HONG KONG DAILY PRESS, THURSDAY, JULY 16, 1931.
Listen!-
RADIO
If you want Best British it is undoubtedly Components, it is undoubtedly
IISSEN
TRADE MARK.
WE KEEP REGULAR STOCKS
**
AND
ACCEPT FORWARD
ORDERS.
Apply for Catalogues
FEATURES
A BATTERY SET
SET CONVERTED FOR USE ON A. C. MAINS.
A FEW OF THE DIFFICULTIES AND CHANGES EXPLAINED.
In the first place, the question As a matter of fact, in these cír- of overloading in the output valve euinstances the overlonding is liable seems to be a very dificult one. to be very Lad indeed, and consc-
Grid Return Connections.
Provided you have got the fila. ment wiring done as well, ne possible
carrying it out with twisted dex (possibly with metal covering, such
MUSIC.
ANALYSING SPEECH AND bands The twelfth-pass all fre- quencies below 42.3 evoles and thỏ thirteenth all above 8,000 cycles. A fourteenth filter is sometimes used to cover the extremely high fre quencies between 8,000 orcles and 11,500 feley. Further amplification is provided after the transmitter qutput has passed through the filter,
In the reproduction of speech and music, not only in broadcasting bug in sound pictures, enginoors!
oors now have to know exactly what the sounds consist of There are two variable quantities in sound: name ly frequency of vibration and amplitudo.
A broadenst sound consists, as a rule, not of one frequency but of any; and these are of various am Plitudes. The peculiar quality of sound depends upon which fre- as is now obtainable), and provided quencies are present and upon their A Point to Remember. you have kept it away from gird relative amplitudes. These vari- Now take another point about and plate loads and L.F. transables in sound account for the dif conversion-the fact that because formers, the best thing to do with ferent timbres of the same note as O valves have a very much great indirectly-heated valves is to tryplayed by a piano, a violin, or er magnification they are liable to earthing first one side of the heater other musical instrument. cause instability. If your D, set and then the other, and then, ifIt is interesting to note that, was only just held down" work you have got a centro-tayed wind-
Many do not seem to roulise that ifquently many people have been they convert a detector and two rather disappointed at the results L.F. to A.Q. they must use a large of their conversion to A.C. output valye, if they intend to tuno-in their set fully to their local station.
That is, if they expect to get out of it very much more volume on their local than they. did on their battery set.
The Two Alternatives.
It will be clear that menaurement can only be made on one frequency band at a time, so the selection being played or the worde being spoken must, for complete annlysis, bo repeated fourteen or Afteen times; onto to allow readings for each of the fourteen frequency bands and once for all bands taken together. ***
Tests with this now. epparatus: have boop made on speceh using male and female Voices; also in
A.C valves · give" tremendous ing on moderate H.T. voltages auching on. the L. F. transformer second any of the component fro various manners of speaking and
magnification, and we find that in 130, you cannot expect to put the detector and two L.E. stage set in A.C., valves and work with volt we can quito easily get the goal station up to sufficient volume to ages up to 500 without getting in fully load an output valve of the stability such as motor-boating and calibro of the L.S.BA. or the new L.F. howling.. Mazda PP3/400.
use
ary, to this. Usually you will find that the best place is to one or
If you have got indirectly-heated other side of the heater winding. valves throughout, you are quite aafo with this method but if you are using a directly heated valve in the
quencies of a sound are not at varicus ? distances from the reproduced at the correct am microphone. Street noises have plitude, the reproduced sound is also been measured. For musc distorted and unnatural. But we short selections have been played bý seldom hear one sound alone, since most of the common instruments, in speech and music different sounds including piano and organ; and of follow each other in quick succes dutire orchestras composed of differ sion and are recognised as syllables ent numbers of instruments.
So when you convert your set, make absolutely sure that the deteclast stage you are rather up against or notes. The component frequen it, unless your transformer has acies are therefore changing from separate winding for that valve. moment to moment.
In a' directly-heated output cir
tor is perfectly decoupled, and that the output valve has a good choke.
Very few 'readers con L.B.GA.'s, for the simple reason that they need specially-made all. maina aparatus in order to give the required 400 volts and plenty output system in its anode circuit, cuit it is best to use a transformer of milliamps.
otherwise you are liable to get very which has a separate winding for But renders have two alterna- bad motor-beating indeed. In this this valve, and here the centre tap tives. One is to insert a volume connection the resistance and cou-should be taken to girl return, or control so that they need not over-
not the only else denser, decoupling is load their set on the local station,
potentiometer connected
д
Many interesting results havo been obtained from these measure ments, which, by enabling, sound to
In analysing speech and music it, be analysed into ita constituent fre magnitude of each separate fro- eventually lead to mere natural ve- is not essential to determine the quencies and amplitudes, should
quency at every moment, but it is production in broadcasting and very desirable to know the range sound pictures. of frequency and the manner in which the magnitudes vary over. different sections of this range.
