1930-06-12 — Page 3

HONG KONG DAILY PRESS, THURSDAY, JUNE 12, 1930.

HAVE YOU HEARD THESE?

Here are lists of long-wave and short-wave stations which " should be picked up by anyone in Hong Kong who has a modo- rately good sat suitable for re- ceiving such signals. Success. in- picking up these stations also depends very largely upon far- ourable atmospheric conditions. Readers, are invited to add. tɔ this list should they succeed in picking up any station not in- cluded in either of these lista. -

RADIO

LONG-WAVE STATIONS,

Wave length

(Metres) Station

260 Manila

Cali Kilo- Sign K.Z.I.B. 1;133

cycle

277 Shanghai

K.S.M.S. 1,085

380 Tientain

C.R.C. 1,070.

345 Tokyo

310 Shanghai K.P.C. 907 390 Peping

.C.O.P.K.. 43 J.O.A.K. 870 333 Hiroshima J.O.F.K. $30

355 Hong Kong

Z.B.W.

540

337 Bombay

V.U.B

840

361 Sapporo

J.0.1.K.

$30

J.O, D.K.

$40

J.O.C.K.

510

370.4 Calcutta,

300 Keijo

370 Nagoya

380 Kumamoto 300 Sendai

365 Dairen

308 Rangoon 400 Osaka 410 Canton

415 Manila'.

· SHORT-WAVE STATIONS:

STATION

CALL SIGN

67.65 Dobintz (Germany)

43.5

32. Sydney.

31.5%

31.48 Schenectady

2.B.L.

827310

ניס

V.U.C

509.0 J.0.0.K. 700 J.O.H.K. 770 J.D.A.K. 760 V.U.R 734 J.O.B.K. 750 C.AL.B. **39 K.Z.R.M. 798

Tix (Hoxe Kora) or WORKING

FEATURES

DETECTION AND THE LOW FREQUENCY AMPLIFIER.

FURTHER STAGES IN RECEIVER CONSTRUCTION.

The discussion of high frequency amplification in these cofumos a week ago took us from the serial (or imput) to the detector stage of the receiver.

To means

Although, as already peinted out. high frequency amplification is by an essential factor in receiver design, at least one stage of low frequency amplification (fol- lowing the detector valve) is necce- sary if loud-speaker reception is required. The number of stages of low frequency amplication will usually exceed those of high; fre- quency, and in sets designed for powerful reception of distant stations as many as four or five stages of low frequency will be

4,434 Mon., Wed & Fri., 6 p.m. & 2 am.. incorporated in the receiver. 4,000 10 p.m.

0.000 Tuo., Thurs., Sat, 5 p.. 6,900 Sunday midnight

7,142 Daily 6.30 p.m. 11 p.m. 7,310 Not regula

7,730 Daily 1 pan

6,108 Tues. & Fri., 0 p.m.-1 a.m.

9,003 Not regular

0,620 | Fri, 3 am. Sat. 3 am, & 10 am.

9.500 Not regular

A.F.K.

60.14 Khabarovsk (Russia)

RAD

36.7

Nanen

A.G.J.

3.291 Not regulár

50.

Moscow

R.EN.

Rome

1.M.A.

42.

Perta

C.A.G..

41.3

Singapore

V.S.1.4.D.

39.8

Kootwijk (Holland)

P.C.L

$7.

Bangkok (9iam)

HSARJ

0,250 Not regular

3.1.0.

W.3.X.A.E.

9,530 | Daily 7, n.m.

31,20 Eindhoven (Holland)

| P.C.J,

31.28 Sydney

2.F.C

31.

Nairobi (Kenya)

7.1.0.

9,677 Midnight Baily

28.5 Sydney

2.M.E.

10,626 Not regalar

27,8

Bandoeag

P.L.R.

11,020 Midnight-3 a.m. daily 11,781 7.30 p.m. & 3.am, daily, except

Saturday and Sunday

24.5

Manila

K.LX.B.

