Over The : AERIAL :

Waikato Times, Volume 113, Issue 18903, 24 March 1933, Page 8

Over The : AERIAL :

BY RHEOSTAT

THE COMING WEEK. Sundays. —lYA: Service from St. David’s Presbyterian Church; 8.30, relay of Municipal Band from Albert Park. 2YA: 7.0, Service from St. Peter’s Anglican Church; 8.15, Concert by Hutt Valley Leidertafel. 3YA: 6.30, Service from St. Andrew’s Presbyterian Church; 8.15, studio concert. Monday —lYA: 11.0 talk; 3.30, home science talk; 7.30, agricultural talk; 8.0, studio concert. 2YA: Talks, 11.30 “Health Hints or First Aid”; 3.0, “Selection of Dress Material ”; 7.40, “Books, Grave and Cay”;. 8.0, studio concert; 10.0, dance music. 3YA: 11.0 Description of First 'Cricket Test; 3.15, Home Science talk; 7.35 W.E.A. session; 8.0, concert by Derry’s Military Band. Tuesday —lYA: 11.0 talk; 7.35, Music Lovers’ Competition; 8.0 Studio Concert, “ A World Tour,” interspersed with description of swimming at Tepid Baths; 10.0, dance music. 2YA: Talks, 11.0, “Fabrics and Fashions”; 7.40, j “Fo-r the Alan on the Land”; 8.0 studio I concert. 3YA: Talks, 11.0 “Fashions,” 7.30, “Sunlight and Vitamins”; 8.0 studio concert; 0.30, dance music. Wednesday. —lYA: 11.0, talk, “Women’s Interests”; 7.30, W.E.A. session; 8.0, studio concert; 9.30, dance music. 2YA: 11.30, talk, “■Hollywood Affairs”; 7.30, (Music Lovers’ Competition; 8.0 studio concert. 3YA: 11.0, talk, “A Day’s Outing”; 7.30, Addington Stock Market reports; 8.0, studio concert; 10.0, dance music. Thursday. —lYA: Talks, 11.0 “Electric Apparatus"; 3.15, Home Science; 7.30, W.E.A. session; 8.0 studio concert. 2YA: 3.15, Home Science talk; 7.30, W.E.A. session; 8.0 concert by Port Nicholson Silver Band. 3YA: 11.0 talk, “The Care of the Hair ”; 7.35, Music Lovers’ Competition; 8.0, studio concert. Friday.— lYA; 11.0, talk; 11.25, description of Second Cricket Test match, at Eden Park; 5.50, resume of test match; 7.30, sports talk; 8.0 studio * concert. 2YA: 7.40, talk, “Tourist and Health Resorts;” 8.0, studio concert;. 9.30, dance music. 3YA: 11.0, talk, “'Feeding the Family”; 7.30, W.E.A. session; 8.0, studio concert. Saturday. —lYA: 11.25, Description of Second Test Match at Eden Park; 7.30, Hortilcultural talk; 8.0 studio concert; 10.0 sports summary; 10.10, • Old Time dance music. 2YA: 7.30, 1 W.E.A. session; 8.0, studio concert; 10.0 sports summary; 10.10, dance music. 3YA: 8.0, studio concert; 10.0, sports summary; 10.10, dance music.

MID-ATLANTIC TALKS.

WIRELESS PHONE’S OPERATION. HOW A CALL IS MADE. Let us see what happens when, say, M? Smith, of Leeds, picks up his telephone to speak to his business associate, Air Jones, travelling to New York on the Majestic, at present 2000 miles west of Land’s End, says T. W. 'Bennington in The Wireless World.’ Air Smith will have previously “hooked" his -call by telephone, and the long-distance operator will now announce, “ Mr Jones is on the line, Go ahead, please.” On Air Smith saying, “Hallo, Jones,” low frequency impulses set up by bis voice pass over the wive line to the Leeds exchange, and from there to the long-distance switchboard in the General Post Office, London. From here they are sent to the radio-telephone terminal in the same building, and, passing through the hybrid set, are amplified, and the volume level adjusted by the technical operator. Next, after having set up currents which operate a relay and “ clear the circuit ahead," they pass over a wire line to Rugby, where they are once again amplified and used to modulate

the high frequenoy carrier of the transmitter, by which means they are carried aoross the 2000 miles of ocean to the Alajestio’s receiver. Here, after amplification, they are separated from the high frequency carrier, and after being adjusted to the correct level, arß sent down to the telephone earpiece where Mr Jones is listening, and reproduced as sound waves. A similar series of events takes place on Mr Jones replying—from his telephone to the Majestic’s transmitter, thence to Boldock and the London terminal, through the hybrid set, long distance switchboard, and local exchange, and, finally, to Air Smith’s earpiece.

SILENT TUNING. AIUCH-NEEDED IMPROVEMENT. ■Some recent receivers have a system of uiet A.V.C. called “Q.A.V.C.” J which in effect is a method of shortI ing the L.F. system when the set is I tuned into the hetween-carrier region. Such circuits require an additional valve. This valve is coupled to the A.V.C. system in such a manner that its bias is very low when the set is not tuned to a carrier. Therefore the valve has a high plate current, and across a resistor in its plate circuit appears a large voltage drop. This voltage is applied to the grid of the first L.F. valve in addition to its usual bias voltage. So great is the bias on this valve under these conditions that no plate current flows at all and therefore no amplification results. The valve does not pass any signals through to the loudspeaker. When, however, the listener tunes the receiver into a carrier wave, a strong bias is put on the Q.A.V.C. valve, its plate current decreases, which releases the bias on Hie first L.F. valve. The latter is thereby permitted to pass on to the power stage any programme that is on the carrier. Thus tuning away from a carrier with such a circuit means simply that the listener hears nothing at all until he is tuned to the carrier. There is no hetween-slation noise. There is one very interesting variation of this .scheme. The additional valve has a very sharply tuned input circuit coupled to the intermediatefrequency system. Its plate circuit has control of the first L.F. stage as before. But so sharply tuned is this circuit that nothing at all is heard until the receiver is tuned within 1 k.c. of the exact centre of the carrier. Therefore the listener gets all the programme or nothing. Distortion caused j by incorrectly tuning a superhetero- | dyne is avoided by this circuit. \

TESTS OF NEW VALVES. THE LATEST TYPES. The following is the result of tests made by experts between the latest iron-dust coils, called 'Ferrocart, and the present air-coned tuning coils. Readers can draw their own conclus- | ions as to the importance of the new invention. Inspection of the curves of both types of coil makes it clear at onoe that over the hulk of the wave range the new coils, and especially those wound with Litz, are not in the same class as the standard screened coil that we use to-day, says a writer in an English journal. To find a worthy oompetitor for the Ferrocart coils it is necessary to go to the most efficient type of inductance that has ever enjoyed popularity, and to make comparisons with the large Litzwound coils introduced in 1926 and used as standard in sets for some years subsequently. The Litz-wound Ferrocart coil has a magnification a j little inferior to Litz-on-ebonite (3in. diameter) and a little higher than Ltiz-on-paxol'in. The comparison is, however, a little unfair in that the inductances of the Litz Coils were nearly double that uf the Ferrocart coil with which they so closely compare. With more nearly equal andjictancejs the curve for the Ferrocart coil would almost certainly fall below both Litz coils, and not between them. The movement would, however, be quite small, and the fact remains that for ail practical purposes the Litz-wound version of the new coil may he regarded as equivalent to the hightlyeffleient three-inch Litz-wouncl inductances. These coils fell out of use for tv;,9 reasons, the most important ■of which was that they could not be screened without losing .their excellence unless an extravagantly large screening-box was used.