MUSIC FROM MANY COUNTRIES by wireless withi TELEFUNKEN 40 Long range All-Electric receiver with station selector for use with batteries Lighting
mační.
with
or
· TELEFUNKEN
LOUDSPEAKER
ARCOPHON
HONG KONG DAILY PRESS, THURSDAY, JANUARY 29, 1931.
TADIO4
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-Shameen.
Swatow
-Gebr. Roese,
TELEFUNKEN
LONGEST EXPERIENCE-LATEST DESIGN.
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The Famous Blue Tubes
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Exclusive Features:--
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FEATURES
THE MAGNO-DYNAMIC LOUD-
SPEAKER.
ITS BRILLIANCE OF REPRODUCTION IS PROBABLY
UNEQUALLED.
WILL IT DISPLACE THE MAINS-ENERGISED FIELD MAGNET?
For the second year in succession n Farranti laud-speaker has recorded the largest number of votes in the loud-speaker section in the voting competition arranged by the Wireles, World in eonncetion with the Olympia Radio Show. This year it was the Magne-Dynamic moving-coil unit which so favourably impressed visitors to Olympia.
permanent magnet model is only very slightly less; indeed, 'a' direct comparison would be necessary in order to appreciate the difference.
Frequency tests over a
range
This is hardly surprising, for now | machine so that it is not necessary | gised electro-dynamic loud speakers that the flux densities provided by to leave a magnetising coil inside showed that the sensitivity of the
The polo pieces are permanent magnets have been the core. brought up to the standard set by electro-plated to prevent the forms mains-energised field magnets. The tion of rust in the air gap, which complication, expense and mainten- is only 0.075in, wide. With this ance of A.C, rectifiers and the magnet a total flux density of 13,000 naxielics associated with EMFs lines per square centimetre is oh-from 50 to 0,000 cycles revealed when switching of D.C. mains fields, [tained, and the useful flux density that the response in the middlo In designing the permanent in the vicinity of the moving-coil is register is sensitively uniform from magnet special attention has been 8,000 lines per sq. in. This figure 200 up to 3,000 cyclca. Above and directed to the question of perman-is obtained by making use of a below these limits the characteris- The increased output ence, and in this connection the specially designed instrument in tie risen. designers are able to draw on 401 which the movement of the search down to 20 eyeles is sufficient to give body to general result without years' experience in the manufac-coil is limited to 3/16 in.
The design of the diaphragm and introducing objectionablo "boom." ture of permanent inagnets for electric meters and measuring in-moving-coil is similar to that of the It is from 4,000 cycles upwards that struments, in which perma.ence of other moving-coil loud-speakers in the response is so unusually good, calibration is of prime importance. the Ferranti range. The 90-degree and the regulfing brilliance inpart- It is, therefore, interesting to find diaphragm is of comparatively small ed to the quality is probably un- that the steel alloy in the field diameter, and is fitted with a cen-equalled by other loud-speakers, magnet contains as much as 35 per tring device at the apex to prevent cent, of cobalt and is by no means lateral movement of the speech cheap to produce. The design of coil, the magnet has been patented, and it is magnetised in special
SOME USEFUL HINTS. When joining up a flexible wire to the terminal on the top of the bulb of a screened-grid valve, re- member that the thread on the nut should not be strained by tighten ing with pliers, as a good finger tight connection is quite satisfac- tory.
*
Comparisons with the records of previous tests, on the inainn-cher-
seven-no joke for a person with only a dry battery or a small mains eliminator.
Do not forget when you build your next set, or if you consider Buying a mains unit, that you want to take carefully into consideration You want to those milliamps.
The choice of a permanent magnes moving-coil. loud-speaker is nigni- Acant, for it is generally believed that this type is destined ultimately to dispince the older type of mains energised field magnet.
make sure you can supply all the milliamps required by your net at the correct voltage. If you are on the mains there is no need to grudge a few milliamps to your power valve-it will repay you but if you use dry batteries you have to be more careful.
Do not destroy the leaflets, and HAVE YOU HEARD THESE?
instruction charts which you may get from time to time when purchas ing components. Uso a drawing-pin to held them all inside the lid of the set, where they will always be easy to find and may prove invalu- able if you decide to alter the cir- cuit in some way.
•
The lead-in from an indoor aerial, as from an outdoor aerial, should generally come from one end of the parallel wire (or wires), or from the centre.
"
for
An extra pair of "hands holding small work while it is sol. dered can easily be improvised by slipping a strong elastic band over the handle of a pair of pliers.
The golden rule for successful soldering is to keep the iron and work clean, and at the correct, tom- perature.
*
*
The numbers on & tuning dial have no direct relation to wave. length, but merely indicate the posi tion of the moving plates in relation to the fixed plates.
•
If you wish to relate the figures on your condenser dials to the wave- lengths covered you must "cali- brate
11 the set.
[“Calibration " simply means the -preparation of a list, chart or table showing wave-length 6gures, and the corresponding condenser dial reading.
A calibration "curve" not only onables you to refer back to stations previously picked up but it also shows you the condenser readings for other stations.
