Wireless Broadcast

Star (Christchurch), Issue 17216, 6 December 1923, Page 11

Wireless Broadcast

Contributed bi

"Aerial.”

LISTENING FOR W.O.R. There appeared iu the daily papers a tow days ago an announcement that testa, would commence on Saturday, December 1. between AY.0.11., New Jersey, and New Zealand, Australia and Japan, and that the wave length to bo used would be 405 metres. The people at W.O.R. requested amateurs m this country to listen in, and report their results later. Here’s a great chance for those of the radio fratemitv wbo indulge in broadcast-listening. Don’t think that you will not have a chance of hearing W.O.R. just because you may only have one or perhaps two vaives. A super-heterodyne is not needed at all. because if the station can’t be heard on the receiver to be described then it will not be heard at all in Now Zealand. That is, provided a. decent detector tube is used, and also a good aerial- This does not mean that the aerial lias to be seventy feet high, though of course the higher the better Articles have appeared in this column on beroro. so no space will be taken up \sith a description of this part of the station, except to say that the aerial should be well insulated and above any surrounding objects, such as trees or buildings. If a T aerial is used see that tie leacLs come from it at the exact centre. Now. for the gear. The following articles are needed : —One variocoupler. two variometers. a varibale condenser, and a couple of valves, with a rheostat for each The usual batteries and phones are also of course required. The coupler and variometers can be of i almost any standard snake, so long as toe much woo'l-or moulded material is not used in their construction. The circuit is a well known one: with a single stage of radio frequency amplification and a dovector. A step of audio frequency amplification may be adde-l if desired. A pretty black rubber panel is not necessary, nor even desirable if the set i,s to be only a temporary affair. Simply spread the instruments out on a table, so that they can be wired up easily, and in the order shown in the drawing. lie careful not to put the variometers close

together. Mount ■ the first valve, which is the amplifier, between, them, keeping the variometers at least ten inches apart. The grid condenser, which is between i lie plr.te. of the first and the grid the second valve, should have a capacity of .0003 to .0005 myds. A condenser -.vii.li a, grid leak already on ,it will not do. as in this case the high ten,ion oi “ 1? ” battery will be leaking through or. lo the grid of the second tube, thereby spoiling rectification. A separate leak must be used, and be connected in the manner shown. ft an •exceedingly soft or gaseous tube is u.-yfcd for detecting, then the grid leak i w ill probably not be needed. The ly any comment at all. A few minutes practice will show an intelligent person how to operate the set. The primary of the coupler should be *et so as to include about fifty turns of wire, when the average site amateur aerial is used. The aerial tuning condenser should have a capacity of at least .0007 r.yds. and should of a RADIO! RADIO! 4 LL Parts for ruakine S*ts in Stock. A Lowest Prices in Town. Come and see These prices for yourself. Special Discount to Club Members Join the Radio Society of Christchurch and get this discount. Application forme r an he obtained from A .1 DACOMBE AND CO..

good make. Shoddy condensers are responsible for a lot of losses in signal strength- Last Sunday morning T saw a well-known local amateur mount a similar set for trial on a three-ply panel. Mounting all the gear and wiring it up, took him about an hour , and a half. AIL. connections should be' soldered neatly, without allowing a lot- of paste to collect at different points. Clean soldering is north while, and resin flux is the .correct thing to use. With a little ckrfe and attention to details, this outfit works fine, and results are surprising to say ; the least. r Any listener hearing the transmission from W.O.R. is requested tp notify ” Aerial.’’ Thai station will transmit every evening from December 1 to December 15. from 8.30 p.m. till 10.30 p.m. New Zealand time. The operator of 3AB tells me that his signals have at last been heard outside Sydenham. A letter from an Auckland amateur states that JAB’s speech fend music are very loud and clear, more so. in fact, than some of the Wellington stations. Mr Vincent’s •set is “5.5.5..” safe, sane and sensible for a ’phone set. Heising modulation is used, one five-watt tube as an oscillator and a similar valve as a modulator. This system gives a greater percentage of modulation than any other, but lire the slight disadvantage of broadening the wave, besides being very hard to get just right. Once it is right, however, it “stays put” till someone upsets it again. Our one and only B.C.L. Later, 3AM. is now rising grid leak modulation in his transmitter, and is certaiulv putting out better speech lately His best DX so far is to 4AG, Mr Slade. Dunedin. 3AM is using the usual five watts on 140 metres. 3AF reports that the furthest point his signals are reported from to date is Auckland. Two amateurs in the northern citv have reported hearing his Morse. These are 1A A and IAC, * Messrs Edwards and Sparkman respect-

