Questions and Answers

Radio Record, Volume VI, Issue 13, 7 October 1932, Page 10

Questions and Answers

86." (Wellington).-When, I connect e the aerial and earth on my crystal to the same two terminals on an 8-valve set, a station comes in louder when JI tune the crystal set, . A.: This is because your crystal set is acting as an aerial tuner. There is no need "to use the erystal set as a whole. It would be just as effective to take the aerial and earth leads from both sides of the variable condenser,

‘"TOUMPKIN" (Pohue).-Can a short~ wave adaptor be constructed to work the speaker of my set? A.: Yes; you would need an a.ce. adaptor, details of which were published in the 1930 "Radio Guide." You could cut out the "B" battery shown there and take the connection directly from the plate of the detector valve. The approximate cost would be £5 or £6. F C. (Auckland).-How many Daniells * cells do I need to charge a 2-volt accumulator? A.: Four. 2.-I have constructed the crystal and one-valve set in the 1929 "Guide," using the valye stated. It is a wonderful set on phones, but it is mushy when connected to the speaker. In this case there are five volts on the plate and 20 volts on the auxiliary grid. A.: There is something wrong with your speaker. You should get almost 20 volts on the plate. (Try out another speaker and you will be surprised at the results,

re Aw (Wellington) -My set, with automatic volume control, intermittently goes mushy, and I can only get the distant stations to a certain volume. Is this due to the volume control? A.: Apparently there is something wrong with the functioning of this control and we would strongly advise you to get in touch with the agents who sold you the set, and get it overhauled. 2-I have 100ft. aerial and cannot separate 4QG from JOHK, or 3BO from vith A.: Your aerial is too long, Wither shorten it 20ft. or more, or use in series with it a pre-set condenser, preferably a semi-yariable one. | "TNCK TAIN" (Chch.).-What is the | undistorted output of my speaker? | A.: From 3-4 watts. | 2-Would it possibly handle threequarter of the output of pushpull pentodes? A.: No; about half, 3.-What would be the voltage drop, using the field as a choke to pass a 100 mils at 350 volts? A. : 250 volts, A KM. (Taumarunui).-I am consider- * ing the purchase of a new battery set, and I am considering a 4-valve allwave set and a 2-volt "Super Six." A.: The "Super Six" is an excellent set if you use an aerial adaptor so that you ean use an aerial. Otherwise we recommend the 19382 "Outspan," fully described in this month’s issue of the "Radio Times." This set, with the valves recommended, is one of the most economical, yet powerful, battery sets we liave yet described. It can be worked from the new air cell, which does away with the necessity for charging an accumulator. Furthermore, it is thoroughly modern, haying one single.dial control. The "Super Six" is our next choice, particularly the new version of single dial control. The "Super Six’ is a set described by ourselves, and you | could obtain your parts from ‘any dealer,

©. P.H, (Westport):-I was told that if I connected. a shortwave convertor to my 8-valye superhet, it would: make it a superhet. on broadcast, A.: Yes, this is the case if your convertor has broadcast coils; otherwise it , would be a shortwave superheterodyne set, We cannot see any way in which you can connect your four aerials to earth with one switch, unless it is one with four contaets and one moving arm, ‘The moving arm would be earthed when you push into position its contact with all four. If you wished to connect all in turn to the main aerial switch you would need one of the stud switches, with the main wire connected to the moving arm and the ditferent aerials connected ‘to the studs. Ke (Waverley).-What. is the correct yoltage and amps to charge a 6-volt battery? A.; It should be charged at a potential of 6 "volts 2 amps. It is usually necessary to put the charging voltage above this in order to get the 2 amps chiirging rate. 2.-I have an old car to charge my "A" batteries, but I Have to carry the about 150 yards up a steep hill, Could I run two wires from the generator to the house, to save carrying the batteries? . : Yes. Use fairly heayy wires, say or 70/29, and put up the charging rate of the generator until you get 2% amps at your battery.

86® (Napier),-I can only get 45ft. for my aerial, and am at present using a triple wire with fairly good results, A.: This aerial seems quite all right, although if the wires are separated by 6ft. or so, you are getting really a very long aerial, perhaps too long for selectivity. 2.-My valves have been in use for 1500 hours. Would it improve reception if I renewed them? A.: In all probability yes, although some valves have a very long life, "(XNURIOUS" (Chceh.).-I use a 4-valve commercial set. Is it possible to get socket adaptors that would fit any make of valve, for as it is now, no other valve: will fit? A.: It is a little risky altering the type of valve in a set such as this. We think you Would be far better to keep to ‘the original. You could, nevertheless, get adaptors if you took the set to a reliable dealer, 2.-Would a dynamic speaker be better than my 66R? I want more volume. A.: Your set will not handle a tre mendous output, but it would, we think, (Continued on page 24.)

Information Coupon (To be used with all requests for information.) Name of set seeeveneegceseesseose: Model COT CROCE OREO SESR OSES TO ESESOOD Name POSH OOS CRORREEEEOE SHOT HREEOS Address SePoneoesosvesvaseseoqgeserer POSH POS TS ROHSSSSHESHEHSOLECECERTSSAEE PSP OHSEHHEHOT SSO SSOSEEHESEHSESCEDRETESEE Nom de plume ..scccccesceces To be kept in subsequent inquiries Please Note:(1) Be specific and brief, tabulating, it possible (2) Write legibly. and on one side of the paper (3). We do design cireuits. (4) Limit three questions. unless 1/- is enclosed, (5) Postal queries Hmit three questions, Enclose stamped envelope and 1/- fee,

Questions and Answers (Continued from page 10.). give you good results from the dynamic you speak of. However, how would you energise the field supply? LQ8s (Hawke’s Bay).-What is the minimum number of valves required to give phone reception in daylight of 2YA at a distance of approximately 160 miles? A.: Probably one valve would do it. 2.-Am I doing any harm by attaching phones to the terminals of the speaker, using both at once? No, providing that there is not a high ‘potential across your speaker. By "high"? we mean something in the region of 180 volts upwards. gws (Wellington).-Would it be an advantage to substitute four or six volt valves for the two-volt ones in my shortwave set? A.: None whatever. The two-volt valves are quite as good as the 4 and 6. 2.-Would an aerial 35-40ft. high and 25ft. long be suitable for shortwave reception? A.: Yes, it would be admirable. I UDION" (Napier).-My set, using .83 amps, runs No. 6 cells flat after 40 hours’ use. Is this in order? A.: Yes. You would be far better to put in a bank in series parallel. Purchase, say, 9 cells, connect them' as you would for the ordinary set in groups of three. Then connect the free positives together and the free negatives together. Take one lead from each of these points to the set. ’ 2. Would the Daniells cell described in the "Times" and regulated by a rheostat be suitable to supply the current need for the set? A.: It is a little bit too much. However, the experiment will be worth trying. You may have to put two sets of Daniells cells in parallel, and we think you would get results. 8. I recently constructed the "Neutron Four," and could get the local stations cuite clearly with the detector valve out of its socket, without any other wiring changed. Was the high-frequency stage, which is biased, acting as an anode bend detector? A.: Yes. 1 TEDDIF (Wellington): I cannot cut out 2YA, and it comes in all over the dial. I have tried a wavetrap without success. A.: A wavetrap should do the job. Probably a local dealer would lend you . another one. Yours may not be efficient, or perhaps you are not adjusting it carefully.