1931-09-17 — Page 2

HONG KONG DAILY PRESS, THURSDAY, SEPTEMBER 17, 1931.

EVERYTHING

TABLO

GE.C. ELECTRICAL

your guarantee

GECOPHONE ALL-ELECTRIC RADIO SETS

and

RADIO GRAMOPHONES SPEAK FOR THEMSELVES.

DEMONSTRATIONS DAILY

from 11.00 a.m.

All apparatus to the value of £5 or over can be supplied on hire purchase terms.

Free service for 3 months

G.B.C. SHOWROOM Queen's Building, Chater Road, Hong Kong

sram Valves

PURITY OF TONE

Listen!-

If you want Best British

Components, it is undoubtedly

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FEATURES

A TELEVISION GOOD NEWS FOR

DEVELOPMENT.

BRITISH SETS TO BE MADE

· ̈IN-U.S.A

ately in the United States.

AMATEURS.

RADIO SERVICE.

SUPPRESSION OF LOW OR note suppresagra, By using a low

·HIGH NOTES.

HOW TONE IS adjusting the reproduction for the THE LIFE OF A VALVE, conflicting needs of speech, and CONTROLLED.

music,

A good average life for the early Not all tone controls are high-type of dull-emitter was about a

year, by which time if the fla frequency choke instead of the con- ment had not actually burnt out, denser in serica with the variable the emission usually fell off to such resistanco, low notes can be sup pressed. This means, that the tone a rained. Usually there is only just onough low-note reproduction to give antisfactory balance to high notes For this reason lone con trol is more often applied to the suppression of the high notes than of the low.Amateur Wireless,

To meet an ever-growing demand London, August 14-Negotiations in Hong Kong for officient Radio

Quite apart from volume control, have been concluded whereby the Service Mesars. Arnhold have open-

modern sets often include a device mase-production of Baird Television of a depot at 81, Bonham Strand for modifying the tone. So-called sets in dobe started almost immedi- East, telephone 90313, where re-tone controls are Atted extensively

to radio gramophones. pairs and adjustments to wireless sets will be promptly attended to under expert European supervision Whether you are already an owner of a wireless set or whether you aro merely interested in wireless- as every one is now-a-days-they can help you.jav

A director of Baird Television, Ltd., London, is sailing in the Bremen for New York to-day, and Mr. J. L. Baird, the inventur, is to follow him shortly to put the work in hand. There will be an | all-British staff Ag

"This is the most important step

If you desire to have wireless

→First of all, what do we mean by tone! As a rule, low-toned repro- duction means absence of high

production means absence of low notes Conversely, high-toned re

notée. From this point of view, tone control is simply a means of suppressing either high or low notes, an

With suitable components: it is

GRAMO-RADIO NEEDLES,

degree that the value was hardly worth the current it consumed. Nowadaya tha modern valvo will, under normal conditions, last for anything between 3,000 and 5,000 hours, which on en average of 3 hours use each day, gives an ac tive life of between 3 and 5 years, Of course, there are exceptions, and valves made ovon two or three youra ago, do not always come up to this standard.

A pick-up is usually designed to

The beat way to test a valye for.. work with a needle of a definite senile decay, e, falling off in

forward in the business dense that installed in your home they will quite prhoticable to do either; but, po and a needle having very dif-electron emission is to replace it

has yet been made in television,!!.

aubrait a list of sets obtainable. said Mr. Baird last night, locally according to the amount Naturally I am very pleased you wish to spend and will arrange about it, for although it does not mark any now, technical develop erect a suitable aerial for you:

In such cases they make no ment it seems likely to open UP charge for their services; you only an entirely fresh outlook. Before

the end of this year our American pay for materials, supplied. possible points. It consists of a

For a quarterly subscription of

ferent characteristics ought not to

the makers are to be obtained judge by results be used if the results intended by temporarily by a new one, and

But there are certain records which seem to need rather speciali CHANGING THE GRID BIAS. attention Afer quality being

grid bies on bny output or power It is not advisable to adjust the

company should be in a position to 85 paid in advance they offer you resistance. The action of this series having a selection of them. Many valve whilst the ace is actually in

supply all demands for televisión: ↑ sots at a substantially cheaper |price than the £25 for which a' set:

can now be bought.

the following advantages:quite easily.