12,240 Nightly

22.35 Schenectady

V.2.X.O.

18.88 Handoeng

P.LLG.

18.4 Kootwijk (Holland)

P.C.Li

17.4

Bandoong

189

Bangkok

P.H.L

10.3

Kootwijk (Holland)

P.C.K

16.74 Bandoeng

P.LE

16.4

Nancy (France)

10,351 Daily 3 m.

13.98 Pittsburg

W.6.X.K.

21,540) Not regular

24.53 Chelmsford (England) 5.8.W.

18.88 Huizen (Holland)

P.L.F. H.S.1.P.J.

12,800 4 km. Wed., Fri., Sat. 16,102 Daily 6.30 p.m. to midnight 16,804 Daily 7 p.m.

17.280 Daily 8pm to midnight 17,751 Sundaya 7 p.m. & midnight 17,700 Drily 10 p.D.

18,404 Each afteraron

10,220 Daily C,30—7 p.m.

The detector, or more correctly termed rectifer valve, since its duty is to rectify the high frequency impulses to low frequency, can take its input either direct from the tuning circuit or from a high fre- quency amplifier, while its putput is coupled, usually by a trans. former, to the first low frequency | valve.

Rectification....

The most popular methods of rectification are the anode-bend system and the cumulative or leaky gad.

2

Each method has ite advantages but for sensitivity the grid leak tatlod is generally considered

erior. The anode-bund rectifier does not necessitate the grid resist ance and condenser of the grid leak method, and thereby a small saving on the initial cost of the receiver is 'cffected.

NOT A NOTE IS LOST-

So Perfect are the Reproduction Qualities

If a LOEWE FE 63

9 tube set

is used

(BY

COHERER."]

Caleas, however, the set is only

The oscillating (signal) current is

for reception of a local station, or induced or "picked-up" (electro one or two efficient stages of H.F.magnetic induction) by the second- amplification opened," the detector ary coil and this, being applied to method is not to be recommended, the grid of the following valve, the weak impulses on the grid meeting amplified signal current is passed on for a further stage of amplifica "with practically no response.

tion.

Selecting a Transformer.

At the same time, with a suit. able H.F. circuit, the anode bend method proves superior to the cumulative grid with regard to quality of reception.

that the

It will thus be scea choice of a method of rectification depends largely on the strength of the high frequency impulses that ean be applied to the grid of the detector.

A low frequency transformer has a definite ratio, which may be taken as the gain in the induced current in the secondary to the applied cur- rent in the primary.

In selecting a transformer, not only the ratio but the impedence should be taken into consideration with respect to the valve that is being employed in the same stage, as with all good makes of tes former there is supplied tabulated date as to the instrumenta' char- acteristics and capabilities, similar to that supplied with valves. A reference to the two renders the selection of such a component com,

L.F. Coupling. Coupling between the detector and the Srst. L.F. valve and be tween subsequent L.F. valves carparatively easy. be effected by a transformer, e choke coil, er a suitable arrange ment of resistances and denser known as resistance-capacity coupling.

2

ANDII-

Loud-Speaker Coupling, Modera power valves, the last stage of a receiver, some taking a high tension voltage in the region of two or three hundred, the coupling of loud-speakers to this

the loud-speaker, the H.T. current finding its way to the mode of the valve only through the primary winding of the transformer. The secondary of the transformer, carry- ing the induced oscillating current, being connected to the loud speaker, it follows that the fall signal current will pass through the speaker windings but none of the direct curreal. Such a transfornier- would have to be of a more robust nature than that employed in drdi. nary low frequency valve coupling, especially when following a valve of pestode capabilities.

STENODE RADIO CLAIMS.

VISION AND SPEECH OVER

ONE WAVE-LENGTH.

Further claims of the possibilities.. of the invention of Dr. James Robinson, known as the Stenode Radiostat, are made in a report which the inventor and Mr. Percy Harris, assistant general manager, have made to the proprietors of the British Radicstat Corporation. Lad.

