1930-05-01 — Page 2

THE HONG KONG DAILY PRESS, THURSDAY, MAY 1, 1930.

For Better Result

TRY

MULLARD

RADIO

FEATURES

TUNING THE RECEIVER.

THE USE OF COILS AND CONDENSERS.

It has been explained how an cscillating current flowing is an open circuit, such as an aerial is capable of creating electrical waves, the length of which will depend on the frequency of the charge generat- ing the oscillating current.

[BY_" CONERER."]".

The electrical characteristics on which the frequency of an oscillat-- ing current depend are inductance and capacity, any aerial having a defnite factor of each depending on its size and shape.

A transmitting station's energy is built up by condensers and induc tances to bring the discharge to the

the designer of which boasted that he could tane out the bass of a Pianoforte solo and just listen to the treble!

IN RADIO.

Thus, energy lost in the input ANOTHER NEW · ERA. side of the valve (grid) might be fully restored by the energy im- parted from the resetion coil. This increases the signal voltage appli- ed to the set, thus again causing an increase on the output side (anode) of the first valve. Hence,

SETS OF ASTONISHING POWER.

The selectivity of a set in its capability of fine tuning and, in an endeavour to obtain maximum selectivity, tuning other than in the aerial circuit is resorted to." oscillations once set up would con-fication had been invented by two

Another important factor in aerial tuning is the elimination of the resistance of the aerial without losing the induced transmitted cur-

Tent.

Avoiding Interference. Where the difference in frequency

This is achieved by allowing the of two stations is only a few kilo cycles (in Europe 8 ko..is the mini-aerial circuit to pass through an mum of separation) a high degree inductance coil to earth, no me- of selectivity is required of the "chanical connection being made be receiver, to bring in the station tween' this circuit and the remain- required only.

der of the set.

Similarly, a station of high power in the neighbourhood of the receiver

Such waves have the property of producing a disturbance similar to their origination." It follows, there--¡ frequency required for the station's fore; that electrical waves will pro-wave-length. At the receiving end dure oscillating currents in a receiv-similar instruments are incorporis apt to cause interference even ing aerial of the same frequency as ated in the receiver to bring the THE BEST BRITISH MAKE the current causing the wave.

aerial to the required frequency.

THE

MASTER VALVE British & American Bases Available

SINCERE'S

SOLE DISTRIBUTORS

A oscillating current will not dow easily in a circuit unless such a circuit has the same frequency as

the errent.

It is obvious, then, that the "natural" 'frequency of an aerial being suscaptible to only one wave, means have to be adopted whereby its frequency can be varied to cover the band of wave-lengths required.

BUY BRITISH & BE PROUD We have just unpacked a Shipment of ALUMINIUM BASE-BOARD & PANELS. Suitable for Short Wave Receivers and other sota that require Screening &

OTHER BADIO & WIRELESS PARTS

(Guaranteed British Made).

The Receiving Circuit. Therefore the action of varying

By inducing the current received in the first coil by electro-magnetic induction into another coll in the when the wavelengths are separ- closed circuit of the receiver, the ated by twenty or thirty metres maximum aerial current is obtain The matter of selecting one wave-ed without the resistanos of the length without interference from aerial wire, other is, where broadcasting is con-

the tuning condensers and coils incerned, one of great importance, receiver is to bring the receiving especially in countries where there aerial into phase with different are several stations working within

a radius of a few hundred miles transmitting stations.

In America, for instance, where A receiving circuit, then, is cap- able of selecting currents whose fre- there are fifty or more broadcast quencies are within a narrow banding stations in one town, selectiv

ceiver.

It was probably in Chicago, where there are 74 broadcasting stations, that the expression “dis- connection of the aerial is the culy sure means of being free from in terference" originated.

This is the most common turn- ed. circuit, and is the method known as aperiodic-aerial tuning. Other more or less elaborate ar rangements involving the use two or three zurzed circuits in one receiver, resulting in extremely fine tuning, have to be employed for

Reaction.

of

A popular method of increasing the signal voltage of a receiver is by employing reaction, referred to in the local receiving licences as

back-coupling.”

of that of the tured circuit, and ity is the first essential of a re-long-range reception. choking back those currents whose frequencies are outside that band.

Such a system brings wireless communication to a similar level as telegraph communication, diferent wavelengths acting separate lines and connection being effected by tuning to a required wave.

There are naturally many limita- ence from undesired stations, in spite of very fine tuning..

ORIENTAL COMMERCIAL & CO., LTD. tions which give rise to interier-

BANK OF CANTON BUILDING,

TEL. C. 4405.

NOT A NOTE IS

LOST-

So Perfect are the Reproduction Qualities

If a LOEWE FE 63 9 tube set

is used

16 H

The Super-Selective Set, In such a district a set would require a degree of selectivity ap- proaching that of a home-made set

HAVE YOU

tinue indefinitely and, being in ductively coupled to the aerial, would energise the latter.

Avold Decillation.

The receiving aerial is thereby functioning as a transmitter, the energy radiating in the form of electrical waves and causing that annoyance to neighbouring listeners kaown as "oscillation."

