RADIO TOPICS

New Zealand Herald, Volume LXI, Issue 18707, 13 May 1924, Page 6

RADIO TOPICS

by thebmxos. AHATBTJE eeseaeoh. -The I formation ,of a technical and research branch of the Auckland Radio i ■ "- Association is a step in the right direcH>? tion. Untold ' good can accrue from the facility thus offered to local experi;»menters to meet frequently and to > inter- . change ideas. % The members of the section may together carry out research work of Wluo. The editor of an English journal, in discussing such experiments by radio societies, expresses surprise that more attention has not been paid by the amateur and experimenter to directional radio "as- this is a subject< which holds a peculiar fascination, and in which there are '- important investigations yet to bo made. It is well known that important progress has been made in all branches of radio communication to which the amateur has devoted his attention. The present • state of high frequency amplifi- - cation: and short ; wave transmission and ■, reception owe much of their development ?' to - the amateur, and in addition there are other channels of progress to which the amateur has contributed largely.. In the case of directional radio, however, . the amateur has little, if anything, to his credit, probably for the reason that he has not so far turned his attention to the subject seriously. • . any - people who have not taken up direction-finding work seem to be of the opinion that no satisfactory results are . possible . where the apparatus cannot be installed at a location free from shielding effects. This, however, is not the case, since provided ?:; the shielding effects remain .constant they can. in most cases be allowed and compensated for. The compensation will hold good over , a fair wave length band, , but. will have to be modified where a . considerable change in wave-length is made -? : Such circumstances only add in terest to . direction-finding experiments. ? '??The? association could do other important work in carrying out experiments on 100 meters and less.'A'complete record of the - intensity, nature, duration, and • • possibly the ; direction of atmospherics over a long " interval' of time would provide much-needed' information. It is to be hoped that the technical section of the A.R. A. " will ; devote? itself seriously to ... assist in the investigation ''of some of the . problems in- radio; now requiring a solu- ' tion. , ' ! A BRIBABLE CHANG®. All broadcast listeners regard the interference • caused on all. wave-lengths by the broadly-tuned spark transmitters of the New Zealand, commercial stations as a : cause '5 for ? a just grievance since the • trouble can to a large extent be eliminated ??;- with little difficulty. It is .of • interest . therefore to learn i that at a meeting of the Radio Science League last week in Wellington the ?: assistant-telegraph engi- • ?'\ neer, Mr.? Gibbs, - announced that valve , transmitting attachments wilT;.be installed shortly at the New Zealand stations. Interrupted continuous waves will be used in ■; preference ,to straight C. W. to facilitate ■??: the" calling, tip .of ships and for the sake of ; ships equipped with crystal - receivers or - non-regenerating valve V sets. - The .•? I.C.W. signals are much broader in tuning than straight C.W. and this means that . * some interference will "still be experienced, . bnt it will not be over so wide, a band 'of ' wave-lengths. Listeners-in > will welcome -. the : change-over, and, no doubt the : Gov•'••••V ernment officials 'will "'J find : a much im- .- -proved transmission' efficiency as has been ; the case ; with the Sydney valve station. • .VIS. - ■■■■■■'■ : ? J, ' ItADIO AND ESPERANTO. , * The proposed universal language, Esper:.:anto, « being given a . filip ;by its advocates pointing out the necessity, for. a common method of? speech owhen:. international; broadcasting comes to pass. In England . an organisation called ."Internacia Radio A socio " has recently ? been >; formed with the object or facilitating relations be- ; tween radio users, amateur and profes- •: v sional, in all parts of the world, by means ,::of Esperanto.? The president of the new ;; association .is • Dr. Pierre; Corret, ' a well--known 'amateur. - London has already ■ heard Esperanto broadcast, in speech and song., Many of - the ' listeners blamed their loud ,i speakers, and could not■ understand why: the instrument