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THE CHINA MAIL,
RADIO TOPICS
NEW TYPE OF VALVE
Suppose, now, that a positive SPECIALISED BROADCASTS?. field were introduced Into the valve
simply to counteract the effects of It is claimed that the Dutch sta- THE SHIELDED GRID.
this electron cloud, and that it tions broadcast the most educa were placed nearer the lament tional and specialised matter. The [By N. M. Goddard, B.E.]
than the grid. A comparatively language courses are graded with In the year 1888 Edison noticed small field would be necessary, great care and a listener can start in an ordinary electric light lamp and it could easily be done by in- on a now language every quarter. an effect which formed the basis troducing B fourth electrode, There are four courses in the Eng. of subsequent investigation in the which would, of course,. have to lish language at present. evolution of the valve. This was be of such a nature that It would From Hilversum and Kuizen.
From Hilversum and Huizen that if a metal plate were placed not cause any obstruction to the within the glass of the lamp and flow of electrons, and Hanca would there are specialised courses on not connected in any way inside have to be open like a grid. Such "Shipping for Bargees and Their the lamp to the Alament an electrode, placed between the Familles," "How to Make Handy
small
current would flow filament and grid, would reduce Objects," Steriography, Book-keep-
+
RO
in the circult to which the plate the space charge effect, and thus ing, and Esperanto, in addition to was connected. For some time no- enable the grid to be of greater dozens of other subjeca, thing further was done until in utility, and so increase the am- By comparison general crit/lelam 1905 Fleming produced a two elec- plification of the valve, but its true that the B.B.C. in England trode valve, which was used pure would not in any way reduce the have not set out to cater for the ly as a rectifler. A little while grid plate. capacity of the valve. specialist. There are plenty of later De Forest added the third As a matter of fact, we have at casual and haphazard talks on electrode or grid, and we then had the present time quite a number of most subjects, but definito the valve as we know it to-day.
high amplification valves, but as policy seems to be followed as fa Now although great strides this characteristic is only obtain the case in many other countries. have been made in the past 20 ed by narrowing the grid spaces, Recently, Milan gave a course of years, and although special pur. the grid-plate capacity is increas- talks on stamp .collecting, indeed, pose valves have been evolved and ed so much that there is the one of the cleverest series that| The have given satisfaction, the funda- greatest difficulty in controlling could have been broadcast. mental characteristica of the valve oscillations due to the feed-back only danger of that course would are much the same as they were that there is energy in the plate collector. One talk on a subject effect. This is due to the fact be to, make every Italian a ́stamp in the beginning,
From the point of view of satis- circuit at a high potential compar- such as this leads no one any- factory performance within its ed to that in the grid circuit, and where. It wanted to be followed own limits the present-day valve as the two elements are equivalent up by a series.
the Mid-American sta gives no cause for complaint, but to two plates of a condenser, some It does not give us the amplifica tion which we would like in radio frequency stages, and it has an Inherent tendency to cause self- oscillation by reason of Its inter- electrode capacity. If these faults could be eliminated, or at any`rate: considerably lessened, we should
One of
of this energy will feed back, and tions has a series at present on will be lost to the plata circuit, "Careers for Women." There are na well as causing self-oscillation, plenty of articles in daily news- It would obviously be of great ad papers about choosing careers for vantage to reduce this capacity if one's daughters, but there have only. been one or two casual talks we could.
on the subjects from the English studios.
THE PLACING.
Let us now consider the effect
Talks to be of any value will
be able to obtain better results of placing the extra electrode be- have to be "specialised" and made
from any circuit.
AN ELECTRODE.
come these .difficulties
to a very
tween the plate and the grid. By so interesting that the series will making it sufficiently open and ap-grip as the B.B.C. series on "Music Lately there has been produced plying a suitable positive poten- and the Ordinary Listoner" has a valve which promises to a ertial, we could make sure that it gripped.
would cause no obstruction and A series on Morse Signale great extent. It has a fourth elec- would counteract the effects of the would be of great educational in
Again, it would terest to the average listener, and trode, which is very similar in ap-space charge.
could be pearance to the ordinary grid, but make the grid more effective, and these
demonstrated. of which the functions are entire-Bo increase the amplification of the There is no subject on which the ly different.
time it average listener is We shall consider valve, but at the same
BO ignorant, briefly the purpose and effect of would produce another and very and yet there is no subject so sys- this additional electrode, but be-Important effect, and an effect for tematically ignored in the B.B.C. fore doing so shall discuss in a which we have been striving for programmes. few words some of the conditions years in connection with radio fre- A Canadian station has given a mat with in the ordinary three elec-quency amplification, viz, reduc-series of talks on Mores although tion of grid-plate capacity. The to listener within a hundred miles
trode valve.