Reaction can be used to advant age without causing this trouble by decreasing the coupling of dis

reaction and tance between the

generate oscillations, or in the aerial coil until the valve does not wards (well-known to listeners at home) of Captain Eckerslely: "Don't do it!"

·WEED-END RADIO FEATURES.

A SPECIAL DANCE PROGRAMME.

STUDIO CONCERT BILLED

FOR SATURDAY,

A special dance programme will be broadcast on Friday from 9.13 to 12 midnight, and Studio

AL

TO-DAY'S PROGRAMME.

The radio world was startled two years ago by the announce. ment that a new system of ampli

American radio engineers, Com ander E. H. Loftin and Mr. §.

Y: White.

The system" was tried out, but. though it was conceded that a high- ly important principle had been discovered, there "were grave and insurmountable de- apparently fects in its practical application.

Commander Loftin

and Mr. White were convinced, however, that they were on the right track,. and they continued their experi- ments until these defects were eliminated. They have now given to the wireless community details of an achievement which, like the screened grid, opens up another new era in radio practice.

This achievement bag an import ang bearing on wireless in Great. Britain, for it is the direct out- eorie of the system of high power radiation of which Brookinan Park is the pioneer in the British Isles. Stations operating on 20 to 20 kilowatts" demanded better qual ity of reproduction. The essentials of this better quality of reproduc tion were improved types of valves, r transformers, and loud speakers.

Two Valves.

In its new and improved form the Loftin-White scheme is in brief a direct coupled system of ampli- fcation, the plate of one valve be ing connected directly to the grid of the next valve with neither transformer nor condenser between. Set of astonishing power can be constructed on this principle with three valves only, a detector and two ampüfiera, or even on two valves.

The refinement of cabinet work in recent types of wireless receivers and radio gramophone combina-

new profession.

Bre

The received current, after hav-Concert at 9 p.m. on Saturday:- ing gone through the first valve

11 to 11.30 a.m.-Commercial Newstions has brought into existence a stage, is passed through a coil so

11.30 to 12.30-Chinese programme. induced back into the first buning-

12.30 to 9 p.in.-Programme of Vic placed that some of its energy is coil.

tor Records by Courtesy of Mesers. Tsang Fook Piano Co.: 6 to 6.30 p.m.-Children's Hour. 6.30 to 8 p.m.-Programme of Victor Records by Courtesy of Messrs. Toang Fack Piano Company: Lohengrin-Prelude " (Wagner)

Philadelphia Symphony Orches

HEARD THESE?

Here are lists of long-wave and short-wave stations which should be picked up. by anyone in Hong Kong who has a mode- rately good set suitable for ra- celving such aiguals. Success in picking up these stations also depends very largely upon fav ourable atmospheric conditions. Readers are invited to add to this list should they succeed in picking up any station not in- cluded in either of these lists.

LONG-WAVE, STATIONS.

Wave length

Call Kilo-. Metres) Station

Sign cycle 230 Manila K.Z.I.B. 1,153 277 Shanghai K.S.M.S. 1,085 280 Tientsin C.R.C. 1,070 310 Shanghai K.R.C. 987 320 Peping C.O.P.K. 945 346 Tokyo J.0.A.K. 870 253 Hiroshima J.0,F.E. 850 355 Hong Kong 2.B.W.. 846

V.U.B. 357 Bombay

840 J.O.L.K. 830 301 Sapporo ses Keijo J.O.U.K.

820 J.O.C.K. 610 Y.U.C 800.8 380 Kumamoto J.O.G.K. 500 300 Sendai J.O.E.K, 770 385 Dairen

J.D.A.K. 760 V.U.R. 754 J.O.B.K 760

C.M.B.

732. K.Z.R.M. 720

370 Nagoya 370.4 Calcutta

398 Rangoon 400 Osaka 410 Canton 413 Manila

SHORT-WAVE STATIONS.

STATION

CALL SIGN

67.68 Dobintz (Germany)

60.13 Khabarovsk (Rustin).A.97.

KILO

TIME (HONG KON=)

OF WORKING

4,434 Mon, Wed" & Fri, 6 p.m. & 2 am. 4,900 | 6—10 p.zi..

7,142 Dally 8.30 p.m. & 11 pm,

7,810 Not regular

7,780 Daily 11 p.m.

.

A.F.K.

12:30–1.30 p.m.

5---5.30 p.m.

58,7 Napan

A.G.J.

5,291 Not regular

50. MOBDOW

B.F.N.

6,000 Tue, Thurs, Sat, 8 p.ic.

43.5

Rame

1.M.A.

6,896 Sunday midnight

42.

Ferih

44.G.

41.3

Bingapore

V.B.LA.B.

38.8

Kootwijk (Holland)

P.C.L.

37.

Bangkok (Siam)

82.6

Bydony

31.55 Melbourne

81.48 Schenectady

H.S.4.P.J. 2.B.L. 3.1.0. W.3.X.A.F.

31.20

Eindhoven (Helland) PCJ

31.28 Sydney

2.F.C.

81.

