HONG KONG DAILY PRESS, THURSDAY, JUNE 12, 1930.
+
PAB10
HAVE YOU HEARD THESE?
Here are lats of long-wave and short-wave stations which should be picked up by anyêne in Hong Kong who has a mode- rately good set suitable for re- ceiving such signals. Success in picking up these stations also depends very largely upon tav. 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 lata. -
LONG-WAVE STATIONS.
Wave length
(Metres) Station
200 Manila 277 Shanghai 280 Ticatsin '310 · Shanghai
320 Peping 345 Tokyo
365 Dairen
305 Rangoon
43.5
40
41.3
STATION
Singapore
Call Kilo- Sien cycle K.Z.I.B. 1;153
K.S.M.S. 1,083 C.R.C. 1,070 K.R.C. C.O.P.K. 9-45 J.O.A.E.
870 333 Hiroshima J.OF.K. $50 333 Hong Kong 2.6.W. $18 337 Bombay V.U.B 361 Sapporo J.O.I.K. 366 Keijo 370 Nagoya • J.O.C.K.
$10 370.4 Calcutta V.U.C 509.0 360 Kumamoto. 3.0.0.K. 790, 300 Sendai J.O.H.K. 0 'J.D.A.K.. 760 V.C.R. 731 J.O.B.K. 750
C.M.B. K.Z.R.M. 798
J.O.D.K.
1440 $30 520
400 Osaka
410 Canton
413 Manila
SHORT-WAVE STATIONS.
. . CALL SIGN
P.C.L,
HSAPJ,
67.65 Dobints (Germany)
A.F.K.
60.12 Khabarovsk (Bussia)
R.A.97,
£6.7
Namen
A.G.J.
CO.
Moscow
REN.
Bomg
1.M.A.
Forth
QA.G.
V.S.1.&.B.
36.8
Kootwijk (Holland)
Bangkok (Siam)
Sydney
2.B.L.'
31.55 Melbourne
J.L.Q.
31.49 Schenectady
W.EX.A.F.
31.20 Eindhoven (Holland)
P.C.J.
31.28 Sydney
2.F.C.
31.
Nairobi (Kenya)
28.5
Sydney
7.1.0. 2.M:E.
27.8
Bandoeng
P.LB
37.
32.5"
35.5 Chelmsford (England)] 5.S.W.
Kootwijk (Holland) Bardoeng
RAG
Manila
23.35 Sobevectudy
"1888 | Handoeng
18.4
17.4
16.9
Bangkok
10.88 Huizen (Holland)
30.3
25.74 Bandoeng
15.5 Nancy (France)
Kootwijk (Holland)
13.93 Pittsburg
If
a
K.L.X.E.
WX0.
P.L.G. P.O.L. P.L.F.
IIS.1.P.J.
KILD
CICLES
Thx (Home Kora) OF WORKING
FEATURES
DETECTION AND THE LOW FREQUENCY AMPLIFIER.
FURTHER STAGES IN RECEIVER CONSTRUCTION.
The discussion of high frequency amplification in these columns & week ago took us from the serial (or imput) to the detector stage of the receiver.
[BY COHERER."1
Special research is also being, chr ried en in connection with the ap- plication of the Stenode Radiostat system to television. It is well-
the loud-speaker, the H.T. current and it is announced now that an finding its way to the anode of the apparatus has been constructed valve only through the primary enabling the number of channels winding of the transformer. The operated on land lines to be multi- secondary of the transformer, carry-plied by a factor which is far im ing the induced oscillating current, excess of the present requirements being connected to the loud-
of the press speaker, it follows that the full signal current will pass through the sneaker windings but none of the direct current. Such a transformer would have to be of a more robust miure than that employed in ordi-known that a satisfactory service.
by television involves the simultane- nary low frequency valve coupling, Culess, however, the act is only The oscillating (sigual) current is especially when following a valve öf
ous reception of pictures and sound. At the present time experimental for reception of a local, station, or induced or picked-up" (electro-pentode capabilities.
transmission of television are using one or two effcient stages of H.F.magnetic-induction) by the second-
two wave-lengths one for television amplification opened, the detector ary coil and this, being applied to
signals and the other for sqund. method is not to be recommended, the grid of the following valve, the amplified signal current is passed weak impulses on the grid meeting
ou for a further stage of amplifica- with practically no response.
tion.
Selecting a Transformer.
At the same time, with a suit- able B.F. circuit, the anode bend method proves superior to the cumulative grid with regard to
geen
Although, as alrendy pointed out. high frequency amplification is by no means up essential factor in receiver design, at least one stage of low frequency amplification (fol- |lowing the detector valve) is neces-
sary if loud-speaker reception is quality of reception. 130
required. The number of stages of low frequency amplification 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 incorporated in the receiver.
4,434 Mon, Wed. & Fri., 6 p.m. & § am. 4,000 (10 p.m. 6,201 Not regular
6,000 Tue, Thurs., Sat., 8 p.m... 6,806 Sunriny saidnight
7.142 Daily 6.30 p.m. & 17 p.m.
7,310 Not regular
Daily 11 pm.
