WIRELESS NEWS

Press, Volume LXVIII, Issue 20523, 16 April 1932, Page 10

WIRELESS NEWS

(By ".MAX.") Tills weolc Mr It. A. McLennan's article on a real DX receiver is continued, but not necessarily with the original -wording, as we have no diagram before us to refer to. The circuit lor the detector is a conventional shunt feed with condenser re-action, and is contained within a metal screen, together with two radio frequency chokes in series instead of the usual single one. From the lower end of the second choko 'a lead passes mto the second screened box for the audio stages. The junction has connected to it a one mfd non-inductive by-pass condenser with the other sido. earthed to the screen. The lower sido of the tuned input is earthed direct, as is the usual practice. The'aerial is coupled to the top side by means of a very small condenser made up by twisting two half uicn long portion/of wire together, .the and leak direct iroiu Hie and to uie negaine lead to the lUamcnt and a ,UU<5 condenser is used between me ochei Jilament lead and tho screen, ihis condenser ensures smooth re-aotion ovei ail bands The leak must bo or high-class goi.g tt, Hashed metal type as ono source of noise ilea m an mdiliucnt leak The iirst K.l'\ ckuko is ior the shorter uavca and is wound upon an übonito rod and careiully as noises develop at this point. Iho second choko is a conventional broadcast choke, also boiled in wax. Jho gnd condenser should be of mica insulation and above suspicion.

Turning to the audio section, we find a departure from tho accepted system. The primary of tho first transformer is shunted by a condenser above .am a 50 COO ohm resistance below tho two being in scries. The value oi tho condenser is anywhere between .1 mfd and .5 mfd and of high insulation resistance The oD.OOtI ohm resister must be wire woundofsmall swe oi similar to Lie grid leak. A iaik,ci due of resistance would give greater amplification, but » not worth the extra battery voltage necessary lho (cad from tho second choke is joined to the junction of tho resister and couoctiscr and the plate current to tho detector has to go through another resistance, preferably a compression tvi e of 100.000 or 200,000 ohms bcW,re the plate terminal is reached. There are thus two chokes and two rfHstiinncs botweon pl«te :ukl (detector positive). The second resisttvice is shunted to the screen by . to 5 mfd of proved merit. A one mid condenser from the terminal of the second resistance is optional. There is no direct current through the primary of the first audio transformer, onlv the voltage variations in the output of tho detector (limit up across the HO 000 ohm resistance) g'»ng through t primary, via the- condenser.

Glancing at the diagram again, it lf > seen that the cores ot the transformers are earthed, as is the core of the output transformer, the use of the latter being a guard against feedback, which is liable to set up an audio howl, apii sometimes mistaken for threshold howl. The threshold howl is eliminated bv the system of coupling the detectoi to tho first audio. ■ The transformers should bo of reliable make ami with permnllov cures, and tlic higher ratio one should be the first. - Ordinary resistance-coupling could be employed, bn; tho step-up gain of tho transformer vould be lost. Ilegoneration control is bv a variable condenser, but finer results nre obtained with the second (variable) resistance in tho detectorrlato lead. A potentiometer of 2000 ohms is in the socond compartment, and the slider has the plus "C'"conr,pried to it, while the outside terminals cro across the "A" battery leads as usual. A stamped addressed envelops will procure a copy of the circuit diiignun il nnv reader is sufficiently interested and desires one.

It had been confidently hoped to have two Fultograph machines on exhibition at the stall of the Radio Socicty Inst week at the fair, but littlo difficulties cropped up in both the sending and receiving side. For example, a special paper is necessary lor iodising, and sonic work is required to find a suitable kind. Then there were troubles in preparing a suitable negative, the absence of sunlight preventing pxporiments with a bichromate process in time for the fair. However, tho difficulties will be overcome shortly.

The transmitters were kept busy handling messages of greetings, somo three hundred being handed in during tho four evenings. A relay was used to operate the transmitter which was situated in a nearby room. Tho receiver had to contend with tho hum from tiiP r>|pot,nr> light wirns, which were a few inches away only from some parts of the very short aerial. Howover, contact with the local amateurs who were relaying the messages to northern and southern amateur stations was managed successfully.