First of all this type consists of result is achieved. In this manner. of the station can hope to get with- three parts, the filament, the grid, We have a solid plate, a very open in striking distance of any sea and the plate. When the filament grid, and the normal grid in that for a few years, nor be troubled is heated it acts as a source of order. There is capacity between much by Morse signals.
grid, electrons, which shoot off at a the plate and the extra
One French station breadcast a high velocity. The plate is given. but this capacity is relatively series of very successful talks on a positive potential by means of a
of the open- First Aid a year or so ago. A B battery or its equivalent, so that ness of this grid. There is also German station about the some of these electrons, which are capacity of a like nature between time broadcast a series on Aero-
amall
because
Jame
negative particles of electricity, the normal grid and the extra grid, plans Construction. are attracted to it and cause a so that between the normal grid In any case it is specialisation current to flow in the plate cir- and the plate there are two capa-that will pay and make us mas- cult. The grid is interposed be- cities in series, both of which are ters of few things, instead of be- tween the flament and plate, and smaller than the usual grid-plato ing bored with the casual talk. acts as a control to govern the capacity. Now, the effect of plac- In this matter at least, other number of electrons that will reach ing capacities in series to produce countries are giving the lead to the plate, and hence vary the cur- a resultant capacity which is very the B.B.C. What are we going to rent which flows. Now, the grid much smaller than either of the do about specialised broadcasts? is generally at a negative poten- components, so that in this parti- And C.B.A. might add "All sugges- tial, and will tend to prevent the cular construction we have enor- tions are welcome." electrons wandering away from the mously reduced the grid-plate filament, and it is only by putting capacity; in fact, almost eliminat-
GRID-LEAK VALUES?
TUESDAY, AUGUST 7, 1928.
DAILY CROSS-WORD PUZZLE.
(This cross-word puzzle has been made by an szpert but our readers are toarned to look out for occasional phonetis-epellings, such as harbor, ploso, and althoj)
મ
19
20
122
33
36
EX
IS 16
12.
18
י
16
22
23
25
126
37 138
25
46
50
5)
52 53
58
59
163
165
[68
HORIZONTAL 1-Part of a doorframe 4-irritate 7-Fleshy portion of
JAWI
B-Boy's name (short) 10-Personal pronoun 11-Negativa 13-8llance.by force 14-Placa
15-Bultable 17-Joker 19-For example 20-Venture 21-Happy 23-Parent 24-Ward off 25-Motal
27-Confined
90-Mounting of a jewel 32-8warm of young
fish
33-Pointed weapon (pl) 35-Detect 36-Deface
37-Bird
40-Hositate
42-Conjunction 48-Bundles of grain 47-Repositories for the
dead
60-Husks of grain'
61-inflammatory
dicesse
83-Confunction
£2 45
144
57
62
(67
169
THE INTERNATIONAL SYNDICATE.
HORIZONTAL (Gone) 54-Bird |-56-Draft animal [07-Exclamation [88-To cut hay 60-Bird's beak 61-Give peln 62-Title' of respect. 65-Beseech 65-Take notice
(Latin-abbr.) 66-Canadian provinca
(abbr)
67-Apex 68-Not any 69-Metal or wooden
band
VERTICAL 1-Container for
liquids 2-Part of verb "to 3-Dafied
4-Answers B-Preposition, &-Depressed 7-Mctor fuel B-To tinge 10-Witch
13-Touch lightly 13-Costume 14-06 ashore 16-Acid
18-Gand
--Cor-diet
VERTICAL (Cont.) 22-8mall spooka 24-Govering of an
aalmal
26-To pinch 28-Preposition |29–Elderly, women
30-Play carelessly an
stringed instrument [31-Empire' 6tate
(abbe.) |34-Hydraullo engine.
37-Exclamation 38-Egunare- 39-0lrd
40-Tissue forming body
of tooth
|41–Mischievous |42-intermittent faver
43-Balt fastanor
| 44–Profix magning from
be" 46-Blender
(46-Conceited
48-Enwrap
|49–Mark caused by
wound
53-Watch pocket. 55-Recede
56-Male human being 57-Part of the human
body
59-A protuberance |62-Staep in 'iquid
54-Procand 157-Preposition
(The solution of the above cross-word puzzle will appear in to-morrow's issue along with a new croge-word puzzle.)
YESTERDAY'S SOLUTION. UNSPENT A9309TS NEE COD BEE DWL AWE HUM EVE 200 TURBULONT
R RD3 ELAPSE- TENANT
ENTHATED MOET
15 SUP P JELL_RENES LORE GED ETHOGAL R_NAME ENULATING V PAT ATE ADO SPA ERA ROT RED KIT SCALEDS ZACNUTE
**THE INVIAMATIONĪNS SYNDICATE,
becomes possible to employ larger therefore coupling condensers, passing lower frequencies for the desired bass notes, while effective-
a relatively high positive potential ed it, and with it all its harmful upon the plate that the repelling effects upon circuit efficiency.
