1927-11-29 — Page 11

∙10

BIG

SALE

LADIES' RAIN` COAT

$5 Start

WHITE SHOES

SUMMER HAT

$1.00

$3.00

ALSO

Remarkable Reductions

in all Departments.

YEE SANG FAT CO.

Hong Kong's Artistic Photographers

PHOTO TAKEN DAY AND NIGHT

The

YING MING STUDIO

No. 50-52, Queen's Road Central.

DEVELOPING, PRINTING AND ENLARGING.

(Official Photographers of the "China Mail.")

́SAND-LIME BRICKS.

Best machine made bricks Highest tests and uniform qualities.

For Economy, Quality, Beauty, Durability and

Satisfaction unsurpased.

YEE YICK SAND-LIME BRICK CO.,

CHING IU NAM

Manager.

Factory:-Canton.-

Hong Kong Office, 148, Queen's Road, West, 1st Floor. Telephone No. C.3882.

"CARNATION" MILK

SAFE FOR BABY

"From Contented Cows"

PHOTOGRAPHIC XMAS CARDS.

LARGE SELECTION.

Good Wishes

LOCAL AND CHINESE SCENES.

LEE

FONG.

No. 7, Wyndham St.

CHI WAH. TAILORING, Once known as Chison. Perfect fit guaranteed. 9, Wyndham Street.

Tel. C. 4028.

TANG YUK, DENTIST Successor to

the late SIEN TING, 14, D'Aguilar Street.

TERMS VERY MODERATE Consultation Free.

THE CHINA MAIL,

RADIO TOPICS

RADIO APPARATUS.

REVIEW OF RECENT PROGRESS.

WORKING OF THE VALVE.

WIRELESS NOTES,

THE TWO-VALVE RECEIVER,

The special correspondent "The Observer" writes:---

of

Judging from the correspondence

is a very considerable demand for that has come to me recently, there

A good two-valve receiver consist-:

When the receiving aerial le tuned to sympathise with the transmitting aerial, bath "throb," pulgate, or oscillate for the same The annual exhibition of wireless frequency, and then one la said apparatus and accessories, organised to be synchronized with the other. by the Radio Manufacturers' Aa-This, in effect, is all there is in

tuning. sociation and opened at Olympia on Saturday last, affords an excellent and fro between aerial and earth When aerial oscillations pass to opportunity for surveying the pro-pass through the inductance and gress made during the year in this tuning section of the set, thia ing of a detector and an amplifier, particularly interesting branch of does not constitute reception. applied science.

These currents or oscillations are designed to give reasonably good but material, as it were, which the quality in head telephones, with operator has to handle in order to sufficient selectivity to cut out the obtain audio-frequency results, local station and receive 5 GB and

Rectification, detection, or, to use a term which we would rather one or two others. Such a receiver employ, interpretation, occurs may be worked very economically, when the aerial currents are and will give a very great deal of applied to the detector valve pleasure to one or two listeners, through a grid condenser. The valve, the grid condenser, and the ing tied to the apparatus by the tele- provided that they do not mind be grid leak are three ingredients which may be said to make up the phone cords. Quality is not diff rectifying unit. The valve alone cult to achieve in a two-valve would not detect.

In a valve there are three entire-eet is far better in this respect than ceiver, and a good telephone head- different component parts. One is the majority of loud-speakers now the filament, the other is the grid, on the market. But so and the third in the anode.

small When piece of apparatus is not suitable the filament is heated by the flow of for working a loud-speaker unless an electric current through it mil-it is situated within a mile or so ilons of units of electricity, known of the transmitting station. In as electrons, Ay from it and

are no

circumstances is it suit- attracted to the anode.

The reason why this attraction tion of distant stations.

a loud-speaker recep- occurs is simple to understand loud-speaker work power is ab- when it is remembered that, in electricity, like

solutely necessary. The minimum attracts unlike. requirements are given by a power The plate is rendered positive by valve that will dissipate about be the application of a potential from tween one and two watts, that is to the .T. battery, The electrons eny, it will take a current about 10 given off by the filament are nega milliamperes when fed from a 120- tive, and these electrons try to volt supply and suitably blased. close to a transmitter is used for negative

If a two-valve receiver situated loud-speaker work, the output valve should be of this type.

When organised broadcasting was instituted in this country a few years ago, less than a dozen firms were engaged in the manufacture of wireless apparatus, and the ex- tent to which the industry has de- voloped since that time may be gathered from the fact that nearly 200 Arms; the majority of them manufacturers, are now exhibiting their products at Olympia. At the moment, there seems to be every likelihood that this development will continue, sa the number of listen-ly ers is still increasing; and there Is a strong tendency for those per- sona, who were at first contented with the almplast and cheapest ap- paratus, to install more elaborate sets in order to obtain improved re- sults. This tendency will undoubt edly be strengthened as the policy of the British Broadcasting Cor poration in providing listeners with alternative programmes is develop.

éd.

transmitters and

make the anode as

con-

If the filament is a poor one, or if

able for

re-

For

The usual kind of two-valve set

con-

TUESDAY, NOVEMBER. 29, 1927.

