1932-06-02 — Page 2

Page

HONG KONG DAILY PRESS, THURSDAY, JUNE 2, 1932.

IMPORTANCE OF EARTH CONNECTION

VARIOUS METHODS

EXPLAINED.

RADIO

FEATURES

tightened up after it has been square, which is buried wrapped round the pipe.

feet or

s under the ground: the plate has tinned surface, so that it is an

If a really effective job is desired, then a special collar should be sented on the pipe, the earthsy matter to solder a wire to it. wire in connected to a ing on the

If the soil in which the plate ia collar, and any corrosion which buried is reasonably moist, this is might occur will not affect the pipe, superior to any water pipe: It" should he added that sweating on to a water pipe is best done by În plumber or someone killed in the

work.

1

לי י

Watch the Taps.

1.

or gome-

THESE RADIO COMPONENTS.

CAN CONDENSERS BE

MATCHED?

The first variable condenser I ever owned cost me £8. It was a

Every professional wireless "en-biscuit tin, copper tabe, gineer examines his earth periodi-thing similar is usually equally eully as it is one of the most effective. If possible the earth vulnerable yot most important plate should be buried directly links in the system, and if everynderneath the serial lend-in. This is smooth and ensily controllable:

Present-day wireless was born on the day when Marconi firat con-

neeted his aerial circuit to the

earth. That was in 1895. Previous

to this, experimenters, had not dreamed of making any connection to the ground as they thought that the energy would naturally run away to earth and be lost. *

Instead of this, as Marconi re- one cleaned their "earth" periodi marked when receiving the Nobel enlly they would obtain much better prize in 1000, the new arrange- | resulta and give the water people inent (earthed-aerial system) nos no opportunoty of causing troubler only increased the distance over i One imagines that what the, water which I could communicate, but i also seemed to make the unsmis sion independent of the effect of intervening obytnoles."

coats

whole condenser range while, if one

is pulling in that far, far distant I station lost in a deep hole between the jagged edges of two powerful jammere, one has a smooth vernier, which can be whisked round for an

infinitesimal scale movement.

out. if you have enough cireuitu. This is where American practive is so good.

Of course, the Extenser condén- ser is a first-class device boenhas

The Use of Trimmers."

Of course, indretances are never i exactly the same, so the condenser manufacturen gives us trimmiera,”? These trimmers exist merely to it does away with the long-short compensate for lack of matching switch. But all that I have said of induetaners, but they do not about condensers applies to the Ex- ensure that, as the spindle is turn-tenaar as to any other condensar.

In conclusion, the real import- retain an exact equivalent with its its robustness and its ability to stay neighbour or neighbours. Thus, a put. As the mechanical "problema good idea is to make one of there hate the sensible receiving-act I

designer knows he cannot get elements so that it has shita in the theoretically perfect matching, so vanes and a pair of pliers can move he uses three or four units. of a these slita this way or that to en-

condenser with peak tuning and knows that a little mismatching sure matching over the full range doesn't matter-Capt. P. Eckersley of adjustment. Even then does the in Pupular Wireless, condenser stay put to within one- tenth of one per cent? I doubt it.

A sheet of Bopper is, better still,

I need hardly say, finally, thased, each condenser element will ance of the ganged condenser is in but not so hard-wearing and is magnificent affair, with vanos mill eales must be attached to the more expensive, and of course, theed from the solid. It had ball spindle of the condenser directly, bearings had ahe-distance ad- bigger the sheet the better.

not to a handle which has an in- justment Even the "plates were

direct connection to that spindle. known to hors:

So I turn to ganged condersers To-day the variable condenser

heenuse only a few shillings, it

here the discriminating seldom, shorts, and its movemens buyer needs to exercise discretion.

First and foremost, supposing for fine adjustment. Our thanks

one unit of a two-unit kanged con- and congratulations to condoneer designers and makers!

denser was per cent. different from another at a wave-length ad- justment of 300 metres, and equal to the unit at 500 metres. Then the two. circuits would be exactly in tune at 500 metres, but about 5,000 cycles out of tune at 300 the rondenser, the air is the diefee-There is, in fact, nothing very

metres. This is a very consider. trie, as with an ordinary air con- much to say about the single unitable error, an error which makes denser, and the ground, parti- | variable condenser. It is such its influence more and more felt as ane goes down to shorter and cularly that immediately below the standard article, and its use and aerial is the other plate of the abuse is so well known as hardly to shorter waves: to

Thus, the nearer the merit comment. condenser.

companies are really up against in the clumsy earth wire which hak been hastily wrapped round the pipe and forgotten for years. Naturally corrosion has taken place and the water companies have a case. However, even the worst

Caused by Copper.

