NOTES AND COMMENTS

Radio Record, Volume I, Issue 41, 27 April 1928, Page 8

NOTES AND COMMENTS

(By

Switch

A BRUSSELS scientist considers that migratory birds are guided by the same electro-magnetic waves as are employed for broadcasting. ‘This sugests a reason why the start of the ’B.B.C. winter programmes coincides with the flight of the birds from that country. AS soon as a joint has been soldered it should be wiped over with a clean duster in order to remove the liquified flux, which is otherwise liable to cause leakage. FOUR violins, valued at £3000 each, were used récently in a musical art quartet, including Sascha Jacobsen, who broadcast from an American station. The violins are four Strads, purchased by Felix Warburg. OMMUNICATION was established with fourteen amateur stations in six States-from un aeroplane flying in Canada recently, as a result of tests planned by local radio experts. The greatest two-way distance coyered was with two amateurs in Oakmont, Pa., 500 miles away. Communication was maintained for an hour and a half whilst the craft was in the air. MBE. LLOYD GEORGE and has daughter have given wireless sets to the North Wales Blind School at Rhyl, England. "The sound waves from a loudspeaker ate’ not projected evenly. The higher notes go straight forward, while the lower notes tend to go off sideways, and even round towards the back of the instrument. This is referred to as "spillizg."" A good plan to eliminate this trouble is to place the speaker close to and facing away from a wall, so that some of those elusive low notes can be reflected again to the front. A DEVICE that can ke. used as a fixed crystal, a traasmitter microphone, an amplifier, a telephone, a stethoscope, a hand microphone, a phonograph amplifier, a morse code practising device, a taiking light, a submarine signaller, a detector, a grid leak, loudspeaker transmission, and for hundreds of other useful and interesting experiments, is on sale in America priced at 4s, each. ‘Switch’? has one of these little devices, which resembles a miniature carbon microphone. MATEURE who build their own cab.inets will find that an excellent stain for oak can be made by mixing Japan black and turpentine in equal quantities. The liquid should be applied with a rag to the well sandpapered surface, and with two or three coats a rich brown coat will be obtained ERIODCAL.Y you should run a rag ‘soaked in kerosene up and down your aerial in order to remove the soot and dust, which make for poor reception. Whilst on the job, don’t forget the insulators, which also collect aurt. Contrary to general supposition, it is not advisable to solJer leads to your aerial, for unless \ good connection jis made without the use of the solder, the resistance of the latter wii cause very poor reception ‘THE folloy, iz. Associated Press message was published in the United States dailies:-Algiers, March 17North Africa has caught the radio traze, and Arab chiefs are saying farewell to their steeds in exchange for the latest seven-tube sets guaranteed to get all Europe. Barcelona, Spain, is very loud in this part of the world, and Milan, Italy, also is clear. ‘The most appreciated station, however, is London when Aimerican jazz is transmitted. AMERICAN aniateurs form district clubs ani name them in various manners, A few of them are: ‘‘Browsville Racket Raisers," "I appa Key," "Busted Valve Club," etc. ‘The ‘Rag Chewers’ Club" is also well known znd a branch has been formed in Australia, BOUT 98 per cent. of the telegrams received in the United’ States from Sweden are being dispatched by radio. It is the policy of the Swedish Telegraph Board to use radio for the transmission of messages in all ‘cases where there is no telephone or other rable directly available. The new Swedish Government radio station has provided increased speed and efficiency in transmitting messages and has made poss‘hle a redaction in rates, the United States Dej artment of Commerce says, WELI-KNOWN valve firm, advertising in "The Wireless World" (a British periodical), claims that the filaments of their valves are strong enongh to hang p*‘ctures on and are tong enough to dry the week’s washing. DSTORTION due to high frequency currents getting in on the low frequency side o, a receiver may be prevented uy the insertion of a high resistance, in series with the grids pf audio frequency valves, Bes-wike is easily soldered owing to the fact that it is already ‘Ainded.,