THE SINCERE Co., LTD. but can get really good, pure method. It is certainly the chen-across the filament wiring and the Knowledge of both average and
SOLE DISTRIBUTORS.
HAVE YOU HEARD THESE?·
LONG-WAVE STATIONS.
Call Siga
Here are Usts of long-wave --- and short-wave stations which khould be picked up by anyons (0) in Hong Kong who has a mode rately good wet suitable for re- ceiving such signals. Success in. picking up these stations also depends very largely upon fav- ourable atmospheric conditions. Readers are invited to add to this list should they succeed in pleking up any station cluded in either of these lists.
*
MAN-MADE STATIC.
Some power-transmission' lines return taken to the slider of that peak magnitudes is desirable. This already carry current at a preaure potentiometer,
A Necessary Compromise."
information can now be obtained by means of new apparatus design ed in the Acoustical Research De If a common winding is employpartment of the Bell laboratories.
The sound to be measured is first ed, you will probably find it best
picked up by means of a condensor
-
volume, and use en indirectly-heat-pest, but there is a method which ed A.C. valve of the A.C.P.I type is slightly more efficient, and it
of £23,000 volts, and stops are being. or a directly-heated valve of the
taken to increase this to 380,000 P.X.4 variety. On distant stations certainly does conserve H.T. energy.
volts. At such pressures the chief they can then put their volume
The Output Filter. control over to "lond" and get full
problem is to prevent corona dis It is to use a good LF, choke
charge and arcing" across the in- advnatage of the tremendous instead of the usual 28,000-ohm re
actual magnification given by A.C. valves. sistance, with a mid condenser not to connect any other heaters to microphone, such as is commonly intors. Apart from the
About Overloading.
between the choke and the earth.
earth, merely taking the centre used for making sound pictures and loss of power, leakage of this kind
On the other hand, if they only
Thero is another point which point to H.Tand cath. It is a used by many American broad acts up other disturbances, which want to work their sets from A.O. seems to be not too clear to many father a compromise, but more casting studios. The sound is then may interfete seriously with wire- merely from the point of view of readers-the output filter of the set. trouble is usually encountered in amplified to some convenient level less reception. Accordingly the in- convenience, and do not want the When automatic bins is used the small sets (without S.G. valves) by before being passed on to the messuilators used for power trans- earthing the filament of the direct saring apparatus. One mensure missions are now being tested up to volume of the set to be any differ-return from the output filter con-
ment gives the averago amplitude 2,000,000 volts. The actual tests aro darkened room, so and the other measurement gives carried out in a the peak amplitude.
that the faintest corona, glow is at
AL
Ware "length
Kiloent from that obtained when a bat denser through the loud speaker toy-heated output than in centre- (Metres) Station
cyclo 200 Manila"KZIE. 1,188
tery was used, they can quite safely earth should not be made (as in the lapped earthing of the indirectly-
heated valves. 277 Shanghai K.S.M.S. 1,033 scrap their intermediate stage and battery set) to H.T.-, or to earth, 345 Tokyo, JO.A.K. 870
take the detector, transformer-con- but taken direct to the cathode of Where an S.G. valve is used the 353 Hiroshima J.O.TK 880 253 Hong Kong Z«B.W,・・ 848
pled, straight to the output valve, the last valve. Otherwise the L.F. heater usually has to be earthed 257.1 Bombay
using for this something of the impulses in your anode circuit are close to the valve, and then it is order of the A.C.P, or the Mullard going to go through the basing repractically cential to employ a 104V, Marconi M...4, and so on. sistance, and will tend to cause separate winding for a directly But there is one thing they must fluctuations in "the" gird circuit of heated output valve. Many mains not expect if they stick to the the valve, with a possibility of power transformers maké provision
V.U.B. 840
361 Sapporo J.O.I.K. 830 300 Keijo
J.O.D.K. 820 370 Nagoya J.0.C.K. 810 370.4 Calcutta...V.U.C. 509.9 350 Kumamoto J.O.G.K, 790 300. Sendei*» J.O.H‚K, NTO 395 Dairen J.Q.A.K. 760 400, Osaka
J.O.B.K. 750 C.M.B. -739 K.Z.R.M. 625
410 Canton 4460 Manila
SHORT-WAVE STATIONS.
Кто
67.55 Dobintz (Germany)
60.13 Khabarovek (Bussla) B.A.07.-
6,201 Not regular
66.7
Nancow
to.
Mosco
43.5
Rome
1.M.A
V.8.1.AB.
OF WORKING
thres valves, and that is to be able giving rise to trouble.
for this, and it is best, when con-
to get their local station fully And now as regards hum. What sidering the purchase of a trans- tuned-in without a volume control is the best carthing system for an former for the building of your with AC. valves and an output A.C, set! Unfortunately this demains unit, to bear this in mind type of quite ordinary calibre with pends on a certain amount of ex and use one of the makes having out any trace of overloading. periment.
this separate winding.
