Questions and Answers

Radio Record, Volume VI, Issue 21, 2 December 1932, Page 23

Questions and Answers

rer PHAR LAP (Napier) -On switching on the power to my set it hums for about five minutes before starting, recep tion then coming in suddenly. ; A.: There is something wrong your set, probably a defective resistance. The onty way to locate:this would be with ingtruments. If the trouble‘ originated only after you had a serviceman to the set then bring him, back and ask him to complete the job. ~ B $.D. (Wanganui).-Yes, we shail Ye endeavour to publish in the "Radio Times" an oscillator ‘valve circuit suitable for Morse practice. ‘ H.T, (Wellington).-If the rasping _ * noise is present when you are ad~ the volume control we presume there is something wrong with that part of the set. The jumping of the programme would also indicate that there is something wrong with the volume control. ,.2. Should Christchurch buzz on some a ee merE aT more than others? No, it does unfortunately, and asfar as we can maké out thig is a raspinéss in the carrier wave which originates at the station , itself.’ . 8. Should an 8-valve set secure more American stations than K¥FI, Los Angeles? _ : ; A.: It altogether depends upon locality. 4, What is meant by dx? Can an or. dinary broadeast set owner become 4 xer? ° . A.: The term "dxer’’ is applied to those who are interested in bringing in longdistance broadcast stations, and dxers im general do not ‘possess short-wave outfits. The word "dx" means "distant." 5. Yes, your valves are uite good, and it is doubtful if any others would produce better results. _ 6 J. G. Henderson, Street, oe . % Ys Auckland always a hard to bring in? A.: It fades rather badly. (Note-Our limit is three questions without a shilling fee. What are you going to do about it?) AGW: (Wanganui): Is it possible to use 4 pentode in my present fourvalve battery operated set so that it will give me greater: lift? A.: A pentode valve will probably give. you greater lift, but it is necessary that it be matched to the speaker by. 2 special matching transformer. N D. (Auckland): I wish to use finer * wire and a smaller former for the "Rejecta Two," At present I am getting good results, A.: You could use-a 2in. former and 26 gauge d.s.c. wire, winding on 80 turns on the main coil and 40 on the small coil. For reasons of efficiency we do not advise you to.make a smaller coil than this.. . we Both sun and rain decrease the of my "Rejecta Two." Can this be overcome? A.: This is due either to a defective erystal or to your aerial and earth system, See that all joints are good, that the connection with the ground is perfect, and that the aerial can in no way contact the leads going to the ground. LOBENZO (Taranaki): What causes the speaker to get hot? : A.: That is due to‘the large amount of current which is passed through the field winding. Unless. it is unbearably hot, it is quite normal. 2. If I touch any part of the chassis with a screwdriver, the speaker picks it up. Is this right? . A.: Yes, we think this does not indicate a fault. CHARGER (W. Coast): When 3ZR shifted to.2490 k.c., the volume of that station dropped natil it. was. not

ia comfortable to liste. to. About: three miles away a friend has a ‘set, and the — volume on this has increased.- What,can be done? wag Pi A.: This is due probably either to your location with respect to the station or more probably due to the. peaking in your receiver. In ygur particular receiver, 1800 k.c. is a frequency at which there is less amplification than at other frequencies, and in your friend’s set vice versa. We suggest you trim the cone densers, carrying out this ‘opération, on 1800 ke. ' " 2. I often have the set on when the "BR" batteries are charging, and the noise from the dynamo comes through. ‘How ean I prevent this? Ve 8 ‘A.: You cannot’ do go practicably. D*>N (Nelson): From 540-720 ke., I can bring in only 4YA. with the volume full on. A.: Hither the set is designed: so that amplification takes place below a part of the dial or the ganged condensers are out of alignment. Have them lined up. 2. The A.F.C. gets yery hot..- Is this all right? A.: It is probably built of wire which is of too small gauge. However, you can do nothing for it, = ~~ °° 8. Working on an average of 8% hours a day, it costs 7/6 a month for power. Is this as good as any other set? A.: Yes, that is quité the normal consumption for a set of that description. Kr (Napier): We are worry we can not give you the short-wave coils for the 1982 "Outspan Four," It -is purely a broadcast set. Lo 2. T have a 15 volts C battery and wish to supply a valve with 4% volts, negative. What value of resistance would I require in connection? : A.: You cannot break down a © battery by a resistance. Your best plan would be to shunt a 2000 ohms potentiometer across it and take the moving arm to the’ grid return. on which you wish to place 44 volts. Vary it until you get the right value. You ‘would need to dis» connect the potentiometer when you are not using the battery, otherwise you would run it right down. 3. What is the amplification of A422 Sp. ? Ax: About 250. S JS. (Taita): XY have a local made ® gix-valve electric set, which hag 2 very. pronounced hum. It fades and deyelops into a crackling noise after the set has been running a short while. A.: This is due to a broken down electrolytic condenser. Mee! (Hinau): The Daniell Cell charger will not work for me, yet it zegiatered 8 volts without the accumuator. ‘ A.: Are you leaving it on your ac cumulator continuously? Are all the external conrections sound? It may pay you to add a few more cells and bring the number up a little. Are you quite certain you are connecting: it the. right way round, that is, the copper rod to the positive terminal of your battery? D*74. (Auckland) : I recently tried paralleling an Osram 610 and-a 171A. valve. There was a decided loss of yolume. . : A.: No wonder. You must. parallel valves of the same type. Further than that, you probably caused the voltages on all the valves to drop as the powerpack was designed not to take the extra. load imposed by the paralleled valves. You will not get greater amplification in any ¢ase, only greater undistorted output and in 2 three-valve set paralleling: is quite unnecessary,.-In fact it is.a wapte.