QUESTIONS AND ANSWERS

Radio Record, 17 July 1936, Page 48

QUESTIONS AND ANSWERS

" 8.L." (Patearoa): If you send in a * diagram of the circuit that you are using as it is now we will be better able to see what is happening. ‘There are severa] possibilities which could be operating to produce the fault that you. are having and we do not wish to send you on a wild goose chase by giving one which may not apply. "TOM THUMB TWO" (Awakino) : The 1C4 valves would give a greater sensitivity and better economy than the 34 valves. A.: The volume control would be the same as used in the "Birthday Five." A.: The automatie volume control can be used just the same by connecting the return end of the grid leak to the bias resistor, ‘ "QE." (Belmont): Yes, the all-wave ¢ equipment you mention is an advantage if you are experiencing interference and if it is installed properly. A.: The shortest earth lead possible and the serial about 100 feet of wire; including the lead-in. The aerial should be as high as it is convenient to erect, a vertical wire being the best. A.: Pioperly used, the metal valves are especially advantageous on shortwave, and are slightly better on broadcast, This is a general statement, as there are valves in the metal series which have not equivalents in the ordinary types and these metal ones are better ‘in their characteristics than any of the glass ones that. are nearest to them in chara«terisies, "R T." (Shannon): The rea:tion con- * trol could well be the throttle type and the resistance R2 can be included in either of the tuned circuits of L4C8 or L8C2, to act as an adjustment of the strength of oscillation in that quenching circuit. The value of this resistance would probably be about 1000 ohms fer an average case, but will have to be found by experiment, Try several values of volume control that you have. Let's know your results, " W.C." (Hastings): The e'reuit you * show would be euitable provided that. the detector part would work down about 20 metres, and that the meter to show the effect were a rectifying type. The signals, put into the meter as it is, would be alternating in character and would not have any effect on a d.e. instrument, ° "D818" (Invercargill): There is no need for separate licences under the conditions which you state the sets are working. ‘ "PUZZLED" (Kelso) : The "Sky Hawk" is still a good set, but there is another more ambitious and more sensitive described in the 1986 "Radio Constructor’s Guide" under the title of the "De Luxe Shortwave Six." This set, if carefully made up, is really excellent and until, and if, we redesign this, using metal valves, it is easily the best yet. "Kh JS," (Papakura): We are at a * loss to understand why the coverage is so low, as the cirenit seems correct and ‘the condenser you: are «sing will cover a greater range than you get. if the coils are right. In the "Radio Con structor’s Guide." of 1986, there is a table on page 156 where, in column four, the coverages for your condenser are given for the different coi] diameters, We suggest that you eheck the wiring of

your set carefully with the diagram, ticking off on the diagram each wire as you trace it, as it may be that you have another coudenver in parallel with your tuning condenser by mistake. Check ‘also the coils with th'g table, Write again and let us know the result.

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