= "PHAT the radio habits of the average set owner have changed completely since the introduction of rae dio to America, and tbat buyers of radio sets are demanding the same mechanical perfection ‘hat they seek in an automobile, is the contention of a leading San Franc.seo radio trader. He declares that the type of chassis of any radio forms the one certain means by which the buyer can. determine the tonal quality of the set. AFTER they have been cleaned with household ammonia a-zumulator terminals should be snieared with vaseline in order to keep them from core roding. NE terminal of the storage battery is either painted red, or has the plus sign (a cross) stamped in one terminal, and the minus sign (a dash) in the other, ‘he binding posts on ihe receiver show ‘‘A plus" and "A minus’? respectively, so that no one should go wrong in making the proper connections. pe not think that because the lead-in is covered with an insulating mat crial it can be permittcd to touch the edge of the roof. When wet, it is likely to prove a good conductor. ‘The reason is that the total resistance natural to the receiver is greater than that of the air gap between the lead-in and the roof, and electricity follows the line of least resistance, Besides rain running down a lead-in goes along the outside of the insulated wire. and provides an electrical path to earth where the lead-in touches the roof, side of the house, or window-sill. GELDOM do any two receivers per form exactly alike, although the difference cannot be detected by the untrained user. Very often a receiver of three or four valves will do better im ene locality than will a super-hetero~ dyn of eight in another.

mY UCH emphasis has been placed by loudspeaker manufacturers upon widening the range of frequencies or musical notes, which a loudspeaker is able to reproduce. This has been one of the great problems of loudspeaker design. Quite closely tied up with this endeavour has’ been the desire for the loudspeaker: to reproduce signals of greater volume than ever before, due to the use of power tubes and high plate | voltages in the last andio stages, | AS an analogy to what takes place at a broadcast station, one can visualise pumping gas ito a large tank. "When the tank is filled, there will be back pressure if the force of the pump is not greater. The tank must explode or leak fast enough to take care of the increased pressure. That is exactly the case with radio, broadcasting, except that the generators pwnp electricity into the aerial, the voice vibrations being superimposed on the cartier voltage. When the aerial is filled, it discharges into the air, The frequency of these discharges determines the wave-length | of the station-that is, the kilocycles per second. Wave-lengths are measured from the peak of one wave to the peak of the succeeding one. O not make the mistake of attaching an earth wire to a gas pipe. Vhat is a violation of insurance and fire laws, and voids a fire insurance policy. The cold water pipe furnishes the best earth, and the set should be so placed ag to furnish the most direct line to the pipe. Ifot water or steam radiators often make good earths, also. Never connect any radio wires to an electric radiator. TPHUERE are now wearly 140,000 wireless receiving licenses in the State of Victoria. ‘This is more than the totel number of licenses issued in all the r Axstralian States together. uu United States Government Radio € Comunission recently announced: "Although the conmission has received many complaints of interference caused by stations wandering from their assigned channels, it has been disposed to treat the offenders with Jeniency, beeause of the mcchanical difficulty of maintaining frequency. With the recent development of devices for transmitter control, and the increased necessity of maximum utilisation of the available wave-lengths, a mere drastic poliey Will be aderted % [POL LOWING is the record of Mr. W. Robinson, a Wellington listener, residing in the hilly suburb of Brook-lyn:--New Zealand: LYA, 172, 2YA, Ir, BYA, 8ZC, 4¥A, and 89ZF. Australian: 2BL, @1C. @GB, 2Ul, 2kY, QUW, 8LO0, 8AR, 8UZ, 38Db, sBy, 406, §CL, SDN, SKA, 7ZL, and T7HL. U.S.A.: KFON, KGO, KIUD, KYA, KMTR, KPO, Japan: JOAK. Philippines: KZRM. India: 7CA. Tie uses a six-valve (S-volt valves) imported receiving set.

