Useful Hints for the Novice

Radio Record, Volume I, Issue 11, 30 September 1927, Page 3

Useful Hints for the Novice

(By

AJAX

There is 10 more acceptable form of home entertainment than broadcast listening, with its endless variety and interest, With the introduction of a high-class broadcast service-in New Zealand, wireless as a hobby has undergone a complete change and is now invading the homes of all and sundry. Previously broadcast listening was the pastime of people who were mainly interested in the techriical wonder of it. Now there are thousands who buy wireless sets without the slightest desire to become deeply acquainted with the technical side of radio. Unfortunately it is not possible for the tadio dealer to go into all the detailed instructions necessary to the proper installation and operation of a receiving ontfit when it is purchased by a beginner-a novice whose sole object is to obtain interest and entertainment with his oufit and without any desire to become acquainted with the technicalities of it. Take the novice with a crystal set. He should realise that strength of reception is obtained through the quality of the crystal and the efficiency of his ‘aerial and earth connection. There are some crystal sets on sale with tuning devices which limit the desirable length of the aerial. The novice should ascertain from the dealer what length of aerial is recommended for that particular set. Generally speaking, the longer and the higher an aerial is for a crystal sect the better will be the reception. As the strength of reception with a crystal set also

depends largely upon the amount of electrical energy picked up by the aerial it comes as a natural factor that the longer the aerial the greater the energy it will pick up. However, if the aerial device is too long for the tuning devices within the receiving set, the set cannot be adjusted to the length of the aerial and the set is rendered out of tune with the aerial. Weak reception is accordingly inevitable. If an aerial is rather on the short side this is, for tuning purposes, compensated for by throwing into series or adding to the length: of the aerial a coil of wire inside the set. It will be patent to anyone that the coil of wire inside the set is a poor substitute for picking up electrical energy as compared with an aerial exposed aloft to the waves from the broadcast station. The same can be said of the tuning condenser, which is placed in parallel with the tuning coil within.the set. This makes out a good case for .having one’s aerial as long as possible compatible with the aerial tuning ‘device within the crystal set. , An aerial which is screened from the broadcast station is at a disadvantage. It has been conclusively established that intervening objects close to an aerial cast a radio "‘shadow.’’ A radio "shadow" differs from a light shadow in the peculiarity that the former converges to a point, whereas the latter broadens out. Therefore, although an object. may be directly between the broadcast station aerial aud the listener’s acrial, unless the object is close to the listener’s aerial there is no screening effect. But to run an aerial so that it is screened by the close proximity of a house or trees which are between the broadcast station and the listener’s aerial is fo reduce strength of reception very substantially, An average aerial should be free from screening effect, and at least 30 feet above, not only the ground, but above every object. An aerial suspended to 30-feet masts has its electrical height proportionally reduced if it passes directly over a hedge, tree, fence, or building. In the cities it is seldom one can erect an aerial of a good length without its passing over one or more of such objects. If the tree happens to be on the listener’s own property he can improve matters by cutting it down or reducing its height, but other objects, such as fences and buildings, have to be tolerated. The best way of overcoming these disadvantages, if the aerial cannot be placed so as to avoid passing over them, is to raise -the height of the aerial. I have seen an aerial for a crystal set placed on ‘two tenfoot masts on the top of a two-storied house, with a long galvanised iron roof. ‘The owner nurtured the mistaken idea that his aerial was 45 feet in height, but reception was relatively poor. Acting on advice, he increased the height of his masts to 25 feet, and reception increased in volume quite three-fold.

To obtain the maximum advantage from an aerial, the lead-in should never be longer than the actual aerial. Jt is also bad practice to bring the leadin back underneath the aerial to the point where it enters the house. A good plan is to arrange the aerial so that the lead-in comes away from it at right angles to it. The lead-in should, if possible, not be brought within four feet of the side of the house, or any projection fron the house, until it is run through the wall or window frame. The receiving set should be as close as possible to

¢ the point where the lead-in enters the room. ‘This sayes loss of signal strength. It is a good plan to use about 14 feet of rubber-insulated wire for the lead-in. It can be spliced on to the "tail"? of thie aerial and then firmly soldered. ‘The nearer end of the aerial should have its "tail" twisted around it five or six times, and then the twists should be securely soldered, otherwise the aerial will unwind and sag badly. Always bring the lead-in away at the very extremity of the aerial, The aerial should not come closer than five or six feet from the mast, the insulators being so paced as to keep it that distance away. It is better to usé galvanised iron wire for the halyard of the aerial instead of rope. The latter gets tight in wet weather and loose.in dry weae ther, and ‘it is subject to rot unless specially prepared for the purpose. ‘fhe lead-in wire should not be fine? in size than the aerial. If it ‘is come posed of finer-gauged wire, this cam be compensated for by a great2r number of strands. The earth wire forms part of the aerial system and may be liken ed to a drain. ‘herefore the heavier the gauge of wire the better, so that it offers a minimum of resistance to the electrical current. It is not gene erally known by the novice that the .finer the wire the greater the resistance, unless the wire is stranded, and then the greater number of strands compensates for the fineness of its gauge. No single-wire aerial should be finer than 14 gauge. The stranded wire makes a very excellent aerial, and seven strands of 20 gauge is a deserve edly popular type. An aerial should be well insulated to prevent leakages. Many listeners are satisfied with two insulators at each end of the aerial, but I prefer at least three at each end. Generally speaking, the quality of insulators on the New Zealand market are excellent. The ‘shell’? and the "egg" types of insulators possess the advantage of tremende ous strength for their size, and there is no danger of their carrying away. At one time there was a cheap type of insulator on sale which had a metal hook at each end, and some purchasers found that the hooks pulled out under the heavy strain on the aerial occasion ed by gales. A hetter-made insulator | of similar design is now on sale, and it has stood severe tests. It is not a bad plan to !ower the aerial vecasionally to clean off rust stains and dust of soot which have lodged on the insulators. ‘This will avoid electrical leakagd across the insulators. Weavy rain wil wash dust or soot off insulators, but Jrust stains require personal attention. When an aerial is being erected it is advisable to clean the insulators before they are hoisted up, as they may have become muddy or dirty through lying on the grounl.