A new radio monthly is to hand, the copy being one of the second issue. It is called "Radio Monthly" and is published in Sydney. Tlie Technical Editor is "Don B. Knock, well known to most radio enthusiasts by name at leas r . The journal is printed on excellent paper, which ensures clear photographs, and tlie reader is giv t plenty of matter of interest. Constructional articles will keep the experimenter busy, and the BCL is not forgotten. Space is occupied in notes, etc., for amateur? and short-wave enthusiasts and tho magazine shows promise of being well supported.

American manufacturers of valves are placing a new series of penthodes on the market for use with small power supplies. A two-volt type takes only .06 of an ampere for the filament, and it is understood that a four-volter consumes a similar amount. These valvea make quite good radio frequency amplifier in suitable circuits, and they should be very useful for portable receivers where light batteries are chosen. Provided th< correct system of coupling the output_to the speaker is used, good volume and tone will be had, quite sufficient to meet a portable's requirements.

The vexed question of the right to use gramophone records is causing fresb interest to be taken in the subject. The Performers' Rights Association is the controlling body which fixes the fees to be paid. There is no ueed to cover the gi-ound again, but the writer thinks that the only way to settle the matter is by legislation or perhaps Court action. On the Continent it appears that the same attitude in rqgard to using records is being taken up. Probably the expenso of fighting the Association to have -m equitable arrangement made is the stumbling block. If it is correct that the composers themselves receive no additional benciit from these fees, thou it is quits time some aetion is taken, it possible. Scattered broadcast sta-, tions with little capital behind them are not in a position to act alon„, but comlined action might bo possible.