In short-wave reception, whey preventing blocking or choking effect of the grid can be over- Therefore, by placing the fourth ther relay broadcasting or code, by lowering the grid leak resist- come. There is also another effect electrode between the plate and the grid leak is quite critical in ance. The use of a variable grid which tends to prevent this flow, grid a valve is produced which has value. Experimenters report, try-leak in resistance coupling is and it is caused by the electrons very great advantages. It is high- ing as many as 50 grid leaks be shown in Fig. 3. In impedance- themselves. The filament is sur- ly efficient as to plate potential; fore the satisfactory value has coupling the arrangement remains rounded by a cloud of them, all it has great amplification and been found. The best value is the same.
of which are negative. Some of practically no grid-plate capacity, usually between 4 and 8 megohms. It is well to note in passing that them reach the plate, some simply so that it is practically self- With a satisfactory variable grid resistance coupling is capable of shoot off and float close to the stabilising.
leak, however, any and every value responding to very low frequencies, filament, so that any which follow
LINCLAIMED TELEGRAMS.
THE GREAT NORTHERN TELEGRAPH CO., LTD.,
OF DENMARK.
The following unclaimed tele- grama are lying at the office of the Great Northern Telegraph Com- pany (Limited) of Denmark:
Y. V. Alliv, from Shanghai. Mapocho Sailing, from Shanghai. A.P.C, from Shanghai.
Y. V. Activ, from Shanghai. Pak Ngok, from Kobe.
S. Reppert, Victoria Hotel, from (Shanghai.
E. V. JESSEN,
Superintendent.
Hong Kong, 2nd August, 1928.
THE EASTERN EXTENSION
AUSTRALASIA & CHINA TELEGRAPH CO., LTD.
The following Unclaimed Tele-
As regards the actual wiring of la instantly available, and whon with the result that there is some-grame have to force their way through the valve, it is just the same as the best value is found it may be times set up a low-frequency oscil Telegraph Co. office, Hong Kong:- this cloud or field. This collection that for ordinary type except that left permanently in circuit. In lation, due to coupling between cir- is called the space charge, and the the additional grid is connected to the case of the variable grid leak culte, known as "motorboating." plate has to overcome this as well a point on the B battery. The the lug insulated from the abell The simplest way to offest motor-
is lying in the E. E
Salamstone, from Singapore.
E. A. LEGGATT, as the resistance offered by the diagrammatic connections of a should be connected to the grid of boating when it does occur is to
Superintendent. grid. It is, therefore, easy to see valve of this are shown in the the tube, and the shell to the Fmake the amplifier less efficient at that a considerable part of the sketch, where the valve is in cir plus
Hong Kong, 2nd August, 1928. detector socket terminal. low frequencies, which in turn Bug- plate potential is utilised solely cult as a radio frequency amplifier, This is a better arrangement than gests the use of lower resistance for the purpose of counteracting At first it would appear that the connecting the leak across the grid grid leaks for one or more stages, The decree regulating all ex- THE HONG KONG OPTICAL CO. these effecte.
extra grid, being at a positive condenser, because when the shell Actually the space charge, be potential, would cause an extra is grounded to the tube filament together with smaller blocking or noitation in Colombia, which was cause it is so much closer to the current to flow, but actually the no hand capacity effect. Is Intro lowering of the grid leak resistance laat January, and against which coupling condensers. Often the faued by the Minister of Industries grid, is the more harmful, so that amount of this is so small that it duced. if we could do away with it we may be neglected...
in the first or second stage will foreign all interests strongly pro- Resistance Coupling. should only require a much small- One of ita chief advantages is Aside from the detector, the grid serve the purpose. In this respect tested, has been suspended. er plate potential to obtain re- 'that' erdinary neutralisation leak has an important function to a variable grid leak, substituted for sults equal to those obtained at methods are no longer necessary, serve in resistance and impedance the first or second fixed grid leaks, The first planetarium to be present, and the grid would also which is in itself a great simpli- coupling. While the plate couple will serve na a simple cure. be much more effective. In other fication." It is, however, very ing resistance usually is not criti-' All in all, adjustable grid leak re-structed. words, the amplification factor necessary to take great care with cal, the grid resister is of consi-sistance is virtually a necessity in Michigan at a cost of £100,000. The would be improved without alter, the design and lay-out of the cir- derable importance. By means of any circuit for which maximum effi- plan of the building will follow the Ing the other characteristics.
cult
precise resistadco of grid leak, itciency is a prerequisite,
German model.
'Phone 2282.
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erected in America is to be con- on an island in Lake
ROCKED IN §
BEAUTIFUL
THE CRADLE -
BRAVO!
BRAVO!
DO YOU WANT?
Price List of Flower and Vegetable Seeds for 1928 SEASON
with brief cultural instructions and approximate time for
BOWING.
The opportunity of forwarding you a copy, will be a pleasure and your commands will have our best attention.
GRACA & CO. Dealers in Garden Seeds, Post-
age Stamps, Pictura
cards, Toys, etc.
Post.
No. 10, WYNDHAM STREET,
P. O. Box No. 620. HONG KONG
OF THE
DEEP
HE CERTAINLY IS BRAVE TO TRY TO GIT AWAY WITH.
THAT-
BRINGING :: UP FATHER.
ITMANK GOODNESS-
THAT WA LAST SONG-E ONLY REGRET~ I GOT HERE SO "SOON-
DIDN'T YOU UKE ITSI THINK NË DINGS WI BUCH FEELING-
“YES-HIS LAST
SONG MADE ME FEEL SEASICK-
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