a ee Gy 11h to it that the Icad-in from the aerial does not rest on or run closcly parallel to a copper roof or any ther metl; that it is not shielded by structural steel, or that the acrial is not close to or parallel to overhead tramway wires, or high-tension (high voltage) lines, ‘These have absorption characteristics, and will not permit one’s receiver to get enough encrgy to operate. They will be a souree of conSiderable noise, too. B PATITERIES (or high-tension) are usually composed of from two or four units of 45 volts each. When the plus of each is connected to the minus of the next unit, the voltages increase in proportion to the voltage of each unit added. ™~e. A BROADCAST listener in Shanghai 4 writes to the New York ‘Radio News’ :-‘‘At present, there are four broadcast stations in this city, which regale the radio audience with regular ‘programmes.’ All of them are superpowerful, namely, one one-quarter kilowatter, two onc-twentieth-kilowatters, and one two-hundredth kilowatter. The two intermediates have such a perfect system of high-tension sunply, and such delicate provisions for adjustment of wave-length, that they give a beautiful mixture of nerve-racking noises, and merrily overlap a score of metres on either side of their chaginel. While it may be an easy matter for+an American BCL to tune out a wee local station of, say, ten to twenty kilowatts’ power, «nd bring in DX, having a dif ference in wave-length of ten to fifteen metres, it is practically impossible for a Shanghai fan to get over these giants and pull in a DX station twenty or more metres above or below the scale." TPARING care of a radio receiver is much the same as anything else. One does not go around with the works of his watch exposed. We get enough dust inside with the case tightly closed. Dust in a set decreases its efficiency by gathering on the plates of condensers, varying its capacity. -Moisture lowers the efficiency of the set. Always keep | your set closed.

a : | | r prtiii storage battery is the source of supply for lighting valve filaments, and supplies of six yolts-more than enough to light standard 6-volt valves. ‘That is whv a variable resistance or rheostats are put on the receiver. Of course, this is not true in receivers which use the new A.C, valves. In this case, transformers have been designed to deliver the proper voltage, and do not uecd controlling ap. paratug,,

