1930-09-18 — Page 2

INDUCTANCE

HONG KONG DAILY PRESS, THURSER

SEPTEMBER 18, 1930.

RADIO

FEATURES

AND THE

LOW

FREQUENCY TRANSFORMER.

AN EXPLANATION OF A USEFUL COMPONENT.

[By COHERER.”]

BROADCASTING FOR

THE EMPIRE.

HOW THE NEW 5S W COULD BE ESTABLISHED,'

WIRELESS FOR THE BLIND.

FUND £25,000 SHORT.

More than 10,000 homes of blind people in England will be without It is understood that a definite wireless oring to the inadequate scheme of Empire broadcasting will resources of the British Wireless be laid before the Imperial Con-for the Blind". Fund. This state- foreace when it assembles in Londonment was issued by the fund's towards the end of this month. committee at the close of its meet

The scheme already tentativelying last month. drafted embraces a great increase in the power of the Chelmsford short-wave station, the provision of

Beyond the furt that the low is employed, wound in the form of These losses in a transformer, a coil with an iron centre. Induct-although some are unavoidable, are "frequency transformer is a means of coupling two valves with ampliance also plays an important part for the most part the result of in tuning coils, chokes and loud cheap wire, badly wound coils and acation, little is known to the aver- age wireless amateur of the action speakers; its unit is the Heary, inferior iron used in the care. As or construction of this useful milk-henry being one thousandth the lose of electrical energy is article. Depending for its action part and the micro-henry a mil transformed to heat it will be appractical re-arrangement of the parent that the best makes of trans-hours of broadcasting as will give on mutual induction, it will be as lionth part.

formers are cheapest, the action of heat in such a very fine wire cans the oversea States of the Empire a well first to discuss this principle

at parts of the representative service at the most ing a "burn-out on which such a great deal of

windings which cannot be repaired.. wireless theory is based.

Mutual Induction,

an

Transformer Construction. The low frequency transformer is constructed of two coils wound ont upon the other, insulated from each

iron. The first or primary col takes the current in its first stage being connected to the anode of the proceding valve.

rh

Maina Transformers.

A sequence of changes in theiher and based upon a core of soft The current flowing in these coils being very small, it is possible to flow of current in any vircuit will

use a very fine wire and thus get a give rise to a magnetic effect or

useful transformer into quite a small compass.. It will be noticed field of force around that circuit,

The alternating nature of this that the transformers used for It is obvious then that with.

current sets up a strong field of stepping up or down the mains oscillatory or alternating current farce into the immediate surround supply to suit the voltage of ao considerably this effect is always present so longings which is absorbed or induced all-electrical set are

by the secondary call in the form larger and heavier. This, of course, as the current is switched on, while of a similar current of a power is due to the fact that a much with a direct current it only takes depending on the ratio of the turis thicker wire has to be employed to place at the second the current is of the two coils. The usual prae stand up to the heavy current ap-

tice in receiver design is to emplied to it. switched on and off. This quality play transformers, with a step-up in a conductor is termed inductance ratio of two, three or four to one, and its ability. of inducing or, pass in which case ing a current in a nearby conduc-secondary are greater than those of the primary by that ratio: Actual ly the turns of the secondary are made slightly in excess of the ratio the transformer is designed for, & margin having to be allowed for certain losses of energy in the trant ference of power.

tor is termed induction.

A short straight length of wire has little inductance but the in- ductive effect is greatly increased when a considerable length of wire

}

The

Transformer Uses,

A survey just completed show that 18,000 homes require rots and that the cost of supplying them will be at least £45,000. The fund a second wavelength, and such is still £25,000 short of this amount, and the committee last night issued an appeal for help in order that distribution of sets might be main tained..

convenient hours.

About 4,400 sets have already been given to blind persons. Up to the present time the committee Many difficulties lie in the way has receited £15,000 from the gen of such & service if it is is to be eral public, 1,000 sets -from really effective. The two chief obradio trade, and an engagement stacles are the cost and the time gift from a gentleman who offered factor.

to provide sets to all. blind re- sidens of Gloucestershire.

Strange Finance.

The former, a technical correspon- dent points out, could be met, in part if not wholly, by a more reasonable apportionment of the fees paid-by licence holders. There is a popular misconception that these fees, which at the present moment approximate £1,500,000 per

annum, go to the British Broad- casting Corporation.

