NEWS AND NOTES

Southland Times, Issue 20011, 27 October 1926, Page 14

NEWS AND NOTES

(By

“Reflex.”)

Readers are invited to contribute items of local interest for publication in these colums. Letters should be addressed to

“Reflex,” c/o Southland Times Office, and should reach the office not later than midday on Monday for insertion the following Wednesday.

Readers who are situated alongside tramlines will find that a separate earth connection remote from the high pressure water supply will diminish the amount of interference experienced.

Readers who are building sets are strongly advised to use the new UX socket; the contact? in this socket are very much better than in the old type, and there is an entire absence of tube noises.

It is not generally known that a piece of hard coal, non-bituminous, will act as a detector in a crystal set.

The trouble with resistance coupled amplifiers is that they will not carry enough power for good loud-speaker volume. Impedance coupling is superior in many ways as it is easier to construct, requires less B battery, and yill operate a large speaker.

Licenses issued by the P.M.G. of Australia total 134,739. New South Wales has a percentage of 1.8 to every 100 people, while Victoria has 4.6 sets to every 100 people. The figures for New Zealand for the current year are: Receiving licenses 6,590, transmitting licenses 105, dealers 477, and experimental transmitting stations 2. Licenses in Britain exceed 2,000,000.

4ZB is not transmitting on Wednesday nights until further notice.

A Waikato amateur wireless enthusiast, working a three-valve Anchoradio, got in touch with Oakland, United States, recently when an excellent musical programme was heard quite distinctly. On the following evening the new Auckland station relayed from the Pitt Street Church, when every word of the sermon was heard on a loudspeaker as distinctly as though the listenersin were in the edifice itself, while the choir singing and the solos were splendid. It would almost seem that while the work of the churches can be materially extended through the medium of the radio, the churches are likely to suffer in the way of congregations if people can enjoy the services without moving from their firesides.— Otago Daily Times.

Quite a good earth connection to a set may be made by taking a wire lead from the set and running it, by the shortest possible route, to a cold-water pipe, to which it may be attached by means of one of the many types of “earth clips” which are to be had at any radio shop. When making earth connections in this way always select a portion of the water pipe near to the place at which the pipe enters the ground, and never, under any circumstances, connect up the earth lead of the set to a hotwater pipe, for this would mean that the current from the set would have to traverse all the hot-water system of the house before it finally entered the ground. Gaspipe earths are an abomination. Not so much because there is any real danger of fire (that would only occur if the aerial were struck by lightning at a time when it was directly connected to the gaspipe earth), but more on account of the fact that most gaspipes contain a number of red or white lead joints. Now these joining materials are substances of considerably high electrical resistance, and thus the current from the set would have to overcome the combined resistance of the joints before it finally entered the ground. Which fact would, of course, make for weakened and poor reception. SUNSPOTS AND WIRELESS It is more than probable that with the advent of wireless on a big scale we shall j have another means of studying the varying influences of the sun upon the earth. | Everyone knows that sun-spot activity var- ■ ies during a period of about eleven years, j and that in sympathy with these changes ' certain phenomena, particularly magnetic storms and displays of aurora, are much in evidence. Cyclical changes in the growth of trees, melting of “snows” on the planet Mars, and colour changes on Jupiter, have also been ascribed by various observers to solar activity. But never in the world’s history have so many people been directly l interested in sun-spots. The reason is, of course, that the age of wireless broadcasting has come, and thousands of people who hitherto' did not give the matter a thought are interested in any plausible explanation of bad conditions of reception. Just at the present time, for instance, we are finding it | exceedingly difficult to receive Australian ; programmes satisfactorily. This is not by any means due to the disturbance of .“static,” but just that the signals will not come through. Someone informs us that there is a huge sun-spot in evidence, so what is more easy than to ascribe the trouble to that? Now there is a very great difference between a rough and ready generalisation of that kind, and the careful investigation, observation and recording of data demanded by a scientist. The present approach to a maximum period of activity should provide plenty of scope for scientific investigation of that kind. Broadcast listeners can do their part by recording conditions of reception from day to day. Transmitting amateurs can do more because they can ascertain whether conditions are local or general, and, moreover, they are in a position to find out whether short or long waves are specially affected. At the present time short-wave amateur work over the whole world is remarkably difficult. There is every likelihood that the appearance of a large spot on a particular part of the sun’s disc may be correlated with difficulties in wireless transmission, especially with short waves. A few days ago we were in the line of “fire” of a particularly vicious one. TO USE You can now take time and carefully consider the best instrument and arrange i the mechanical lay-out in the best possible manner, writes “Static” in the New Zealand Times. In connection with this line of work, let us start at the beginning of the set and work right through from aerial to ’phones. The antennae system as the aerial and ground combined are known will receive first attention. Possibly by this time your aerial has become corroded, or the joints bad; this is not a desirable condition, as it interferes with good reception. If the wire is weak replace it with new material and resolder all joints. Seee that the ground clamp is making good contact and use brass or copper ;■ iron should not be used. Ground clamps of a cheap variety are to be shunned. Coils or inductances, as they are sometimes termed, are to be found in every type of set, and take many forms; but in the sets in use to-day, there are only a few types which may be considered seriously. Under this heading come various instruments. such as radio frequency transformers and couplers or vario couplers. All of these are good, but in the type first mentioned, the most important point to watch is insulation. If the coils comprising the transformer are wound on tube, this tube should have very thin walls. K The wire should be of medium size, say, 24 gauge

