1931-08-13 — Page 2

HONG KONG DAILY PRESS, THURSDAY, AUGUST 13, 1931.

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FEATURES

PURE TONE AND HOW TO GET IT

HIGH-FREQUENCY AND DETECTOR SIDE OF SET CAN

#ZUCAUSE DISTORTION.

If for some unaccountable reason, a set won't give good undistorted results when first made up, or if it deteriorates after a while, the average owner immediately suspects the low-frequency side or the power supply. This is because he realises that if the high-tension drops the purity is bound to fall off, and that if, as power valves do not improve with age, the output cap abilities of set decrease after a while, it is the low-frequency side which should be suspected.

the right impede, and with these values it is general to have a low impedance valve of about 10,000 ohms,

Power Detection.' With any of these non-distorting schemes there is a snag and in the case of power detection there is the trouble that with a valve of a low impedance, working with a more appreciable positive bias the anode current may be as much as milliamperes, and an H.T. voltage of 100 or even 150 may be called for.

''ן

TO-DAY'S WIRELESS

PROGRAMME.

BROADCAST BY Z.BW, ON

355 METRES.

11 to 11.30 am-Stock quotations, 11.30 ..--Chinese programAJO. 12.30 p.m.-European programine. 74 p.m.-Local time and weather Li" report.

1.30 p.m.-Rugby Press news, "mail į notice, ste:

ly cut off at the beginning, no amount of faking can reintroduce them at the end, and if the reprosp.n.-Close down. duction appears fair their it is only of Victor and H.M.V. records 16 to 3 p.m.-European programme an acoustic delusion.

supplied by Messra. S. Montric to 0.28 p.m.

& Co.

You should arrange your tuning so that, although it is selective, it does not alter the tone. Inefficient tuning coils may need a lot of re action to make them selective, while a properly designed coil may give In this way it is often overlook

quito 'good selectivity without the ed that the high-frequency and de

This current may be sufficient to necessity for forcing reaction and tector side of a set can equally upset matters if the set is to work | well, be the cause of a bad distoren o battery or an eliminator have thereby losing quality. There is ing a fairly limited output. The always the possibility of using a extra milliamperes is, unfortu band-pass form of circuit. nately, "often, a costly mutter; but

High-frequency valves can cause that is not the end of the trouble.

a great deal of distortion if Transformers following ordinary detectors are designed to give good wrongly used, particularly on fair. characteristics with the usual small ly weak stations, which on a good D.C. current flowing through the set can be tuned in at loud-speaker primary. When the anode current strength with quite reasonable is pushed up to milliamperes

tion.

Just consider the detector valve, first of all, because the points here obviously apply to any set which 'has a valve detector. The average general-purpose, set has a grid con- denser and leak and practically the only exceptions to this are Big quality sets which are made dif- ferently with anode bend rectifien tion, or super-hets, in which it is customary, nowadays to have the first stage of detection arranged on anode-bend lince

41

THE SINCERE Co., LTD. | grid detection of which many people impedance of the primary winding

SOLE DISTRIBUTORS,

HAVE YOU HEARD THESE?

Here are Ilia of long-wave and short-wave stations which... zhould be picked up by anyone in Hong Kong who has a mode rately good set suitable for re- ceiving such sigiais.. Success in picking up these stations also depands ydry lirgely upon tay- curable 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 Jength

Call Kilo- (Metres) Station Sign cycle

200 Manila

K.Z.I.B. 1,153 277: Shanghai K.S.M.S. 1,083 343 Tokyo 3.0.A.K. 870 353 Hiroshima J.O.F.K. 560 355 Hong Kong Z,B.W. 357.1 Bombay 381 Sapporo 268 Keijo 370 Nagora 370,4 Calcutta 360 Kumamoto 3D0. Sendai

395 Dairen

400 Osaka

410. Canton 480. Manila

SHORT-WAVE STATIONS.

