TSANG FOOK PIANO COMPANY,
8, Des Vœux Road Central (Entrance Ice House Street) Telephone 24648.
Simplicity itself
One-motion, tuning. Simplified circuit. Units all interchange=" ¿ble.
There's nothing like
The
micro-synchronous
Victor Radio
THE HONG KONG DAILY PRESS, THURSDAY, MAY 29, 1930.
RADIO
FEATURES
THE SCREENED GRID VALVE.
GREATER HIGH-FREQUENCY AMPLIFICATION. -
[Br" COMERER."]
Screen Design.
+
The ordinary triode high-frequency valve, whose duty it is to increase
One can imagine such a screen the incoming signal current before
as being a piece of metal shaped being passed to the detector stage, so as to completely enclose either has always been subject to feed-
one or the other of the two ele back, an uncontrollable reactionments that are giving cause. to the effect that readers this stage, im-troublesome capacity effect. portant to long-distance reception, Such a practice would obviously unstable when called upon to handle prevent the electronic flow which, an input of any strength. This is
as discussed in the last article, is caused by the capacity effect be the essential function of the ther. tween the grid and the anode, and mionic tube. attempts were made, first by Dr. Hut, of Schenectady, four years ago, to prevent this capacity by placing a screen between the two electrodes.
Hull's Erst valve was quite successful. having reduced this inter-electrode capacity to 0.006 "micro-farads, a figure of practically no conséquence even in high-fre- quency amplißention. Unfortunate-
A compromise is struck by per- forating the screen to a grid-like construction, and applying a posi- tive potential. It is obvious that in having thus to provide for the electronic flow a certain amount of undesired capacity will still take place within the tube. It was this
element that caused the unsatisfac
tery initial reception to the screen- ed grid valve already mentioned.
Neutralising Valve Capacity. With the ordinary, triode valve ly this valve was merely experi-inter-electrode capacity was, to a certain extent, overcome by the mental in construction, its commer-
employment of a neutralising con- cial production in quantity not denser. being practicable.
With the earliest S.G. valves the capacity, though too small to be neutralised, was nevertheless suff- cient to cause instability, but recent developments have brought the capacity to au almost negligible figure.
The inter-electrode capacity bas never been completely eliminated. The First S.G. Valves.
being merely brought down to It was more than a year after figure so small as to make its reu- this initial experiment that screen-tralisation too big a feat for the ed grid valves were first placed on smallest condenser it is possible to the market For a long time this construct. new offering 'to the radio amateur tailed to ve up to expectations, and the many promises made of its performance prior to its present tion appeared to he unfulfilled The early difficulties have since been overcome. and the screened grid tube as
high- frequency amplification is now as important a factor as the Pentode Lis for low-frequency amplification. There is a similarity between the two valves, inasmuch as, the screen to overcome the capacity in screened grid valve takes the form of an extra grid.
a means
A RADIO with Living Tone
Я
Even so, the use of the screened grid valve, as with the Pentade, necessitates a special ejrcuit, and any amateur who attempts to re- place an ordinary three-electrode. tube with one of the S.G. type without redesigning his set to meet the change will be doomed to dis-i appointment.
i
Greater, H.P. Amplification.
With a suitable circuit employing this type of valve it is now possible 6 to use two or three stages of high- frequency amplification in cascade. a feature hitherto, impossible with. out employing stabilising devices which resulted in a certain amount" of loss in efficiency.
Screened grid valves have un- doubtedly opened up a new field in receiver design, and it is the new system of component connection required rather than the valve it self that has caused such strides in H.F. amplification per stage.
The latest range of S.G. valves which take their current from A.C. mains give a stage gain of one to three hundred with a remarkable. performance as to faithful handling of received currents without distor tion.
Choosing an S.0.
With such a vast range of screco- ed grid valves on the market the selection of one for a particular type of receiver must present some- thing of a prohler to the average
amateur.
In all cases the main objective sculd be the maximum stage gain within the limit of the inter-elec- trode capacity, that can be handled. This latter will depend on the de-. siga and the coils of the circuit employing the valve.
THE THREE MILLION MARK.
In Great Britain receiving licences have passed the three million, mark. The total, exclusive of licences issued free to the blind, is now 3,008,803. The same mark has just been reached by Germany.
A contributor to the B.B.C. post=" hag last month urged the Corpors- tion to send its waves at a slower need, mentioning that his set was fitted with a slow-motion dia!.
