Radio Broadcast (May 1928-Apr 1929)

276 RADIO BROADCAST SEPTEMBER, 1928 2500 x 2000 5 1500 g 1000 500 CALIBRATION CHART FOR LONG WAVE ADAPTER Made with Kolster Decremeter Detector Oscillatir,g,250' — Antenna.12.000 ohi in Det. Plate Ci _No 40 50 60 SETTING FIG. 2 80 90 100 THE PARTS USED HOME constructed coils for this adapter can be made in this manner: For a coil with a wavelength range corresponding to curve iii-D, Fig. 2, wind on a 2" cylinder a bank wound coil consisting of 13 piles of 20 turns each for the secondary. The winding at one end of the coil. Li, should contain 100 turns and the rotor winding, L3, should contain about6o turns. For a coil to tune as indicated by curve 111-E wind 9 piles of 44 turns each on a 2" form, the other two windings being the same as above. Use about No. 28 s.s.c. wire for all the windings. The other parts specified for this adapter have no special electrical characteristics and parts electrically equivalent to those mentioned in the list may, of course, be used. Ci — Hammarlund type M L-17 variable condenser, 0.00035 mfd. (A 0.0005-mfd. variable condenser may be used, as explained in the text) C2 — Hammarlund variable condenser, 0.0001 mfd. C3 — Sangamo fixed condenser, 0.00025 mfd., with grid leak clips. Li, L2) L3— Silver-Marshall coils, No. 111-D and No. 1 1 i-E Ri — Tobe Tipon grid leak, 6 megohms R2 — Yaxley switching rheostat, 30 ohms (50 ohms for ux-199 tube) R3 — Durham resistor, 10,000 ohms 1 Karas 4" vernier dial 1 Benjamin cushion UX socket 1 Silver-Marshall coil socket, type 515 4 Eby binding posts, small 1 Bakelite panel, T36" x 7" x 9" 1 Bakelite binding post strip, 3 'I v 3" y a!" TB x i x 44 1 Plywood baseboard, 1" x 8" x sr. Celatsite wire WHAT THERE IS THERE are plenty of signals above the broadcast band. Some valuable information is contained in the chart on page 169 of the July issue of Radio Broadcast, and in the table on page 52 of the May issue. All these frequencies are assigned by international conferences in which every important nation is represented. Six hundred meters is the calling wave for ships of all nations on the seven seas. When contact has been established with another ship or the shore, messages are usually handled between 600 and 1000 meters, though the 600-meter wave may be used for messages where calling is not interfered with. This wave is also used for marine distress calls, which are fortunately rare. When the broadcasting stations shut down for an SOS, one can often hear spark signals from the disabled ship itself. Marine direction finding occupies 800 meters. A ship in doubt of its position calls a control station on shore. Then two or more widely separated stations on shore take radio bearings on the ship's transmitter. When these bearings are plotted on a chart their intersection gives the ship's position, which is promptly radioed to it by the control station on shore. When the coastal weather is at all foggy one can hear the radio beacons sending out their distinctive signals. They are small tube transmitters, usually aboard lightships, and their note is c.w. modulated at about 1000 cycles. Their signals may be found on the Department of Commerce navigation charts. A few in the New York area actually checked by the writer are: Nantucket Shoals Lightship — 4 dashes; Fire Island — 2 dashes; Ambrose Channel — single dashes; Seagirt Lighthouse — 3 dashes. By listening to these beacons start up, one after another, it is possible to trace roughly the progress of thick weather along the coast. People who live far inland will miss a great deal of this marine radio, unless they are near the Great Lakes. Long-wave broadcasting has never taken hold in America, but it is important in Europe. Theoretically, the range of a 1400-meter station should be over three times that of a 400 meter station of the same power, but for some reason the long-wave European broadcasters do not seem to get out very well. Perhaps the average receiving antenna is too small for effective long FIG. 3. THE PLACEMENT OF THE INSTRUMENTS FOR DIRECTION FINDING FIG. 4 wave work. Some long-wave European broadcasters using over 10 kw. are: LP, Berlin, 1300 meters, 12 kw.; projected station at Moratala, Sweden, 1304 meters, 40 kw.; projected station at Moscow, 1450 meters, 40 kw.; 5XX, Daventry, England, 1600 meters, 16 kw. (from Citizens Radio Call Book). Trying for these stations should prove interesting during the winter months. Large ships use bands between 2000 and 3000 meters for through traffic, and often attain surprising ranges. Two or three years ago the transport Chateau Thierry worked New York with its 5-kw. arc from a position near San Francisco. Some applications of this long-wave adapter make it useful on small yachts or other ships equipped only with conventional broadcast receivers. By listening on 600 meters in fog or storm, the navigator can get some idea of the number of ships near him, as well as bits of information about the weather and sea from the messages these ships exchange. The Navy weatheand press broadcasts may also come in very handy at times. By listening to the radio beacons on 1000 meters the yachtsman can get a rough idea of his distance from them. It would even be possible to rig up a loop on deck — say about 30 turns on a frame two feet square, connected in series with a large variable condenser and the adapter primary Fig. 4 shows the connections. Signal changes are noted on rotating the loop; the minimum signal means that the beacon is in a direction perpendicular to the plane of the loop. This arrangement should work up to five or ten miles. Though these higher waves are almost unknown to most radio listeners, they play a great and increasing part in the business of the world. The man who is bored with broadcast reception, who wishes to broaden his interest and extend his knowledge, will find a new field in exploring the possibilities of the radio spectrum, above the broadcast bands.