STATION

CALL BIGN

67.65 Dobints (Germany)

A.F.E

60.12 Khabarovsk (Bustin) EA.07.

GO.F Navenw

12.

· 41.8

26.8

87.

Mosco

Bome

Perth-

Singapore

Kootwijk (E‹dland)

Bangkok (Sam)

KIvo

CYCLES

840

though, as it is with a power purity. Screened-grid valves are detector circuit, the transformer frequent offenders because they are primary, may be overloaded as this sometimes operated on a badly steady D.C. current saturates the chosen part of the characteristic. Then, of course, there is power core. This result of this is that the

Trace out the grid circuit connec of the transformer is reduced, betions of your screen-grid valye and cause of the less effective iron core, break the return lead to the nega and then distortion creeps in.

tive of the flament. Insert a small. Because this saturationis

∙12-volt constant, the distortion is not con-

here, or, alternatively, cell stant, and the cure, of course, is to take a flexible taping out to the fit a transformer designed to, have grid-bing battery god for the low, suitable primery inductance value quency side of the set, You may

speak, because it is a comparatively modern erare, without knowing much about it.

It is, unfortunately, only too easy to over-load the average leaky grid detector. The grid of the valve is connected through the leak to the positive side of the filament and a small amount of grid current flows One is apt to pay too little atten tion to the proper values of the

дос

:י.

at the higher D.C. current of 5 find it necessary to put a small milliamperes; alternatively, you condenser across this grid bias grid condenser and leak, and it can fit a by-pass circuit with a tapping, to keep the H.F. currents forgotten that in order to prevent LF. choke designed to carry this distortion due to the grid current current or, in some cases, a resist flowing the values of the grid con-

ance may be used. denser and leak have to be chosen with care.

No matter what remedy is made, the cost goes up because of the extra parts needed. In general, therefore, if you know that distor

drid-Leak Values, Formerly a .0003 grid condenser and a 2megohm leak were used without any question, but with some tion is caused by the detector stage of the dew detector. valves more try altering the grid-condenser and satisfactory working ia to be had.

condenser should be close to the away from the battery, and this

H.F. side so that the H.F. currents are by-passed long before the bine battery is reached. A 1-microfarad fixed condenser is emple.

give two other distortion troubles. High-frequency valves are apt to

They are apt to pass on stray high- with a slightly lower value of grid leak values, but do not get too near frequency. current which upset the leak, say one-megohm or even less, to power detection unless you can working of the detector and low- and a grid condenser of smaller afford to run such a circuit,

frequency stages and, secondly, be capacity; any .0032.

With all circuits there is the cause of the

enormous amplification

6

Band Belections.

Suite Francais? (Foulds).-The Band of H.M. Coldstream The Bells of St. Malo" (Rimmer).

Guards.-B9751/B2752,

TELEVISION FOR THE MILLION."

DEVELOPMENT PLANS IN

AMERICA.

Some of America's, best electrical and wireless experts, working dur- ing the past your in the Victor Talking Machine Laboratory at Camden, New Jersey, have evolved a television set which is comparable "with the carphone "tago

broadcasting.

Hundreds of American wireless amateurs are now putting it to nightly tests.

By the end of next year the sit will be placed on the market-till in the crystal set" stage-by tlio Radio Corporation of Amerien.

By the end of 1933 it is expected will be in many thousands, perhap that its greatly improved successor

millions, of homes.

It is intended to bring the net Remuer Fidelis March (Sousa), to perfection, and to commercialise -The Band of H.M. Coldstream it slowly, because it cannot ha Guards.-:647. Manured in the public service of foreseen what changes may be Chal Romano Overture" (Ketel-broadcasting, or how such huge hey).The Band of H., Cold vested interests as the screen and stream Guarde.-B2500,

the stage may be affected:* 6.99 to 6:49 p.m.-

25,000,000 UESTS.

}

Poem

✓

Organ Solos, (Fich).