DAILY CROSS-WORD PUZZLE.

(This cross-word puzzle has been made by an expert but our readers are warned to look out for occasional pametia spallings, such as harbor, plow, and altho.)

כון

G

14

[15

19

$234

20

2.1

125

2b

12.9%

34

39 40

14

7

156

38

42

45

48

49

51

*152.

153

55.56

59

57

158

60

62

@THE INTERNATIONAL SYNDICAT L

HORIZONTAL

HORIZONTAL (Cont.)

VERTICAL (Cont.))

1-To flow slowly

3-To investigate

144-To rub out

47-To attend to

16-Cut down 10-A coln

B-Locality of minoral·|48-Nobility

18-Consumed

rprings

"A grassy fald

160-Not quick

19-Perform

151-Symbol for tantalum 20–Zealous

-Used to alture fish [62-Ai qued 1.-Place of Napolion's [66-Streat (abbr.)

first exile 12-Cuffix denoting

j56-End

57-Performed by one

comparativa degres]59-A large body of 15. Finny 17.fiother

19 O-y

21-Observed

22-To cut with the

teeth

14-Crawi

26-A small tomor 27-To make broader 18-Blood venrei 30-Sour 22-A vegetable $3-A ceremony

35-Tinwaru ini.) 37-Satiat

$9-A spiritual being 42-To lick up

water

60-Alaa

61-Coloring matter 162-Suffix donating condition

VERTICAL

1-A herolo paem

2-A short staff 4-9eg

5- loud try

22-Spirits (alcoholic)

22-Finish

25-Danger

27-To trace lettera 29-Hetal

$1-Aricciate of Royal'

Academy (abbr.) 34-Domestic animal 30-A fat plato-like

substanca

37-A blemish 38-An avergreen trea 40-A nare

41-A flying inacct 143-Native of Arabla 145-Too

6-A continent (abbr.)]40-A drunkard

B-College degrea

(abbr)

A kind of cheese

|10–A ̧ hawk-like bird

12-Among

115-To in

48-To lay on 49-Bird homes 62-Geznod Ilving

63-Evil destiny

56-For instance 158-Observe

(The solution of the prove cross-word puzzle will appear in to-morrow's issue awong with a new cross-word puzzle.)

excuses

18

An would be expected in an ex- hibition intended for the general public, the exhibits consist mainly of complete receiving sets, compon- themselves. The more positive the ents for their construction and ac-anode, the greater the effort of cessories for use in connection with the electroic stream, as it is called. the various apparatus. The trans- to make it negative. Thus there is mitting side of the industry is, how- an immaterial yet very real ever, represented by the exhibit of nection between the two, the British Broadcasting Corpora- tion, This includes two complete the valte is old, the electron stream is sadly lacking in selectivity. My is work. If the H.T. battery in own idea of such a set is that the a model of the nearly exhausted,

the control room of the London broad-stream is weak again because asist of an untuned aerial coll and

electron tuning arrangements should casting station.. Of the transmit lesser cffort is made to negative the a tuned secondary or grid coll. ters ahown, one is a 61kw. "Q" type anode since it is not so intensely The new Dubilier "Toroid" coil is telephone set designed and con- positive. We see at once then, how almost ideal for the purpose. It is structed by Marconi's Wireless poor reception can be occasioned so made that the primary, or serial Telegraph Company, Limited. It by an inefficient filament and a run-coil is totally enclosed in a second- comprises four panels, for rectifier, down or partially exhausted bat-ary coll so wound that it has prac drive, oscillator and, modulator res

tery.

tically no But we will assume that the H.T. with a suitable variable condenser field. In association pectively. A motor-generator set supply is good, and that the valve of about 0.0006 micro-farads maxi- supplies single phase current at 500 filament is vigorous. We will mum capacity, shunted across the volts and 300 cycles, and this is suppose that everything 18 O.Kprimary, it will cover the complete with the fact that a Dutch station stepped up to 10,000 volts by a All the time the aet it switched on broadcast band, and the longer served as the link between the static transformer, rectified and these millions of electrons are wave-length broadcasting stations Motherland and smoothed on the rectifier panel, and rushing off from filament to anode. can be received by changing one Dominions, It one of her supplied to the anode of the valves But this is not enough to give us coil. Such a receiver

high time signsis,..

as this is that protests and promises and an the other panels. The filaments

very suitable for the home con- Between the filament and the structor to attempt, as there is very at home, and the short-wave station of the rectifier valves are heated by plate there is the grid, and this grid little chance of going wrong,

were done away with low-tension alternating current, but acts as a sort of interrupting con- detector may be one of the new blood overseas was put into opers- The that is demanded by those of our the other valve filaments are sup- trol. It responds to the oscilla-high impedance high magnification tion. If the United States can do plied from a secondary battery. tions in the aerial and inter- valves, such as the PM5b or The ordinary choke-control method rupts the flow of electrons on DEHG10 if a six-volt accumulator lands, to say nothing of that ama- the it, and Australia and the Nether of modulation is employed in this their passage to the anode. The is to be used, or the DEH210 or teur genius 2 NM, why cannot we слее The other transmitter ex-functions of the grid are dependent SP18B when heated from a two-volt de 8 hibited was constructed by Messrs. Thus the oscillations in the aerial be by means of one of the resist- on the oscillations in the aerial, accumulator. The coupling should' Standard Telephones and Cables, influence the flow of electrons. The ance capacity unita Limited, and has a Geneva rating oscillations in the aerial, are

