TIPS AND JOTTINGS

Radio Record, Volume I, Issue 52, 13 July 1928, Page 13

TIPS AND JOTTINGS

Tickler Coils. AILING anything more definite, the turns on a tickler coil for use in o regenerative circuit can be reckoned at about two-thirds the number of turns on the secondary coil, This proportion, however, does not hold true in all cases, especially when valves of the 199 type are used, In this case, the size of the tickler coil will, have to be increased, as this valve does not oscillate as freely as the 201A type. The distance between the secondary and tickler coils also affects the size of the coil; and the use of resistors or condensers for controlling the regeneration also changes this value. . The actual size of the tickler coil can easily be determined when the set is in operation. If the regeneration is too. strong, and cannot be controlled, the tickler turns should be reduced, while, if sufficient regeneration is not obtained, more turns should be put on. ~ New YTickler Control. (THE absorption tickler control deait with in the 2 rf. BrowningDrake can be carried out quite well with an ordinary filament Bradleystal. The writer has found this method entirely satisfactory. Eliminator "Motor-hooting." MERICAN experience is showing | that there is more liability to ""motor-hooting" from eliminators in which there is a continuous tapped resistance running from positive to negative, as in the potential divider system, than where a separate resistance and condenser is employed for each voltage, as in the "Record" eliminator. R.F. Valve Impedance. "THE yalye for which the BrowningDrake was originally designed. to use in the R.F. stage is the 199, with an impedance of 16,500 ohms, and too great a departure from this figure is not always desirable. And this is not the only cirenit for which a valve of about the above impedance has been found most suitable in R.F. stages. Protecting Battery Terminals. THE usual prescription for protecting accumulator terminals from corrosion is a liberal smearing of vaseline, but the results are not always as desired. A better, but less known, com~ pound is a mixture of castor oil and turpentine mixed in equal parts by yolume, This preparation will clean terminals that have become very dirty, and they will not corrode again if kept tl‘aly smeared with this mixture, which will not harm either celluloid, ebonite, or glass. Neutralised Superhets. LTHOUGH receivers of the superheterodyne type are supposed to operate on a frame or loop aerial, and not on an outside aerial, listeners who wish to employ a superhet. may now enjoy the advantages of the outside aerial. This is possible through the introduction of the Radiola series of neutrolised superheterodynes, of which there are seven different styles.

The Moving-Coil Loudspeaker, M'TIS type of speaker has so far been "~ -_- little in evidence in New Zealand, shough its reproduction is Glaimed to "e the most perfect yet. This type of, peaker is expensive to purchase, and sts more to run than does the ordinary speaker, as there is a powerful electro-magnet to be supplied with stcady Girect current whilst in use. For home-construction it is necessary to purchase the necessary castings as accurate machining is an essential feature. When such castings are availa -e in New Zealand, constructors will be able to do their own winding and make and fit the cone for such speakers. A New Resistor. NEW wire-wound and shielded resistor bears the Igranic brand, and will be found a great ifnprovement over the usual type of fixed resistance. Suitable clips are also provided. The 80,000 ohm resistor is stocked by the International Radio Co., Wellington. Colvern Coils. HH "Colyern" or Collinson coil formers provide a handy means of plugging in a set of tuning coils at ‘one operation. On these formers, which have six pins fitting a suitable base, primary, secondary and tickler, or any other combination may be wound and. the whole plugged in with one operation without chance of mistake. The large size is 2$in. and the small 238-8in, diameter and can be obtained with or without copper shield. The smaller size can be obtained ready wound as a split secondary. These formers are stocked by Messrs. Thos. Ballinger and Co, Ltd, Victoria Street, Wellington. The UX250 Amplifier. Few listeners in’ New Zealand will at present be very interested in the new power amplifier, capable of delivering over three times the undistorted yolume of the 210, ‘The latter valye is a goal which few here have yet reached. The new valve is highly suited to public demonstration work, and no doubt its output will be made good use of at the coming elections. As a transmitter, the new valve is rated at 25 watts as against 74 watts for the 210. The plate yoltage ranges from 250 to 450 volts and plate current from 28 to 65 milliamperes,