Since then everyone has earthed their aerial crenit-mostly to the cases of corrosion brought to their pipe--and wireless has simply good notice cannot be so had as ahend, Now, bowever, certain

justify cutting off the wireless earth water companion are objecting to like they would the water supply. the use of their water pipes as a

Theoretically, at least, the water wireless earth on the grounds that pipe is not the best of earth, dumage is thereby done to the although it may be the most con- pipe.

venient available. Especially does this apply where taps arc inserted lictween the earth connection and the mains, for the threads of the tap may be coated with some in- sulating compound to make a water- tight job, and thus a high resiat- ance is set up in the aerial cireuit.

"As it happens, wireless lateners are not the only people affected, for the talephone companies fre quently use the water pipe for oarthing their telephones-as a matter of fact, it is probable that we first copied the iden of a water- pipe earth from that source,

chies also, viretricity panies make use of the water pipe for an earth.

some

In

-

To ensure a tight connection, the carth clip used by telephone com- panies is very useful, for hy means of two screws the wire can be

The Burled Plate,

The most effective form of earth is that invariably used in, flu professional wireless world, namely the buried, earth plate,

This consists of ค abeat of galvanised iron about

ARCTURUS

LIFE-LIKE

TONE

18 inches

THE BLUE TUBES for every RADIO

7 SECOND ACTION

will ensure the earth wire being as short as possible, and conform to the wireless requirements of the noril system.

But there still remains a great deal to be done, mers particularly when the units of a variable con-. denser are ganged together on the

For instance, the aerial system can be regarded as a condenser; the aerial itself forms one plate of same spindle.

earth, connection is to the ground immediately below the nerial the more effective will be the wireless Bet,

Those Dry Earths,

Some people complain that their buried earth is not so good as the water pipe, although they may have buried quite "an elaborate affair. This is generally beenuse the soil in which they have buried the plate is of a particularly dry and insulating nature. Some parts of the earth's crust are quite good insulators, and this insulation is increased if the ground is, dry. Wetting the earth; will cure the trouble, and if possible the earth plate "should not be buried under the eaves or porch of a house, but in the open where it will receive plenty of rain. In sensitive Beta, by the way, a long earth wire will tend to cause oscillation, but it is better to have a long earth wire rather than on earth" buried in dry soil.

The type of ground upon which the house is built is, of course, very important from the wireless earth point of view. For example, Zenneck's theoretical calculation shows that the particulr wireless waves which will travel for 700 miles over wed soil will only travel for 5 miles over very dry soil.

זי

Counterpoise Connections.

+3

A Personal Prejudice.

I have, however, a personal pre- judice. I like to grip hold of a handle and turn the bloomnig thing. I hate scratching about with my finger-nails on the rough surface of the periphery of the adjustment

wheel. I like those slow-motion

But these are the things which help.

Obviously the stronger the whole (a)-Very Robust Construction.-

device the better. Flimsy and un- sound mechanical practico means variations with use, and with tem- perature change

spindle, for example, gives mecha- nical hysteresis, You turn one to- wards a setting and, the condenser

FOR

British Instruments

British Music

(b) Compactness. -- A Jong British Composers British Publishers remote from the handle lags behind British Pianos

One of the fundamental disadvan, the ones nearer, When you set tages of "band-pass" in that a one in tune the other is not in tune. 1 per vent error makes a profound But turning back leaves the far- difference to the response cure. away condenser more in tune, the

For instance, with capacity coupled circuit this per cent. error might mean that the two

Pumps of the band-pass response curve would, instead of just spread knobs very much, I do not thinking the curve over the Icoal station, it a fundamental disadvantage that actually give full tuning to two dia- one cannot sweep quickly through tant stations, and include the one

you wanted, too! the range:

।।

19

Of course, ideally, one has a The question remains, "Cun

Tobust handle which one can honest-condenser manufacturers guarantee. ly catch hold of and sweep, ina.absolute matching of condensera?"

I do not think they con. turn of the fingers, though the

HAVE YOU HEARD THESE?

Here az Usta of long-warS 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 siguals. Success in picking up these stations also depends very largely upon fav ourae 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.

In a similar way this applies to the "earth," for dry ground offers much greater resistance to the oscillatory currents in the aerial circuit than does damp ground.

58.7 Of course, a connection to the

50. carth is not altogether moves- 43.6 Aeroplanes manage without

the counterpoise.

A

LONG-WAVE STATIONS.

