1932-05-05 — Page 2

HONG KO

Page

FEATURES

TECHNICAL NOTES. really remain set. It depends, of by trying, so to speak a measure rings, and in practice in certain course upon the particular con of it. For instance, you may try struction of a pro-set condenser, fusing a small value of grid leak, but in some as these vary quite buned to perhaps half a mogom considerably within a short period instead of the conventional two of being, adjusted

mogobme.

་་

conditions the method is readon ably astisfactory. To deponds very largely upon the strongth of the in- coming signna,

IMPROVING YOUR

RECEPTION

Why is it that two sets made from similar designe can be so total

In caused by excessive H.T. on" dotector. If reducing the JUSSIT T" BRSCU"a" "oure, try the op poslto increase the LT slightly.. This doesn't mean puiting # volta. Bearing in mind that you have

on 4-volt valves Is marely means If this produces an improvement reduced the working part of the ly different, and why do you suma---see that your detector valve is in some ways, it may at the same characteristic curve of the valves, times find a set that is beautifully gotting all the L. T. volts that you time upset the resotion, and thay buscado são that is the incoming easy to handle while another, and think it is will have to be corrosted. A simple sigpid are exceptionally strong, quite simil way of counteracting the interfersucht as the signals, for instanca, brüta enco with the rosion is to use a from the dread station, you may run pretentiometer across the low ten into distortion. So if you are Another reason why dificulty may sion, and councet the grid leak to thinking of nang this method, you sometimes be experienced in gang the slider of the potentiometer in have to deaide beforchand whether ing up circuits, is because the coilsstead of to LT. position,

the signals you intend to receivó are not properly matched.

will bo strong enough to cause dia-

With ganged condensors a trim ming condonker is generally provid ed across one or more of the ofrenite so that they may be brought into If, therefore, you are using gang tune." This method is fairly. con- fed condensers and the ganging doen youient in many ways "hut" some not seem to be quite perfect, it is times the opacity of the aerial willa kood plan to try adjusting the Bompletely, upset the whole of the pre-set condenser again, as in all tuning, and as serial capacities "probability you will and that this vany very grondly, it is important has changed slightly. to have some cans of avoiding interference with the tanning in

this way.

One arrangement which is often used is to introduce a condenser of small capacity in series with the aerial, and before the point at which the sarial lond is connected to the top of the tuning coil. The capacity of this condenair may be as small as 35, or oven 25 miero miorofaradi. With this arranger

حمام

At the same time, it is often a

This does not necessarily mean to good plan to use a higher valua say that the coils are not in them of HT on the detetor than is com selves matched, but it may be that monly used. This naturally de when they are in their working:pends upon the type of valvayem. positions, circumstances alter their ployed as detector, and with some effective inductive values.

types the value of H.T. must be comparatively low, but with certain high impedance valves which are often used as detectors, as much as

necessary for the best fesults.

MATCHING COLS.

tortion owing to the limitation, of the working part of the curves.

COMPONENTS AND TONE

"Look to the Dat.!!!! First, and foremost, if you have a set whose behaviour

tameable variety, look to the

detector..

Very often in a large multi-valver the EF stages give trouble, but far more often the detector is not doing it bit. Furthermore, figuras Referring to the question of the still prove that the vast majority tone of the reproduction at the of sets in this country are som loudspeaker this depends upon the partively simple three-valvers, obdrnoterjaties of various compon-mostly without H, and in the ante used in the circuit and some cases there is very little that can

TO DAYS WIRELESS PROGRAMMES

BROADCAST BY ZBW

„ON 355. METRES.

10 to 11:30 ;mi--Stock quotations. long30.Chinese programme

12:30 pr

penn Arogramme. Victor and H.M.V. recorda"

time and weather report.

Dirty witch re contacte, atraggling flex leads to the accumu labor, flament rheostata in partie cular (although one seldom seen them in use now), all have animack of bringing down your voltage just sufficiently to load you into rome

kind of, trouble..

1:30 pm. Rigby Pre news, ma

nótives, ate.

& pm-Close down

6 to 8 pm-European programme 6 to 6:30 pmt-Doctor Radio

give the last two clues of the Radio Treasure Hunt,

Lastly, look to your grid-lenk.. Very often the substitution of a loak of higher resistance than the 6.10 to 6.45pm, one in us will cure ploppy Frede tion without any other adjustments being made.

Another annoying trouble that all know is "hand capacity”. This

ment the aerial tuning will alternistinear to tuning condenser 100 volts, or even more, may be times; altogether; apart from any misbehave itselt except the date is more prevalent an short-wavers

only a very slight amount with differens aurials; so that the upset | in the trimming department is re- latively small.

VARYING THE TONE.

actual tone control device at the for output, you can do a good deal to give the bone any; particular desir- Now to get down to details. The

Ploppy *** Reaction...