-WATCH THE, PENTODE..
Horo are lists of long-wavO and short-wave stations which should be picked up by anyone in Hong Kong who has a mode rately good set maitable for re- ceiving such 'signals, Success in picking up these stations also depends very largely upon fav. ourable atmospheric conditions. Readore are invited to add to this list should they succeed in picking up any station not in- cluded in either of those lists.
LONG-WAVE STATIONS.
WATO length (Metres) Station
200 Manila 277 Shanghai 280 Tientsin 310 Shangbai 320. Peping 345. Tokyo 353 Hiroshima
Call Kilo- Sigo cycle. K.Z.I.E. 1,153 K.S.M.H. 1,085 C.R.C. 1,070 K.R.C. C.O.P.K. J.O.A.K.
J.O.F.K., "860
V.U.B.
355 Hong Kong Z.B.W. 357 Bombay 301 Sapporo 383 Keijo
370 Nagoya 370.4 Calcutta 380 Kumamoto 300. Bendri 305 Dairen 308 Rangoon 400 Oka
410 Canton
413 Manilo
SHORT-WAVE STATIONS.
STATION
Carl Brux
KILO
945
870
840
840
3.0.I.K. 830
J.O.D.K. 820
800.0
J.O.O.K. 810 V.U.C J.O.G.K. 700 3.0.H.K. 770. J.D.A.K. 760 V.U.R 754 J.O.D.K. 750
C.M.B. K Z.R.M.
TIME (HOND Eoxo)
OF WORKING
129 798
4,434 Mon, Wed. & Fri, 6 p.m. & 2 a.m. 4,0900-10 p.m.
5,000 | Tuok; Thumm, Sat, 8 p.m.
6,808 Bunday midnight
7,142 Daily 6.80 p.m. &-11 p.m.
7310 Not regular
8,308 Taus. & Fri., 9pm-1a.m.
67,65 Dobintz (Gormany) 60.12 Khabarovsk (Russia) 66.7 Νατόπ 60. Moscow
A.F.K. B.A.97.
A.G.J.
5,201 Not regular
REN.
435
Kome
1.M.A.
41.3 $1.8
22,b
Porth Bisgapore
BAG.
V.8.1.A.B.
Kootwijk (Holland) Bangkok (Bikm)
P.O.L
7,730 Daily 11 p..
81.55 8148
31.
27.8
2.B.L. B.IO. Schenectady
W.3.X,4,F. 0,650 Daily 7 a.m. 81.20 Eindhoron (Holland) | P.CJ. $1.29
.F.O. Sydney Nairobi (Konya) 7.LO. 28.5 Sydney
#SAPJ.
0,230 Not regular
Z.M.E.
10,620 Not regular
Bandcong
PLR 25.53 Chelmsford (England)] 5.8.W.
If you use a pentode watch it carefully, for pontodes have a truly way of getting rid of nilliamps, without one knowing. One reckons the plate of a pentode may take 19: 100 Bangkok
་་་་་་་་་ལ་འབྱུས་གྱི་ཀྱི་ཉི་qa Tsau /
inandoons
25.0 Nancy (France)
get the screening grid, wine ly. "ent up" another 3 or 4, de
THE SINCERE Co., LTD. wending on the make of the valve
DISTRIBUTORS.
Some pentode valven take as much ne 96 milliamps on the anode when properly binssed, and on top of that the acrooning grid takes another (Continued on next Column.)
0,600 Not regular-
•
0,020 Fri. 3 am Sat, 3 am, & 10 am.. 9,590 Not regular
́9,677 | Midnight daily
11,020 Midnight—9 nm, dally 11,761 7.30 pm. & 3 a.m, daily, except
Baturday and Banday
| 12,740 | Nightly
12,850m. Wed., Fri., Bat.
16,102 Daily 030 p.m. to midnight
17.280 Daily 8 pm to midnight
240
Manila 20.85 Bobonectady 18.89 Bandoeng
ELX.E..
W.2.1.0.
PLG.
.18.4 Kootwijk (Holland)
Vendoong $17.4
F.C.L.
|16,804 | Dally 7 pm, 2005,
P.L.F.
H.8.1.FJ.
landi
17,761 Sunday 7 p.n. & midnight 118,401 Each efternoon
TEST Daly & A
WELL.
· 15,00 || Pittsburg
| 21,540 | Not regular
Lallowance must be made for summer-time" in most Euro pean countries, which is one hour ahead of trus time.]
AC SG3
Set
ENTIRELY MAINS OPERATED
A sensation in 3 valva sela, with 1 watt undistorted output; enough power for any, moving coil or dynamic loudspeaker.. A not that will appeal to you whetlier you are interested in porfect 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 perfect reception
use
$4
* MAZDA” Valves, large stock newly arrived
RADIO batteries made by new process minimis- ing deterioration "PERTRIX" 150, 100, 60, 45 volts and C. batteries.
Ebonite "TROLIT" and Pressed Fibre Panels cut in any size. Loudspeakers, and various parts are also obtainable.
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