HONG KONG DAILY PRESS, THURSDAY, NOVEMBER 27, 1930.
RADIO
FEATURES
SOME REMARKABLE NEW VALVES,
OUTSIDE CONTROL OF ELECTRONS.
TO OPERATE WITHOUT FILAMENT HEATING.
Not just now tpyes of old valves, but completely new valves, built up. on different principles; principles which have been tried innumerable times in many laboratories but have reached the practical stage only now,
In the one case there are the new Arootron valven developed by the German Telefunkon people, and in another ease there are the dew Photovalves working without the dsual low-tension current, which, however, are not quite if ripe "for the market na yot, although ano firm already makes them.
External:" Grid.”
In the case of the Arcotron, the firm wished to develop a cheaper valve for the cheap kind of all- mains local station loud-speaker receiver working with two or three, valves, The Argatrons are on the market, in two types; one as recți- fier, that is as detector valve, and one as L.F. amplifier valve. difference between the two lies in the amount and kind
gas contain ed in the valve.
The
The "grid" is in the form of an outer metal conting on the ginas bulb, the anode and the directly heated cathode are within. Owing to the "grid" being away from the entkode there is a comparative freedom from mains hum and gen- cral insensibility of the valve to smaller variations of the cathode temperature,
❘
The
How It Works,
The action is quite simple to ex- plain. The variations of potential applied to the outer coating of the valve influence, by way of the glass, the stream of electrons flowing the anode, The only difficulty in older types of this valve which had no practical use was the necessity of making the form of the valve so that the outer coating on the glass would have a sufficient influence on the interior happenings, and this has been obtained by the very thin
and flat form of the whole.
The new Photovalves rely on the same principle as the photo-electric colla, i.e., the sensitivity of certain chemicals to light. The cathodes of the Photavalves are made of light sensitive materials so that the moment light strikes them, thoy begin to emit electrons, and natur- ally they vary the intensity of the electron emission according to the intensity of the light striking the valve.
Now there are several methods of having a permanent and unvarying source of light. One can have no electric lamp on D.C. mains burn ing near the valves, but in the case of A.C. of even as high as 50 cycles Der seccad one gets hum owing to the slight variation in the intensity due to the A.C."hills and daler."
EVERYTHING GE.C. ELECTRICAL
your gumonter
GECOPHONE
B.C. 3049. SCREEN GRID FOUR PORTABLE RECEIVER,
CABINET MODEL, IN SOLID MAHOGANY. An entirely new model incorporating the new "STORK" Loud Speaker movement and “HIFLUX" Transformer.
PRICE COMPLETE: £26.0.0
B.C. 3036. SCREEN GRID SHORT WAVE RECEIVER.
THREE VALVE MODEL.
Por wavelengths of approximately 14 to 100 metres. Motal caso, finished dark brown crystalline enamel. Icoorporates two tuning condensors with double spaced ranes. A potentiometer is fitted for varying the bias on the detector valve. A soroon grid valve procodes tub dotector, and this enables the sot to oscillato easily on all wave bands irrespective of the length of the aarial; there are no blind spot. By naing appropiate coils, this set may be used on ordinary broadcast wavelengths.
PRICE: £15. 0. 0.
A
Another Method. The there is much betler method of having a source of, light, Have a small acon tube or ray close to the cathode and have it fed from the anode source of current. This type of valve reminds one of a scoond kind of light-sensitive valve.
This works on a similar principle. A neon ray is made to pass between two electrodes and electrons are drawn off from this ray by means of the usual anode. In the case of this valve, which really is not light ensitive but uses a ray of ignited gas as a cathode, the voltages have to be very high, especially for the acon ray.
In the case of Ardenne's Photo- valves more or less normal voltages can be used, only one drawback being experienced. The emission of the cathodes he has used up to now is not very great, even when ex- posed to brilliant sunlight. that reason the Photovalves as yet would seem to be best for resist- ance capacity amplification.