For instance, suppose one of the

For any other metal part for that matter, this will have the effect of roducing its inductance ahd, of course, "throwing out the matching

There are various forms of tono ed quality by choosing one, or more misbehaviour may consist of course, you must have the moving | EFFECT OF AERIAL of the coile as a whole,

control, the simplest being an ar of the components in the proper several things. First is sleppy CAPACITY.

So you see that it is nes only a rangement of choke or condenser in way. Another prrangement which in question of getting the coils matchsarios with a fairly high rasistance.

reaction. There is no need for me

For instance, a low frequency to detail the gruesome symptoms

”" :‛,,n”

than any other receivers, and as generally due to poor layout and unnecessarily long wiring Of

vanes connected to earth; if you do not do this you may be quite cortain of trouble. Alay one very

sometimes. sed, is to connect the ed in the first instance, but also it The object of the resistance (a transformer may have a rising you all know the sickening thudful cure for this on short-wave

matched in their operating condi- simply to control the amount of finite characteristic curvo at the is equally important to he

have them variable resistance, by the way) is characteristic, that is to say, a rise with which some sete go in and sets is to remove the earth...

tions

aerial to a tapping on the ting coil, preferably a toping fairly near the earthed end of the coil to that the effect of the aerial capacity is greatly diminished. Of course, they may at the same time reduce the signal strength, and it

Without going to the length of is a question for you to decide quite popular a few years back. making a regular tone control, whether the signal strength will In caso spade tuning may not however, you can often obtain much stand reducing. E

bo familiar to the present day improved results from your long On the other hand the sun. Boneration of radio amateurs, apeaker" by connecting simply necting of the aerial to a point total plate was adapted in rela on the Luning coil nout the earthed tion to the ebil, in scissor fashion, fixed condenser across the output and will, as a rule, have the effect so that the effect upon the tuning circuit or across the loudspeaker it of sharpening up the selectivity, of the coil could be readily sell. This bas the affect the reducing Of these two arrangemente, the justed small condenser in series with the Anyway, all this shows you how the strength of the upper audio fre- aerial will often give a greater important the effect of neighbour quencies to an amount which in signal strength than the other. ing metal parts may be upon the cresas with the capacity of tho

tuning of the coils, and before condenser going to any elaborate trouble with: your ganging you should first of

by-passing which is brought about This alteration of the inchictive by the choke or condenser. The con- hine of the coil due to tao predoser, of course, jets through the one of the metal plate, is the lower ones. basis of a system of tuning known agapade, tuning, which wLS

In many manufactured receivers ms or other of the two arrange ments mentioned above is used in le of the trimming condenser.

***PRE-SETS! FOR

TRIMMERS

Talking about trimmers for gang. nd condensers, many of you prab ably use pro-set condensers for this purpose, and the question arises as to how long those presset condensers

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11

20

out of oscillation when you move lightest bouch Your set is not the reaction control, even with the oscillating you hear faint music up comes the reaction control, the music getting louder, louder and clearer, then-sor-freech-you are

A Concert.

Piano Solo Rococo (Palm-

Piano Solo-Le Peti

Blana" (Thart).-Benno Mpi-

19tich.-E492.

Sang Song

Afton Water" "(Burns). Annie Laurie Mar: Garden (Soprano)-1490. Violin Bolo E Bateau

(Boating) (Debussy).

Violin Solo-La Fille Aux

"Chevaux, de Lin (The Maiden, with Flaxen Hair) (Debusay- Hartmann)-Fritz Kreisler.

1308.

(Continued, on Page 5).

You may look upon these as two

bination of ploppy reaction and very small diffeuities but the com

hand-capacity effects is often dead ly enough to make strong men break down and woep Not only does the set shriek at you just as you trasgotting your station nicely but when you base and do it all over again.

performance ad lib, and really MUSIC. found him; he disappears the

higher andiofrequency end. A transformer of this kind will tend to bring out the higher notes with greater strength and so is useful in cases where the loudspeaker, for instance, only reproduces the higher notes poorly, same cases tho tuned sircuits in a set may have oscillating hard and you have to the effect of reducing the loudness Think of the man next door, too, of the higher notes, and a trans- if he is listening to that particular former of this type will go a long station way towards remedying the defeat.

PRESENT-DAY LAYOUTS.

It is not more than two or three years ago that we' used to aim at

80 back

epeated the

minute you move one finger away there must Now to cure it. First, see how from the dials. And yet much H. T your detector is get-be, thousands of sets like this still ting; saven times out of ten you in use will and that bad reaction control (Continued on Page 4.).

A large condensor will weaken laying out a set with plenty of Fall make sure that the coils are them considerably, a small 'conden.spacing between the various com

properly matched in their operater will only weaken them slightly. ponents so as to avoid any inter HAVE YOU HEARD THESE? Ling positions.

POWER-GRID DETECTION.

A good deal has been said lately about power-grid detection. With out going in for full-blooded power- grid detection, however, you can often obtain a distinct advantage.