Notes From Far and Near

BROADCASTING, i TODAY'S PROGRAMMES. 3TA, CHRIST CHURCH (980 Kilocycles.) 3 p.m.: Gramophone recital. 4.30: Sports results. 5,0: Children's hour, conducted by Aunt . Pat. ti.O: Dinner music. 7.0: Keua and reports. 7.30: Sports results 6.0. Concert Programme. March, Studio Orchestra (Conductor, Harold Heclc), "Bonnie Blue Bonnets" (De Ville). Overture, Studio Orohostru, "Pique Dame" (Suppe). «f; (.ording—Ensemble. "How do iou Do. (Holt). 8.18: Recording—Xylophone, Victor Sterling, "The Great Little Army ' (Alford). 8.21: Tenor, Ernest Rogers, (a) ' My Love is J.i Leo a Red, Red Rose" (Trdtl.) ; (b) -Mavounieen" (Benedict). 8.28: Recording Piano, Schutt and Cornell, Canadian Capers" (Cohen). 8.31: Humour Hie Chatterboxes, "Cheery Chatter (West). 8.41: Recording—Whistling, Guido (iialdini, "Oreola" Tango (Ripp). 8.41: Soprano, Miss Cecily Audibert, (a) "Littlo \ votte (Hitydu Wood); (b) "Tho Open Door (Dure). B.l'J: • Recording—J. Harold Murray, "Smile, Legionairo" (Cadman). a.52: Studio Orchestra, "Squirrel Dance' (Smith) 8.SO: Recording—.Musical Coinody Company, "One Heavenly Night" Vocal Gems. 8.50: According—Humour, Randolph Sutton, "You Dio If You Worry. 0.1: Weather forecast and station notices. !J.a: Recording—Variety Company, "An Imaginary Broadcast." 9.!): Selection, Studio Orchestra, "Alaid of tho East" (Ncale). 9.22: Soprano, Cucily Audibert, (a) "But Why!" (Logan); (b) "Roses o£ To-day" (Ranzato). 9.27: Recording —Organ, Terenco Casey, "Crazy Pirouette" (Frisk). 9.i;0: Humour, The Chatterboxes, "If Wo Wait Till .ho Cows Come Homo" (Gallatly). 'J.4O: Foxtrots, Studio Orchestra, (a) "Rambling Down tlie Roadway" (O'Hagan) ; (b) "I'll Still Belong to You" (Brown). !).47: Tenor, Hruest Rogers, "Good Company" (Adams). 9.51: Recording—FoxtroU, Walter Miller and Company, (a) "Harmonica Harry" (Baxter); (b) "Tho Clatter of tho Clogs" (Flynn). 0.30: Yalse, Studio Orchestra, ".Jolly Fellows'' (YolBtcdt). 10.0: Danco music. 3ZC. O.uO: Children's session. fi.ls: Dinner music. U.4D: Sporting and genera] news. 7.15: Musical items. 7.43: Contract bridge talk by Mr \Y\ Shackle. 8: livening concert. 10: Dance music. 11: Close down. 2YA, WELLINGTON (720 Kilocycles.) !: p.m.: Solected recordings. 3.30 and 4.30: Sports results. 5.0: Children's hour, conducted by Uncle Jasper and Aunt Molly. 0.0: Dinner music. 7.0: News and reports, 7.30: W.K.A. session, R. J. Waghorn, M.A., "The Earth and Slan—Man's Origin and Early History." 8.0: Concert programme, liecording—Band of IJ.M. Grenadier Guardu, "Martial Moments" (arr. Winter). 8.8: Ton or, Chas. Williams, "Song of Songs" (Moya). Quartette, The Lyric, "Shadow March" (Protheroe). 8.14: Fantasia— Salon Orchestra (Conductor, M. T. Dixon), "Tosti's Popular Songs" (arr. Godfrey). 8.22: Humour, Phil Smith, "Wottle" (Ilurst). 8.28: Songs at tho piano, Muriel Johns, (a) "My Castlo in Spain" (Friend); (b) "The Pretty Littlo House that Jack Built" (Long). 8.34: Selection —Salon Orchestra, "Wildflower" (Youmans). 8.44: Tenor, W. Roy Hill, "Bells of Littlo Weston" (Thompson). Quartet, Tho Lyric, "Musical Trust" (Iladley). 8.50: Recording—Humour. Amos and Andy, "Is Everybody in Your Family as Dumb as You Is!" (Gosden). H.SG: Baritone, Will Goudio, "Don't Marry Monday" (Richards). 9.0: Weather report and station notices. 9.2: Recording—Light Opera Malo Chorus, "Songs of Good Cheer" (arr. Byng). 9.10: Songs at the piano, Miss Muriel Johns, (a) "I Cun Sco a-Rain- ; bow" (Malcolm); (b) "Happy-go-Lucky ' Lane" (Young). 9.16: Violin, with orches- i ' tra—W. Haydock, Violin Song from j "Tina" (Rubens). 9.20: Humour, Phil i Smith, "Riley's Cowshed" (Hargreaves). 9.32: Bass, W. Binet Brown, "Old Clothes I and Fino Clothes" (Shaw). Join-in Songs, Lyric Quartet, (a) "Mermaid"; (b) "Polly Wolly Doodle"; (c) "The Three Crows." 9.42: Record —Piano, Raio da Costa, "Victoria and Her Ilussor" (Abraham). 9.48: Novelties, Salon Orchestra, (a) "A Motor Ride" (Bidgood); (b) "Littlo Leaden Soldiers ' (Pierne). 10.0: Dance programme. 11.0: .Sporting summary. SUNDAY. OTA, CUEIST CHURCH 2 p.m.: Gramophone recital. 5.30: Children's song service by children of Anglican Sunday schools. (i. 15: Musical recordings from studio. 7.0: Relay of evening service from Christchurch Cathedral. Preacher, Rov. R. de Lambert. Organist and Choir Conductor, Dr. J. C. Bradshaw. 8.30 (approx.) : Concert programme. Relay of programme I from 4YA, Dunedin. 3ZC. 1011.30: Musical Items, fi. 15-7.15: Dinner music. 8: Evening conceit. 9.30: Close down. 2YA. WELLINGTON - p.m.: Selected recordings. 2.30: Relay of t'edication Ceremony and Handing over to the City of the Wel.ington Citizens' War Memorial. Selected recordings. 6.0: Children's song service, conducted by Uncle Goorge, assisted by the children's choir from the Cambridge Terrace Congregational Church. 7.0: Relay of evening service from the Salvation Army Citadel. 8.15 (approx.): Concert programme. Relay of Band Concert by tho Wellington Municipal Tramways Band from St. James' Theatro (Conductor, E. Franklin).