and much of such action.
Still further distortion is intro- cheaper to maintain than its
the horn fitted to equivalent two valve receiver induced by which one valve is used as English makes of loud spoakur. detector. It has the further ad- The object of the horn is to give vantage of minimising what is to amplification, which it accom
account of inest valve-set users the annoy.plishes only
its resonance, Apart from ango of continually having to
Hipparent It
increaso recharge accumulators.
is such true that this has been greatly strength as is obtained from Exactly reduced by the introduction its directional effect. of the dull emittor valve, but as in the case of the diaphragm, there is still a great reluctance this resonance give distortion on the part of many people to owing to the variation of ampli- discard the plain hot tungsten tude with the frequency of the wira valve in their favour. This signal. The resonance of the is partly on account of their first material of which the horn is cost and partly because of the constructed is partly overcome in Bone makes by constructing it of danger of impairing them by
This trouble has fibre or somit other weakly reson- overheating.
material-in one Cuse been rather prevalent, and is due, ating
A material no doubt, to the valves pluster is used.
which does not appear to have receivers de- being fitted in signed for the bright filament boon tried out which should type of valve. The filament give good results, is papior-]
The final mache.
of CLUSD resistances for use in connection
resonanco of with theso aro unsuited for trouble is the
a kind of organ inexperienced uso with the dull the horn as omitter valve, but with sets pipe, attempts to get away from which are seen in sume of the specially designed for uso with
weird and wonderfully shaped this valve there should be no dfficulty in oliminating this part- horns on the market, many of icular trouble, though their high which introduce "baffling," which prico, as compared with that of shows itself in the muffled sounds the bright filmont type, will, no and blurred speech given by the doubt, militate for some time aga-struments. This latter trouble, inst their more extended use.
1184
however, can be overcome by drilling one or more small holes of about 18in. diamotor at tho point at which the balling is occurring. This normally occurs at the apex of the sharply curved) Barrow portion of the horn.
BPERFECT LINK. This feeling on this part of the public for the avoidance of the uso of Valves owing to the diffi- culties of battery-charging is
Continentul makers have most- uvidont in the devices, such
olectro-magnetic amplitiers, ly attacked the question of in- which have been brought out to creasing the acoustic efficiency obviate the use of valve ampli- of the instrument otherwise than fiors. In general, however, the by adding-a-horn-or-trumpet The low officioney of results are not so good as those to it. obtainable with a good valve am- the diaphragm is due to the fact plifier, although here, as in most that its diameter is small compur- things, there are good anded with the wave-longth of sound. bad valve amplifiers. In many Thoy have increased its size from cases discordant loud-speaker 3in. or 4in. to 12in. or 15iu., when effects. are unjustifiably ascribed it becomes comparable with the to the loud speaker, when the real wavo-length of sound, with a con- cause of the trouble is the am-suquent increase in the acoustic plifier. Most of the initial dia-efficiency. In order to keep down! favour which broadcasting not at the inertia, which would result in its inception was due to the poor à loss of officiency and distortion, results obtained on many loud- these large diaphragms, are made poaker oquipments at that time. of parchment, pleated to give the This con- Much
has progress
beennacossary rigidity. nado since then, but there struction on the whole gives a is still considerable room for better clarity of tone and a greater: in the loud freedom from distortion than the improvement
horn typo, but still loaves much is generally ro speaker. It cognised as the most inefficient to be desired. and imperfect link in the chain of broadcasting, and a large and profitable field awaits the pro- ducer of the perfect instrument. week try to evolve a general The loud speakers on the scheme applicable to all classes market to-day can be divided of schools primary secondary, into two classes. One class is alectro-magnetic and the other and technical.