STATION
CALL BLON
TIME (HONG KONG)
AFE
4,434 Mon... Wod. & Fri, 0p.m. & 2 am 4,000 6-10 pm
A.G.J.
REN.
6,000 Tues, Thurm, Sat., 8 pm;
6,890 Bunday midnight
NEW TELEVISION INVENTION.
7,142 Dally 0.80 p.m. de 11 p.m. “
7,810 Not regular
7,780 Dally 11 p..
8,108 Tues. & Fri, 0 pimel am.
2.B.L. J.L.O. W.2.X.A.F.
0,230 Not regulas
9,503 Not regular
9,600 Daily 7 Am.
31,28 Sydney
BI.
Nairobi
(Kenya) LO
28.5
Bydney
27,8
Bandoers
3.7.C.
2.3.2. PLB
9,550 Not regular
10,526 Not regular
11,00 Midnight-9 km. dally
Q.A.G.
P.O.L
HSAPJ.
+49 Perth
41.8 Singapore
28.B
Kootwijk (Holland)
87. Bangkok (Biam)
82.5 Bydney
81.56 Melbourne
81.49 Behenectady
32.50 Eindhoven (Holland) P.C.J.
25.68 Chelmsford (England) 5.8W,
24.0
Mazila
2335-Schenectady...
18.68 Bandoeng
18.4 Kootwijk (Holland)
174
Handoeng
10.0.
Bangkok
10.3
Kootwijk (Holland)
16.74 Bandoeng
$15,5
Nancy (France)
18.pa- || Fitoaburg -
ז'
K.L.X.E. W.2.1.0... PLG. P.O.L.
Pla
*
H&LPJ. P.C.K...
PLEA
9,620 Fri. 8 Am. Bat. 8 am, & 20 sm.
0,077 Midnight daily
7.80 p.m. & 8 am, daily; arcept
Saturday and Sunday
11,751
12,240 Nightly
12,850. Wed., Fri, Sat
10,102 Dally 6.30 p.m. to midnight
10,804) Daily 7 pt.
12.050 Daily 8 p., to midnight
17,230
17,751 Bundaya 7 p.m. & midnight 18,404 Each afternoon
10220 Daily 5.807 p.m.
19,851 Daily &
21,660 Not regular
[Allowansa“must be made for "* sommer-time ”*; in most Em
tries, which is one hour ahead of trus times]
5t
According to a message from New York, P. T. Farnsworth, & young mathematical wizard who is techni-
a noct
One of the great claims of the now the frequency band is narrowed by Farnsworth invention is that tele a distorting process and
'and this dis vision images of good detail can be torted signal is transmitted, being fransmitted through frequency only changed back to its original hands no wider than in common use form at the receiving end. It ie for broadcasting. The absence of
worked the first time he tried it!!!
moving parts, of inertia effects and interesting that Farnsworth con cal director of Television Labora of complicated mechanical devicca coived this idea entirely mathema tories, California, has greatly im is claimed to permit transmission tically. He set up the necessary pressed the Federal Badio Commis of any desired amount of detail equipment in his laboratory and it sion with a demonstration of a now The Farnsworth
system requires tube claimed to make television im only 20 kilocfeles for conveying pic mediately practical. This inventor tures and sound. :)"?
- I gather?: that | tho backers- bas applied dor authority to A professor of the University of Farnsworth operate a high-power television Califorais states: The results are
hose to put his in: vention into effect as soon as the station in New York:
impressive. The principle involved This tube, which red
Radio Commissión agites. has no is quite unlike single sideband teld! moving parts; is "claimed tophone transmission, where the car | Farnsworth really has overcome nocomplish electrical scanning, con- rier and one side band are suppress- difficulty of the frequency band re- verting light wavea into electrical waves and transferring theen -back- again into an image, still or moving
therea asmitter der anded at qured for traimofitting images,”
thu
the "ropelver. In ~ Farnsworth's de- ¦ har "certainly mando a great con-
velopment the
ecessary width of tribution to tele
science.
In order to analyse a sound into onte detected. When a flash- constituent bands of frequencies, ¿¦ over" does take place, it is a most up of 13 filters is employed. impressive sight, whilst the noise is Ten of them divide the range' from like the bursting of a high ex- 62.5 to 8,000 cycles into, convenient plosive.
RCA
VY224
Caffe til 12.
VČANA AUTEM,
Rudiotron
Look
Put new life in
the old set
Good Reception
depends on
UNIFORMITY
Use
RCA Radiotrons
the red and black carton. (? ♥4] and the famous ROA trade-mar
AUTHORIZED DISTRIBUTORS -
THE WING ON CO., LTD.
Tel: 2687127
RCA Radiotron
III. HEART OF YOUR ENREG SEL