QUESTIONS AND ANSWERS

Radio Record, Volume V, Issue 33, 26 February 1932, Page 11

QUESTIONS AND ANSWERS

FRANK

KEE

\ EOoNoMx THREE (Gisborne): Your . request will be borne in mind and be dealt with either in the "New Zealand Radio Times" or in the 19382 ‘Radio Guide." H G. (Dargaville): We could give you *a circuit for a stage screen grid to go in front of the Super Six, but we are not certain if the P. and T. would pass it. It is not sufficient to submit a circuit to them. One must give them a built-up receiver for test. 2. It is questionable whether an s.g. first detector would be worth the added

difficulty of wiring it into the circuit and getting it to work properly. 8. Specifications for a short-wave frame aerial will be given. C B.A. (Pukerua Bay): We regret we * cannot forward. layout diagrams of sets which have not been described in the "Radio Record.’ Surely you can find'a good two-valve receiver in either previous "Records" or .the forthcoming "Guide." Watch for the "New Zealand Radio Times"; there are going to be gome good circuits in that. Ac (Wanganui): If your set will oscillate there is nothing wrong with your coils. The fact that you are receiving Morse stations appears to settle the question as far as oscillation is concerned, for a set cannot receive Morse stations unless it will oscillate. Try another radio frequency choke if you cannot receive broadcast stations well, and also be very patient with your tuning. (GREENHORN (Christchurch) : There appears to be something wrong with your set, for you should be able to bring in at least Dunedin and Wellington, strong enough to be satisfactory. We

suggest you get in touch with the dealer who sold you the set. R W.W. (Nelson): You will find the * address you want in the January "Radio Log." Pp*28Mo (Christchurch): Yes, your set has an untuned rf. valve followed by two tuned valves. It is not surprising the volume control would not operate on low consumptive valves, as it is of low resistance, and consequent upon a small flow of current oceasioned by the filament of the valves you are using the volume control has very little effect upon the voltage. The valve should, nevertheless, be almost as efficient as the one for which the set was © designed. You should use 221's with a six-volt accumulator. You should be — able to neutralise the set quite satisfactorily by starting at the valve nearest the detector. and covering one filament leg with silk and adjusting the neutralising condenser nearest it, until the signals disappear, or almost do so. Then put that valve back properly and reneat the procedure. °

2. To operate a "B™ class transmitter you must pass an examination laid down by the P. and T. Department. For the syllabus write your local radio inspector. A Morse Certificate is not necessary. H D.C. (Wanganui): Send us a work- * ing sketch of the cross-bar and we shall criticise it for you. We really cannot tell you very much from_ the scanty sketch you have sent. Send the specifications with it. Four pounds and a half is rather weighty, we think, and would put undue strain on the aeriai mast. The cost of becoming a member of the DX Club is 2/6, which is the price of the badge and certificate. We are sending you a circular concerning the club. ATUDENT (Wairoa).-Your valve combination appears to be quite a good one. We have not tried the actual combination ourselves, but we see no reason why it should not be equally as good as the one we specify.

(SHOKE (Dunedin). -NX171 is exactly the same as a UX171, only the former is not made by the Radiotron Company but by a company under license to them. 2. Microphone bar amplifiers are uite out of date. Do not worry about them. You may go to a lot of trouble and be disappointed. PARTHQUAKE (Karamea).-We cannot locate the circuit of your set, but if the valves are not of the screen grid type we suggest you use 221 in all stages except the last, where you should use @ power valve of the B605 class. We suggest that you have your valves tested. Consult "Radio Questions and Answers" for a possible solution for your trouble. There are many:things that might be wrong with your set. O B. (Invercargill). — A dealer could * tell you better than we the approximate cost of the Super Six. Alterations are not necessary in order to use a pentode, merely connect an auxiliary grid to "BRB" Specifications for, a_ shortwave frame antenna are published elsewhere this week. af B.H. (Marlborough).-A battery char- * ger could be worked very satisfactorily from a windmill. Write Johns, Ltd., Auckland, who will possibly be able to

help you. It is not practicable to replace the secondary battery with the Daniells Cell, which could be used for the "A" battery. Why not try an air-cell? That would be more satisfactory than going to 2 sreat deal of trouble in getting your ac« cumulator charged. BISHOPSCOURT (Dunedin).-Are you quite cettain that it is an amateur transmitter whe is worrying you? Get in touch with the local radio inspector, who will be able to help you. It is very rare indeed that the amateurs interfere with broadcast listening. BUNG (Hamilton H.).-Yes. Yes. The wire didn’t arrive, H.B. (Onehunga).-Write R. BE. * Coury, Pitt Street, Raetihi, for fur ther particulars.

H.G, Oamaru).-I have a grid coil * tuned of 130 turns, of 28 d.s.c. tuned with a .0002 condenser. 4YA comes in at about 45, but I appear to be unable to get below 260 metres. Commercial Morse stations come in on the other end of the dial. How can I extend the tuning range? A.: Take a large number of coils off your grid coil, say 15 to start with, then when you get 4YA p near one end, your range is about right. A correspondent has had great success with the "Hagle Five." Within three hours of building the set he logged 10 N.Z. stations, 20 Australians, and 8 Americans, about 260 metres. ; 9 Wonld a battery version of

super-het, shortwave convertor be satisiac= tory with the "Eagle Five’? A.: That is more than we can say; Wé beliéve it would. 8. In a case of motor-boating in @ transformer and 2 stages of r.c, amplifier, would a 2 mfds. condenser across thé "B44" supply be sufficient, or would resistances be required? A.: Probably you would have to use de-coupling resistances. However, try the condenser and also try reversing the cone nections to the primary of your transfor mer. A different value in grid leaks im the r.c.c, amplifier will frequently have & very beneficial effect in overcoming motor boating in an r.c.c. amplifier. F H. (Dunedin).-Since using an elimim * ator I cannot bring in outside star tions with my four-valve B.D A.: You will have to borrow a vol meter and check up the voltages of al your valves. It is possible there is somes thing wrong with the eliminator. Ha your valves tested. XYZ (Napier): Yes, you can add an other pentode providing it is in push» pull with the last one, certainly not following a pentode. You do not need 2 stage between a pentode and the detec tor. A V.N. (Grey County): Your battery ¢ should require charging ahony once a month,