8,105 Tuos. & Fri, 9 p.m.-- ..
9,230 Not regular
9,503 Not regular
9,530 Daily 7 s.m.
9,600 Fri, 3 am, Sat. 3 am. & 10 am.
9,600 Not regular
9,677 Midnight daily
10,826 Not regular
11,020 | Midnight-3 a.m. dally
| 11,751 | 7.30 p.m. & 8 a.m. daily, except
Saturday and Sunday
12.240 Nightly
12,880 4 m. Wed., Fri., Sat. 16,10% Daily 6.30 p.m. to midnight 10,304 Dafly 7 p..
17,280 Daily 8 pm to midnight 17,751 Sundays 7. p.m. & midnight
17,769 Daily 10 p.m.
P.H.I
P.C.K.
18,104 Each alterasou
-P.L.E.
19,220 Daily G.30.
W.S.I.K.
10,351 Daily 3 in.
21,640 Not regular
The 'detector, or more correctly termed rectifier valve, since its duty is "to rectify the high frequency. impulses to low frequency, can take its input either direct from the soning circuit or "from a high fre- quency amplifier, while its output
coupled, usually by, a trang- former, to the first low frequency I valve.
Rectification.
The most popular methods of rectification are the anode-bend system and the cumulative or leaky grid.
Each method has ise advantages, bat for sensitivity the grid leak method is generally considered ingrior. The anode-bend 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 effected.
NOT A NOTE IS LOST
So Perfect are the Reproduction Qualities
LOEWE FE 63 9 tube
is used
set
It will thus be
that the 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.
L.F. Coupling...... Coupling between the detector and the first L.F. valve and. be- tween subsequent L.F. valves can be effected by a transformer,, a cboke coil, or & suitable arrange- ment of resistances and a con- denser known as resistance-capacity coupling.
The limitations of this R.C.C. method are many, the most pro nounced being a loss in amplifica tion per stage as compared with transformer coupling, and u falling- off or lack of response to the higher sound frequencies.
The method enjoyed a fairly widë 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- inent in low frequency transformer design, R.C.C. can no longer be 'considered to bold this superiority. and with its other limitations. its popularity is 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· fife camel-insulated wires, each coil consisting of thousands of turns and wound about a core of kin 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.
A low frequency transformer has a definite rallo, which may be taken as the gain in the induced current in the secondary to the applied cur- rest in the primary.
I 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 trans former there is supplied tabulated data as to the instruments' char- acteristics and capabilities, similar to that supplied with valves. "A reference to the two renders the selection of such a component com. paratively easy.
Loud-Speaker Ocupling.
Modern power valves, the last stage of a receiver, some taking high tension voltage in the region of two or three hundred, the coupling of loud-speakers to this
13
STENODE RADIO CLAIMS.
VISION AND SPEECH OVER ONE WAVE-LENGTH.
产品
Further claims of the possibilities. of the invention of Dr. Jamer 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 Radiostat Corporation, Ltd. the application of the invention wid It has already been stated that revolutionise Innd-line telegraphy,
When the Stenode Radiostat sys- tom is used it will be possible for both television and telephonic sign- als to be transmitted in the channel now exclusively used for the tele- vision signals, The Stenode Radio- stat systems, it is claimed, supplies the one thing lacking for à 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 broad. casting service in that country.
(Other Wireless on Page 3.).
BUY BRITISH & BE, PROUD We have just unpacked a Shipment of ALUMINIUM BASE-BOARD & PANELS. Suitable for Short Wave Receivers and other sets that require Screening
OTHER RADIO & WIRELESS PARTS (Guaranteed British Made).
1
last stage by means of a trans ORIENTAL COMMERCIAL & Co., LTD. popular, former is becoming increasingly Such a method prevents the high tension current passing through the delicate windings of
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THE NEW SCREEN-GRID 4.VALVE SET
TELEFUNKEN 40
NOVEL
STATION-SELECTOR
TELE
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For Better Result
TRY
MULLARD
REQUIRES FRAME AERIAL ONLY WITH NEW BARIUM TUBES.
CAN ALSO BE USED WITH LOEWE SHORT
WAVE ATTACHMENT.
Demonstration Hours :--
1-11.30 a.m. 12.30-1.30 p.m.
5-5,30 p.m.
During demonstration hours expert European advice is given-
on all Wireless matters.
Loewe`R 533 A.G. 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.
TOR TRADING ASSOCIATION LTD.
CANTON
CARL-SCHROTER, Manager-5TH FLOOR, CHINA BLDG.
TELEPHONE 24610.
THE BEST BRITISH MAKE
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TELE FUN KEN
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"Showroom:
KOWLCOH
TELE
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PEKING BUILDINGS,
27 NATHAN ROAD
Alo Obtainable- Mesra WAH MEL ELECTRIC St
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TELE
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