en ONG aerials, as a rule, are best if. one has a selective receiver, or. ue with which it is easy to separate , ie various stations. With the advent high power broadcasting, however, 12 has to live a considerable distance roni such stations to bring in one without hearing another in the background. For that reason, many radio manufacturers recommend an acrial of between fifty and sevent-five feet. ‘he aerial could be of No. 34 twisted strana enamelled wire. No. 18 rubber-coycred wire makes an excellent lead-in. QSCE upon a tinie the New York "Radio News™ regularly devoted a large proportion of its space to amatcur transmission, morse code work, te., but broadcast listeiting has so overwhelmed amateur transmission in general interest that the ‘‘Radio News" now allots very little space to the "ham.’? In reply to the criticism of a correspondent, the New York paper says :- ‘The ‘Radio News’ caters to the greatest number of radio enthusiasts. This majority is composed of those people who are intercsted only in the ‘ar phases of radio reception, and who have little knowledge of the radio code, and less of transmitting practices. You are quite correct in stating that ‘Radio News’ is devoted to the interests of the broadcast listener; that is our aim, but not quite completely so, as we do publish enough technical articles to appeal to those more advanced radio fans who can appreciate them. The people who can read good code are ‘comparatively few in number, and their. special intcrests are covered by a magavine which has no other function." | [TX the ordinary tuned radio-frequency receiver, the elliciency is "highest when the dials are tuned to the shortest wave-length; and, as the wave-length is inereased, the eflicieney decreases steadily. he result is that, on the waves between 400 and 500 metres, where much of the listening actually takes place, the sensitivity of the set is often only one-third of maximum. Qn the other hand, makers of the best tuned radio frequency sets have embodied methods of overcoming this disability. 1 round numbers, the average American home spends 50 dollars (£10) a vear for soft drinks and ice cream; for tobacco, about LOO dollars (£20) a year; for telephone, 30 dollars (£6) a year; for radio, 28 dollars (£5 12s.) a yeur; while the automobile costs 420 dollars (£84) a year, more than fifteen times as much as the clectricity bill, } ADIO dry batteries should always be tested for their voitage, as that is an important thing to know. Turthermore, they should be tested with a highgrade, high resistanec voltmetre. ‘The ordinary piucket volimectre has a much }lower resistance tham the radio valve, and its indications will be lower than that actually impressed hy the battery to the tube. A low resistance instrument, therefore, mty condemn the battery too severely. RRANGEMENYS were completed in New York recently, whereby radio fans were able to Listen to the broadcast of a nimpsical comedy, and the next day purchase ile exact programme, including the radi> announcements, in the form of a phonegraph record. ‘The first programme of thi3 kind was given over WRAL on Marck: 11, between 5.30 and p.m. "OATERMOS" (Shorndon) writes ~~ Let us hope that when the Wellington Radio Society is appointing a representative for the society on the ‘public relations’ committee with respect to broadcasting matters, that they will weigh carefully the personal attributes of the candidates. The representative should be an experienced listener, and not a five-minutes in the game syub. He shonid be a man of good judgment, and not given to venting hot air. We should not have a reputation for putting his foot in it when he opens his mouth in public.. He shonld not be an individual who is secking the oppointment mercly for self-glorification, and the free advertising he is likely to get out of the position for his own business purposes. The society has a serious responsibility before it, and it shonid be prepared to make a judicious selection. ‘The appointee should have the confidence of "~ the genetal body of listeners, and, above all, should have an unimpeachable record. If the man who is appointed does not fit this bill the "pablic relations" conimittce is doomed to failure so far as the Wellington listeners’ faith in him is concerned.’ T pet is first be understood that a "C" battery is not a cure-all. It will not increase the range of your set, nor will it make a simple one-valve set operate from a loop, nor give loudspeaker volume from the Australian stations with one valve, when used on an aerial, The primary purpose of a "C" battery is to put a negative bias on the grid element of the valve, thereby preventing a flow of current from the filament to the grid; it reduces the "B" battery drain considerably, producing a saving in four yearly "B’’ battery "Hs. Tt also affords clearer reception by reducing somewhat the noises in a set, A *,C’ battery is nsed to advantage only in cases where the "RB" hattery voltage is in excess of 50 volts, "C" battery is most commonly used on the amplifier valves, and the cirenit can be arranged so that but one Piva battery takes care of both empl Bitsy Fi ,

A NUMBIER of broadcast. listeners, on ® recent evening, picked up YXF, Downes Grove, Illinois, U.S.A., power 5000 watts; wavelength, between 280 and 290 metres. ‘he slation was testing, and asked for reports. The American attempt to use the new word "radiocast"’ in pice of "broadcast" has apparently failed completely, and the former term is seldom seen in print. An American radio writer says: ‘Without explanation, ask 100 people in the street what "radiccast" means, and if they answer at all it will be a guess that it has something to do with the receiving instrument, as a radio set to-day is generally accepted as a receiving set, not a transmitter. Ask that same 100 what "broadcast" means and they will tell you, and tell you corzectly." | SERIES means batteries connected positive to negative. ‘This method of connecting gives a yoltage equal to the sum of the voltages of the individual batteries or cells. Thus, a 224 volt "B" battery is composed of 15 cells connected in series. ‘Iwo "A’’ batteries connected in series giye 3 yolts.

If you use a wotor-car storage bate tery for lighting the filaments ye sure it does not excced six volts. There are several makes of such batteries on the market whose voltage exeecds six volts, and if they are used in conjunction with six volt valves, there is a good posibility of the flaument being burned out, unless the rheostat lias been turied fully "ont’? before lighting the filaments, Sometimes a set will ecase funciioning or will function pootly on the Jast stage of audio-frequenvy amplification. This is almost always dae to 2 poor comncclion in the jack that precules the last stage or in one of the preecding jacks in other stages. IF you have this trouble, look in between the small silver contacts in the jacks, and nutice whether or not they close properly when the plug is withdrawn from them. Sometimes the springs weaken and do not allow them to close as they should The remedy is to take out the jack and bend the offending spring hack into position, and then to repluce the jack.