{ ively. Only the former station has been actually worked, however. I A certain member of the R.S.C. who resides in Lincoln Road has announced his intention of installing a transmitter. with the object of keeping the ether round Christchruch alive with music: when 3AO is not on the'job. and another member, who assert* that he has not the time to undergq an examination for a Jincense, recently confessed (in private) that ho has “got the wind up badly.” Never despair, 013.. : you’ll get there some day. I recently overheard a. heated argument about that “static elimination." T thought it- was dead long ago. Seems it was buried deep. Last. Thursday the Radio Society held its usual weekly meeting. The usual business was disposed of quickly, and then a lecture was given by Mr F_ Vincent. The speaker took for his subject, Coupling.” Step by step Air Vincent dealt with his subject, treating it very fully, and making it very easily understood. At the same time, tuning was explained, and those beginners present were easily enabled to grasp the principles of coupling and tuning. At the conclusion of his instructive and entertaining talk, Air

Vincent was accorded a hearty *ote of thanks. No doubt many listeners have heard 3AC transmitting every evening this week, and wondered why. Just another stunt. A receiver lias been installed in the Grand Theatre by a member of the R.S.C., and last Saturday afternoon I was invited to go along and have a look round. It appears that two aerials had been erected at the theatre, and one of them is indeed a puzzle. 1.-sing the front aerial, tilings were fine. Lost. Friday night, the transmission from 3AC could be heard all over Cathedral Square, when the Magna.vox loud speaker was placed on the balcony of the theatre. 1 am reliably informed that every item was distinctly beard. On Saturday the other aerial was used, and the apparatus installed in the theatre just below the screen. When l got there, some music was issuing from the loud speaker. but it was very “ thin ” indeed, and

the operator seemed thoroughly dis j gusted. The. apparatus was then cart- ! ed upstairs again and installed in the j operating box. with the front aerial in j use again. This time- the music simply roared in, and could be beard very easily all over the auditorium. The trouble* in the other case must certainly have been the aerial. Which was i screened badly by adjacent buildings : The receiver used was made up l>y Af. j Cosgrove, a member of the R.S.C'.. and j i\as of the Cocaday four circuit type. A j detector and two steps of audio ampli- j fication was used, with only sitxy-seren | volts on teh amplifier tubes. The output from the receiver was fed directly to the loud speaker, withotu any power amplifiers at all. Considering that only three valves were used, the results were very creditable. The November issue of the “New Zealand AYir'eless and Broadcasting Nows” contains some useful information. An article by “ Grid ” appeals very much to me. and if all amateurs read the article, and promptly act on its advice, there would be more pleasure in listening in. I recently tried out a new Milliard valve. It is known as the P.A.3. and is intended for use as a power amplifier. or a low-power transmitter. Used as an amplifier behind one stage of tuned radio frequency and detector, and with .130 volts on the. POA.3. it was equal easily to two ordinary amplifying tubes. It is similar in appearance to the Alullard “R ” valve, and should be found very useful for working a. loud speaker.

CORRESPONDENCE. BBC.”—The Neutrodyne receiver has not. boen described in this column sc far. and nobody that I know has even tried, it. Yes. super-regenerators seem to be off. “Afani tux for report.” f can recommend the Hartley circuit. Works well with a five-waiter.