Radio Broadcast (May 1928-Apr 1929)

302 RADIO BROADCAST ADVERTISER Notes on the l99 TELEVISION is now an accomplished fact. Experimenters will welcome the Raytheon Kino -Lamp, the first television tube developed commercially to work with any system. Uniform glow over the entire plate, without the use of mirrors or ground glass, gives it perfect reproduction qualities. Kino-Lamp is the latest achievement of the Raytheon Laboratories which have made so many original contributions to radio science. Write for information RAYTHEON MFG. COMPANY Cambridge, Mass. /Raytheon^ " F>tP-Cell * Available in both bard vacuum and gas filled extra sensitive types— each in rwo sizes. Write us for special specifications. 6( By W. H. WENSTROM Lieut. Signal Corps, U. S. A. T iHE article on the "Cornet" multiwave receiver, which appeared in the June number of Radio Broadcast (pp. 77-79) has evoked a number of inquiries as to the operation and use of the set, especially in regard to the possibility of its employment as a portable receiver. The following notes have been prepared to answer these inquiries, and to give additional data to those who have built the set and wish to increase its flexibility and range as much as possible. Portable use: This circuit is admirably adapted to portable use. While not as sensitive as some multitube arrangements, it is far simpler and more dependable. Dry cell tubes are recommended, and the construction should be made more compact and mechanically stronger. It is advisable to mount all parts on a heavy bakelite panel. A single wire antenna about 50 feet long, and made fast at the free end fairly high up on some convenient object, is probably best. Unless a good ground is available a counterpoise, or insulated wire laid along the ground under the antenna, should be used. Other things, such as the frame of an auto, may be used as a counterpoise. Use of dry cell tubes: Down to and including the 40-meter band uv-199 or ux-199 tubes can be used without any circuit changes whatsoever. In the 20-meter band the 199 tube begins to be rather cranky as an oscillator. Some lines of attack on its unwillingness to oscillate are: 1 . Adjust potentiometer 2. Pick best oscillator out of several tubes 3. Connect a small condenser of "neutro" type between plate and grid. 4. Increase tickler turns. In general, the 199 tubes will be quite satisfactory, used with either adapters or 199 sockets. The overall gain is something like half that of storage battery tubes. Several 199's must be picked over to find a really good detector which, when found, will fall considerably below a Ceco H or UX-200A in sensitivity. A possible combination would be a Ceco H as detector and a 199 as audio amplifier. Coil for 200-550 meter band: A standard Silver-Marshall type No. 1 1 i-a coil may be used. With this coil the circuit as shown in the diagram on page 78 of the June issue tunes up to about 400 meters. To cover the remainder of the band, a Sangamo 0.0001 5-mfd. fixed condenser is connected in parallel with the condenser marked O. Drake's Radio Cyclopedia. By Harold P. .Manly. Frederick J. Drake & Co., Chicago. Second Edition, 1928. Price: S6.00 IN THE field of radio reception this should be a useful book, but the title is misleading, for in spite of its 920 pages, 1000 illustrations, and 1500 subjects, it is not a radio encyclopedia. Such a work, in any complete and satisfactory form, still remains to be written. "Drake's Radio Cyclopedia" is printed without page numbers, making it easy for the publishers to insert new material as it appears, somewhat at the expense of the reader who dislikes to turn pages unnecessarily. The material is arranged alphabetically; if, for example, you want to read up on "Leakage Flux," you go through the L's until you reach the desired (Continued on page 304) TUBES last longer when their filament temperature is controlled by AMPERITE, which is the only self' adjusting tube control. Entirely unlike fixed resistors. Keeps tubes burning at their rated voltage, despite "A" current variations— protects against blow-outs — gives clearer reception and easier tuning. Insist on AMPERITE. A type for every tube— battery or A.C $1.10 with mounting (in U. S. A.) at all dealers. -^^[diall Qompatty SO " ipi 50 FRANKLIN ST.t NEW YORK FREE— 'A m perils Blue Book"of new circuits and conslruction data. Write Dept. R.B.9 She "SELF-ADJUSTING ".R/tfarAtf 0 Bought Your New Dynamic Speaker Yet? WELL, when you do, look for the Elkon Rectifier — you'll find it on good dynamicspeakersabout in the position shown above and you can't fail to recognize it, by its solid, husky appearance. For your own protection make the dealer show you the Elkon name plate on the end of the recti' fier. You'll find it in the better dynamic speakers — no matter whether in sets, cabinets or separate units. Elkon Rectifiers .Standard equipment on the better Dynamic Speakers, "A" Eliminators and Battery Chargers