QUESTIONS AND ANSWERS

Radio Record, Volume V, Issue 28, 22 January 1932, Page 11

QUESTIONS AND ANSWERS

FRANK

KEE

The Technical Editor will, through these columns, be pleased to help readers experiencing trouble with their sets. Queries are limited to three-for more than this a shilling fee is charged, and a similar fee is payable for queries answered by post. Supplying layouts. circuits and solutions of intricate theoretical problems is beyond the scope of this service. | A eoupon must accompany all requests for information. Nonappearance of the coupon in any issue cannot be regarded as a reason for its not being used. * Address all queries, The Technical Editor, Box 1032, Wellington.

f -D*4mcC: Would my reception be improved if L installed a pair of head- \ hones? Fs A,: Itis doubtful. By installing phones you would pick up a tremendous amount of noise which would probably drown the weaker stations. An article on this subject appeared in the "Radio Record" of August 7, 1931. M.C, (Mokau): The Daniel cell eharger was fully described in the ‘Radio Record’ dated November 7, 1930. A B.N. (Grey Country): I have a five- * valve commercial set, and use PM6° in the last and second-last stages. Are my valves placed correctly? A.: Up to the second last stage, yes, but you should not use PMG6 in that position. It is unquestionably a last stage valve, and should not be used elsewhere. Substitute it with a valve of the 221 class, Otherwise your valves are quite satisfactory. 2, When I remove the wires from the bias battery, reception is clearer and stronger. If I reverse the wires reception is still better. The black wire goes to + and the brown to -. A.: We cannot help you, for we do not know where the black wire should go. Trate it out, if youcan, and see if it goes to A- or B-. If that is the case then ‘your connecting it to + is correct. If the © battery is reversed you will run down yorr B battery, shorten the lives of the valves, and incidentally introduce distortion. It seems, however, that by connectjng the black wire to C-++ you are correct. Jy A. (Kartigi): I have a six-valve set, * and am using 5 201A and PM6 detector. Are these valves right? A.: You should not use 201A in the

last stage. ‘The valve in this case should be of the B605 high gain power valve type, suitably biased. 2. My aerial is 75 feet at one end and 85 at the other end, and I am using 150 volts B. Is this too much? _ A.: Your aerial is quite good, and you have ample 5 battery. It is certainly not too much, and you will appreciate the high voltage when you install a power valve in the last stage. Krom your sketch we cannot pick out which is the power valve, but you can detect it by finding the plate wire and seeing if it goes to one of the speaker terminals. Perhaps an easier way would be to find the valve which is eonnected directly with one of the speaker terminals, M42 B. (Auckland): I have a erystal set which functions perfectly on my next door neighbour’s set and elsewhere. When I put it on my own aerial and earth I cannot get a sound. What is the matter? A.: We do not know. If you are quite eertain your aerial and earth are irreproachable, our only suggestion is that you have a defective lightning arrestor in the circuit, TNTERESSANT (Christchurch): You have not said what type of condenser you wish to use. Presuming you use .00015 for tuning and reaction, the following specifications should suit your requirements :-30 to 50 metres, secondary 84, reaction 104 turns (80 d.s.c.) ; 16 to metres, secondary 6a4, reaction 5} turns (30 d.s.c.) ; 10 to 16 metres, secondary 24, reaction 3 turns (30 4d.s.c.). UZZLED (Westland): See the dx eolumn for your first query. 2. What form of aerial is desirable if you wish to receive the maximum number of stations, including the reception of stations in daylight? A.: The Beverage aerial is best. The full details were published in "R.R." of October 3, 19381, 38. Does the power of the set gradually decrease as the "A" battery is discharged ?-~Yes, USIC LOVER (Auckland): My 4 valve a.c, set oscillates on the lower end of the broadcast band. A.: Have you an efficient earth on the set? Try another 551 valve in the correct socket. See that all the shields are making perfect contact with the main shield, Sailing this insert 500 ohms grid suppressors between the coil and the grid of the valve. This should not be necessary, however. 2. What is the best method of connecting a pickup to a set? A.: By breaking the grid and connecting | jfhe pickup between this point and 3. The set contains an t.f. choke wound on a wooden formet. Would a shield choke make any difference? A.: Quite possibly, as this unit may be picking up stray rf, currents,

Curious (Timaru): What kind and what is the filament voltage of an Ozarka type A valve? A.: We do not know the make, but the chances are ten to one that it is a 201A type of valve. This is a general purpose valve employing five volts on the

filament, and 45 to 180 on the plate. can be used in any socket of a batbes set except the last. 2. Can dry cells be recharged from @ bicycle generator? (Concluded on page 24.)

Questions and Answers (Continued from page 11.)

A.: No; a dry cell manufactures its own electricity. A storage battery converts electricity passed into it into chemical form, from which it is reconverted later to ordinary electricity. 8. Which is the best three-valve shoriwave circuit? A.: Hither the "Kestrel Three" or the "Night Owl Three." The latter is the less expensive, and is easier to build an’ control. y) } EW CHUM (Levin): Occasionaliy my set becomes quite dead, but moving the dial a little up and down will often bring the signals back again. A.: This sounds like dust between the yanes of your condenser, or bent vanes, If you cannot locate the trouble your self, call in a serviceman. Do not interfere with your set too much, as you may introduce further troubles. Have the valyes tested