The actual fact is, however, that aconsiderable proportion of this sum is filched by the Post Office and

che Treasury.

the turns of the A transformer only being set in action when an alternating current is applied to it, it will be seen that the passage of a direct curreat'

The point at issue is that the through the primary will have no effect on the secondary. Thus it is B.B.C, receives only 64.2 per cent. that although the primary of a low of the licence revenue, the other frequency transformer used for in- 33.8 per cent. being shared between tervalve coupling has to provide a the Post Office and the Treasury path for the high tension (D.C.) The B.BC. is even worse cff than passing to the anode, it is only the these figures show, for, aftor pay signal voltage that is transferredment of income tax and allowance to the secondary and so to the grid for depreciation; its net income is only 57.7 per cert, of the total sum. of the next valve.

EVERYTHING 9.E.C.) ELECTRICAL

your guaranter

TENACIOUS COATING

KEEPS YOUR SET

AT PEAK PERFORMANCE

It's not the filament ut the coating

on it that counts

MADE IN ENGLAND. Sold by all Wireless Dealırs.

Osram

Valve

A similar useful purpose is served by the output transformer som times employed between the cou- pling of the last valve and the loud-speaker.

To protect the vindings of a loud. speaker when a powerful set is used, it is the practice to connect the last valve to the primary of a trans- former, the scndary being can Bected to the lond-speaker, this instead of the usual practice of con- "necting the loud-speaker between' the high tension positive and the anode of the last valve.

Only the signal voltage is requir- ed. to drive the loud-speaker and by the transformer coupling the isolated. high tension D.C. is Especially is this method useful when a long length of wire is used between the set and the loud- speaker; a "high potential running. through this wire will eventually cause leakage in insulation with consequent drain on the high ten- sion supply:

SOME USEFUL HINTS.

One of the best ways of testing the condition of a low-tension ac- cumulator is by means of a hydro- meter. Instructions for use are supplied with the instrument.

*

Although tap water is sometimes. used to renew the level of the elec-" trolyte in an accumulator, its use is risky, and distilled water. (ob- tainable at any chemist's) is far better.

If your outpat filter is to incor purate only one condenser instead of two, be sure that its insulation.

is above suspicion, as it will have to bear the full voltage of the H.T. neross it.

Ovalves

with the "TENACIOUS

COATING

WRITE fü "OSRAM WIRELESS GUIDETM (1925 Edition). Seni

Oro of the lesser-known edvan- tages of an output filter circuit for: the loud-speaker is the fact that it frequently improves stability.

The core of a maing transformer should be earthed, and should be the double-wound type in which the winding that is in direct connee- tion with the supply mains is effec- tively separated from all other winding, either by an earthed metallic screen, or by imanlation capable of withstanding 1,000 valts

AC.

A rattling on your loudspeaker is sometimes caused by a small nut getting loose.

A common cause of bad humming noise is frequently caused by a break in the earth lead..

Oficial Loot,

Last year the Post Office took £183,760 and the Treasury £341,049.

(flentinued on next Column, ́~

the

During the past three years the Post Office has taket £496,198 and the Treasury Less,851 of the public's licence fees, sums far more than enough to put the Empire broad- casting scheme on a satisfactory and

permanent "basis.

The time factor presents difcul- ties not so easily adjusted. It means, in effect, that broadcasting would have practically to be con-

tinuous for twenty-four hours if all parts of the Empire are to be served. This, in existing conditions at any rate, is out of the question,

but it would be quite possible, given a fair financial basis, considerably

Announcing the Arrival of

FIRST SHIPMENT

OF

ATWATER KENT.

RADIO

The Very Latest in Modern Screen Grid Radio; Distinquished by

COMPACTNESS, SIMPLICITY AND TONAL PERFECTION.

Every Set Carrie's a Warranty from Manufacturers.

You have known the Name of Atwater Kent, But have You seen the Famous Apparatus?

Come and Then Inspect It.

to extend the present broadcasting THE SINCERE Co., Ltd.

hours."

An addition of four hours to the broadcasting now takes place on normal eleven hours during which week-days would be a substantial contribution towards the standard

ultimately aimed at. It would be impossible, however, without a much fairer allocation of funds that ob- tains at present.

HAVE YOU HEARD THESE?

Here are lots 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 re- ceiving such signals. Success in picking up these stations also depends very largely upon fav. Durable atmospheric conditions. Readers are invited to add to this list should they succeed in picking up any station not, in cinded in either of these lists.