now widely de- made. This unit should be suitable of 11 kw. The Geneva rating, it pendent on the modulation of the for use with a high-impedance may be explained, is that adopted transmission by electrical impulses valve. The output valve may be by the Union Internationale de set up by the microphone in the any small power-valve or low-fre- Radiophonie, and, is the power sup- every sound made in the studio is the accumulator. A small power- studio. We can, therefore, say that quency amplifying valve suitable to plied to the anodes of the final os- cillator valves. In the standard the detector valve, and as the DEP610 will give excellent results. made to influence the grid of valve such as the DEP210 or set, choke modulation is carried out grid influences the vice in the Reaction at low power,

and the modulated anode, circuit-such as

necessary in such a re- a loud ceiver and, not abused, will not wave is amplified by successive, speaker-must be influenced as harm the quality to an appreciable stages of power amplification. A well.

degree. It is best applied in the similar set to that exhibited has re-

simple "capacity" coupling manner. cently been installed at the Kalund-

Were it not for this grid inter- To do this an H.F. choke is connect- borg Station of the Danish, Tele- ruption the sound heard in headed between the plate terminal of the phones or speaker would be no more resistance unit and the plate of the graph Administration.

than an unintelligible rushing valve. From the plate of the valve Probably the most interesting noise. As the grid interruptions a lead is taken to a 0.0003 m.f. development in receiving apparatus, occur the diaphragm of the speaker variable condenser, the other side that has occurred since the previous or the headpiece is pulled first in being connected to the aerial. This exhibition, is the four-electrode in one direction by the influence of will give quite sufficient reaction screen-grid valve, different forma of the plate circuit, and then back to for all ordinary purposes. Such a which are exhibited by various its original position. This push receiver will be almost the ideal valve manufacturers. These valves and pull movement, as we have said two-valve apparatus. are specially designed for high-fre- waves audible to the ear.

in previous article, produces sound quency amplification, their suit- ability for this purpose arising from the fact that the inter-elec- trude capacity is neutralised by the employment of a screening grid ba- tween the ordinary control grid and the anode, as well as by the ar rangement of the electrodes. En gineering."

!

Effect of Grid.

When the valve was first invent- ed by Dr. Fleming it had but two electrodes, filamont and anode. It was De Forest, who added the grid and thus produced the valve as we now know it.

The possibility of using short waves as a link between the broad- casting systems of two widely separated continents was again, de- monstrated when the descripton of Besides the grid condenser, which the bantam-weight boxing match be- permits the passage of an indirect tween two men, one of whom was a current only, we have the grid leak, South African, was picked from whose task it is to leak away any Daventry by the famous Dutch sta- accumulation of negative electrons tion, PCJJ, transmitted on 30,2 me- from the grid. Thus the term,, tres from Eyndhoven, received by a

· FOR COUGHS AND COLDS,

"leaky grid rectification." When changeable weather or ex-

station in Capetown and rebroad pasure to cold and wet results in plifying valves is very simiin

The process that occurs in am- cast yet again from the Cape Town

to and Johannesburg atationa. bronchitis. start at once taking Cham that which happens in a dotector may have the opinion that the mat One berlain's Cough Remedy, Standard for over fifty years, and strongly recom. valve, only, in the case of LE. am- ter transmitted was hardly worthy mended for stubborn, weakening plification, the valve functions to of the very fine technical achieve- coughs. For sale everywhere.

amplify, and does not detect. ment; but that does not do away

FOR SALE.

STANLEY GIBBONS, LTD.

AND

SCOTT STAMP & COIN.

CO., LTD.

POSTAGE STAMP CATALOGUES

FOR

1928.

ACA & CO.

Vyndham Street.

620. Hour Kong

ĮYOU MAKE ME SICK-HERE

WE ARE IN CAIRO AND YOU

DON'T SHOW ANY AMBITION TO SEE THIS QUAINT OLD CITY-NOW YOU GO OUT, " AND SHOW AN INTERES; LOOKING AROUND AND IT'LL BROADEN YOUR

MIND!

BRINGING UP FATHER.

WELL-IFT MUST- I MUST-ILLCO IN THIS PLACE. BUT 1. SUPPOSE I'LL BE

BORED TO

DEATH!

1927, by Int'l Fonture Service, Inc: Great Britain righon rust

SORRY-SIR: BUT THE ONLY THING WE HAVE" ON THE MENU TO-DAY IS- CORNED BEEF AND CABBAGE,

TOO

·BAD!

YESTERDAY'S SOLUTION,

MAXI

B CUT

M

GAN MAN PUIG

D

PAD BUS

UIG

G

MA

FTHE INELEWATIONĀL SPADICATE.

PUBLICITY.

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