For
the Arst really commercial use of It will be interesting to watch for the Photovalves, though we already have the first sets working with the Arcotrons. But the Photovalve in- corporates quite now principles. and they do seem to provide onc batteries and current supplies. way of getting away from IT.
SOME USEFUL HINTS.
If you and when soldering you have to hold the iron on to the surface for rather a long time, it is a sign that the iron is not hot enough or that the places to he soldered are dirty.
•
+
One disadvantage of dirty sur faces and poor heat from the sol- dering iron is that you are liable to raolt adjoining ebonite, etc., through failure to get a quick joint.
•
Remember that the point of the soldering iren should be kept clean, Bad must not touch an ebonito or any similar surface, or it will im mediately require re-cleaning,
A choke-condenser output for the loud-speaker greatly assists is over. coming motor-boating.
.
If the many advantages of a short earth lead were generally realised there would be a decrease in the sale of wirel
+
Generally speaking, an increase in the high-tension on the detector. valve will mean increased strength of reaction.
If you are unable to get reaction when your condenser is all in, ex- cept towards the lower end of your tuning range, a small fixed conden ser, anally .0001 or less. connected aeroas the reaction condenser is an improviantion worth trying. 1
When reaction seems much loo strong and it is inconvenient to take off turns from the reaction winding, the effective capacity of the reaction condenser can be re duced by joining a fixed condenser of about equal capacity: in series with it. (The smaller the capacity in series the greater the reducing. effect).
TRANSFORMER ADVICE.
A point that should be remember- ed when choosing a transformer for: a set, and you are considering its characteristics, is how will it per form under overload!
This point is always considered in the case of power transformers and should receive overs, attention. in wireless work. Not so many o to. 1 transformers would be used, I am sure, wore overload charac teristics fully considered. DAN
Have you ever noticed that the distortion produced. by overloading in much more pronounced when the coupling transformer has a ratio of 6 to 1 instead of, say, 3 to 11, One day there wil be intervalvé trans- formers of 1 to 1 ratio.
The effect of overloading will be good design having this ratio,
HAVE YOU HEARD THESE?
Horo are lists of long-wave
· and short-wave stations which should be picked up. by anyone In Hong Kong who has a mode. rately good sot suitable for re calving such signals... Success in pleking up these stations also depends very largely upon fav curable atmospheric conditions, Readers are invited to add to this list should they succeed in ploking up any station not in cluded in either of these lists..
LONG-WAVE STATIONS.
Wave Iength (Metres) Station
260 Manila 277 Shanghai 280 Tientsin 310 Shangbai 320, Peping.
345
Call Kilo- Sign
cycle K.2.1.B. 1,153 E.B.M.B. 1,085 O.R.C. 1,070 K.R.C.
C.O.P.K. 045 J.0.A.K. 870
353 Hiroshima J.O.P.E. 550 846 353 Hong Kong Z.B.W. 357 Bombay
V.U.B. 840 331 Sapporo 360 Keljo
370 Nagoya 370.4 Calcutta 380 Kumamoto
300 Sendai 365 Dairen 308 Rangoon 400 Osaka 410 Canton. 413. Manila
SHORT-WAVE STATIONS.
STATION
CALL BION
930
J.O.I.K.
J.O.D.K. 820 3.0.0.K B10
809.0 V.U.C J.0.G.K. 790 J.O.H.K. 770 J.D.A.K. VU.R J.O.B.K. 750
C.M.B.
760
754
E.Z.B.M. 798
TIM (Hong Kono) OF WORKING
4,434 | Mon, Wed. & Fri, 0 p.m. & 2 BAD. 4,993 6-10pm,
5,201 Not regular
0,000 Tren, thur, Bat., 8 p.me
Boma
67.65 Dobinta (Germany) 60.12 Khabarovsk (Rusein) 66.7 Nauen BO. Moscow $9,5
A.F.K. [R.A.97.
