1930-11-20 — Page 2

HONG KONG DAILY PRESS, THURSDAY, NOVEMBER 20, 1930.

RADIO

FEATURES

CHOOSING RADIO BATTERIES.

LOW-TENSION ACCUMULATORS.

PRACTICAL HINTS ON THEIR SELECTION.

During the course of three or four amateur spends yvare the average much more on buying H.T. bat- teries than he dora on accumulators But for supplying low tension.

I think most of us will agree that the accumulator is the greater nuisance.

It is convenient to get, ante many well be so where a two-valver employing only two 1 valves. isusulator harged regularly every nouth, for it is an interval of time concerned.

that is easily remembered. Also, The ordinary Loolanche, such as is used for supplying current for the beginning of the month especi house bells, will not do the job pro-ally always seems to bring with it perly, and there are several firin many other things that have to be that market wet typo Leclanche done. batteries specially designed for radio purposes:

Another Alternative. You want two cells to supply one or two two-volt valves, and as the pressure developed by such a

One does not want to buy an ne. cumulator that will last more than one month per charge, for regular charging is essential for the good health of the battery. One should work out, approximately, how many hours of listening, or hours of ne

pen in a month.

Having bought an H.T. battery and connected it to the sot, apart from an occasional voltage test, it givos no trouble at all, until, after sone months, it begins to run down, and the question of replace-battery will be three volta a filanter use, are likely to haɲ.

ment arisca.

Leclanchés for L.T.

But as well as the necessity of periodical tests, the accumulator also requires periodical charging and topping up and cleaning However, if the mains are not available for supplying LT. an accumulator is generally regarded a being essential, that is, at least, for larger sola.

L

ment theostat is necessary.

Where

1 do not suppose many peopl anything above about a quarter of listen for longer than an average an amp is required it is a good of three hours per day over the whole of the month, so a hundred plan to have paralleled coils.

Complete batteries can be pur-hours ought to cover such a period, chased in stout wooden cases. No although a very keen amateur, who turally they are fairly large and does a great deal of experimenting, fairly heavy, but they will give may impose a greater demand on

L.T. than that. good sovice up to six months or even longer with very little voltage variation. And after that new ele- ments can be obtained at quite rea- Bonable prices to bring the batteries p to scratch again. Batteries of this kind should prove of consider- able interest to country listenera,

An alternative that is well worth considering in the case of smaller receivers in the primary battery, and this can take the form of either & dry battery, similar in all res pects except in size to an H.T. battery, although, of course, only the two or three cells are needed; Awet type of Lealanche cell.

The drez thing one has to do when These really are propositions well cne goes about buying a L. T. aea worth considering, but only, in the cumulator is to determine exaat- Where they what son one requires for the rns of smaller sets. total current required for the filn-job. It is not a good principle to ments of the valves is not above, buy the largest capacity one can say, half an ampere, a primary | afford. Always nima to buy a bat cell may even prove to be an econo-tery that will last just over the mical proposition. Certainly this month for every charge.

01

The

Always Allow Margins. However, ho can always keep a, log for a few weeks in order to arrive at a fairly accurate calcula

tion.

The noft thing to do is to find Even if you have the mins, dea-out how much LT. current the set pite its disadvantages, thero is a takes. You will get a close enough it to be anid for the use of a small figure if you add the rated ean- sumptions of the valves together. acetinulator, trickle charged.

Supposing the set in question is four valver, employing three valves rated at 1 amp, and one 25. This gives you a total of 55 anperes. To get at the ampere. hour consumption of that set over 100. hours multiply the hundred by .55. The answer is 35.

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Thus, you see, our

Four-valver

will need an accumulator capable of an output of 55 nmpere hours.

That is not a usual rating, but 60 ampere houre is to be found in

all accumulator catalogues, and the extra five is a nice little mar gin.

By the way, you should never work down to the last ounce of an Gyvumulator. And in`a paper cal- culation oho must always allow for practical discrepancies in this particular instance the valves may be taking just a little over their specifications

The vokage your accumulator should give depends, of course, upon the voltage rating of the valvos. Nowadays buttery wives are al most completely confined to two- and six-volt ratings (Four volts common rating for mains valves.)

Remember This.

Having determined the ampere- hour capasity required, make sure that you buy an nocumanior that' is rated at the peeded figure for an output of a continuous nature approximating the consumption of your set.

That sounds a little involved; lot us look at it in detail.

The ex- ample we have, taken shows an ac- cumulator of sixty ampere-hours is required. This is to say, aa ne- cainulator which will give 55 am- orea for a period of 100 hours with a few hours of service to spare as a margin.

It is unlikely that you will come across an accumulator that has its jampere-hour capacity rating based on an output of exactly as amperes. A Variable Factor.