Of late the low-loss craze in condensers has assumed tremendous proportions. Just I what constitutes a low-loss condenser is a ’ moot question among many of those well ; versed in radio theory and practice. The j writer holds no brief for any condenser and i is not trying to “knock” so-called low-loss; typfes. Many are of excellent construction.] Only let me reiterate that you should avoid I all insulation in condensers, except those j of bakelite, Celeron, radion, glass or glazed | porcelain. One or two condensers have recently appeared on the market using the lattermentioned substances of insulation. Fixed condensers play an important part in a set. When you buy the particular capacities designated by the article you are following in the construction of your set, do not get cheap types that are insulated with waxed paper. Spend a little more and get good condensers. You will be well repaid in the end. Fixed condensers can cause more trouble, in the set —and that trouble is much harder to locate than anything else; buy. a reputable make of condenser which is provided with mica insulation. Another source of great trouble to the radio constructors is the grid leak in the detector circuit. Here again the purchaser should be most careful in choosing this little unit. This is not an expensive unit, but requires a deal of consideration. Most of the verj’ cheap leaks are turned out in rapid production and suffer accordingly. The writer has tested many leaks 'of the same make which were marked with the various resistances from 4 —5 megohms; most of them had a resistance of about 3 I megohms. Thus it is shown that you cannot always go by the markings of the cheapest of these instruments. Well-known and widely advertised leaks are very reliable and you need not hesitate in purchasing them. In choosing rheostats some precaution should be used. Since all vacuum tubes are slightly different in characteristics, and require a rather’ critical control of the filament current which is supplied by the A. battery, rheostats or controlling devices are necessary. Several fixed instruments of this nature are for sale and are quite satisfactory in amplifiers.

However, in detector circuits acontinuously adjustable resistance is quite necessary. In the fixed type it will be noticed that as the A battery gets weaker so does the fixed rheostat or (balast resistance as they are sometimes called) ; that is why it is not advisable to use it in the detector circuit; but if the batteries are always kept up fully charged, there is any amount of pressure to keep the resistance working well.

The carbon pile or compression types or wire-wound resistance are more adaptable in the detector circuit. With the former a much more vernier control can be obtained than the latter. See that the base of the wire-wound instrument is of good insulating material, and that the contact arm is quite springy and makes good, firm contact. If the base is of soft material and should soften by the heat it will throw the resistance coil out of alignment, whereupon the consequent operation will be rendered rough or impossible. The same remarks can be observed with regard to the potentiometers.