HAVE YOU HEARD THESE?
Boré 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 set suitable for re- colving 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 ta cluded in either of these lists.
LONG-WAVE STATIONS.
Wave length
(Metres) Station
260 Manila
Call Kilo- Sign cycle K.Z.I.B. 1,153
277 Shanghai, K.S.M.S. 1,083
230 Tientsin
310 Shanghai
320 Peping 343 Tokyo 353 Hiroshima
C.R.C. 1,070 K.R.C. 907 C.O.P.K. 945 J.O.A.K. 870 J.O.F.K. "930
355 Hong Kong Z.B.W. 214 357 Bombay V.U.B. 840 **361 Sapporo .J.O.I.K. 230
380. Keijo
J.O.D.K. 820
370 Nagoya J.O.C.K. 810 370.4 Calcutta; V.U.C- 800.9 380 Kumamoto, J.O.G.K. 700 300 Sendai J.O.H.K. 770 J.D.A.K. 760
395 Dairen
308 Rangoon V.U.R. 754
400 Osaka
"410 Canton
J.O.B.K 750
C.M.B. 732 K.Z.F.M. 726
TO-DAY'S WIRELESS
PROGRAMME.
BROADCAST BY Z.B. W. ON 338 METRES.
11 to 11.30 h.m.-Commercial News. 11.30 am to 12.30 p.m.-Chinese
programme.
Shuster and Philips). Sophie Tucker, Comedienne with Ted Shapiro and His Orchestra. 4:38 pm New Sullivan Selve tion" (Arr. Dan Godfrey), H. M. Grenadier Guards Conduct-8 ed by Capt. George Miller.
7.54 p.m.-" Fighting Strength
(Herberte Jordan) and "Radio, Quick March" (Herman Peck- ing), Regimental Band of H
Grenadier Guards. p.m.-Chinese programme.
7.04 p.m. From The Canebruke" 0 p.m.-Weather report, (Gardner) and Estrellita 19.30 p.m.-Close down.
...
M. Ponce), Violin Solo by Al-
bert Sammons (at the Piano:
Gerald Moore).
19.30 to p.m.-Programme of 1.10 p.m. Will O' The Whispers" For Better Result
6.30
Columbia Records by Courtesy of Messrs. Anderson Music Co.: to 6.30 p.m.-Aunty Letty and Aunty Joy will entertain the Children..
to Sp.m.-Programme of Columbia Records by Courtesy Music of Messrs. Anderson Company:
i)
6.30 p.m. Bitter Sweet (Noel Coward) Columbia Light Opera Company with Orchestra. 6.38 p.m. Faery Song, from The Immortal Hour" (F. Macleod and R. Boughton) and The Minstrel (Helen Taylor and William Easthope Martin), Heseltine, Tenor with Orches-
6:44
6.50
tra.
p.m.-Zip Zip" (Byron Brooke) and
Whispering Pines W. Byrne), Sir Don Godfrey conducting the Bourne-
outh Municipal Orchestra. p.m. He's Tall, Dark And Handsome" (Tobias and Sher- man) and ** Virginia (Bryan,
(Gershwin and Gershwin) and "This Year
of Grace" (Coward), Norah Blaney, Comedienne with Piano.
7.16 p.m." Anita (Pollack and
Clare) find "Progressions (Len Fillis), Banjo Solo by Lea Filis (Sir Bright at the Piano).
Mi
7.99 p.m. The Thistle" (Lyddle-
ton, arr. Winterbottom), HM Grenadier Guards Conducted by Capt. George Miller.
7.30
. The Bing Boys are Here: I Stopped; I Looked; I Listened" and Another Little Drink Wouldn't Do Us Any Harm." Trio: "Violet Loraine, Alfred Lester and George Robey.
cert
7.35 p.m.-"Petite Suite De Con- (5. Coleridge-Taylor), New Queen's Hall Light Or chestra,
4
7.46 p.m. Petit Suite De Con-
cert No. 3 and 4" (S: Colr ridge-Taylor), New Queen' Hall Light Orchestra.
BUY BRITISH & BE PROUD: We have just unpacked a Shipment of
ALUMINIUM BASE-BOARD & PANELS.
Suitable for Short Wave Receivers and other asta that require Screening &
OTHER RADIO & WIRELESS PARTS (Guaranteed British Made).
ORIENTAL COMMERCIAL & Co., LTD.
BANK OF CANTON BUILDING, TEL. 24405.