LONG-WAVE STATIONS.

Wave length

(Metres) Station 260 Manila N

277 Shanghai 280 Tientsin 310 Shanghai 320 Peping

Call Kilo Sigu crele E.Z.I.D. 1,153 R.S.M.S. 1,085 C.R.C. 1,070 K.R.C. 967 C.O.P.E. 948 870

345" Tokyo . J.O.A.K. 353 Hiroshima J.O.F.K. 650 355 Hong Kong Z.B.W. 846 357 Bombay V.U.B. 840 361 Sapporo

J.O.I.E. 330 303 Keijo 370 Nagoya 370.4 Caloutta 360 Kumamoto 390 Sendai.... 355 Dairen 288-Rangoon 400 Osaka .420 Canton 413. Manila

SHORT-WAVE STATIONS.

STATION

CALL BIGM

67.45

30.

Dobinte (Germany) 60.19 Khabarovsk (Russia)

Nanen 60.7

Moscow

A.F.K. B.A.97.

AGJ.

40,5

Kome

Perth

418

Singapore

87.

89.8 Kootwijk (Holland)

Bangkok (Biam)

824 Sydney

81.55 Melbourne

6.A.G.

7.9.1.4.8.

F.C.L.

HSA.P.J.

KILO

CYCLES

J.O.D.K. 820

·J.O.C.E... 310 V.U.C 809.9 3.0.G.K. 790 J.O.EE. '770 J.D.A.K. 760 V.U.E. 751 JO.B.K. 750 CM.B. 738 "K.Z.E.M. 728

TIX (Hong Koxe)

OF WORKING

4,434 Mon, Wed, & Fri, 6 pan, & 2 a.m. 4,900 6-10pm,

6,291 Not regular

6,000 Tues, Chars, Bst., 6 pm.

6,803 Bunday midnight.

7,142 Daily 6.30 p.m. & 11 p.m.

7,310 Not regular"

7,780 Daily 1 p.m.

8,108 Tues, & Fri, 0 p.m.-1 a.m.

B.J 9,230 Not

3.1.0. W2.X.A.F

Schenectady 81,48 Band (Holland) F.C.

81.20

81.28

81.

Sydney

(Kenya):

28.6

27.8

25.62

7.LO

2.ME.

PLE.

d (England)) 5S.W.

248 Manila 22.35 Schenectady 18.88 Bandoeng

Kootwijk (Holland) 184 .17.4 Bandoeng

10.9

Bangkok

16.88 Haizon (Holland) 16.8

Kootwijk (Holland)

15.74 Bandoeng

15.6 || Naney (France)

18.93 Fitteburg

0.003 Not

9,620 Dally 7.

9,620 F-18 m., Sat. 8 am, & 10am.

9,500

Not regular

6,677 Midnight daily

10,628 Not regular

11,021 Midnight-3 am, daily

11,76130 Saturday and Sunday

& 3 m. daily, except

K.LIB. 12,240

W.3.X.O PLC.

4 Am. Wed, Fri, Bat Dally 0.30 p.m.

to midnight PCL18,304 Dally 7 pm,

*PHI POK

P.LE.

17280 Dally 8 pm to midnight 17,761 Sundays. 7 p.m. & iidnight 17,769 | Dzily 10 p.m.

18,40% Each afternoon

10.22 Daily 5,30-7 patt

19,861 Daily Bam.

| 21,60|||Not regular -

[Allowance must be made for "simmer-time in mort Euro- pean countries, which is one hour ahead of true time.]

SOUTH CHINA SOLE AGENTS.

A RADIO

THE

LOEWE FE 63.

tube set

the most

A new shipment, just arrived, is one sensitive instruments for long distance and recep- tion with six stages of high frequency,

This set is fitted with new Barium tubes and requires a Frame Aerial only. Can also be used with LOEWE short wave attachment.

Newly arrived

Loud Speakers of various types.

Pertrix Batteries 150 and 100 v. Gramophone pick ups of best quality.

Gramophone Electric Motors.

B Eliminators a speciality to fit Pilot Super

Whasp and any other sets.

Demonstration Hours

11-11.30 am.

12.30-1.30 p.m. 5-5.30 p.m. Daring demonstration hour expert European advice. is given on all Wireless matters.

THE

CANTON TRADING ASSOCIATION, LTD.

CARL SCHROTER, Manager-

5TH FLOOR, CHINA BLDG. TELEPHONE 24610.

ri