An Autumn Serenade" (Becce)

Reginald Foort.-E2388. "Schon. Rosmarin" (Kreisler).;

A Brown Bird Singing" (Haydn Wood). Reginald Foort, B2334

Souvenir di Valentino" (Wood). Valse Mysterieuse (Meale).

-Arthur Meale.-B3060,

The Radio Corporation, which, with the General Electrio Company and the Western Electric Company, |practically, controls thei field, han prepared for television develop ments by acquiring control of the. National. Broadcasting Corporation.

Television transmission stations 'will be erected on top of the new Lexington-avenue, New York, and £fty-storey R.C.A building in

"on top of the new £100,000,000

p.m. Stock quotations, mail""Radio City" which the corpora notice, etc.

6.40 to 7.29 p.D.-

1:

Song-"So Tired."

Song-Out in the New Mown HayAnn Tenn (Comedien. ne).-B2063,

IL

tion is "constructing in New York in co-operation with Mr. John D. Rochefeller, junior, r* p*w**

Another powerful station will be erected on the Pacific Coast, and there will be others in various parts of the country.

Mr. David Sarnoff, president of Orchestral You're Just R.C.A., estimates: the potential

Lover."

users of a national television ser- Orchestral--"Two Little, Blue vice a 20,000,000 in America alone,

Little Eyes."Rudy Vallee and 0 £2,000,000,000 Combine his Connecticut Yankees-22879.The Radio Corporation and the Song Now "You're in My Western Electric Company have a

Arms.""

practical, monopoly of the.processes If You Should Ever Need of wound recording and reproduc Me"-Gene Austin (Tenor)tion, and are closely affiliated with all the leading American film and Orchestra" Maria, My Own."" Orchestral Siboney"÷Alfredo estimated that the total capitalis

theatro companies. It has been Brito and his Shoney Orch.

Song

22697.

22665

Song By the River Sainte

Marie," Song- Beautiful Love."-Lewis

James (Tenor).--22693. 7.20 to 8 p.m.--

Etudes, Op. 10" (Chopin). Played by Wilhelm Bachaus M-43,

Pianoforte Solos.

8. p.m.-Local time and wenther

report.

concert. 8.03 to 10.30 p.m.-Chinese studio 10.30 p.m.-Rugby mid-day Press

news.

10.33 p.m.-Close down. J.O.C.K. 810

V.U.B. B40 J.0.1.K. 830 J.O.D.K 820 V.U.C 609.9 J.O.G.K. 790 J.0.H.K. 770 J.Q.A.K. 700 J.O.B.K. 750 C.M.B. 739 K.Z,R.M. 025

Tix” (Howa Kona) OF WORKING

A.G.J.

5,201 Not regular

REN.

1.M.A..

6,000 Tuek, Thurs, Sat., pan, 6.898 Sunday midnight

6.A.0.

B.C.L

V.8.1.A.B.

B Sydnoy! 2.B.L.

31.55

Melbourne

81.48 Schenectady

93,20

83 18

7,142 Daily 0.80 p.m. & 11 pm 7,810 Not regular

If you suspect that detector stage

SHORT

tion of all the interests involved in the huge electrical, wireless, gramophone, music, theatre, and Alm combine is not far short of £2,000,000,000.

::

"The immediate problemia before what it is convenient to call the

to transmit pictures, and with the televisiontrast are concerned with finding wave-lengths on which safeguarding of, their vast invest ment in the business of talkie pro- duction and exhibition.

The wavelength problem can probably be solved without much diculty in America, but it will be R extremely difficult matter in Europe, as television, in the course of time, will be an all-day feature.