1.-If you have a break-down or trouble of any kind 'phone 20513choson that its impedance is less 18. surprising what wide differences. by the action of the negative

f

are high-note suppressors. By pro as a rule, we find that tone controls gressively reducing the high note response of the receiver we obtain the effect of a progressive lowering of the final output tone.mat frot is shunted across one of several sorts of needles that you can hardly

secured by using a special needle. The high-note filter or tone con-

There are so many maken, and condenser in series with a variable try them all, but it is well worth

interesting tests can be carried cat operation. A power valve is de arrangement- can be understood

The relative strength of the high signed to pass a much heavier cur- Let us consider the action of the and low notes depends to an ex-rent than any other valve in the tent upon the type of needle and. it set. Normally this is choked down condenser. Its capacity is 60

"Just how great the demand will wireless fitter to put things right. the tone control is connected.

and they will send you an expert than that of the circuit across which in tonal qualities can be detected

by trying various needles. be it might not be safe to predict-Your incur no extra charge which the tone control

With the finer necdies a grip Examples of the circuits across ought to be used. If the pick-up But the Americans are very keen for their services and only pay for ahunted are the pick-up, primary of affective weight of the pick up arm has a device for adjusting the and they have the advantage of materials supplied. They guarantee the output transformer, and the upon the record, then this ought to being able to do television broad such materials to be of the best winding of the loud-speaker. bo regulated according to the type casting all day long."

As the impedance of the tone con af needle. With some types the trol at the higher audible frequen-effective weight can be very little. cies is chosen so that it is slightly less than of the parallel circuit, the high notes kro by-passed through the condenser, and there The batteries will be collected foro not through the pick-up, from and delivered at your house transformer, or loud-speaker. under their own arrangements, A given condenser capacity has disposal without any further obliga-ed for any particular frequency. 4.Their expert advice is at youran impedance that can be calculat tion on your part, and they shail Obviously, a progressive by-passing be pleased if you will consult them of high notes implios a progressive as often as you like or any matter variation in the condenser's imped- connected with wireless,..

Mr. Sydney AT: Moseley, the director of Baird Television, Ltd, who is leaving for Now York to-day, will do so in company with Mr. Lean Osterwoil, the representative of American banking interests which are financing the undertak ing. "Mr."Osterweil and one of his colleagues came to London recently to disenes the details of the mass production plan.

I

quality and at reasonable prices,

3.If your set is battery-operated terme can be arranged with them for the regular charging and ex- change of batteries....

HAVE YOU HEARD THESË? ·

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 get suitable for re- deiving auch signals, Success in picking up these stations also depends very largely upon fav- ourable atmosphoria conditions... Beadors 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.

WAYO length (Metres) Station

200 Manila 277 Shanghai

Call

Kilo Sigu eyole KZI.B. 1,153 K.S.M.S... 1,093

870

850

840

345 Tokyo J.O.A.K. 333 Hiroshima · J.O.F.K. 355. Hong Kong Z.B.W. .846 357.1 Bombay V.U.B. 261 Sapporo J.OLK." 890 306 Keijo J.O.D.K. 820 370 Nagoya J.O.UK. BID 370.4 Calcutta

800.0

V.U.C.

380 Kumamoto, J.0.0.K.. 700

300 Sendai

395 Dairen

400 Osaka

410. Cantos -480. Manilata

SHORT-WAVE STATIONS,

07.63. Dobints (Germany)

KILO

· 3.0.H.K.. 770 J.Q.A.K. - 760 J.O.B.K....750 C.M.B. 739 K.Z.R.M. 025

TIME (HOND Xeno) U

...WORKING,`

4,434 Mon, Wed. & Fri, 0 ÿ. & 2 sam 4,0906-30 pm.

6,000 Tues, Laura, Sat, 8 p.. 6,898 Bunday midnight

7,143 Dally 6.30 p.m. & 11.p.m. 7,810 Not regular

7,750 Daily 11

9,280 Nos regular,

HSAPJ. 8,108 Tuss. & Fri, 0 pm-1 mil 2.E.L.

W.2.X.A.F.

1,603 Not regular

STATION

CALL SIGM

AFF. 60.12 Khabarovsk (Russia) | EA97. 56.7

Nouony

·A‚G.J.

6,091 Not regular

59! Monca

B.F.N.

49.6. Bome

1.M.&.

42.

Parth

6.A.G.

41,8

Bingapore

V.6.1.A.B.

15.8

Kootwijk (Holland) POL

17

Bangkok (Blam).

83.6

Bydney

31.55 Melbourne

81.48 Bahenootady

$1.20 Bindhawan (Holland) P.C.J.

81.28 Sydney

2.3.0.

SL

Nairobi (Kenya)

23.5 Bydney

S.ME.