Wave length

Call Kilo (Matres) Station

Bign cycle 260 Manila E.ZI.B. 1,153; 277 Shanghai, K.S.M.S. 1.083 345 Tokyo J.O.A.K. 870 353 Hiroshima J.O.F.K. 850 355 Hong Kong Z.B.W. 246 .357.1 Bombay 361 Sapporo 383 Keijo 370 Nagoya 370.4 Calcut

,830..

*.U.B. 340 J.O.LK. J.O.D.K J.0.0.K.

810 V.U.C 809.9

380 Kumalagio J.0.G.E. 790

300 Sendai

305 Dairen

400 Osaka

410 Canton 480 Menila

SHORT-WAVE STATIONS.

STATION

CALL BIOM

67.85 Dobintz (Germany) 60.19 Khabaroval (Russia)

ON

Srini

་་་་་

J.O.H.K. 770 J.Q.A.K. 780

J.O.B.K. 750

C.M.B. 732 K.Z.R.M. 025

Timm (Hona Howa)

OF WORKING

Mon, Wed ‚& Fri., 6 p.m. & 2 12.xo 4,990 6-10 p.m.

5,291 | Not regular

A.F.K.

4,484

B.A.7.

Наподи Mosco

A.G.J.

RE.N..

6,000 | Taer, Taurs, Sat. 8 p.m.

Roma

1/2.4.

6,806 || Bandiy midnight' «

Perth

6.A.G.

JLTY.

41.8

Singapore

V.8.1.A.B.

it by using the system known as

28.B

Kootwijk (Holland)

F.C.L

37.

Bangkok (Bla)

HS4P.J.

86.2

Sydney

J

2.B.L

0,280 Mot raguiar

To use a counterpoise it is only

31.55

Melbourne

3.1.0.

...

31.18

Bahenectady

W.2.X.A.F.

necesary to run another aerial

3150

LONG LIFE

wire along the ground or

floor and connect it to the earth terminal on the set. The best results are anally obtained when the counter- poise aerial is immediately below 24.5

23.85 the ordinary werin provided the

18,88 atter is fairly high up. The coun-

18.4 terpoiss principal is also useful sometimes for cutting out bad elec trical interference.

81.28

Badhoven (Holland) P.C.. Будаву

31,

Nairobi (Kenya) 7.1.0.

28.0

Sydney

2.M.E.

1.10,526 | Not regnînr

21.8

Bandong

25.33

P.LR. Chelmsford (England) 5.B.W.

Manila

K.I.KR.

Schenectady

Bandoong Kootwijk (Holland)

P.C.I..

10.0 10.3 18.74

17.4 Bangkok

Bandoung

P.L.F. H.8.1.P.J.

17,761 Bunday*.7 pm & midnight

Kootwijk (Holland)

P.C.K.

Bandoeng

P.LE.

19,220 Daily 5.80-7 p.m.

185

Nancy (Peace).

19,351 Dally

13,93

Pittsburg

W.8.X.X.

21,540 Not regular

others less. This can be observed. A badly-designed condenser shaft actually twists and flexes, giving quito incoherent results.

Difficulty in Matching, (c)-Smoothness of Movement Obviously, if the units are inclined to stick they will never function properly.

I doubt if absclüte matching, even if once obtained, continues during the life of the condenser. With band-pass arrangements this is fatal to accurate tuning. But if you do not gang band-pass circuits you get into such a mess with tuning as to render the scheme im practicable. Ganged bund-paas in perfect in thepry, it may be made to work, in practice, I doubt its ability (because most ganged coo- densers vary) to stay put,

With cascade peak tuning this mismatching of condenser units is not so important Things, average

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SOLE AGENTS.

Then, of course, there is always the loop or frame aerial to fall

back upon should the worst come

to the worst.

W.2.X.O, P.L.G.

7,147 | Daily 6.30 pm, & 11 p.m.

7310 Not regular,

7,780 Daily 1

8,108 Tuos, & àrl., 9 p.m.-1 am,

8,508 Not regular

9,580 Bally

·9,820 | Fri, 8 m., Eat. Sam. & 10 am,

-9,500 † Nod spłukan

·6,677 | Midnight daily

11,020 Midnight-8 a.m. daily 11,7517.80 p.m. & 9 a.m. daily, except

Saturday and Sunday

12.240 Nightly

12,860. Wed., Print,

16,107 | Daily 6,80 p.m. to midnight ∙16,304 Daily 7p.m.

17:280|| Daily 8 pin to midnight

18,404 Kach afternoon.

Allowanes must be made for "summer-tims” in most Euro- peazi ocuntries, which is one hour abead of trun time.]

Hear it in our Showroom, open 6-7 daily, or request a des monstration in your home. Expert and scientific service with every sale.

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Top Floor.

King's Building. Opposite Star Ferry, Phone 23748.