WAVE RECEPTION

Use A

chance of getting distortion through possible with modern valves, the NATIONAL “SW 5” THRILL BOX

of your set is causing distortion, then you can try a 1-megohm grid ultra sharp tuning. Because selec leak and you can also fit a .0005 | tivity-is so badly needed nowadays maximum pre-set condenser in many set users are apt to forget place of the present fixed can how truly charp their tuning is denser. The pre-act condenser Tuning, in general, is far sharper does not cost much and you'

The average single circuit tuner,

4,431 Mon., Wed. & Fri, 0 p.m.2m have the advantage that you can than it was two or three years ago 4,990 6--10 pm

alter it to suit the valve and de- and unless one uses special circuits, tector circuit. Once upon a time it is easy to cut off the high notes. it was quite common to have a variable grid condenser, but within the past few years we have, un which needs plenty of reaction to fortunately, regarded the leaky make it tolerably selective, is a bad grid detector circuit, as beyond im-offender in this way, provement which is certainly a mistake

7,780 Daily 11 p.m.

i.

HSAPJ 8,108 Tues, & Fri., 0pm-1am..

1,230

Not regular BLO. 0,503 Not regular W.2.X.A.F. 9,550 Dally 7.m.

Eindhoven (OR) £20

Lordnes

Sydney (Koxys)

| 7L0;

9,020 Fri, 8 Bat. 3 am, & 10 am. 0,600 Not regular

81,

0,077 Midnight dally

29,6

2.M.E.

10,626 Not regular

27.8

Bandoeng

PLR

25.68 Obelsford (England) 5EW.

245 Manila

23.88 Bobenectady

16.88, Bandoeng partike

Kootwijk (Holland) Bandoong Bangkok

18.4

174

100.

16B

16.74 Bandpeng?

155

18.03 Pittsburg az

Kootwijk (Holland). Nandy (F)

K.1.X.B.

W.Exo.

•

11,020 Midnight-8 a.m. daily... 11,781 7.80 pp & 3 a.m. daily, except

Saturday and Sunday i

|12,240 Nightly

13,850 4m. Wol, Fri., Sat. P.L.G. 10,102 Daily 6.00 pm to midnight P.O.L 16,804 Dally 7 pm P.L.F

17280 Dally 8 pm, to midnight FLB.1.P.J. 17,781 Bundays7 p.m. & midnight P.C.K

18,404 Each afternoon P.LE. 10,220 Daily 30-7 p.m.

19,851 Daily 8 a

WS.KK. -1540 Not regular

Allowance must be made for "summer-time" In most Euro- pean countries, which is one hour ahead of trus time.)

detector is needlessly overloaded.

HF. Troubles..

The first trouble can be prevent- ed by having good H.F. choke ar

11

rangements, and d perhaps, a stopper resistance in the grid lead of the fixat low-frequency valve after the detector. Also an EF stopper circuit can be included in the. anode lead of the high-frequency valve. If the H.F. valve is a three. electrode with aperiodic choke

Power-grid detection, like anode

As one comes near the oscillation coupling, ne is popular in many bend

detection,

withstandpoint and the heriál damping is transportable sets, then the provi greater signal voltages than the reduced, by slacking off any series sion of a stopper circuit often im ordinary leaky grid circuit with capacity in the serial lead, there proves the quality. the usual values

CIT

High-note Loss.

is, noticeable loss of high notes.

The second point, overloading of A power-grid detection circuit has if the set hus, a low frequency ride the detector by the H.F. salve, can the same connections as the leaky which does not give greater ampli be cured only by fitting an H.F. grid, but a still smaller condenser, ficdtion on the lows than on volume control. This can be a .0001 microfared as a rule, and the "high, this H.F cut-off effect rheostat in the H.E. valve filament

Etill maller grid look about anywhunteracted by the low lead (it should-be i -megohm-are used. It is import frequency may sound reasonable side), or an “aerial ant, too, that the valve should have but as the higher tones are definite-trol may be fitted.

ALL MAINS RECEIVER

Range 14-550 Meters

AC MODEL TY224

DC MODEL:

RCA 282

-RCA 280

-UX 280

RCA 231

Matched RCA Tubes

Complete Kit for both models are available,

Inspection and Enquiries are Always Welcome, THE WING ON CO LTD.

Distributo

volume con

TEL. 20671.

TEL. 96672,