Nairobi (Kenya)

7.L.0.

9,077 Midnight daily

28.5

Bydney

2.M.E

10,628 Not regular

27.8

Bandoerg

P.L.E

REQUIRES FRAME AERIAL ONLY WITH NEW BARIUM TUBES.

CAN ALSO BE USED WITH LOEWE SHORT WAVE ATTACHMENT.

Demonstration Hours

11-11.30 am. ̈

WE HAVE JUST RECEIVED A SHIPMENT OF

"Pertrix 22 High Tension Dry Batteries

100 volts and 60 volts.

--

NEW PARTS, RECEIVING SETS and LOUD SPEAKERS will also arrive within a fortnight.

THE CANTON TRADING ASSOCIATION LTD.

CARL SCHROTER, Manager-5TH FLOOR, CHINA BLDG.

TELEPHONE C. 4610.

25.63 Chelmsford (England) 5.8.W.

-245 Manila

WZX0. PLG

8,108 Tues & Fri., p.m.1 a.m.

regalar

9,230 Not

9,503 Not regular

9,630 Daily 7 Am

4,620 Fam, Sat 3am. & 10am

9,500 |· Not regular

11,020 Midnight-3 a.m. daily 11,761 7.30 pm: & a am. daily, except

Baturday and Sunday

12,240 Nightly

12,850 4 m. Wed., Fri, Sat. 18,102 Daily 6.30 pm to midnight 10,204 Daily 7 p.m.

17.280 Daily 8 p.m. to midnight

17,761 Sundayi 7 pm; & midnight,

23.35 Schenectady

38,88 Bandoeng

18A

174

Kootwijk (Holland) Randoeng

P.C.L

P.L.F

16.9

Bangkok

ILSLPJ

TULI

16.3

Kootwijk (Holland)

-15.74 Baadoeng 15.5

P.C.K.

·PLE

Nancy (France)

19,251 Daily 8 au.

13.93 Pittsburg

V.8.LK.

21,540 Not regular

18,404) Each, afternoon

19,220 Daily 6.30~7 p.m.

tra.

Wireless enthusiasts who can afford expensive receivers growing more and more critical of the appearance of their instru ments Costly woods and lacquers are being employed for the housing of these sets, and the necessity has arisen of ensuring that the whole effect is not nut of harmony with the fittings and furniture of the rooms in which they are to be in- stalled.

TSANG FOOK PIAN

COMPANY.

Beau Soir (Evening Fair)" (Paul

Bourget-Claude Debussy) and This need has been met by the "Clair Deiune (The Wistful employment of experts, who first in- Moon) (Paul Verluin-Josseph spect the furniture and colour Szale, Op. 83 No. 1.), Mary schemes of the rooms, and then Garden, Soprano with Piano. select the designs which will best 'My Hero Mediey"

(Oscar harmonise with both. Strauss) and Unrequited Love (Paul Lincke), Inter- national Orchestra" Direction" of Nathaniel Shilkret. (L'africana-Deh Ch'io Ritorni (Eend Me Toward The Vessel)" (Meyerbeer) and "Addio (Good- Bye)." (F. Paolo Testi), Enrice Caruso: Tenor with Orchestra. *Macuable" (Rowe MacMurrough

arr. Chemet) and A Dream (Charles B. Cory-J. C. Bart- lett), Riner Chemet, Violin Sole with Pinno. Tip-Toe Thru' The Tulips with Me (Al Dubin-Joe Burke) and "Chant of the Jungle " (Arthur Tread-Nacio Herb Brown), Jesse Crawford, Wurlitzer: Organ."

...

#

Cooking Breakfast For The One I Love" (William Rose-Henry Tobias) and "When A Woman Loves A Man" (William Rosc- Ralph Rainger), Fanny Brice, Comedienne with Orchestra. The Lost Chord" (Bix, Arthur Sullivan) aud "Great I$ Jehovah (Schubert-Arra Why J. A Parks), Jessic Williams and The Motmon Tabernacle Choir."

When I'm Looking At You" (0. Grey H. Stothart) and The White.Dove" (Grey-Lehar-Stot- hart), Lawrence Tibbett Bari- tone with Orch "Alcina

Suite" (Handel) and "Alcina Suite-Menuet-Musectte and Menuett" (Handel), Phil- harmonic Symphony Orchestra. of New York.

Alcina Suite-Gavotte-Sarabande- Gavotte" (Handel) and "Alcina Buite-Menuet-Gavotte-Tambuṛi- no" (Handel), Philharmonie- Symphony Orchestra of "New York. "Lotus Land (Cyril Scott) and Hungarian Dance No. 17" (Brahma-Kreisler), Fritz Greis-

ler, Violin Solos.

h. Der Staigers, Cornet s010

with Goldman's Band

8 to 10.30 p.m. Chinese pro

Det gramine.

0 p.m.--Weather Report.

10.30 p.m.-Close down.

8, Des Voeux Road Central

(Entrance Ice House Street)" Telephone C. 4648.

Simplicity itself

One-motion tuning. Strin circuit. Units all inter

able.

There's

Victor

Radio