It has already been stated that the application of the invention will revolutionise land-line telegraphy,

and it is announced now that an apparatus has been constructed enabling the number of channels operated on land lines to be multi- plied by a factor which is far in excess of the present requirements of the press.

Special research is also being carr ried on in connection with the ap- plication of the Stenede Radiostat system to television. It is well- known that a satisfactory service by television involves the simultane ous reception of pictures and sound. At the present time experimental transmissions of television are using two wave-lengths one for television signals and the other for sound.

When the Stenode Radiostat 875- tem is used it will be possible for both television and telephonic sign- als to be transmitted in the charme now, exclusively used for the tele vision signals. The Stenode Radio- stal system, it is claimed, supplies the one thing lacking for n success- ful television service.

Demonstrations have been given. to certain important German groups for whom apparatus is being manu- factured for experimental operation in connection with the public brond- casting service in that country.

(Other Wireless on Page 3)

BUY BRITISH & BE PROUD We have just unpacked & Shipment of ALUMINIUM BASE-BOARD & PANELS. Suitable for Short Wave Receivers and other sets that require Screening

&

OTHER RADIO & WIRELESS PARTS

(Guaranteed British Made).

last stage by means of a trans-ORIENTAL COMMERCIAL & Co., LTD.

The limitations of this R.C.C.

former is becoming increasing y method are many, the most pro- popular. Such a method prevents nounced being a loss in amplifica-the high tension current passing tion per stages compared with through the delicate windings of transformer coupling, and a falling- off or lack of response to the higher sound frequencies.

The method enjoyed a fairly wide popularity & year or two ago, on the score of purer amplification and better quality of reproduction than that obtained with the transformer method. With the recent improve

ent in low frequency transformer design, R.C.C. an no longer be considered to held this superiority. and with its other limitations its popularity falling off.

Transformer Coupling.

Those readers who have taken the trouble to dissect a low fre- quency transformer are aware that it is made up of two coils of very fine enamel-insulated wires, each coil consisting of thousands of turns and wound about a core of lamin- ated iron.

.

One coil acts as the primary and, in addition to receiving current from the preceding valve; it pro- vides a path for the supply of direct current to the anode, the other side of this coil being connected to the high tension battery or mains unit.

BANK OF CANTON BUILDING, TEL. 24405.

THE NEW SCREEN-GRID 4-VALVE SET

TELEFUNKEN 40

NOVEL

STATION-SELECTOR

¿TELE-

For Better Result

TRY MULLARD

REQUIRES FRAME AERIAL ONLY WITH NEW BARIUM TUBES.

CÂN - ALSO BE USED WITH LOEWE SHORT

WAVE ATTACHMENT.

Demonstration Hours :—

11-11.30 am. 12.30-1.30 p.m.

5-5.30 p.m.

During demonstration bours expert Europeau advice is given-

on all Wireless matters.

Loewe R 533 A.C. set with Loud Speaker $150

gives splendid volume."

"Pertrix" High Tension Dry Batteries

150 volts, 100 volts, 60 volts and 45 volts. Heavy, Super Duty. NEW PARTS, RECEIVING SETS and LOUD SPEAKERS.

CANTON TRADING ASSOCIATION LTD,

CARL SCHROTER, Manager-6TH FLOOR, CHINA BLDG.

TELEPHONE 24630.

THE BEST BRITISH MAKE

THE

MASTER VALVE

SINCERE'S

SOLE DISTRIBUTORS

TELE FUN] KEN

TELEFUNKEN

SIEMENS CHINA CO..

Co.,

PEDDER BUILDING, 4TH FLOOR, HONG KONG,

TELE FUN

PEKING BUILDINGS,

KEN

27, NATHAN ROAD,

Also Obtainablé--- Messrs. WAH MEI ELECTRIC CO.,

HUNG MING ELECTRIC CO.. 157, Das Vaux ROAD. ANDERSON MUSION CO., ST. GEORGE'S BUILDING, TON HOUSE SZERET.

TELE FUN KEN?