QUESTIONS AND ANSWERS

Radio Record, Volume VIII, Issue 45, 17 May 1935, Page 48

QUESTIONS AND ANSWERS

"ME (Christchurch): A resistor can be used in place of a filter choke only in cases where the "B" drain does not exceed about 5 or G mils. This method of smoothing will not be suitable for the set you are planning to build. * A THOS" (Hikurangi): ‘There is n? danger whatever of damaging the yalves if the volume control is turned full on when the set is switched on, though if the set- happens to be tuned to a poweiful station, you will need no reminder to turn the volume down. K J.F. (Te Kauwhata): The .00005 ¢ mfd. variable condenser used in the "Haglet Two" described in the 1935 "Radio Constructor’s Guide" is not a reaetion condeuser but a series aerial condenser. If you h've not one on band then try connecting a length of flex about n foot long to the aerial terminal and then merely twist the lead-in around this for a distance of 6 inches or so. This should provide the necessary coupling, which is adjustable. The circuit you enclose for adding a 2A5 output pentode will work satisfactorily theugh it woul be better to use a 50,000 ohm resistor for the plate load of the 56. Tf you find you cannot cut the ,volume down sutiiciently by turning back the reaction control, then replace the quarter megohm grid leak of the 56 wit) a potentiometer of the same value, taking the grid to the moving arm. C G. (Nelson): You will find that * one of the converters described iu ‘the May "Radio Times," now on sale, will work splendidly with your set. KE: (Wellington): The cost of running your receiver is approximately the same as that of running an ordinary: 60-watt household electric Jamp. The winter edition of the "N.Z. Radio

Call Book,’ now on sale, will give you all the information you require on logging shortwave and broadcast stations. A 3-foot length of iin. water pipe driven into the ground and with a fairly heavy gauge earth lead well. soldered or clamped to it would make a suitable earth for your set. J R. (Dunedin): The converter we aid- * vise you to build is the battery model of that described in the May "Radio Times." However, if you wish to build up your own from the circuit you enclose, several minor alterations

should be made. Virstly, a 18-plate midget condenser should be included in series with the aerial; otherwise you may have difficulty with obtaining smooth reaction over all bands. Secondly, the chok: CH1 should be omitted, or if you like include it in series with CH2. Thirdly, .00025 mfd. is quite large enough a capacity for the coupling condenser C4. Suitable turn details for the coils are as foilow :-

The above details are given assuming that the coils are to be wound on valve base formers; use 24 or. 36 gauge d.s.c. for both windings. ‘ S G. (Auckland) : Would it be possible * to wind the broadcast coils of the "Waglet Two," described in the 19385 "Radio Guide," similarly to those of the "Tom Thumb Two," i.e., with the elec-tron-coupled reaction winding wound over the secondary? If so, how many turns would be required on the reaction winding? A.: Yes, this could be done, provided, of course, that you use the connections for the coils as shown in the coil diagram for the "Kaglet Two." Twenty turns on the smaller broadcast coil and 25 on the larger should be sufficient, Note.-The s.w. grid windings of the "Tom Thumb Two".-are put on with 24 d.s.c., which is specified in the parts list; 30 d.s.c. could be used, but it rather fine for short-wave. O B.E. ( ): Is it a difficult task to * change a set over to use 2-volt valves instead of 6-volt? A.: Tt depends on the types of valves your set uses, and these you have not given. However, if your set at present uses Philips valves, then no ‘doubt you could find suitable equivalents in the new 2-volt series of valves whiich has just been announced by these makers, Tull characteristics appear in the reference section of the 1985 "Radio Guide." The saving in "A" and ‘B" battery, consumption, if any, will depend on the charac- _ teristics of the valves you intend to use. Most sets now use 2-yolt valves.

"PE KOON" (Gisborne) : You will find full details of the choke you are planning to wind are contained in tbe reference section of the 1985 "Radio Guide." An explanation of the ehart appears in Section 7, under the heading, "Audio Chokes." C G.L. (Christchurch) : On local stations the volume of my t.r.f. set suddenly jumps from zero to full. The yalves are O.IX., and I have renewed the yolume control, The fanlt does not occur on stations other than locals, A.: The only suggestion we can make is to give your aerial and earth system a thorough overhaul. A poor or intermittent contact could cause the trouble you mention,

An Apology to Readers We regret that owing to heavy pressure on space it has been necessary to hold a number of "Questions and Answers" until next week.

Band: Grid: Reaction. 20-metre 7 3 40-metre 16 6 80-metre 27 9