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SOLE DISTRIBUTORS

Listeners have their own particular action. Now, however. are the days Lastes and fancies as regards the of compact arrangements, and in modifying of the tone for different view of the great, advances which items, diace bands, instrumental have been made in shielded com- music, songs, and so on.

ponents, and in the use of shields between components, layouts and A SET OF CONDENSERS.pce greatly economised. In some nuor quite a useful ar rangethent can be made by using

J

There is, however, all the differ- once in the world between a com- pact layout properly shield and a layout in which the parts are mere ly crowded together. Some of the

a number of fixed condensers of dit ferent capacities..so that any one of them, or any combination, can be connected across the loudspeaker present day portable sets on the The most usefull values of condenser market are really beautiful ex- for trying in this way are about 901, and '002 and somewhat larger

values.

It is not generally much good using just one condenser without any means of varying the effect. Either you must have a set of con densera of different values on hand for else you must have some form

amples of carefully-designed layout and will accommodate a receiver the equivalent of which, on the old. fashioned arrangement, would have occupied half a dozen times the space

COMPACTNESS AND

SHIELDING.

In arranging components close!

of control such as the variable high together, it is essential to avoid

resistance-in-serios with the con

densor

CONTROLLING. HF, AMPLIFICATION.

stray "couplings which will render

· Here are Hints of long-WA78: and short-wave stations, which should be picked up by anyone In Hong Kong who has a mode rately good set suitable for re- ceiving anal signals, Success in picking up these stations also depands very largely upon fav. curable atmospheric conditions. Readers are invited to add to this list should they succeed in ploking up any station not m-

cluded in sither of these Leta.

LONG-WAVE STATIONS.

K

WAYS: length

Call Siga cycle K.Z.J.B. 1,158

(Metres) Station

960 - Manila 277 Shanghai K.S.MLS. 1,083, 345 Tokyo, JOAK 870 353 Hiroshima 30.7K 850 355 Hong Kong Z.B. W 848 * 357,1 Bombay V.U.B., 840, 361. Sapporo J.O:LE.” #820 360 Keijo J.O.D.K8R0:2) 370, Nagoya

1.0.0.K BIO 370.4:Calcutta: V.E.C 800.9

380 Kumamoto JOG.K -890 Benda JOHT

306 Dairen! TAQ.A.K. 700 100 Osaka 1.0.B.K. 750 410 Canton C.M.B. 732

K.Z.RM. 480 Manila

625

SHORT-WAVE STATIONS.

STATION

CALL BLOT

60.7

48.8

Nauenw Moncio

Parth

863

B.PN L.M.A

Ко

“Taxx (Hoxa Kowa)-

OF WORKIND

4,436 Mon, Wed & Frí, & pim. ★ 2 asm.

· 4,090 [0-10pm 6

5,291) Not regular

6,000 Tucs

6,806 Bunds

640417,169, Dally

VOLAR

•P.C.L

F.C.E;

7310 Not reg 74780 Dall

ESP ́8,000 | Tam, & 119.

2BL, SUM 990 Not regular 3509 Not regula

WRIA.F. 9,580 Daily

9,030 Fri 8 m. Bak 1 am, & 10 am. 3,800 | Net rega

PC. 2.2.0.0

Bálky

10600 Not

11/Midal

11,761 7.30 p.m.

WAKO. FLG M16,10% PC.L

87.65 Dobintz (Germany) ARK the sot entirely unstable Thielis 60:19 Khabarovsk (Russia) 97

MAGLI one of the reasons why, when, you are setting to work to make a re- ceiver from published design or There are various methods for blue print, you should be so very 38.5 Kootwijk (Holland) regulating the amount of high-fre careful to keep to the designer's in- 1786) Bangkok (Max)

Sydney quency amplification obtainable in

structions.

31.58 Kalbourne

Schenectady set, although they all have their

Always bear in mind that before 81.48

120 Eindhoven (Holland) particular drawbacks. One method a design is published, in "P.W."

81.99 Sydney which is very commonly used is a for instanco,

detail of the 81 Bairobi (Kenys)

2.M.E. 38.6 Bydney potentiometer in the screen circuit arrangement is carefully thought | Bandoeng

PL of the screened-grid valves. Tout by experta and tested,

25.53 Chelmsford (England) 5.5.W potentiometer may be adjusted others is really no need for you to as to reducu the voltage applied to depart from it in any way. If you

28.35 Sahenectady the sareen" below the normal value are expert yourself and you wish,

18.88 Bandong- and this will have the affect of for some particular reason, to 19 oblik (Holland) course, of reducing the ILF. am modify the design, you mayý be quite plification: Howell able to do it, but for the 199 Bangkok

It is important to note, however, majority of amateurs it is a verT that the reduction in amplification : wise plan not, tou risk introducing || 16.74 is brought about according to this modifications especially in regard%20

18.08 method by changing the charsoteris. I to soreening, which may only run tice of the valves, since the imped you into trouble. Stick faithfully anon of the valves in increased and to the, designer's layout, and you the slope is reduced. Now this should get the full results of which may be all very well, over a certain / the sot i capable::

and

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