"A month after we have the electro-dynamic in its action. is usually tho plane completed," said an au-In the electro-magnetic type the thority to a Pross representative, armatură
the whole of the London schools diaphragm, though in one or two could be equipped with necessary examples, such as the balanced armaturo type, the diaphragin in acted upon directly by "And there will be no difficulty not about finding oporators, for there the electro-magnats. In this type is probably not a school in which one cause of distortion is obvious. there is boy or master who has As the armature vibratos under mado himself acquainted with the the action of the varying flux it alters the field strength as it mean-time. will bo. similarly
subject." broadcast,, the 3.30 signal from The Communications Depart- Glasgow, it is stated, line at-approaches or rooodos from the pole faces, and as a result the 2LO only, and the othors simul- mont, says a Tokyo mossago, ready decided to adopt tha
amplitudo of vibration of the dia- will commonco phragm will not be proportional taneously rolayed from every established a 15 kilowatt radio scheme, and
apparatus at the Oboshi station within the next few days. Tho to the signed ourront strength. B.B.C. station in the country. In June last year and has been firet offorts will take the form of In the oldctro-dynamic, <type, But there is now another wire-making oxporimonts with it since, an hour's, looture oach wook, however, however, where the coll and attached to the diaphragm moves loss chook on British clocks and
The apparatus, provided with music, history, solonce
boing the probable in a constant magnetic Gold, the watches available, as apparatus the vacuum tubo, was successful Fronch has been fixed to "Big Ben," the and proved able, with only ong-subject.
amplitude of vibration will be strictly proporational to the famous clock in the 320 ft. high | fifth of thả oleotris power requir tower of the Housos of Parlia for the spark systom," of dis
signal current. ment, by means of which and an patabing messages 1,000 miles in underground cable to 2LO. ite the daytime and 2,5000 milos at chimes and hour bell are simult-
At half-past nine one night ro- rently, reports
a London
paper, the seconds lick of the mean
To relieve the tedium for hun- timo cluck
Groenwich in
dreds of thousands who lined the Observatory Wis heard six Thumes-sido on the afternoon of times (the last, louder than of April 5, the British Broadcast- A national advisory conunittee the others exactly at 9.30) bying Company engaged the band has been formed and will this hundreds of thousands of listeners of the Grenadier Guards to play in throughout Great Britain by at the London studio.
This special musical
pro the miracle of wireless and the co-operation of the British Brond-ramma lasted from 2.30 p.m. to 4.30 p.m., and owners of loud casting Company. This unique speakers in gardens on the nine timo signal, as accurate as humiles of river bank between and Mortlako woro man ingenuity can make it, was Putney inaugurated by the Astronomer invited to entertain therewith the waiting crowds. It was arranged Royal speaking at the London that a narrative of previous tacos station of the B.B.C. and in and outstanding incidents bo future twico every wook-day, broadcast during the afternoon. at 3.30 and 9.30 p.m., and on Sundays at 10 p.m., Groshwich
aneously broadcast all over the country at 7 p.m. on weekdays and .3 p.m. on Sundays,
SUCCESS OF THE VACUUM SYSTEM.
apparatus.
night. An experiment was made communication was establisher!
MAIN DEFECTS.
The main distortion arise from
+
"POTTED" CHURCH SERVICES.
The Rev. James Smith, St. Goorgo's-in-the-West : Parish Church, Abordeon, who recently mado an attack on Sunday broad- casting, has been inundated with letters on the subject from as far south as Kent and from the Orkney lales in the north.
Mr. Smith states many seem to: have missed the point that ho was not opposed to Sunday broad- casting if it could rouch non- churchgoers and cause them to Rnd their way to the church or take an interest in Christian: matters. He had not yet heard of anyone who had been converted by Sunday broadcasting, but he ktiew of very many to whom the services of the church had boon the turning point in their spiritual life.
No one could gainsay the valuo to the sick, the aged, or tho infirm that broadcasting might have; but nothing could alter the fact that this was a
now and cany, a tompling and a selfish way of gotting potted." church Borviços by nombore of the church instead of going to their own church to take part in public worship and offer their means for the maintenance and spread of
at night with the new apparatus at a range of 3.500 miles. The the diaphragm and the horn, recently between the station and station reported the result to the Tho diaphragm will have the Gospel. the as, President Jefferson whon Tokyo Department.
•
1924
RADIO
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THE HUMAN ZOO
Coriglil 1923 1
Pablo Ledger C
LITTLE GIRL WHO KEPT ON PLAYING.