THE NEW SCREEN-GRID 4-VALVE SET GETS YOU THERE ANY DAY!
TELEFUNKEN40
NOVEL
STATION-SELECTOR
NO OUTDOOR AERIAL-NO FRAME
AERIAL
LONG-DISTANCE RECEPTION GUARANTEED MUSICAL RANGE 7 OCTAVES
WILL WORK FROM A. C.-OR
D. C.-MAINS OR FROM BATTERIES
TROUBLE-FREE RADIO
AT LAST!
TELE
FUN
KEN
TRY
MULLARD
THE BEST BRITISH MAKE
THE
MASTER VALVE
British & American Base's "Available
SINCERE'S
SOLE DISTRIBUTORS
THE
LOEWE FE 63
9 tube set
.is one of the most effectively sensitized instruments of the age, and reproduces the human voice, and music, flawlessly.
This set requires a Frame Aerial only with new Barium tubes. Can also be used with LOEWE short wave attachment..
Demonstration Hours:—
11-11.30 am.
During demonstration hours expert European advice
riven on all Wireless matters. ....
THE
CANTON TRADING ASSOCIATOIN, LTD.
CARL SCHROTEE; Manager-- OTH FLOOR, CHINA BLDG.
TELEPHONE 246107
413 Manila
SHORT-WAVE STATIONS.
STATION
CALL SIGN
עולס
CYCLES
· TIME (HONG KONG)
OF WORKING,
56.7
60.
43.5.
42.
41.3
$1.85 Dobintz (Germany) A.F.E. 50.12 Khabarovsk (Russia)
Клиен Moscow Rome Forth Singapore
4,434 Mon, Wed, & Fri, 6 pm. & 2 8.0.
B.A.97.
4,000 6-10 p.m.
A.G.J.
5,201 Not regular
RE.N.
6,000 T, Thurs., Sat, 8 p
LH.A.
8,898 Sunday midnight
BAG.
V.B.1.A.B.
38.6 Kootwijk (Holland)
38,5 Bydney
31.56 Melbournis
2.B.L. 8.1.0.
12.30-
-1.30 p.m. 5-5,30 p.m.
31.48 Schenectady
W.2.X.A.F.
21.20 Eindhoven (Holland) | P.C.J. 31.28 6ydney
28.5 Bydnay
23. Bandoeng
2.F.C. 31. Nairobi (Kenya) 7.LO.
2.M.E. PLE 26.53 Chelmsford (England) 6.S.W
P.C.L. 37. Bangkok (Biam) 654PJ.
7,142 Daily 6.30 p.m. & 11 p.m.
7730 Daily 11 p..
8,108 Tues. & FIL, 9.p.m.---1 am.
"9,230 Not regular
9,503 Not regular
9,620 Fri 8 Sat, 3 km, & 10 am,
9590 Not regular
9,677 Midnight daily
11,020 Midnight 3 m. daily
11,751 7.30 p.m. & 8 a.m, dally, except
Saturday and Sunday
7,310 Not regular
9,630 Dally 7 AL
10,528 Not regular
Showroom
24.5 Manila
X.1.X.E
12.240 Rightly
ZLIK
18.88 Bandoeng
PLG.
18,4
Kootwijk (Holland) POL
10,102 Daily 8.40 pim. to midnight 18,804 Daily 7 pm
KOWLOON
17,4
Bandoeng
· 16.9-
Bangkok
16.88 Huizen (Holland)
P.L.F. H.8.1.P.. P.H.L
17280 Daily 8 pm to midnight 17,751 Sundays 7 p.m. & midnight
17789 Dzily 10 pán.
PEKINO BUILDINGS,
16.3 Kootwijk (Holland) F.C.K
.18,404 | Each afternoon
16.74 Bandowng
P.LE.
19,220 Dally 5.30–7.p.3.
TELEM
FUN |KEN?
27, NATHAN ROAD.
16.5
(France)
19,351 Delly 8.
33.93 Pittburg
WJIK.
21,640 Not regular
TELEFUNKEN
SIEMENS CHINA Co.,
PEDDER BUILDING, 4TH FLOOR, HONG KONG.
Also Obtainable:
IAM MRI KINETOIN E. 185, Dra Veux ROAD.
HUNG MING ELECTRIC CO., 157, Drs Vaux ROAD. ANDERSON MUSIC Co
ST. GEORGE's Building,
ION HOUSE Brasxr.""
TELE
FUN KEN