A.G.J.
R.F.N.
1 M.A.
6,896 Sunday midnight
Porth
GA,G,
7,142 Daily 0.80 p.m. & 11, p.13.
41,2
Singapore
28,8
Kootwijk (Holland)
P.C.L.
Bangkok (Siam)
82.6 Sydnoy
31.58 Helbontag
42
37,
a148
Schenectady
V.S.1.A.B.
H.S.4.P.J.
2.B.L. J.L.O.
W.a.X.A.E.
81.20 Eindhoven (Holland) | P.C.J. 01.28
11. 28.5 27.8.
28,68
W.2.1.0.
7,810 Not regular
7,730 Daily 11 p.m.
8,108 Tum, & Fri, 9 pate−1 am.
9299 Not regular
0,503 Not regular
0:830 | Dally in
9,820 Fri. 3 m., Sat, 3 nm, & 10 mm,
9,500 Not regular
9,077 Midnight daily
11,023 Midnight-- a.m. daily
11,701 7.80 p.m. & 3 n.m, dally, except
Baturday and Sunday
12,240 Nightly
Sydney
2.F.O.
Nairobi (Konya)
7.0.0.
Hydney
2.M.E.
10,598 Not regular
Baudoux
P.LB:
Cholmsford (England)
6.8.W.
245 Manila
K.L.X.R.
22.36 Sabenestarly
18.88 Bandosz
18.4
Kootwijk (Holland)
17.4
Bandoong?
10.0
Bangkok....
16.8
Kootwijk (Holland) ·
15.74
Bandoeng
P.C.K P.LE,
16,8
Nancy (Franco) |
13.08
Pittsburg
W.BL.K.
P.L.G.
P.O.L
F.L.B. H8.1.PJ.
13,869 4 am, Wod, Fri, Eat. : 10,102 Dally 6.30 p,m, to midnight|| [18,304| Bally 7 p.
17,250 Daily 8 pm to midnight 17,781 Sundayî 7 p.m, & midnight 18,404 | Each siternoon
10,220 | Daily 5,30,-7 p.m. 19,851 Daily 8 am,
310 Not regular
[Allowance must be made for "summer-time in most Euro- pean countries, which is one hour ahead of true timė,)
MUSIC FROM
MANY COUNTRIES
by wireless with TELEFUNKEN 40
Long range All-Electrie receiver with station selector for use with batteries or! lighting mains.
with TELEFUNKEN
LOUDSPEAKER ARCOPHON
TELE
FUN
For Demonstration and further particulars apply to :-
SIEMENS CHINA CO.
TELE FUN
KEN
Office-Pedder Building, 4th Floor. Showroom-27, Nathan Road,
Kowloon Canton Office-Bhameen. Swatow
-Gebr. Roese.
BURGESS
FOR
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Follow the Experienced Users
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SOLE DISTRIBUTORS.
AC-SG3 Set
ENTIRELY MAINS, OPERATED:
A sensation in 3 valvo seta, with 1 watt undistorted output;' enough power for any moving coil or dynamic loudspeaker. A set that will appeal to you whether you are interested in perfect quality from the local station or clear reception from distant stations.
Price only $145.00
Including Mazda Valves (the best British Valves).
Special B ELIMINATOR for any domestic set or made to order for any requirements.
For
use
perfect reception
* MAZDA” Valves, large stock newly arrived
RADIO batteries made by new process minimis- ing deterioration "PERTRIX" 150, 100, 60, 40 volts and C. batteries.
Ebonite "TROLIT" and Pressed Fibre Fanels out in any size. Loudspeakers, and various parts are also obtainable,
further information apply to r~
TELEFUNKEN CANTON TRADING ASSOCIATION, LTD.
LONGEST EXPERIENCE LATEST DESIGN.
CHINA BILDING (5TH FLOO
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THLEPHONE 24810.