10,626 Not regular

27,9- Bendoong

P.L B

25.68 Chelmsford (England)}{5.5.W."

24.0 Manila

KLXR

28.35

Bohansstady

18,88 Bandong

118,4 Hootwijk (Holland)

174 Bandoung

10.0

Bangkok.

PLG. P.CL P.L.F. 1.8.1.P.J.

PLE-

9,580) Dally 7 Kam.

9,820Fri, 9 am, Bat. 3 a.m, & 10 a.m

1,600 Not regular

0.677 Midnight daily

11,020 Midnight-8 am daily

11,761 7.80 p.m. & 3 a.m. daily, except

Saturday and Sunday

12,240 Nightly W.2X.0.4 12,850 4m. Wod, Fri, Sat'

16,102 Dally 6.30 pm. to midnight 16,304 Daily p

P.C.K Kootwijk (Holland) 10.0 16.74 Bandong 15.6 Nanny (France) 13.98 Pittsburg

17,280 Daily 8 p.m. to midnight 17,761 Sunday 7 pm, & midnight 15,404 Each afternoon

19,120 Daily 5.30-7 pm 10,851 Daily B

W.6.X.K. 91,440 Net regula

[Allowance must be made for '“"ummer time" in most Puro pean countries,' which is one hour ahead of trus time.]

ance...

can be

If we connect a suitable resiste ance in series with the capacity, the impedants of the series ar rangement can be varied by alter- ing the value of the resistance. It is easier and cheaper to vary high resistance than to vary a large capacity. That is why high-note filters for tone control always utilise a condenser in series with a yariable resistance.

Condenser Values,

Values of the fixed condenser and the sorica variable condenser depend upon the position of the filter in the set,

Across a pick-up, for example, we might use a condensor of .001- microfared and a variable resistance of 50,000 ohms. These values sto subject to modification. A larger or smaller capacity may be needed with some pick-ups to enable a sufficient range of high-note sup pression to be achieved.

Many pick-ups have a peaked response at the high frequencies. While, this is a great advantage with some records, it means a large degree of needle scratch with others. The suppression of the high notes also eliminates scrotch, which usually has a high frequency.

the

If the tone control is wanted across the output transformer-that 38, across the primary winding--the condenser may have a value of .01 microfarad and the resistance 50,000 ohms.

For done controls across the loud speaker the capacity of the “con- denser may be between 02 and .05 microfarad. As before, the variable resistance should be 50,000 ohmsi Tho value of the resistance is not really oritical, and the 50,000-oħr Eguro is suggested only because it provides a good variation in the impedance of the tone control, and and therefore enables a wide range of tone to be obtained;

It must be emphasised that the above values are only approximate) but they re sufficiently accurate to form a basis for useful experi | mente;

As a rule, it is ben to introduce the tone control late in the ro ceiver, because otherwise, the am plificatios of the initial suppression rather tends to ruin the reproduci tion.

The suppression of high notes. makos the tone mellow, and this is often a good thing when music is being received; but for speech the desired crispness, is obtained Fonly whoa the Tall-complement at high notes is reproduced. Although kond, control is not essential, it

is certainly an excellent means of

charge on the grid, but if the grid is left free, for any perceptible, length of time, the anode' current is likely to rise to a value that An excessive surge of current may may do some permanent damage. for instance, rain the emissivity of the filament, in which case the valve may just as well be scrap- ped.,

Silver —Marshall Engineering Features

All Electric

Superheterodyne

RADIO

FREE SERVICE

TO PATRONS.

FOR

Advanced 1982 Models

8-TUBE SUPERKETERODYNE

CHABBISA (3-SOREEN-GRID & 2-245 TUBES)

TONE CONTROL LOCAL-DÍSTANOR SWITCH EXTENSION SPEAKER JACK TEN K.O. SELECTIVITY SENSITIVITY REDUCED

NOISE LEVEL ILLUMINATED

DRUM DIAL

FULL TONE

MOVING COIL SPEAKER

NO REPEAT POINTS——

No OSCILLATION

COMPACT SIZE

CHASSIS ONLY 12.

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TEL. 20071.

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BRING YOUR RADIO TROUBLES TO THE

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· NOW OPENED AT

51, BONHAM STRAND, E. (Phone 20513), UNDER EXPERT EUROPEAN SUPERVISION

Do you own a Wireless Bet or are y thinking of buying one?...

In either caso,

WE CAN HELP YOU. Write or phone tong pamphlết givi full particulars subscription termi.

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