seemed' to be talking ItaJaan. ; ' Lectures ,• on Esperanto have already been given - from ' a number of English $ and American stations, and it ;: is *proposed? that Esperanto, as ; well 'as other subjects, should be taught by radio. ' - sokes and sons. - > v Correspondents have • written to request a description of ihow; to operate a receiver with a radio frequency stage. Ap- : parently some difficulty?is . being experi- : ; enced - and • the results obtained; are stated to be no better than with,. a straightoat ' detector., , . For • a . single ? stage of , ; , radio frequency, best "results will be ob- : tained with the "tuned j plate.".. method ~ of coupling.- : In . this the plate circuit -is tuned to resonance either - by using a suit- ? ■ 7 able honeycomb coil ).shunted' with ,a Email • variable condenser .{,00026 mfd.) or, for short ' waves, .by ; means of 'a : variometer, .v. The latter method ; will .. be ; found ; very • selective - and; consequent fine toning ; wil 1 . be " necessary. It is most important to = notice . that the '.' sign , . of. I reaction is changed with each additional. radio fre- ' quency _ ,' and ? therefore,, if V a on©- ' stage :ifl added . to the ordinary three--7 coil set having the tickler' coupled ' from the detector valve ito a the > secondary ; in- " ductance, ' the ;'; connections v to: the tickler coil terminals , must ;be interchanged. If the connections are : not. thus reversed results will be negative. •: It :is this point •which V- fis generally overlooked by / the : : l' experimenter. ?;?If : two , stages of radio : frequency are taed? the f . connections must : be again reversed, so that they*are the same as with the * single " valve detector est. ' The , genera! ¥ method :of operation .can J best be found ?by? tuning in to f the V. Jocal broadcasting station on a single ■■ valve. .. Then switch in the radio stage.' reverse the} tickler connections, and vary ?v the . adjustments till the music is heard. A re-adjustment of ; the secondary condenser will be necessary. • - The controls ? v are then varied.. slowly until : the loudes' • ? signals- are heard/: The * natural tendsn.to- oyer oscillation . may; be controlled !by a potentiometer. This arrangement is,- however, inefficient and gives , rise to distortion and it ia ? bettor to - in- . sert a : 4000 ohm non-inductive • resistance In series with the plate variometer. „ This •will give . an excellent • control of ' the oscillation. A' radio frequency stage of amplification . ' will jrive morel . noticeable 4 amplification on distant than von . local ■ stations. Fine control :of all , the - variable —condensers, rheostats, etc.,— ■>: is ' absolutely -i essential -x for. DX - reception. ? ;; ■ A useful officer 'of ? 'thie?^local ?: : radio • : association would be "a? technical • adviser. Provided ?a f member : could be found . to '??•.; devote sufficient time 'to: ? the : l position ? much help could ; thus be gi veri to beginner s: - ■ ?■ 14 ■?' ;?■; t . .?"? A lecturetfce ■ o t . tome radio topic . ? broadcasted; ;7 from tfie ' local ! * station by on(s -of . the visiting naval radio : experts •'would ibe greatly, appreciated. Surely this could ' be arranged. - ' . Concert items from a broadcasting • station were recently given in a tunnel ,under the 1 Hudson (U.S.A.) River. -To ?;: issue, from ;the loud-speaker ■in ; the : form of sound, 1 the ?/ waves > had to? ? travel through 500 miles of ; air? 70 'feet? of Wfter, ?i : 30 : feet of ' mud? and the ! heavy ;s ? ; steel casting 'of ; the tunnel.' Such an ?;■;-. experiment' - demonstrates ? the penetration ;. ofy. radio . waves. • Miners equipped ? with small portable . sets will, in future, ' work • - with less danger. - , J -It is always a pood idea to ■ experiment , with the r. position ,of the • loud-spenkc-V :. , To obviate the , effect -of annoying SiTrU** posstson of the horn to obtain f • ao ? l!stu ' B Should be carethat U be minted out ' -. constructed on' °i ? rf, ■- lov.d-speaker is constru ted on •: a logarithmic law of 'in creasmz aperture and - iatitfsc&v rep od action .of music? and speech cannot & -erected unless? »«<* a horn'- is J ?•:. - 2»"e w ' . loud-spea'cer# are ' freaupittly appearing and -great care should he taken , in choosin? which type to purr hate. ' A if#poor loud-speaker— are many such on th« market-will, completely ' iixin at i, -> Qj'l.arwise good transmission. , j Hi