You see, the apacity of accumu lator varies with its output · An accumulator that is rated ng liv ing a capacity of 80 ampere-hours should, theoretically, give you one ampere of current for sixty hours; two amperes of current for thirty boure or sixty amperes for bour, or in fact any current for. any number of hours the" sum-of- which is sixty.

ona

But in zetual, practice we find that the capacity of an accumula- for-will vary with its output Gen sally speaking, the smaller the current you take away from an accumulator, the longer it will last Per charge and that is the reason for the two ratings that you come

Up against in accumulators, that

"Ignition" and "Actual."

HAVE YOU HEARD THESE?

Here are Hats of long-wave and short-wave staționa which, ahould 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 depande 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 those'ilsts.

LONG-WAVE STATIONS.

Wave length

Call Kilo

(Metres) Station

280 Manila

Sign cycle K.2.1.B. 1,153 KB.M.S. 1,065 C.R.C. 1,070 K.R.C. 907 .C.O.P.K.

277 Shanghai 280 Tientsin 310 Shanghai 350 Peping

348 Tokyo 1.0.A.K. 870

383 Hiroshima J.O.F.K.

Kong Z.B.W.

30. H9 bar

1137

301

346 Kro

370 ta 370.4

600

840

V.U.B

840

J.O.I.B. 830

820

J.O.D.K. J.O.C.K., 810

V.U.C

800.9

380 Kumamoto J.0.0.K: 700 3.0.H.K. 770 J.D.A.K. 780 V.U.R. 154 J.O.B.K. 750 C.M.B. 189 K.Z.R.M. 798

800 Sendni 345 Dairen 308 Rangoon 400 Osaka 410. Canton 413 Manila

SHORT-WAVE STATIONS.

oury

CYCLES

Tixx (Hona KoNO)

OF WORKING

4,434 Mon., Wed. & Fri., # p.m. & 2 a.m. 4,000 610 p.m.

7,142 Daily 6.80 p.m. & 11 p.m.

7,310 Not regular

7,730 Daily 1 p.m.

HSAPJ, 8,109 Thies, & Fri., 0 pm-1 am.

1230 Not regular

0,803 Not regular

0,530) Dally 78.10.

0,020 Fri. 3 am, Sat, 8 am & 10 am.

STATION

CALL SIGN

67.85 Dobints (Germany)

A.F.K...

60.13 Khabarovak (Russia) 50.7

Naven....

R.A.07.

A.G.J.

5201 Not regular

50, Moscow

R.F.N.

6,000 Taos, Thurs., Sat., & p.m.

43,5

Rome

1.M.A.

0,800 Bunday midnight

42.

Porth

0.A.G.

41.8

Bingapore

V.S.I.A.B.

33.6 97.

Kootwijk (Holland)

P.C.L

Bangkok (Siam)

82.6 *Sydney

2.B.L

31.55 Melbourne

3.1.0.

31.48 Schenectady

W.2.XA.F

31.20 Eindhoven (Holland) | P.C.,

11.29 Sydney

2.F.C.

0,600 Not regular

Nairobi (Kenya)

LO

28.6. 27.8

Sydney

2.M.E.

10,620 Not regular

Baddoeng

P.L R

25.68 Chelmsford (England)

5.6.W.

24.5 Manila

K.LX.R.

23.38 Sabenectady

W.2.x.0.

18.88 Bandoang

P.L.G.

18,4

Kootwijk (Hollanıl)

P.C.L.

27.4

Bandoong

E.L.F.

10.0

Bangkok

H.S.1, P.J.

10.2 18.74 Bandoeng 15.5

Kootwik (Holland)

P.C.K.

13,03

Nanoy (France) Pittsburg

81.

P.LE.

W.8.X.K,

0,077 Midnight daily

11,920 Midnight-3 am, dally

11,781 7.80 pin. & 8 am, daily, except

Baturday and Sunday

12,340 Nightly

13,800. Wed., Fri., Bat.

16,102 Daily 6.80 pan. tó miðnight] 10,304 Dally 7 p..

17,280 Daily 8 p.m. to midnight 17,781 Sundays 7 p.m. & midnight - 18,404 Each afternoon

19,220 Daily 6.30-7 p.m.

| 10,351 | Daily 8.4m.

† 21,600 | Not regular

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

A suitable Telefunken Apparatus for every purpose.

The great advantage of Telefunken sels perfect tone-reproduction of long range transmitting stations.

TELEFUNKEN 31W

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TELEFUNKEN 40

The long range All-Electris receiver with station selector will give you many stations. without outside aerial. Ow ing to its simple operation: and high production, the most popular receiver of its class. With the Louds speaker Arcophon 5.

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LONGEST EXPERIENCE-LATEST DESIGN.TE

The ignition rating refers to the For demonstration and particulars apply to

capacity of an accumulator to give

anali currents at intermittent bureta, as in running the ignition coil of a motor car. The actual capacity of an accumulator is its connaity to sunul current of a

period.

(Continued “on Page 3.)

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RADIO BATTERY SERVICË.

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